xref: /external/chromium_org/third_party/icu/source/common/unicode/unistr.h

/*
**********************************************************************
*   Copyright (C) 1998-2013, International Business Machines
*   Corporation and others.  All Rights Reserved.
**********************************************************************
*
* File unistr.h
*
* Modification History:
*
*   Date        Name        Description
*   09/25/98    stephen     Creation.
*   11/11/98    stephen     Changed per 11/9 code review.
*   04/20/99    stephen     Overhauled per 4/16 code review.
*   11/18/99    aliu        Made to inherit from Replaceable.  Added method
*                           handleReplaceBetween(); other methods unchanged.
*   06/25/01    grhoten     Remove dependency on iostream.
******************************************************************************
*/

#ifndef UNISTR_H
#define UNISTR_H

/**
 * \file
 * \brief C++ API: Unicode String
 */

#include "unicode/utypes.h"
#include "unicode/rep.h"
#include "unicode/std_string.h"
#include "unicode/stringpiece.h"
#include "unicode/bytestream.h"
#include "unicode/ucasemap.h"

struct UConverter;          // unicode/ucnv.h
class  StringThreadTest;

#ifndef U_COMPARE_CODE_POINT_ORDER
/* see also ustring.h and unorm.h */
/**
 * Option bit for u_strCaseCompare, u_strcasecmp, unorm_compare, etc:
 * Compare strings in code point order instead of code unit order.
 * @stable ICU 2.2
 */
#define U_COMPARE_CODE_POINT_ORDER  0x8000
#endif

#ifndef USTRING_H
/**
 * \ingroup ustring_ustrlen
 */
U_STABLE int32_t U_EXPORT2
u_strlen(const UChar *s);
#endif

/**
 * \def U_STRING_CASE_MAPPER_DEFINED
 * @internal
 */
#ifndef U_STRING_CASE_MAPPER_DEFINED
#define U_STRING_CASE_MAPPER_DEFINED

/**
 * Internal string case mapping function type.
 * @internal
 */
typedef int32_t U_CALLCONV
UStringCaseMapper(const UCaseMap *csm,
                  UChar *dest, int32_t destCapacity,
                  const UChar *src, int32_t srcLength,
                  UErrorCode *pErrorCode);

#endif

U_NAMESPACE_BEGIN

class BreakIterator;        // unicode/brkiter.h
class Locale;               // unicode/locid.h
class StringCharacterIterator;
class UnicodeStringAppendable;  // unicode/appendable.h

/* The <iostream> include has been moved to unicode/ustream.h */

/**
 * Constant to be used in the UnicodeString(char *, int32_t, EInvariant) constructor
 * which constructs a Unicode string from an invariant-character char * string.
 * About invariant characters see utypes.h.
 * This constructor has no runtime dependency on conversion code and is
 * therefore recommended over ones taking a charset name string
 * (where the empty string "" indicates invariant-character conversion).
 *
 * @stable ICU 3.2
 */
#define US_INV icu::UnicodeString::kInvariant

/**
 * Unicode String literals in C++.
 * Dependent on the platform properties, different UnicodeString
 * constructors should be used to create a UnicodeString object from
 * a string literal.
 * The macros are defined for maximum performance.
 * They work only for strings that contain "invariant characters", i.e.,
 * only latin letters, digits, and some punctuation.
 * See utypes.h for details.
 *
 * The string parameter must be a C string literal.
 * The length of the string, not including the terminating
 * <code>NUL</code>, must be specified as a constant.
 * The U_STRING_DECL macro should be invoked exactly once for one
 * such string variable before it is used.
 * @stable ICU 2.0
 */
#if defined(U_DECLARE_UTF16)
#   define UNICODE_STRING(cs, _length) icu::UnicodeString(TRUE, (const UChar *)U_DECLARE_UTF16(cs), _length)
#elif U_SIZEOF_WCHAR_T==U_SIZEOF_UCHAR && (U_CHARSET_FAMILY==U_ASCII_FAMILY || (U_SIZEOF_UCHAR == 2 && defined(U_WCHAR_IS_UTF16)))
#   define UNICODE_STRING(cs, _length) icu::UnicodeString(TRUE, (const UChar *)L ## cs, _length)
#elif U_SIZEOF_UCHAR==1 && U_CHARSET_FAMILY==U_ASCII_FAMILY
#   define UNICODE_STRING(cs, _length) icu::UnicodeString(TRUE, (const UChar *)cs, _length)
#else
#   define UNICODE_STRING(cs, _length) icu::UnicodeString(cs, _length, US_INV)
#endif

/**
 * Unicode String literals in C++.
 * Dependent on the platform properties, different UnicodeString
 * constructors should be used to create a UnicodeString object from
 * a string literal.
 * The macros are defined for improved performance.
 * They work only for strings that contain "invariant characters", i.e.,
 * only latin letters, digits, and some punctuation.
 * See utypes.h for details.
 *
 * The string parameter must be a C string literal.
 * @stable ICU 2.0
 */
#define UNICODE_STRING_SIMPLE(cs) UNICODE_STRING(cs, -1)

/**
 * \def UNISTR_FROM_CHAR_EXPLICIT
 * This can be defined to be empty or "explicit".
 * If explicit, then the UnicodeString(UChar) and UnicodeString(UChar32)
 * constructors are marked as explicit, preventing their inadvertent use.
 * @stable ICU 49
 */
#ifndef UNISTR_FROM_CHAR_EXPLICIT
# if defined(U_COMBINED_IMPLEMENTATION) || defined(U_COMMON_IMPLEMENTATION) || defined(U_I18N_IMPLEMENTATION) || defined(U_IO_IMPLEMENTATION)
    // Auto-"explicit" in ICU library code.
#   define UNISTR_FROM_CHAR_EXPLICIT explicit
# else
    // Empty by default for source code compatibility.
#   define UNISTR_FROM_CHAR_EXPLICIT
# endif
#endif

/**
 * \def UNISTR_FROM_STRING_EXPLICIT
 * This can be defined to be empty or "explicit".
 * If explicit, then the UnicodeString(const char *) and UnicodeString(const UChar *)
 * constructors are marked as explicit, preventing their inadvertent use.
 *
 * In particular, this helps prevent accidentally depending on ICU conversion code
 * by passing a string literal into an API with a const UnicodeString & parameter.
 * @stable ICU 49
 */
#ifndef UNISTR_FROM_STRING_EXPLICIT
# if defined(U_COMBINED_IMPLEMENTATION) || defined(U_COMMON_IMPLEMENTATION) || defined(U_I18N_IMPLEMENTATION) || defined(U_IO_IMPLEMENTATION)
    // Auto-"explicit" in ICU library code.
#   define UNISTR_FROM_STRING_EXPLICIT explicit
# else
    // Empty by default for source code compatibility.
#   define UNISTR_FROM_STRING_EXPLICIT
# endif
#endif

/**
 * UnicodeString is a string class that stores Unicode characters directly and provides
 * similar functionality as the Java String and StringBuffer classes.
 * It is a concrete implementation of the abstract class Replaceable (for transliteration).
 *
 * The UnicodeString class is not suitable for subclassing.
 *
 * <p>For an overview of Unicode strings in C and C++ see the
 * <a href="http://icu-project.org/userguide/strings.html">User Guide Strings chapter</a>.</p>
 *
 * <p>In ICU, a Unicode string consists of 16-bit Unicode <em>code units</em>.
 * A Unicode character may be stored with either one code unit
 * (the most common case) or with a matched pair of special code units
 * ("surrogates"). The data type for code units is UChar.
 * For single-character handling, a Unicode character code <em>point</em> is a value
 * in the range 0..0x10ffff. ICU uses the UChar32 type for code points.</p>
 *
 * <p>Indexes and offsets into and lengths of strings always count code units, not code points.
 * This is the same as with multi-byte char* strings in traditional string handling.
 * Operations on partial strings typically do not test for code point boundaries.
 * If necessary, the user needs to take care of such boundaries by testing for the code unit
 * values or by using functions like
 * UnicodeString::getChar32Start() and UnicodeString::getChar32Limit()
 * (or, in C, the equivalent macros U16_SET_CP_START() and U16_SET_CP_LIMIT(), see utf.h).</p>
 *
 * UnicodeString methods are more lenient with regard to input parameter values
 * than other ICU APIs. In particular:
 * - If indexes are out of bounds for a UnicodeString object
 *   (<0 or >length()) then they are "pinned" to the nearest boundary.
 * - If primitive string pointer values (e.g., const UChar * or char *)
 *   for input strings are NULL, then those input string parameters are treated
 *   as if they pointed to an empty string.
 *   However, this is <em>not</em> the case for char * parameters for charset names
 *   or other IDs.
 * - Most UnicodeString methods do not take a UErrorCode parameter because
 *   there are usually very few opportunities for failure other than a shortage
 *   of memory, error codes in low-level C++ string methods would be inconvenient,
 *   and the error code as the last parameter (ICU convention) would prevent
 *   the use of default parameter values.
 *   Instead, such methods set the UnicodeString into a "bogus" state
 *   (see isBogus()) if an error occurs.
 *
 * In string comparisons, two UnicodeString objects that are both "bogus"
 * compare equal (to be transitive and prevent endless loops in sorting),
 * and a "bogus" string compares less than any non-"bogus" one.
 *
 * Const UnicodeString methods are thread-safe. Multiple threads can use
 * const methods on the same UnicodeString object simultaneously,
 * but non-const methods must not be called concurrently (in multiple threads)
 * with any other (const or non-const) methods.
 *
 * Similarly, const UnicodeString & parameters are thread-safe.
 * One object may be passed in as such a parameter concurrently in multiple threads.
 * This includes the const UnicodeString & parameters for
 * copy construction, assignment, and cloning.
 *
 * <p>UnicodeString uses several storage methods.
 * String contents can be stored inside the UnicodeString object itself,
 * in an allocated and shared buffer, or in an outside buffer that is "aliased".
 * Most of this is done transparently, but careful aliasing in particular provides
 * significant performance improvements.
 * Also, the internal buffer is accessible via special functions.
 * For details see the
 * <a href="http://icu-project.org/userguide/strings.html">User Guide Strings chapter</a>.</p>
 *
 * @see utf.h
 * @see CharacterIterator
 * @stable ICU 2.0
 */
class U_COMMON_API UnicodeString : public Replaceable
{
public:

  /**
   * Constant to be used in the UnicodeString(char *, int32_t, EInvariant) constructor
   * which constructs a Unicode string from an invariant-character char * string.
   * Use the macro US_INV instead of the full qualification for this value.
   *
   * @see US_INV
   * @stable ICU 3.2
   */
  enum EInvariant {
    /**
     * @see EInvariant
     * @stable ICU 3.2
     */
    kInvariant
  };

  //========================================
  // Read-only operations
  //========================================

  /* Comparison - bitwise only - for international comparison use collation */

  /**
   * Equality operator. Performs only bitwise comparison.
   * @param text The UnicodeString to compare to this one.
   * @return TRUE if <TT>text</TT> contains the same characters as this one,
   * FALSE otherwise.
   * @stable ICU 2.0
   */
  inline UBool operator== (const UnicodeString& text) const;

  /**
   * Inequality operator. Performs only bitwise comparison.
   * @param text The UnicodeString to compare to this one.
   * @return FALSE if <TT>text</TT> contains the same characters as this one,
   * TRUE otherwise.
   * @stable ICU 2.0
   */
  inline UBool operator!= (const UnicodeString& text) const;

  /**
   * Greater than operator. Performs only bitwise comparison.
   * @param text The UnicodeString to compare to this one.
   * @return TRUE if the characters in this are bitwise
   * greater than the characters in <code>text</code>, FALSE otherwise
   * @stable ICU 2.0
   */
  inline UBool operator> (const UnicodeString& text) const;

  /**
   * Less than operator. Performs only bitwise comparison.
   * @param text The UnicodeString to compare to this one.
   * @return TRUE if the characters in this are bitwise
   * less than the characters in <code>text</code>, FALSE otherwise
   * @stable ICU 2.0
   */
  inline UBool operator< (const UnicodeString& text) const;

  /**
   * Greater than or equal operator. Performs only bitwise comparison.
   * @param text The UnicodeString to compare to this one.
   * @return TRUE if the characters in this are bitwise
   * greater than or equal to the characters in <code>text</code>, FALSE otherwise
   * @stable ICU 2.0
   */
  inline UBool operator>= (const UnicodeString& text) const;

  /**
   * Less than or equal operator. Performs only bitwise comparison.
   * @param text The UnicodeString to compare to this one.
   * @return TRUE if the characters in this are bitwise
   * less than or equal to the characters in <code>text</code>, FALSE otherwise
   * @stable ICU 2.0
   */
  inline UBool operator<= (const UnicodeString& text) const;

  /**
   * Compare the characters bitwise in this UnicodeString to
   * the characters in <code>text</code>.
   * @param text The UnicodeString to compare to this one.
   * @return The result of bitwise character comparison: 0 if this
   * contains the same characters as <code>text</code>, -1 if the characters in
   * this are bitwise less than the characters in <code>text</code>, +1 if the
   * characters in this are bitwise greater than the characters
   * in <code>text</code>.
   * @stable ICU 2.0
   */
  inline int8_t compare(const UnicodeString& text) const;

  /**
   * Compare the characters bitwise in the range
   * [<TT>start</TT>, <TT>start + length</TT>) with the characters
   * in the <b>entire string</b> <TT>text</TT>.
   * (The parameters "start" and "length" are not applied to the other text "text".)
   * @param start the offset at which the compare operation begins
   * @param length the number of characters of text to compare.
   * @param text the other text to be compared against this string.
   * @return The result of bitwise character comparison: 0 if this
   * contains the same characters as <code>text</code>, -1 if the characters in
   * this are bitwise less than the characters in <code>text</code>, +1 if the
   * characters in this are bitwise greater than the characters
   * in <code>text</code>.
   * @stable ICU 2.0
   */
  inline int8_t compare(int32_t start,
         int32_t length,
         const UnicodeString& text) const;

  /**
   * Compare the characters bitwise in the range
   * [<TT>start</TT>, <TT>start + length</TT>) with the characters
   * in <TT>srcText</TT> in the range
   * [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>).
   * @param start the offset at which the compare operation begins
   * @param length the number of characters in this to compare.
   * @param srcText the text to be compared
   * @param srcStart the offset into <TT>srcText</TT> to start comparison
   * @param srcLength the number of characters in <TT>src</TT> to compare
   * @return The result of bitwise character comparison: 0 if this
   * contains the same characters as <code>srcText</code>, -1 if the characters in
   * this are bitwise less than the characters in <code>srcText</code>, +1 if the
   * characters in this are bitwise greater than the characters
   * in <code>srcText</code>.
   * @stable ICU 2.0
   */
   inline int8_t compare(int32_t start,
         int32_t length,
         const UnicodeString& srcText,
         int32_t srcStart,
         int32_t srcLength) const;

  /**
   * Compare the characters bitwise in this UnicodeString with the first
   * <TT>srcLength</TT> characters in <TT>srcChars</TT>.
   * @param srcChars The characters to compare to this UnicodeString.
   * @param srcLength the number of characters in <TT>srcChars</TT> to compare
   * @return The result of bitwise character comparison: 0 if this
   * contains the same characters as <code>srcChars</code>, -1 if the characters in
   * this are bitwise less than the characters in <code>srcChars</code>, +1 if the
   * characters in this are bitwise greater than the characters
   * in <code>srcChars</code>.
   * @stable ICU 2.0
   */
  inline int8_t compare(const UChar *srcChars,
         int32_t srcLength) const;

  /**
   * Compare the characters bitwise in the range
   * [<TT>start</TT>, <TT>start + length</TT>) with the first
   * <TT>length</TT> characters in <TT>srcChars</TT>
   * @param start the offset at which the compare operation begins
   * @param length the number of characters to compare.
   * @param srcChars the characters to be compared
   * @return The result of bitwise character comparison: 0 if this
   * contains the same characters as <code>srcChars</code>, -1 if the characters in
   * this are bitwise less than the characters in <code>srcChars</code>, +1 if the
   * characters in this are bitwise greater than the characters
   * in <code>srcChars</code>.
   * @stable ICU 2.0
   */
  inline int8_t compare(int32_t start,
         int32_t length,
         const UChar *srcChars) const;

  /**
   * Compare the characters bitwise in the range
   * [<TT>start</TT>, <TT>start + length</TT>) with the characters
   * in <TT>srcChars</TT> in the range
   * [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>).
   * @param start the offset at which the compare operation begins
   * @param length the number of characters in this to compare
   * @param srcChars the characters to be compared
   * @param srcStart the offset into <TT>srcChars</TT> to start comparison
   * @param srcLength the number of characters in <TT>srcChars</TT> to compare
   * @return The result of bitwise character comparison: 0 if this
   * contains the same characters as <code>srcChars</code>, -1 if the characters in
   * this are bitwise less than the characters in <code>srcChars</code>, +1 if the
   * characters in this are bitwise greater than the characters
   * in <code>srcChars</code>.
   * @stable ICU 2.0
   */
  inline int8_t compare(int32_t start,
         int32_t length,
         const UChar *srcChars,
         int32_t srcStart,
         int32_t srcLength) const;

  /**
   * Compare the characters bitwise in the range
   * [<TT>start</TT>, <TT>limit</TT>) with the characters
   * in <TT>srcText</TT> in the range
   * [<TT>srcStart</TT>, <TT>srcLimit</TT>).
   * @param start the offset at which the compare operation begins
   * @param limit the offset immediately following the compare operation
   * @param srcText the text to be compared
   * @param srcStart the offset into <TT>srcText</TT> to start comparison
   * @param srcLimit the offset into <TT>srcText</TT> to limit comparison
   * @return The result of bitwise character comparison: 0 if this
   * contains the same characters as <code>srcText</code>, -1 if the characters in
   * this are bitwise less than the characters in <code>srcText</code>, +1 if the
   * characters in this are bitwise greater than the characters
   * in <code>srcText</code>.
   * @stable ICU 2.0
   */
  inline int8_t compareBetween(int32_t start,
            int32_t limit,
            const UnicodeString& srcText,
            int32_t srcStart,
            int32_t srcLimit) const;

  /**
   * Compare two Unicode strings in code point order.
   * The result may be different from the results of compare(), operator<, etc.
   * if supplementary characters are present:
   *
   * In UTF-16, supplementary characters (with code points U+10000 and above) are
   * stored with pairs of surrogate code units. These have values from 0xd800 to 0xdfff,
   * which means that they compare as less than some other BMP characters like U+feff.
   * This function compares Unicode strings in code point order.
   * If either of the UTF-16 strings is malformed (i.e., it contains unpaired surrogates), then the result is not defined.
   *
   * @param text Another string to compare this one to.
   * @return a negative/zero/positive integer corresponding to whether
   * this string is less than/equal to/greater than the second one
   * in code point order
   * @stable ICU 2.0
   */
  inline int8_t compareCodePointOrder(const UnicodeString& text) const;

  /**
   * Compare two Unicode strings in code point order.
   * The result may be different from the results of compare(), operator<, etc.
   * if supplementary characters are present:
   *
   * In UTF-16, supplementary characters (with code points U+10000 and above) are
   * stored with pairs of surrogate code units. These have values from 0xd800 to 0xdfff,
   * which means that they compare as less than some other BMP characters like U+feff.
   * This function compares Unicode strings in code point order.
   * If either of the UTF-16 strings is malformed (i.e., it contains unpaired surrogates), then the result is not defined.
   *
   * @param start The start offset in this string at which the compare operation begins.
   * @param length The number of code units from this string to compare.
   * @param srcText Another string to compare this one to.
   * @return a negative/zero/positive integer corresponding to whether
   * this string is less than/equal to/greater than the second one
   * in code point order
   * @stable ICU 2.0
   */
  inline int8_t compareCodePointOrder(int32_t start,
                                      int32_t length,
                                      const UnicodeString& srcText) const;

  /**
   * Compare two Unicode strings in code point order.
   * The result may be different from the results of compare(), operator<, etc.
   * if supplementary characters are present:
   *
   * In UTF-16, supplementary characters (with code points U+10000 and above) are
   * stored with pairs of surrogate code units. These have values from 0xd800 to 0xdfff,
   * which means that they compare as less than some other BMP characters like U+feff.
   * This function compares Unicode strings in code point order.
   * If either of the UTF-16 strings is malformed (i.e., it contains unpaired surrogates), then the result is not defined.
   *
   * @param start The start offset in this string at which the compare operation begins.
   * @param length The number of code units from this string to compare.
   * @param srcText Another string to compare this one to.
   * @param srcStart The start offset in that string at which the compare operation begins.
   * @param srcLength The number of code units from that string to compare.
   * @return a negative/zero/positive integer corresponding to whether
   * this string is less than/equal to/greater than the second one
   * in code point order
   * @stable ICU 2.0
   */
   inline int8_t compareCodePointOrder(int32_t start,
                                       int32_t length,
                                       const UnicodeString& srcText,
                                       int32_t srcStart,
                                       int32_t srcLength) const;

  /**
   * Compare two Unicode strings in code point order.
   * The result may be different from the results of compare(), operator<, etc.
   * if supplementary characters are present:
   *
   * In UTF-16, supplementary characters (with code points U+10000 and above) are
   * stored with pairs of surrogate code units. These have values from 0xd800 to 0xdfff,
   * which means that they compare as less than some other BMP characters like U+feff.
   * This function compares Unicode strings in code point order.
   * If either of the UTF-16 strings is malformed (i.e., it contains unpaired surrogates), then the result is not defined.
   *
   * @param srcChars A pointer to another string to compare this one to.
   * @param srcLength The number of code units from that string to compare.
   * @return a negative/zero/positive integer corresponding to whether
   * this string is less than/equal to/greater than the second one
   * in code point order
   * @stable ICU 2.0
   */
  inline int8_t compareCodePointOrder(const UChar *srcChars,
                                      int32_t srcLength) const;

  /**
   * Compare two Unicode strings in code point order.
   * The result may be different from the results of compare(), operator<, etc.
   * if supplementary characters are present:
   *
   * In UTF-16, supplementary characters (with code points U+10000 and above) are
   * stored with pairs of surrogate code units. These have values from 0xd800 to 0xdfff,
   * which means that they compare as less than some other BMP characters like U+feff.
   * This function compares Unicode strings in code point order.
   * If either of the UTF-16 strings is malformed (i.e., it contains unpaired surrogates), then the result is not defined.
   *
   * @param start The start offset in this string at which the compare operation begins.
   * @param length The number of code units from this string to compare.
   * @param srcChars A pointer to another string to compare this one to.
   * @return a negative/zero/positive integer corresponding to whether
   * this string is less than/equal to/greater than the second one
   * in code point order
   * @stable ICU 2.0
   */
  inline int8_t compareCodePointOrder(int32_t start,
                                      int32_t length,
                                      const UChar *srcChars) const;

  /**
   * Compare two Unicode strings in code point order.
   * The result may be different from the results of compare(), operator<, etc.
   * if supplementary characters are present:
   *
   * In UTF-16, supplementary characters (with code points U+10000 and above) are
   * stored with pairs of surrogate code units. These have values from 0xd800 to 0xdfff,
   * which means that they compare as less than some other BMP characters like U+feff.
   * This function compares Unicode strings in code point order.
   * If either of the UTF-16 strings is malformed (i.e., it contains unpaired surrogates), then the result is not defined.
   *
   * @param start The start offset in this string at which the compare operation begins.
   * @param length The number of code units from this string to compare.
   * @param srcChars A pointer to another string to compare this one to.
   * @param srcStart The start offset in that string at which the compare operation begins.
   * @param srcLength The number of code units from that string to compare.
   * @return a negative/zero/positive integer corresponding to whether
   * this string is less than/equal to/greater than the second one
   * in code point order
   * @stable ICU 2.0
   */
  inline int8_t compareCodePointOrder(int32_t start,
                                      int32_t length,
                                      const UChar *srcChars,
                                      int32_t srcStart,
                                      int32_t srcLength) const;

  /**
   * Compare two Unicode strings in code point order.
   * The result may be different from the results of compare(), operator<, etc.
   * if supplementary characters are present:
   *
   * In UTF-16, supplementary characters (with code points U+10000 and above) are
   * stored with pairs of surrogate code units. These have values from 0xd800 to 0xdfff,
   * which means that they compare as less than some other BMP characters like U+feff.
   * This function compares Unicode strings in code point order.
   * If either of the UTF-16 strings is malformed (i.e., it contains unpaired surrogates), then the result is not defined.
   *
   * @param start The start offset in this string at which the compare operation begins.
   * @param limit The offset after the last code unit from this string to compare.
   * @param srcText Another string to compare this one to.
   * @param srcStart The start offset in that string at which the compare operation begins.
   * @param srcLimit The offset after the last code unit from that string to compare.
   * @return a negative/zero/positive integer corresponding to whether
   * this string is less than/equal to/greater than the second one
   * in code point order
   * @stable ICU 2.0
   */
  inline int8_t compareCodePointOrderBetween(int32_t start,
                                             int32_t limit,
                                             const UnicodeString& srcText,
                                             int32_t srcStart,
                                             int32_t srcLimit) const;

  /**
   * Compare two strings case-insensitively using full case folding.
   * This is equivalent to this->foldCase(options).compare(text.foldCase(options)).
   *
   * @param text Another string to compare this one to.
   * @param options A bit set of options:
   *   - U_FOLD_CASE_DEFAULT or 0 is used for default options:
   *     Comparison in code unit order with default case folding.
   *
   *   - U_COMPARE_CODE_POINT_ORDER
   *     Set to choose code point order instead of code unit order
   *     (see u_strCompare for details).
   *
   *   - U_FOLD_CASE_EXCLUDE_SPECIAL_I
   *
   * @return A negative, zero, or positive integer indicating the comparison result.
   * @stable ICU 2.0
   */
  inline int8_t caseCompare(const UnicodeString& text, uint32_t options) const;

  /**
   * Compare two strings case-insensitively using full case folding.
   * This is equivalent to this->foldCase(options).compare(srcText.foldCase(options)).
   *
   * @param start The start offset in this string at which the compare operation begins.
   * @param length The number of code units from this string to compare.
   * @param srcText Another string to compare this one to.
   * @param options A bit set of options:
   *   - U_FOLD_CASE_DEFAULT or 0 is used for default options:
   *     Comparison in code unit order with default case folding.
   *
   *   - U_COMPARE_CODE_POINT_ORDER
   *     Set to choose code point order instead of code unit order
   *     (see u_strCompare for details).
   *
   *   - U_FOLD_CASE_EXCLUDE_SPECIAL_I
   *
   * @return A negative, zero, or positive integer indicating the comparison result.
   * @stable ICU 2.0
   */
  inline int8_t caseCompare(int32_t start,
         int32_t length,
         const UnicodeString& srcText,
         uint32_t options) const;

  /**
   * Compare two strings case-insensitively using full case folding.
   * This is equivalent to this->foldCase(options).compare(srcText.foldCase(options)).
   *
   * @param start The start offset in this string at which the compare operation begins.
   * @param length The number of code units from this string to compare.
   * @param srcText Another string to compare this one to.
   * @param srcStart The start offset in that string at which the compare operation begins.
   * @param srcLength The number of code units from that string to compare.
   * @param options A bit set of options:
   *   - U_FOLD_CASE_DEFAULT or 0 is used for default options:
   *     Comparison in code unit order with default case folding.
   *
   *   - U_COMPARE_CODE_POINT_ORDER
   *     Set to choose code point order instead of code unit order
   *     (see u_strCompare for details).
   *
   *   - U_FOLD_CASE_EXCLUDE_SPECIAL_I
   *
   * @return A negative, zero, or positive integer indicating the comparison result.
   * @stable ICU 2.0
   */
  inline int8_t caseCompare(int32_t start,
         int32_t length,
         const UnicodeString& srcText,
         int32_t srcStart,
         int32_t srcLength,
         uint32_t options) const;

  /**
   * Compare two strings case-insensitively using full case folding.
   * This is equivalent to this->foldCase(options).compare(srcChars.foldCase(options)).
   *
   * @param srcChars A pointer to another string to compare this one to.
   * @param srcLength The number of code units from that string to compare.
   * @param options A bit set of options:
   *   - U_FOLD_CASE_DEFAULT or 0 is used for default options:
   *     Comparison in code unit order with default case folding.
   *
   *   - U_COMPARE_CODE_POINT_ORDER
   *     Set to choose code point order instead of code unit order
   *     (see u_strCompare for details).
   *
   *   - U_FOLD_CASE_EXCLUDE_SPECIAL_I
   *
   * @return A negative, zero, or positive integer indicating the comparison result.
   * @stable ICU 2.0
   */
  inline int8_t caseCompare(const UChar *srcChars,
         int32_t srcLength,
         uint32_t options) const;

  /**
   * Compare two strings case-insensitively using full case folding.
   * This is equivalent to this->foldCase(options).compare(srcChars.foldCase(options)).
   *
   * @param start The start offset in this string at which the compare operation begins.
   * @param length The number of code units from this string to compare.
   * @param srcChars A pointer to another string to compare this one to.
   * @param options A bit set of options:
   *   - U_FOLD_CASE_DEFAULT or 0 is used for default options:
   *     Comparison in code unit order with default case folding.
   *
   *   - U_COMPARE_CODE_POINT_ORDER
   *     Set to choose code point order instead of code unit order
   *     (see u_strCompare for details).
   *
   *   - U_FOLD_CASE_EXCLUDE_SPECIAL_I
   *
   * @return A negative, zero, or positive integer indicating the comparison result.
   * @stable ICU 2.0
   */
  inline int8_t caseCompare(int32_t start,
         int32_t length,
         const UChar *srcChars,
         uint32_t options) const;

  /**
   * Compare two strings case-insensitively using full case folding.
   * This is equivalent to this->foldCase(options).compare(srcChars.foldCase(options)).
   *
   * @param start The start offset in this string at which the compare operation begins.
   * @param length The number of code units from this string to compare.
   * @param srcChars A pointer to another string to compare this one to.
   * @param srcStart The start offset in that string at which the compare operation begins.
   * @param srcLength The number of code units from that string to compare.
   * @param options A bit set of options:
   *   - U_FOLD_CASE_DEFAULT or 0 is used for default options:
   *     Comparison in code unit order with default case folding.
   *
   *   - U_COMPARE_CODE_POINT_ORDER
   *     Set to choose code point order instead of code unit order
   *     (see u_strCompare for details).
   *
   *   - U_FOLD_CASE_EXCLUDE_SPECIAL_I
   *
   * @return A negative, zero, or positive integer indicating the comparison result.
   * @stable ICU 2.0
   */
  inline int8_t caseCompare(int32_t start,
         int32_t length,
         const UChar *srcChars,
         int32_t srcStart,
         int32_t srcLength,
         uint32_t options) const;

  /**
   * Compare two strings case-insensitively using full case folding.
   * This is equivalent to this->foldCase(options).compareBetween(text.foldCase(options)).
   *
   * @param start The start offset in this string at which the compare operation begins.
   * @param limit The offset after the last code unit from this string to compare.
   * @param srcText Another string to compare this one to.
   * @param srcStart The start offset in that string at which the compare operation begins.
   * @param srcLimit The offset after the last code unit from that string to compare.
   * @param options A bit set of options:
   *   - U_FOLD_CASE_DEFAULT or 0 is used for default options:
   *     Comparison in code unit order with default case folding.
   *
   *   - U_COMPARE_CODE_POINT_ORDER
   *     Set to choose code point order instead of code unit order
   *     (see u_strCompare for details).
   *
   *   - U_FOLD_CASE_EXCLUDE_SPECIAL_I
   *
   * @return A negative, zero, or positive integer indicating the comparison result.
   * @stable ICU 2.0
   */
  inline int8_t caseCompareBetween(int32_t start,
            int32_t limit,
            const UnicodeString& srcText,
            int32_t srcStart,
            int32_t srcLimit,
            uint32_t options) const;

  /**
   * Determine if this starts with the characters in <TT>text</TT>
   * @param text The text to match.
   * @return TRUE if this starts with the characters in <TT>text</TT>,
   * FALSE otherwise
   * @stable ICU 2.0
   */
  inline UBool startsWith(const UnicodeString& text) const;

  /**
   * Determine if this starts with the characters in <TT>srcText</TT>
   * in the range [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>).
   * @param srcText The text to match.
   * @param srcStart the offset into <TT>srcText</TT> to start matching
   * @param srcLength the number of characters in <TT>srcText</TT> to match
   * @return TRUE if this starts with the characters in <TT>text</TT>,
   * FALSE otherwise
   * @stable ICU 2.0
   */
  inline UBool startsWith(const UnicodeString& srcText,
            int32_t srcStart,
            int32_t srcLength) const;

  /**
   * Determine if this starts with the characters in <TT>srcChars</TT>
   * @param srcChars The characters to match.
   * @param srcLength the number of characters in <TT>srcChars</TT>
   * @return TRUE if this starts with the characters in <TT>srcChars</TT>,
   * FALSE otherwise
   * @stable ICU 2.0
   */
  inline UBool startsWith(const UChar *srcChars,
            int32_t srcLength) const;

  /**
   * Determine if this ends with the characters in <TT>srcChars</TT>
   * in the range  [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>).
   * @param srcChars The characters to match.
   * @param srcStart the offset into <TT>srcText</TT> to start matching
   * @param srcLength the number of characters in <TT>srcChars</TT> to match
   * @return TRUE if this ends with the characters in <TT>srcChars</TT>, FALSE otherwise
   * @stable ICU 2.0
   */
  inline UBool startsWith(const UChar *srcChars,
            int32_t srcStart,
            int32_t srcLength) const;

  /**
   * Determine if this ends with the characters in <TT>text</TT>
   * @param text The text to match.
   * @return TRUE if this ends with the characters in <TT>text</TT>,
   * FALSE otherwise
   * @stable ICU 2.0
   */
  inline UBool endsWith(const UnicodeString& text) const;

  /**
   * Determine if this ends with the characters in <TT>srcText</TT>
   * in the range [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>).
   * @param srcText The text to match.
   * @param srcStart the offset into <TT>srcText</TT> to start matching
   * @param srcLength the number of characters in <TT>srcText</TT> to match
   * @return TRUE if this ends with the characters in <TT>text</TT>,
   * FALSE otherwise
   * @stable ICU 2.0
   */
  inline UBool endsWith(const UnicodeString& srcText,
          int32_t srcStart,
          int32_t srcLength) const;

  /**
   * Determine if this ends with the characters in <TT>srcChars</TT>
   * @param srcChars The characters to match.
   * @param srcLength the number of characters in <TT>srcChars</TT>
   * @return TRUE if this ends with the characters in <TT>srcChars</TT>,
   * FALSE otherwise
   * @stable ICU 2.0
   */
  inline UBool endsWith(const UChar *srcChars,
          int32_t srcLength) const;

  /**
   * Determine if this ends with the characters in <TT>srcChars</TT>
   * in the range  [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>).
   * @param srcChars The characters to match.
   * @param srcStart the offset into <TT>srcText</TT> to start matching
   * @param srcLength the number of characters in <TT>srcChars</TT> to match
   * @return TRUE if this ends with the characters in <TT>srcChars</TT>,
   * FALSE otherwise
   * @stable ICU 2.0
   */
  inline UBool endsWith(const UChar *srcChars,
          int32_t srcStart,
          int32_t srcLength) const;


  /* Searching - bitwise only */

  /**
   * Locate in this the first occurrence of the characters in <TT>text</TT>,
   * using bitwise comparison.
   * @param text The text to search for.
   * @return The offset into this of the start of <TT>text</TT>,
   * or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t indexOf(const UnicodeString& text) const;

  /**
   * Locate in this the first occurrence of the characters in <TT>text</TT>
   * starting at offset <TT>start</TT>, using bitwise comparison.
   * @param text The text to search for.
   * @param start The offset at which searching will start.
   * @return The offset into this of the start of <TT>text</TT>,
   * or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t indexOf(const UnicodeString& text,
              int32_t start) const;

  /**
   * Locate in this the first occurrence in the range
   * [<TT>start</TT>, <TT>start + length</TT>) of the characters
   * in <TT>text</TT>, using bitwise comparison.
   * @param text The text to search for.
   * @param start The offset at which searching will start.
   * @param length The number of characters to search
   * @return The offset into this of the start of <TT>text</TT>,
   * or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t indexOf(const UnicodeString& text,
              int32_t start,
              int32_t length) const;

  /**
   * Locate in this the first occurrence in the range
   * [<TT>start</TT>, <TT>start + length</TT>) of the characters
   *  in <TT>srcText</TT> in the range
   * [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>),
   * using bitwise comparison.
   * @param srcText The text to search for.
   * @param srcStart the offset into <TT>srcText</TT> at which
   * to start matching
   * @param srcLength the number of characters in <TT>srcText</TT> to match
   * @param start the offset into this at which to start matching
   * @param length the number of characters in this to search
   * @return The offset into this of the start of <TT>text</TT>,
   * or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t indexOf(const UnicodeString& srcText,
              int32_t srcStart,
              int32_t srcLength,
              int32_t start,
              int32_t length) const;

  /**
   * Locate in this the first occurrence of the characters in
   * <TT>srcChars</TT>
   * starting at offset <TT>start</TT>, using bitwise comparison.
   * @param srcChars The text to search for.
   * @param srcLength the number of characters in <TT>srcChars</TT> to match
   * @param start the offset into this at which to start matching
   * @return The offset into this of the start of <TT>text</TT>,
   * or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t indexOf(const UChar *srcChars,
              int32_t srcLength,
              int32_t start) const;

  /**
   * Locate in this the first occurrence in the range
   * [<TT>start</TT>, <TT>start + length</TT>) of the characters
   * in <TT>srcChars</TT>, using bitwise comparison.
   * @param srcChars The text to search for.
   * @param srcLength the number of characters in <TT>srcChars</TT>
   * @param start The offset at which searching will start.
   * @param length The number of characters to search
   * @return The offset into this of the start of <TT>srcChars</TT>,
   * or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t indexOf(const UChar *srcChars,
              int32_t srcLength,
              int32_t start,
              int32_t length) const;

  /**
   * Locate in this the first occurrence in the range
   * [<TT>start</TT>, <TT>start + length</TT>) of the characters
   * in <TT>srcChars</TT> in the range
   * [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>),
   * using bitwise comparison.
   * @param srcChars The text to search for.
   * @param srcStart the offset into <TT>srcChars</TT> at which
   * to start matching
   * @param srcLength the number of characters in <TT>srcChars</TT> to match
   * @param start the offset into this at which to start matching
   * @param length the number of characters in this to search
   * @return The offset into this of the start of <TT>text</TT>,
   * or -1 if not found.
   * @stable ICU 2.0
   */
  int32_t indexOf(const UChar *srcChars,
              int32_t srcStart,
              int32_t srcLength,
              int32_t start,
              int32_t length) const;

  /**
   * Locate in this the first occurrence of the BMP code point <code>c</code>,
   * using bitwise comparison.
   * @param c The code unit to search for.
   * @return The offset into this of <TT>c</TT>, or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t indexOf(UChar c) const;

  /**
   * Locate in this the first occurrence of the code point <TT>c</TT>,
   * using bitwise comparison.
   *
   * @param c The code point to search for.
   * @return The offset into this of <TT>c</TT>, or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t indexOf(UChar32 c) const;

  /**
   * Locate in this the first occurrence of the BMP code point <code>c</code>,
   * starting at offset <TT>start</TT>, using bitwise comparison.
   * @param c The code unit to search for.
   * @param start The offset at which searching will start.
   * @return The offset into this of <TT>c</TT>, or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t indexOf(UChar c,
              int32_t start) const;

  /**
   * Locate in this the first occurrence of the code point <TT>c</TT>
   * starting at offset <TT>start</TT>, using bitwise comparison.
   *
   * @param c The code point to search for.
   * @param start The offset at which searching will start.
   * @return The offset into this of <TT>c</TT>, or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t indexOf(UChar32 c,
              int32_t start) const;

  /**
   * Locate in this the first occurrence of the BMP code point <code>c</code>
   * in the range [<TT>start</TT>, <TT>start + length</TT>),
   * using bitwise comparison.
   * @param c The code unit to search for.
   * @param start the offset into this at which to start matching
   * @param length the number of characters in this to search
   * @return The offset into this of <TT>c</TT>, or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t indexOf(UChar c,
              int32_t start,
              int32_t length) const;

  /**
   * Locate in this the first occurrence of the code point <TT>c</TT>
   * in the range [<TT>start</TT>, <TT>start + length</TT>),
   * using bitwise comparison.
   *
   * @param c The code point to search for.
   * @param start the offset into this at which to start matching
   * @param length the number of characters in this to search
   * @return The offset into this of <TT>c</TT>, or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t indexOf(UChar32 c,
              int32_t start,
              int32_t length) const;

  /**
   * Locate in this the last occurrence of the characters in <TT>text</TT>,
   * using bitwise comparison.
   * @param text The text to search for.
   * @return The offset into this of the start of <TT>text</TT>,
   * or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t lastIndexOf(const UnicodeString& text) const;

  /**
   * Locate in this the last occurrence of the characters in <TT>text</TT>
   * starting at offset <TT>start</TT>, using bitwise comparison.
   * @param text The text to search for.
   * @param start The offset at which searching will start.
   * @return The offset into this of the start of <TT>text</TT>,
   * or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t lastIndexOf(const UnicodeString& text,
              int32_t start) const;

  /**
   * Locate in this the last occurrence in the range
   * [<TT>start</TT>, <TT>start + length</TT>) of the characters
   * in <TT>text</TT>, using bitwise comparison.
   * @param text The text to search for.
   * @param start The offset at which searching will start.
   * @param length The number of characters to search
   * @return The offset into this of the start of <TT>text</TT>,
   * or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t lastIndexOf(const UnicodeString& text,
              int32_t start,
              int32_t length) const;

  /**
   * Locate in this the last occurrence in the range
   * [<TT>start</TT>, <TT>start + length</TT>) of the characters
   * in <TT>srcText</TT> in the range
   * [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>),
   * using bitwise comparison.
   * @param srcText The text to search for.
   * @param srcStart the offset into <TT>srcText</TT> at which
   * to start matching
   * @param srcLength the number of characters in <TT>srcText</TT> to match
   * @param start the offset into this at which to start matching
   * @param length the number of characters in this to search
   * @return The offset into this of the start of <TT>text</TT>,
   * or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t lastIndexOf(const UnicodeString& srcText,
              int32_t srcStart,
              int32_t srcLength,
              int32_t start,
              int32_t length) const;

  /**
   * Locate in this the last occurrence of the characters in <TT>srcChars</TT>
   * starting at offset <TT>start</TT>, using bitwise comparison.
   * @param srcChars The text to search for.
   * @param srcLength the number of characters in <TT>srcChars</TT> to match
   * @param start the offset into this at which to start matching
   * @return The offset into this of the start of <TT>text</TT>,
   * or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t lastIndexOf(const UChar *srcChars,
              int32_t srcLength,
              int32_t start) const;

  /**
   * Locate in this the last occurrence in the range
   * [<TT>start</TT>, <TT>start + length</TT>) of the characters
   * in <TT>srcChars</TT>, using bitwise comparison.
   * @param srcChars The text to search for.
   * @param srcLength the number of characters in <TT>srcChars</TT>
   * @param start The offset at which searching will start.
   * @param length The number of characters to search
   * @return The offset into this of the start of <TT>srcChars</TT>,
   * or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t lastIndexOf(const UChar *srcChars,
              int32_t srcLength,
              int32_t start,
              int32_t length) const;

  /**
   * Locate in this the last occurrence in the range
   * [<TT>start</TT>, <TT>start + length</TT>) of the characters
   * in <TT>srcChars</TT> in the range
   * [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>),
   * using bitwise comparison.
   * @param srcChars The text to search for.
   * @param srcStart the offset into <TT>srcChars</TT> at which
   * to start matching
   * @param srcLength the number of characters in <TT>srcChars</TT> to match
   * @param start the offset into this at which to start matching
   * @param length the number of characters in this to search
   * @return The offset into this of the start of <TT>text</TT>,
   * or -1 if not found.
   * @stable ICU 2.0
   */
  int32_t lastIndexOf(const UChar *srcChars,
              int32_t srcStart,
              int32_t srcLength,
              int32_t start,
              int32_t length) const;

  /**
   * Locate in this the last occurrence of the BMP code point <code>c</code>,
   * using bitwise comparison.
   * @param c The code unit to search for.
   * @return The offset into this of <TT>c</TT>, or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t lastIndexOf(UChar c) const;

  /**
   * Locate in this the last occurrence of the code point <TT>c</TT>,
   * using bitwise comparison.
   *
   * @param c The code point to search for.
   * @return The offset into this of <TT>c</TT>, or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t lastIndexOf(UChar32 c) const;

  /**
   * Locate in this the last occurrence of the BMP code point <code>c</code>
   * starting at offset <TT>start</TT>, using bitwise comparison.
   * @param c The code unit to search for.
   * @param start The offset at which searching will start.
   * @return The offset into this of <TT>c</TT>, or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t lastIndexOf(UChar c,
              int32_t start) const;

  /**
   * Locate in this the last occurrence of the code point <TT>c</TT>
   * starting at offset <TT>start</TT>, using bitwise comparison.
   *
   * @param c The code point to search for.
   * @param start The offset at which searching will start.
   * @return The offset into this of <TT>c</TT>, or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t lastIndexOf(UChar32 c,
              int32_t start) const;

  /**
   * Locate in this the last occurrence of the BMP code point <code>c</code>
   * in the range [<TT>start</TT>, <TT>start + length</TT>),
   * using bitwise comparison.
   * @param c The code unit to search for.
   * @param start the offset into this at which to start matching
   * @param length the number of characters in this to search
   * @return The offset into this of <TT>c</TT>, or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t lastIndexOf(UChar c,
              int32_t start,
              int32_t length) const;

  /**
   * Locate in this the last occurrence of the code point <TT>c</TT>
   * in the range [<TT>start</TT>, <TT>start + length</TT>),
   * using bitwise comparison.
   *
   * @param c The code point to search for.
   * @param start the offset into this at which to start matching
   * @param length the number of characters in this to search
   * @return The offset into this of <TT>c</TT>, or -1 if not found.
   * @stable ICU 2.0
   */
  inline int32_t lastIndexOf(UChar32 c,
              int32_t start,
              int32_t length) const;


  /* Character access */

  /**
   * Return the code unit at offset <tt>offset</tt>.
   * If the offset is not valid (0..length()-1) then U+ffff is returned.
   * @param offset a valid offset into the text
   * @return the code unit at offset <tt>offset</tt>
   *         or 0xffff if the offset is not valid for this string
   * @stable ICU 2.0
   */
  inline UChar charAt(int32_t offset) const;

  /**
   * Return the code unit at offset <tt>offset</tt>.
   * If the offset is not valid (0..length()-1) then U+ffff is returned.
   * @param offset a valid offset into the text
   * @return the code unit at offset <tt>offset</tt>
   * @stable ICU 2.0
   */
  inline UChar operator[] (int32_t offset) const;

  /**
   * Return the code point that contains the code unit
   * at offset <tt>offset</tt>.
   * If the offset is not valid (0..length()-1) then U+ffff is returned.
   * @param offset a valid offset into the text
   * that indicates the text offset of any of the code units
   * that will be assembled into a code point (21-bit value) and returned
   * @return the code point of text at <tt>offset</tt>
   *         or 0xffff if the offset is not valid for this string
   * @stable ICU 2.0
   */
  UChar32 char32At(int32_t offset) const;

  /**
   * Adjust a random-access offset so that
   * it points to the beginning of a Unicode character.
   * The offset that is passed in points to
   * any code unit of a code point,
   * while the returned offset will point to the first code unit
   * of the same code point.
   * In UTF-16, if the input offset points to a second surrogate
   * of a surrogate pair, then the returned offset will point
   * to the first surrogate.
   * @param offset a valid offset into one code point of the text
   * @return offset of the first code unit of the same code point
   * @see U16_SET_CP_START
   * @stable ICU 2.0
   */
  int32_t getChar32Start(int32_t offset) const;

  /**
   * Adjust a random-access offset so that
   * it points behind a Unicode character.
   * The offset that is passed in points behind
   * any code unit of a code point,
   * while the returned offset will point behind the last code unit
   * of the same code point.
   * In UTF-16, if the input offset points behind the first surrogate
   * (i.e., to the second surrogate)
   * of a surrogate pair, then the returned offset will point
   * behind the second surrogate (i.e., to the first surrogate).
   * @param offset a valid offset after any code unit of a code point of the text
   * @return offset of the first code unit after the same code point
   * @see U16_SET_CP_LIMIT
   * @stable ICU 2.0
   */
  int32_t getChar32Limit(int32_t offset) const;

  /**
   * Move the code unit index along the string by delta code points.
   * Interpret the input index as a code unit-based offset into the string,
   * move the index forward or backward by delta code points, and
   * return the resulting index.
   * The input index should point to the first code unit of a code point,
   * if there is more than one.
   *
   * Both input and output indexes are code unit-based as for all
   * string indexes/offsets in ICU (and other libraries, like MBCS char*).
   * If delta<0 then the index is moved backward (toward the start of the string).
   * If delta>0 then the index is moved forward (toward the end of the string).
   *
   * This behaves like CharacterIterator::move32(delta, kCurrent).
   *
   * Behavior for out-of-bounds indexes:
   * <code>moveIndex32</code> pins the input index to 0..length(), i.e.,
   * if the input index<0 then it is pinned to 0;
   * if it is index>length() then it is pinned to length().
   * Afterwards, the index is moved by <code>delta</code> code points
   * forward or backward,
   * but no further backward than to 0 and no further forward than to length().
   * The resulting index return value will be in between 0 and length(), inclusively.
   *
   * Examples:
   * <pre>
   * // s has code points 'a' U+10000 'b' U+10ffff U+2029
   * UnicodeString s=UNICODE_STRING("a\\U00010000b\\U0010ffff\\u2029", 31).unescape();
   *
   * // initial index: position of U+10000
   * int32_t index=1;
   *
   * // the following examples will all result in index==4, position of U+10ffff
   *
   * // skip 2 code points from some position in the string
   * index=s.moveIndex32(index, 2); // skips U+10000 and 'b'
   *
   * // go to the 3rd code point from the start of s (0-based)
   * index=s.moveIndex32(0, 3); // skips 'a', U+10000, and 'b'
   *
   * // go to the next-to-last code point of s
   * index=s.moveIndex32(s.length(), -2); // backward-skips U+2029 and U+10ffff
   * </pre>
   *
   * @param index input code unit index
   * @param delta (signed) code point count to move the index forward or backward
   *        in the string
   * @return the resulting code unit index
   * @stable ICU 2.0
   */
  int32_t moveIndex32(int32_t index, int32_t delta) const;

  /* Substring extraction */

  /**
   * Copy the characters in the range
   * [<tt>start</tt>, <tt>start + length</tt>) into the array <tt>dst</tt>,
   * beginning at <tt>dstStart</tt>.
   * If the string aliases to <code>dst</code> itself as an external buffer,
   * then extract() will not copy the contents.
   *
   * @param start offset of first character which will be copied into the array
   * @param length the number of characters to extract
   * @param dst array in which to copy characters.  The length of <tt>dst</tt>
   * must be at least (<tt>dstStart + length</tt>).
   * @param dstStart the offset in <TT>dst</TT> where the first character
   * will be extracted
   * @stable ICU 2.0
   */
  inline void extract(int32_t start,
           int32_t length,
           UChar *dst,
           int32_t dstStart = 0) const;

  /**
   * Copy the contents of the string into dest.
   * This is a convenience function that
   * checks if there is enough space in dest,
   * extracts the entire string if possible,
   * and NUL-terminates dest if possible.
   *
   * If the string fits into dest but cannot be NUL-terminated
   * (length()==destCapacity) then the error code is set to U_STRING_NOT_TERMINATED_WARNING.
   * If the string itself does not fit into dest
   * (length()>destCapacity) then the error code is set to U_BUFFER_OVERFLOW_ERROR.
   *
   * If the string aliases to <code>dest</code> itself as an external buffer,
   * then extract() will not copy the contents.
   *
   * @param dest Destination string buffer.
   * @param destCapacity Number of UChars available at dest.
   * @param errorCode ICU error code.
   * @return length()
   * @stable ICU 2.0
   */
  int32_t
  extract(UChar *dest, int32_t destCapacity,
          UErrorCode &errorCode) const;

  /**
   * Copy the characters in the range
   * [<tt>start</tt>, <tt>start + length</tt>) into the  UnicodeString
   * <tt>target</tt>.
   * @param start offset of first character which will be copied
   * @param length the number of characters to extract
   * @param target UnicodeString into which to copy characters.
   * @return A reference to <TT>target</TT>
   * @stable ICU 2.0
   */
  inline void extract(int32_t start,
           int32_t length,
           UnicodeString& target) const;

  /**
   * Copy the characters in the range [<tt>start</tt>, <tt>limit</tt>)
   * into the array <tt>dst</tt>, beginning at <tt>dstStart</tt>.
   * @param start offset of first character which will be copied into the array
   * @param limit offset immediately following the last character to be copied
   * @param dst array in which to copy characters.  The length of <tt>dst</tt>
   * must be at least (<tt>dstStart + (limit - start)</tt>).
   * @param dstStart the offset in <TT>dst</TT> where the first character
   * will be extracted
   * @stable ICU 2.0
   */
  inline void extractBetween(int32_t start,
              int32_t limit,
              UChar *dst,
              int32_t dstStart = 0) const;

  /**
   * Copy the characters in the range [<tt>start</tt>, <tt>limit</tt>)
   * into the UnicodeString <tt>target</tt>.  Replaceable API.
   * @param start offset of first character which will be copied
   * @param limit offset immediately following the last character to be copied
   * @param target UnicodeString into which to copy characters.
   * @return A reference to <TT>target</TT>
   * @stable ICU 2.0
   */
  virtual void extractBetween(int32_t start,
              int32_t limit,
              UnicodeString& target) const;

  /**
   * Copy the characters in the range
   * [<tt>start</TT>, <tt>start + length</TT>) into an array of characters.
   * All characters must be invariant (see utypes.h).
   * Use US_INV as the last, signature-distinguishing parameter.
   *
   * This function does not write any more than <code>targetLength</code>
   * characters but returns the length of the entire output string
   * so that one can allocate a larger buffer and call the function again
   * if necessary.
   * The output string is NUL-terminated if possible.
   *
   * @param start offset of first character which will be copied
   * @param startLength the number of characters to extract
   * @param target the target buffer for extraction, can be NULL
   *               if targetLength is 0
   * @param targetCapacity the length of the target buffer
   * @param inv Signature-distinguishing paramater, use US_INV.
   * @return the output string length, not including the terminating NUL
   * @stable ICU 3.2
   */
  int32_t extract(int32_t start,
           int32_t startLength,
           char *target,
           int32_t targetCapacity,
           enum EInvariant inv) const;

#if U_CHARSET_IS_UTF8 || !UCONFIG_NO_CONVERSION

  /**
   * Copy the characters in the range
   * [<tt>start</TT>, <tt>start + length</TT>) into an array of characters
   * in the platform's default codepage.
   * This function does not write any more than <code>targetLength</code>
   * characters but returns the length of the entire output string
   * so that one can allocate a larger buffer and call the function again
   * if necessary.
   * The output string is NUL-terminated if possible.
   *
   * @param start offset of first character which will be copied
   * @param startLength the number of characters to extract
   * @param target the target buffer for extraction
   * @param targetLength the length of the target buffer
   * If <TT>target</TT> is NULL, then the number of bytes required for
   * <TT>target</TT> is returned.
   * @return the output string length, not including the terminating NUL
   * @stable ICU 2.0
   */
  int32_t extract(int32_t start,
           int32_t startLength,
           char *target,
           uint32_t targetLength) const;

#endif

#if !UCONFIG_NO_CONVERSION

  /**
   * Copy the characters in the range
   * [<tt>start</TT>, <tt>start + length</TT>) into an array of characters
   * in a specified codepage.
   * The output string is NUL-terminated.
   *
   * Recommendation: For invariant-character strings use
   * extract(int32_t start, int32_t length, char *target, int32_t targetCapacity, enum EInvariant inv) const
   * because it avoids object code dependencies of UnicodeString on
   * the conversion code.
   *
   * @param start offset of first character which will be copied
   * @param startLength the number of characters to extract
   * @param target the target buffer for extraction
   * @param codepage the desired codepage for the characters.  0 has
   * the special meaning of the default codepage
   * If <code>codepage</code> is an empty string (<code>""</code>),
   * then a simple conversion is performed on the codepage-invariant
   * subset ("invariant characters") of the platform encoding. See utypes.h.
   * If <TT>target</TT> is NULL, then the number of bytes required for
   * <TT>target</TT> is returned. It is assumed that the target is big enough
   * to fit all of the characters.
   * @return the output string length, not including the terminating NUL
   * @stable ICU 2.0
   */
  inline int32_t extract(int32_t start,
                 int32_t startLength,
                 char *target,
                 const char *codepage = 0) const;

  /**
   * Copy the characters in the range
   * [<tt>start</TT>, <tt>start + length</TT>) into an array of characters
   * in a specified codepage.
   * This function does not write any more than <code>targetLength</code>
   * characters but returns the length of the entire output string
   * so that one can allocate a larger buffer and call the function again
   * if necessary.
   * The output string is NUL-terminated if possible.
   *
   * Recommendation: For invariant-character strings use
   * extract(int32_t start, int32_t length, char *target, int32_t targetCapacity, enum EInvariant inv) const
   * because it avoids object code dependencies of UnicodeString on
   * the conversion code.
   *
   * @param start offset of first character which will be copied
   * @param startLength the number of characters to extract
   * @param target the target buffer for extraction
   * @param targetLength the length of the target buffer
   * @param codepage the desired codepage for the characters.  0 has
   * the special meaning of the default codepage
   * If <code>codepage</code> is an empty string (<code>""</code>),
   * then a simple conversion is performed on the codepage-invariant
   * subset ("invariant characters") of the platform encoding. See utypes.h.
   * If <TT>target</TT> is NULL, then the number of bytes required for
   * <TT>target</TT> is returned.
   * @return the output string length, not including the terminating NUL
   * @stable ICU 2.0
   */
  int32_t extract(int32_t start,
           int32_t startLength,
           char *target,
           uint32_t targetLength,
           const char *codepage) const;

  /**
   * Convert the UnicodeString into a codepage string using an existing UConverter.
   * The output string is NUL-terminated if possible.
   *
   * This function avoids the overhead of opening and closing a converter if
   * multiple strings are extracted.
   *
   * @param dest destination string buffer, can be NULL if destCapacity==0
   * @param destCapacity the number of chars available at dest
   * @param cnv the converter object to be used (ucnv_resetFromUnicode() will be called),
   *        or NULL for the default converter
   * @param errorCode normal ICU error code
   * @return the length of the output string, not counting the terminating NUL;
   *         if the length is greater than destCapacity, then the string will not fit
   *         and a buffer of the indicated length would need to be passed in
   * @stable ICU 2.0
   */
  int32_t extract(char *dest, int32_t destCapacity,
                  UConverter *cnv,
                  UErrorCode &errorCode) const;

#endif

  /**
   * Create a temporary substring for the specified range.
   * Unlike the substring constructor and setTo() functions,
   * the object returned here will be a read-only alias (using getBuffer())
   * rather than copying the text.
   * As a result, this substring operation is much faster but requires
   * that the original string not be modified or deleted during the lifetime
   * of the returned substring object.
   * @param start offset of the first character visible in the substring
   * @param length length of the substring
   * @return a read-only alias UnicodeString object for the substring
   * @stable ICU 4.4
   */
  UnicodeString tempSubString(int32_t start=0, int32_t length=INT32_MAX) const;

  /**
   * Create a temporary substring for the specified range.
   * Same as tempSubString(start, length) except that the substring range
   * is specified as a (start, limit) pair (with an exclusive limit index)
   * rather than a (start, length) pair.
   * @param start offset of the first character visible in the substring
   * @param limit offset immediately following the last character visible in the substring
   * @return a read-only alias UnicodeString object for the substring
   * @stable ICU 4.4
   */
  inline UnicodeString tempSubStringBetween(int32_t start, int32_t limit=INT32_MAX) const;

  /**
   * Convert the UnicodeString to UTF-8 and write the result
   * to a ByteSink. This is called by toUTF8String().
   * Unpaired surrogates are replaced with U+FFFD.
   * Calls u_strToUTF8WithSub().
   *
   * @param sink A ByteSink to which the UTF-8 version of the string is written.
   *             sink.Flush() is called at the end.
   * @stable ICU 4.2
   * @see toUTF8String
   */
  void toUTF8(ByteSink &sink) const;

#if U_HAVE_STD_STRING

  /**
   * Convert the UnicodeString to UTF-8 and append the result
   * to a standard string.
   * Unpaired surrogates are replaced with U+FFFD.
   * Calls toUTF8().
   *
   * @param result A standard string (or a compatible object)
   *        to which the UTF-8 version of the string is appended.
   * @return The string object.
   * @stable ICU 4.2
   * @see toUTF8
   */
  template<typename StringClass>
  StringClass &toUTF8String(StringClass &result) const {
    StringByteSink<StringClass> sbs(&result);
    toUTF8(sbs);
    return result;
  }

#endif

  /**
   * Convert the UnicodeString to UTF-32.
   * Unpaired surrogates are replaced with U+FFFD.
   * Calls u_strToUTF32WithSub().
   *
   * @param utf32 destination string buffer, can be NULL if capacity==0
   * @param capacity the number of UChar32s available at utf32
   * @param errorCode Standard ICU error code. Its input value must
   *                  pass the U_SUCCESS() test, or else the function returns
   *                  immediately. Check for U_FAILURE() on output or use with
   *                  function chaining. (See User Guide for details.)
   * @return The length of the UTF-32 string.
   * @see fromUTF32
   * @stable ICU 4.2
   */
  int32_t toUTF32(UChar32 *utf32, int32_t capacity, UErrorCode &errorCode) const;

  /* Length operations */

  /**
   * Return the length of the UnicodeString object.
   * The length is the number of UChar code units are in the UnicodeString.
   * If you want the number of code points, please use countChar32().
   * @return the length of the UnicodeString object
   * @see countChar32
   * @stable ICU 2.0
   */
  inline int32_t length(void) const;

  /**
   * Count Unicode code points in the length UChar code units of the string.
   * A code point may occupy either one or two UChar code units.
   * Counting code points involves reading all code units.
   *
   * This functions is basically the inverse of moveIndex32().
   *
   * @param start the index of the first code unit to check
   * @param length the number of UChar code units to check
   * @return the number of code points in the specified code units
   * @see length
   * @stable ICU 2.0
   */
  int32_t
  countChar32(int32_t start=0, int32_t length=INT32_MAX) const;

  /**
   * Check if the length UChar code units of the string
   * contain more Unicode code points than a certain number.
   * This is more efficient than counting all code points in this part of the string
   * and comparing that number with a threshold.
   * This function may not need to scan the string at all if the length
   * falls within a certain range, and
   * never needs to count more than 'number+1' code points.
   * Logically equivalent to (countChar32(start, length)>number).
   * A Unicode code point may occupy either one or two UChar code units.
   *
   * @param start the index of the first code unit to check (0 for the entire string)
   * @param length the number of UChar code units to check
   *               (use INT32_MAX for the entire string; remember that start/length
   *                values are pinned)
   * @param number The number of code points in the (sub)string is compared against
   *               the 'number' parameter.
   * @return Boolean value for whether the string contains more Unicode code points
   *         than 'number'. Same as (u_countChar32(s, length)>number).
   * @see countChar32
   * @see u_strHasMoreChar32Than
   * @stable ICU 2.4
   */
  UBool
  hasMoreChar32Than(int32_t start, int32_t length, int32_t number) const;

  /**
   * Determine if this string is empty.
   * @return TRUE if this string contains 0 characters, FALSE otherwise.
   * @stable ICU 2.0
   */
  inline UBool isEmpty(void) const;

  /**
   * Return the capacity of the internal buffer of the UnicodeString object.
   * This is useful together with the getBuffer functions.
   * See there for details.
   *
   * @return the number of UChars available in the internal buffer
   * @see getBuffer
   * @stable ICU 2.0
   */
  inline int32_t getCapacity(void) const;

  /* Other operations */

  /**
   * Generate a hash code for this object.
   * @return The hash code of this UnicodeString.
   * @stable ICU 2.0
   */
  inline int32_t hashCode(void) const;

  /**
   * Determine if this object contains a valid string.
   * A bogus string has no value. It is different from an empty string,
   * although in both cases isEmpty() returns TRUE and length() returns 0.
   * setToBogus() and isBogus() can be used to indicate that no string value is available.
   * For a bogus string, getBuffer() and getTerminatedBuffer() return NULL, and
   * length() returns 0.
   *
   * @return TRUE if the string is bogus/invalid, FALSE otherwise
   * @see setToBogus()
   * @stable ICU 2.0
   */
  inline UBool isBogus(void) const;


  //========================================
  // Write operations
  //========================================

  /* Assignment operations */

  /**
   * Assignment operator.  Replace the characters in this UnicodeString
   * with the characters from <TT>srcText</TT>.
   * @param srcText The text containing the characters to replace
   * @return a reference to this
   * @stable ICU 2.0
   */
  UnicodeString &operator=(const UnicodeString &srcText);

  /**
   * Almost the same as the assignment operator.
   * Replace the characters in this UnicodeString
   * with the characters from <code>srcText</code>.
   *
   * This function works the same as the assignment operator
   * for all strings except for ones that are readonly aliases.
   *
   * Starting with ICU 2.4, the assignment operator and the copy constructor
   * allocate a new buffer and copy the buffer contents even for readonly aliases.
   * This function implements the old, more efficient but less safe behavior
   * of making this string also a readonly alias to the same buffer.
   *
   * The fastCopyFrom function must be used only if it is known that the lifetime of
   * this UnicodeString does not exceed the lifetime of the aliased buffer
   * including its contents, for example for strings from resource bundles
   * or aliases to string constants.
   *
   * @param src The text containing the characters to replace.
   * @return a reference to this
   * @stable ICU 2.4
   */
  UnicodeString &fastCopyFrom(const UnicodeString &src);

  /**
   * Assignment operator.  Replace the characters in this UnicodeString
   * with the code unit <TT>ch</TT>.
   * @param ch the code unit to replace
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& operator= (UChar ch);

  /**
   * Assignment operator.  Replace the characters in this UnicodeString
   * with the code point <TT>ch</TT>.
   * @param ch the code point to replace
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& operator= (UChar32 ch);

  /**
   * Set the text in the UnicodeString object to the characters
   * in <TT>srcText</TT> in the range
   * [<TT>srcStart</TT>, <TT>srcText.length()</TT>).
   * <TT>srcText</TT> is not modified.
   * @param srcText the source for the new characters
   * @param srcStart the offset into <TT>srcText</TT> where new characters
   * will be obtained
   * @return a reference to this
   * @stable ICU 2.2
   */
  inline UnicodeString& setTo(const UnicodeString& srcText,
               int32_t srcStart);

  /**
   * Set the text in the UnicodeString object to the characters
   * in <TT>srcText</TT> in the range
   * [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>).
   * <TT>srcText</TT> is not modified.
   * @param srcText the source for the new characters
   * @param srcStart the offset into <TT>srcText</TT> where new characters
   * will be obtained
   * @param srcLength the number of characters in <TT>srcText</TT> in the
   * replace string.
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& setTo(const UnicodeString& srcText,
               int32_t srcStart,
               int32_t srcLength);

  /**
   * Set the text in the UnicodeString object to the characters in
   * <TT>srcText</TT>.
   * <TT>srcText</TT> is not modified.
   * @param srcText the source for the new characters
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& setTo(const UnicodeString& srcText);

  /**
   * Set the characters in the UnicodeString object to the characters
   * in <TT>srcChars</TT>. <TT>srcChars</TT> is not modified.
   * @param srcChars the source for the new characters
   * @param srcLength the number of Unicode characters in srcChars.
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& setTo(const UChar *srcChars,
               int32_t srcLength);

  /**
   * Set the characters in the UnicodeString object to the code unit
   * <TT>srcChar</TT>.
   * @param srcChar the code unit which becomes the UnicodeString's character
   * content
   * @return a reference to this
   * @stable ICU 2.0
   */
  UnicodeString& setTo(UChar srcChar);

  /**
   * Set the characters in the UnicodeString object to the code point
   * <TT>srcChar</TT>.
   * @param srcChar the code point which becomes the UnicodeString's character
   * content
   * @return a reference to this
   * @stable ICU 2.0
   */
  UnicodeString& setTo(UChar32 srcChar);

  /**
   * Aliasing setTo() function, analogous to the readonly-aliasing UChar* constructor.
   * The text will be used for the UnicodeString object, but
   * it will not be released when the UnicodeString is destroyed.
   * This has copy-on-write semantics:
   * When the string is modified, then the buffer is first copied into
   * newly allocated memory.
   * The aliased buffer is never modified.
   *
   * In an assignment to another UnicodeString, when using the copy constructor
   * or the assignment operator, the text will be copied.
   * When using fastCopyFrom(), the text will be aliased again,
   * so that both strings then alias the same readonly-text.
   *
   * @param isTerminated specifies if <code>text</code> is <code>NUL</code>-terminated.
   *                     This must be true if <code>textLength==-1</code>.
   * @param text The characters to alias for the UnicodeString.
   * @param textLength The number of Unicode characters in <code>text</code> to alias.
   *                   If -1, then this constructor will determine the length
   *                   by calling <code>u_strlen()</code>.
   * @return a reference to this
   * @stable ICU 2.0
   */
  UnicodeString &setTo(UBool isTerminated,
                       const UChar *text,
                       int32_t textLength);

  /**
   * Aliasing setTo() function, analogous to the writable-aliasing UChar* constructor.
   * The text will be used for the UnicodeString object, but
   * it will not be released when the UnicodeString is destroyed.
   * This has write-through semantics:
   * For as long as the capacity of the buffer is sufficient, write operations
   * will directly affect the buffer. When more capacity is necessary, then
   * a new buffer will be allocated and the contents copied as with regularly
   * constructed strings.
   * In an assignment to another UnicodeString, the buffer will be copied.
   * The extract(UChar *dst) function detects whether the dst pointer is the same
   * as the string buffer itself and will in this case not copy the contents.
   *
   * @param buffer The characters to alias for the UnicodeString.
   * @param buffLength The number of Unicode characters in <code>buffer</code> to alias.
   * @param buffCapacity The size of <code>buffer</code> in UChars.
   * @return a reference to this
   * @stable ICU 2.0
   */
  UnicodeString &setTo(UChar *buffer,
                       int32_t buffLength,
                       int32_t buffCapacity);

  /**
   * Make this UnicodeString object invalid.
   * The string will test TRUE with isBogus().
   *
   * A bogus string has no value. It is different from an empty string.
   * It can be used to indicate that no string value is available.
   * getBuffer() and getTerminatedBuffer() return NULL, and
   * length() returns 0.
   *
   * This utility function is used throughout the UnicodeString
   * implementation to indicate that a UnicodeString operation failed,
   * and may be used in other functions,
   * especially but not exclusively when such functions do not
   * take a UErrorCode for simplicity.
   *
   * The following methods, and no others, will clear a string object's bogus flag:
   * - remove()
   * - remove(0, INT32_MAX)
   * - truncate(0)
   * - operator=() (assignment operator)
   * - setTo(...)
   *
   * The simplest ways to turn a bogus string into an empty one
   * is to use the remove() function.
   * Examples for other functions that are equivalent to "set to empty string":
   * \code
   * if(s.isBogus()) {
   *   s.remove();           // set to an empty string (remove all), or
   *   s.remove(0, INT32_MAX); // set to an empty string (remove all), or
   *   s.truncate(0);        // set to an empty string (complete truncation), or
   *   s=UnicodeString();    // assign an empty string, or
   *   s.setTo((UChar32)-1); // set to a pseudo code point that is out of range, or
   *   static const UChar nul=0;
   *   s.setTo(&nul, 0);     // set to an empty C Unicode string
   * }
   * \endcode
   *
   * @see isBogus()
   * @stable ICU 2.0
   */
  void setToBogus();

  /**
   * Set the character at the specified offset to the specified character.
   * @param offset A valid offset into the text of the character to set
   * @param ch The new character
   * @return A reference to this
   * @stable ICU 2.0
   */
  UnicodeString& setCharAt(int32_t offset,
               UChar ch);


  /* Append operations */

  /**
   * Append operator. Append the code unit <TT>ch</TT> to the UnicodeString
   * object.
   * @param ch the code unit to be appended
   * @return a reference to this
   * @stable ICU 2.0
   */
 inline  UnicodeString& operator+= (UChar ch);

  /**
   * Append operator. Append the code point <TT>ch</TT> to the UnicodeString
   * object.
   * @param ch the code point to be appended
   * @return a reference to this
   * @stable ICU 2.0
   */
 inline  UnicodeString& operator+= (UChar32 ch);

  /**
   * Append operator. Append the characters in <TT>srcText</TT> to the
   * UnicodeString object. <TT>srcText</TT> is not modified.
   * @param srcText the source for the new characters
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& operator+= (const UnicodeString& srcText);

  /**
   * Append the characters
   * in <TT>srcText</TT> in the range
   * [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>) to the
   * UnicodeString object at offset <TT>start</TT>. <TT>srcText</TT>
   * is not modified.
   * @param srcText the source for the new characters
   * @param srcStart the offset into <TT>srcText</TT> where new characters
   * will be obtained
   * @param srcLength the number of characters in <TT>srcText</TT> in
   * the append string
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& append(const UnicodeString& srcText,
            int32_t srcStart,
            int32_t srcLength);

  /**
   * Append the characters in <TT>srcText</TT> to the UnicodeString object.
   * <TT>srcText</TT> is not modified.
   * @param srcText the source for the new characters
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& append(const UnicodeString& srcText);

  /**
   * Append the characters in <TT>srcChars</TT> in the range
   * [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>) to the UnicodeString
   * object at offset
   * <TT>start</TT>. <TT>srcChars</TT> is not modified.
   * @param srcChars the source for the new characters
   * @param srcStart the offset into <TT>srcChars</TT> where new characters
   * will be obtained
   * @param srcLength the number of characters in <TT>srcChars</TT> in
   *                  the append string; can be -1 if <TT>srcChars</TT> is NUL-terminated
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& append(const UChar *srcChars,
            int32_t srcStart,
            int32_t srcLength);

  /**
   * Append the characters in <TT>srcChars</TT> to the UnicodeString object
   * at offset <TT>start</TT>. <TT>srcChars</TT> is not modified.
   * @param srcChars the source for the new characters
   * @param srcLength the number of Unicode characters in <TT>srcChars</TT>;
   *                  can be -1 if <TT>srcChars</TT> is NUL-terminated
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& append(const UChar *srcChars,
            int32_t srcLength);

  /**
   * Append the code unit <TT>srcChar</TT> to the UnicodeString object.
   * @param srcChar the code unit to append
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& append(UChar srcChar);

  /**
   * Append the code point <TT>srcChar</TT> to the UnicodeString object.
   * @param srcChar the code point to append
   * @return a reference to this
   * @stable ICU 2.0
   */
  UnicodeString& append(UChar32 srcChar);


  /* Insert operations */

  /**
   * Insert the characters in <TT>srcText</TT> in the range
   * [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>) into the UnicodeString
   * object at offset <TT>start</TT>. <TT>srcText</TT> is not modified.
   * @param start the offset where the insertion begins
   * @param srcText the source for the new characters
   * @param srcStart the offset into <TT>srcText</TT> where new characters
   * will be obtained
   * @param srcLength the number of characters in <TT>srcText</TT> in
   * the insert string
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& insert(int32_t start,
            const UnicodeString& srcText,
            int32_t srcStart,
            int32_t srcLength);

  /**
   * Insert the characters in <TT>srcText</TT> into the UnicodeString object
   * at offset <TT>start</TT>. <TT>srcText</TT> is not modified.
   * @param start the offset where the insertion begins
   * @param srcText the source for the new characters
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& insert(int32_t start,
            const UnicodeString& srcText);

  /**
   * Insert the characters in <TT>srcChars</TT> in the range
   * [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>) into the UnicodeString
   *  object at offset <TT>start</TT>. <TT>srcChars</TT> is not modified.
   * @param start the offset at which the insertion begins
   * @param srcChars the source for the new characters
   * @param srcStart the offset into <TT>srcChars</TT> where new characters
   * will be obtained
   * @param srcLength the number of characters in <TT>srcChars</TT>
   * in the insert string
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& insert(int32_t start,
            const UChar *srcChars,
            int32_t srcStart,
            int32_t srcLength);

  /**
   * Insert the characters in <TT>srcChars</TT> into the UnicodeString object
   * at offset <TT>start</TT>. <TT>srcChars</TT> is not modified.
   * @param start the offset where the insertion begins
   * @param srcChars the source for the new characters
   * @param srcLength the number of Unicode characters in srcChars.
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& insert(int32_t start,
            const UChar *srcChars,
            int32_t srcLength);

  /**
   * Insert the code unit <TT>srcChar</TT> into the UnicodeString object at
   * offset <TT>start</TT>.
   * @param start the offset at which the insertion occurs
   * @param srcChar the code unit to insert
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& insert(int32_t start,
            UChar srcChar);

  /**
   * Insert the code point <TT>srcChar</TT> into the UnicodeString object at
   * offset <TT>start</TT>.
   * @param start the offset at which the insertion occurs
   * @param srcChar the code point to insert
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& insert(int32_t start,
            UChar32 srcChar);


  /* Replace operations */

  /**
   * Replace the characters in the range
   * [<TT>start</TT>, <TT>start + length</TT>) with the characters in
   * <TT>srcText</TT> in the range
   * [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>).
   * <TT>srcText</TT> is not modified.
   * @param start the offset at which the replace operation begins
   * @param length the number of characters to replace. The character at
   * <TT>start + length</TT> is not modified.
   * @param srcText the source for the new characters
   * @param srcStart the offset into <TT>srcText</TT> where new characters
   * will be obtained
   * @param srcLength the number of characters in <TT>srcText</TT> in
   * the replace string
   * @return a reference to this
   * @stable ICU 2.0
   */
  UnicodeString& replace(int32_t start,
             int32_t length,
             const UnicodeString& srcText,
             int32_t srcStart,
             int32_t srcLength);

  /**
   * Replace the characters in the range
   * [<TT>start</TT>, <TT>start + length</TT>)
   * with the characters in <TT>srcText</TT>.  <TT>srcText</TT> is
   *  not modified.
   * @param start the offset at which the replace operation begins
   * @param length the number of characters to replace. The character at
   * <TT>start + length</TT> is not modified.
   * @param srcText the source for the new characters
   * @return a reference to this
   * @stable ICU 2.0
   */
  UnicodeString& replace(int32_t start,
             int32_t length,
             const UnicodeString& srcText);

  /**
   * Replace the characters in the range
   * [<TT>start</TT>, <TT>start + length</TT>) with the characters in
   * <TT>srcChars</TT> in the range
   * [<TT>srcStart</TT>, <TT>srcStart + srcLength</TT>). <TT>srcChars</TT>
   * is not modified.
   * @param start the offset at which the replace operation begins
   * @param length the number of characters to replace.  The character at
   * <TT>start + length</TT> is not modified.
   * @param srcChars the source for the new characters
   * @param srcStart the offset into <TT>srcChars</TT> where new characters
   * will be obtained
   * @param srcLength the number of characters in <TT>srcChars</TT>
   * in the replace string
   * @return a reference to this
   * @stable ICU 2.0
   */
  UnicodeString& replace(int32_t start,
             int32_t length,
             const UChar *srcChars,
             int32_t srcStart,
             int32_t srcLength);

  /**
   * Replace the characters in the range
   * [<TT>start</TT>, <TT>start + length</TT>) with the characters in
   * <TT>srcChars</TT>.  <TT>srcChars</TT> is not modified.
   * @param start the offset at which the replace operation begins
   * @param length number of characters to replace.  The character at
   * <TT>start + length</TT> is not modified.
   * @param srcChars the source for the new characters
   * @param srcLength the number of Unicode characters in srcChars
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& replace(int32_t start,
             int32_t length,
             const UChar *srcChars,
             int32_t srcLength);

  /**
   * Replace the characters in the range
   * [<TT>start</TT>, <TT>start + length</TT>) with the code unit
   * <TT>srcChar</TT>.
   * @param start the offset at which the replace operation begins
   * @param length the number of characters to replace.  The character at
   * <TT>start + length</TT> is not modified.
   * @param srcChar the new code unit
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& replace(int32_t start,
             int32_t length,
             UChar srcChar);

  /**
   * Replace the characters in the range
   * [<TT>start</TT>, <TT>start + length</TT>) with the code point
   * <TT>srcChar</TT>.
   * @param start the offset at which the replace operation begins
   * @param length the number of characters to replace.  The character at
   * <TT>start + length</TT> is not modified.
   * @param srcChar the new code point
   * @return a reference to this
   * @stable ICU 2.0
   */
  UnicodeString& replace(int32_t start, int32_t length, UChar32 srcChar);

  /**
   * Replace the characters in the range [<TT>start</TT>, <TT>limit</TT>)
   * with the characters in <TT>srcText</TT>. <TT>srcText</TT> is not modified.
   * @param start the offset at which the replace operation begins
   * @param limit the offset immediately following the replace range
   * @param srcText the source for the new characters
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& replaceBetween(int32_t start,
                int32_t limit,
                const UnicodeString& srcText);

  /**
   * Replace the characters in the range [<TT>start</TT>, <TT>limit</TT>)
   * with the characters in <TT>srcText</TT> in the range
   * [<TT>srcStart</TT>, <TT>srcLimit</TT>). <TT>srcText</TT> is not modified.
   * @param start the offset at which the replace operation begins
   * @param limit the offset immediately following the replace range
   * @param srcText the source for the new characters
   * @param srcStart the offset into <TT>srcChars</TT> where new characters
   * will be obtained
   * @param srcLimit the offset immediately following the range to copy
   * in <TT>srcText</TT>
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& replaceBetween(int32_t start,
                int32_t limit,
                const UnicodeString& srcText,
                int32_t srcStart,
                int32_t srcLimit);

  /**
   * Replace a substring of this object with the given text.
   * @param start the beginning index, inclusive; <code>0 <= start
   * <= limit</code>.
   * @param limit the ending index, exclusive; <code>start <= limit
   * <= length()</code>.
   * @param text the text to replace characters <code>start</code>
   * to <code>limit - 1</code>
   * @stable ICU 2.0
   */
  virtual void handleReplaceBetween(int32_t start,
                                    int32_t limit,
                                    const UnicodeString& text);

  /**
   * Replaceable API
   * @return TRUE if it has MetaData
   * @stable ICU 2.4
   */
  virtual UBool hasMetaData() const;

  /**
   * Copy a substring of this object, retaining attribute (out-of-band)
   * information.  This method is used to duplicate or reorder substrings.
   * The destination index must not overlap the source range.
   *
   * @param start the beginning index, inclusive; <code>0 <= start <=
   * limit</code>.
   * @param limit the ending index, exclusive; <code>start <= limit <=
   * length()</code>.
   * @param dest the destination index.  The characters from
   * <code>start..limit-1</code> will be copied to <code>dest</code>.
   * Implementations of this method may assume that <code>dest <= start ||
   * dest >= limit</code>.
   * @stable ICU 2.0
   */
  virtual void copy(int32_t start, int32_t limit, int32_t dest);

  /* Search and replace operations */

  /**
   * Replace all occurrences of characters in oldText with the characters
   * in newText
   * @param oldText the text containing the search text
   * @param newText the text containing the replacement text
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& findAndReplace(const UnicodeString& oldText,
                const UnicodeString& newText);

  /**
   * Replace all occurrences of characters in oldText with characters
   * in newText
   * in the range [<TT>start</TT>, <TT>start + length</TT>).
   * @param start the start of the range in which replace will performed
   * @param length the length of the range in which replace will be performed
   * @param oldText the text containing the search text
   * @param newText the text containing the replacement text
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& findAndReplace(int32_t start,
                int32_t length,
                const UnicodeString& oldText,
                const UnicodeString& newText);

  /**
   * Replace all occurrences of characters in oldText in the range
   * [<TT>oldStart</TT>, <TT>oldStart + oldLength</TT>) with the characters
   * in newText in the range
   * [<TT>newStart</TT>, <TT>newStart + newLength</TT>)
   * in the range [<TT>start</TT>, <TT>start + length</TT>).
   * @param start the start of the range in which replace will performed
   * @param length the length of the range in which replace will be performed
   * @param oldText the text containing the search text
   * @param oldStart the start of the search range in <TT>oldText</TT>
   * @param oldLength the length of the search range in <TT>oldText</TT>
   * @param newText the text containing the replacement text
   * @param newStart the start of the replacement range in <TT>newText</TT>
   * @param newLength the length of the replacement range in <TT>newText</TT>
   * @return a reference to this
   * @stable ICU 2.0
   */
  UnicodeString& findAndReplace(int32_t start,
                int32_t length,
                const UnicodeString& oldText,
                int32_t oldStart,
                int32_t oldLength,
                const UnicodeString& newText,
                int32_t newStart,
                int32_t newLength);


  /* Remove operations */

  /**
   * Remove all characters from the UnicodeString object.
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& remove(void);

  /**
   * Remove the characters in the range
   * [<TT>start</TT>, <TT>start + length</TT>) from the UnicodeString object.
   * @param start the offset of the first character to remove
   * @param length the number of characters to remove
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& remove(int32_t start,
                               int32_t length = (int32_t)INT32_MAX);

  /**
   * Remove the characters in the range
   * [<TT>start</TT>, <TT>limit</TT>) from the UnicodeString object.
   * @param start the offset of the first character to remove
   * @param limit the offset immediately following the range to remove
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& removeBetween(int32_t start,
                                      int32_t limit = (int32_t)INT32_MAX);

  /**
   * Retain only the characters in the range
   * [<code>start</code>, <code>limit</code>) from the UnicodeString object.
   * Removes characters before <code>start</code> and at and after <code>limit</code>.
   * @param start the offset of the first character to retain
   * @param limit the offset immediately following the range to retain
   * @return a reference to this
   * @stable ICU 4.4
   */
  inline UnicodeString &retainBetween(int32_t start, int32_t limit = INT32_MAX);

  /* Length operations */

  /**
   * Pad the start of this UnicodeString with the character <TT>padChar</TT>.
   * If the length of this UnicodeString is less than targetLength,
   * length() - targetLength copies of padChar will be added to the
   * beginning of this UnicodeString.
   * @param targetLength the desired length of the string
   * @param padChar the character to use for padding. Defaults to
   * space (U+0020)
   * @return TRUE if the text was padded, FALSE otherwise.
   * @stable ICU 2.0
   */
  UBool padLeading(int32_t targetLength,
                    UChar padChar = 0x0020);

  /**
   * Pad the end of this UnicodeString with the character <TT>padChar</TT>.
   * If the length of this UnicodeString is less than targetLength,
   * length() - targetLength copies of padChar will be added to the
   * end of this UnicodeString.
   * @param targetLength the desired length of the string
   * @param padChar the character to use for padding. Defaults to
   * space (U+0020)
   * @return TRUE if the text was padded, FALSE otherwise.
   * @stable ICU 2.0
   */
  UBool padTrailing(int32_t targetLength,
                     UChar padChar = 0x0020);

  /**
   * Truncate this UnicodeString to the <TT>targetLength</TT>.
   * @param targetLength the desired length of this UnicodeString.
   * @return TRUE if the text was truncated, FALSE otherwise
   * @stable ICU 2.0
   */
  inline UBool truncate(int32_t targetLength);

  /**
   * Trims leading and trailing whitespace from this UnicodeString.
   * @return a reference to this
   * @stable ICU 2.0
   */
  UnicodeString& trim(void);


  /* Miscellaneous operations */

  /**
   * Reverse this UnicodeString in place.
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& reverse(void);

  /**
   * Reverse the range [<TT>start</TT>, <TT>start + length</TT>) in
   * this UnicodeString.
   * @param start the start of the range to reverse
   * @param length the number of characters to to reverse
   * @return a reference to this
   * @stable ICU 2.0
   */
  inline UnicodeString& reverse(int32_t start,
             int32_t length);

  /**
   * Convert the characters in this to UPPER CASE following the conventions of
   * the default locale.
   * @return A reference to this.
   * @stable ICU 2.0
   */
  UnicodeString& toUpper(void);

  /**
   * Convert the characters in this to UPPER CASE following the conventions of
   * a specific locale.
   * @param locale The locale containing the conventions to use.
   * @return A reference to this.
   * @stable ICU 2.0
   */
  UnicodeString& toUpper(const Locale& locale);

  /**
   * Convert the characters in this to lower case following the conventions of
   * the default locale.
   * @return A reference to this.
   * @stable ICU 2.0
   */
  UnicodeString& toLower(void);

  /**
   * Convert the characters in this to lower case following the conventions of
   * a specific locale.
   * @param locale The locale containing the conventions to use.
   * @return A reference to this.
   * @stable ICU 2.0
   */
  UnicodeString& toLower(const Locale& locale);

#if !UCONFIG_NO_BREAK_ITERATION

  /**
   * Titlecase this string, convenience function using the default locale.
   *
   * Casing is locale-dependent and context-sensitive.
   * Titlecasing uses a break iterator to find the first characters of words
   * that are to be titlecased. It titlecases those characters and lowercases
   * all others.
   *
   * The titlecase break iterator can be provided to customize for arbitrary
   * styles, using rules and dictionaries beyond the standard iterators.
   * It may be more efficient to always provide an iterator to avoid
   * opening and closing one for each string.
   * The standard titlecase iterator for the root locale implements the
   * algorithm of Unicode TR 21.
   *
   * This function uses only the setText(), first() and next() methods of the
   * provided break iterator.
   *
   * @param titleIter A break iterator to find the first characters of words
   *                  that are to be titlecased.
   *                  If none is provided (0), then a standard titlecase
   *                  break iterator is opened.
   *                  Otherwise the provided iterator is set to the string's text.
   * @return A reference to this.
   * @stable ICU 2.1
   */
  UnicodeString &toTitle(BreakIterator *titleIter);

  /**
   * Titlecase this string.
   *
   * Casing is locale-dependent and context-sensitive.
   * Titlecasing uses a break iterator to find the first characters of words
   * that are to be titlecased. It titlecases those characters and lowercases
   * all others.
   *
   * The titlecase break iterator can be provided to customize for arbitrary
   * styles, using rules and dictionaries beyond the standard iterators.
   * It may be more efficient to always provide an iterator to avoid
   * opening and closing one for each string.
   * The standard titlecase iterator for the root locale implements the
   * algorithm of Unicode TR 21.
   *
   * This function uses only the setText(), first() and next() methods of the
   * provided break iterator.
   *
   * @param titleIter A break iterator to find the first characters of words
   *                  that are to be titlecased.
   *                  If none is provided (0), then a standard titlecase
   *                  break iterator is opened.
   *                  Otherwise the provided iterator is set to the string's text.
   * @param locale    The locale to consider.
   * @return A reference to this.
   * @stable ICU 2.1
   */
  UnicodeString &toTitle(BreakIterator *titleIter, const Locale &locale);

  /**
   * Titlecase this string, with options.
   *
   * Casing is locale-dependent and context-sensitive.
   * Titlecasing uses a break iterator to find the first characters of words
   * that are to be titlecased. It titlecases those characters and lowercases
   * all others. (This can be modified with options.)
   *
   * The titlecase break iterator can be provided to customize for arbitrary
   * styles, using rules and dictionaries beyond the standard iterators.
   * It may be more efficient to always provide an iterator to avoid
   * opening and closing one for each string.
   * The standard titlecase iterator for the root locale implements the
   * algorithm of Unicode TR 21.
   *
   * This function uses only the setText(), first() and next() methods of the
   * provided break iterator.
   *
   * @param titleIter A break iterator to find the first characters of words
   *                  that are to be titlecased.
   *                  If none is provided (0), then a standard titlecase
   *                  break iterator is opened.
   *                  Otherwise the provided iterator is set to the string's text.
   * @param locale    The locale to consider.
   * @param options Options bit set, see ucasemap_open().
   * @return A reference to this.
   * @see U_TITLECASE_NO_LOWERCASE
   * @see U_TITLECASE_NO_BREAK_ADJUSTMENT
   * @see ucasemap_open
   * @stable ICU 3.8
   */
  UnicodeString &toTitle(BreakIterator *titleIter, const Locale &locale, uint32_t options);

#endif

  /**
   * Case-folds the characters in this string.
   *
   * Case-folding is locale-independent and not context-sensitive,
   * but there is an option for whether to include or exclude mappings for dotted I
   * and dotless i that are marked with 'T' in CaseFolding.txt.
   *
   * The result may be longer or shorter than the original.
   *
   * @param options Either U_FOLD_CASE_DEFAULT or U_FOLD_CASE_EXCLUDE_SPECIAL_I