1// © 2016 and later: Unicode, Inc. and others.
2// License & terms of use: http://www.unicode.org/copyright.html
3/*
4**************************************************************************
5* Copyright (C) 1999-2012, International Business Machines Corporation and
6* others. All Rights Reserved.
7**************************************************************************
8*   Date        Name        Description
9*   11/17/99    aliu        Creation.  Ported from java.  Modified to
10*                           match current UnicodeString API.  Forced
11*                           to use name "handleReplaceBetween" because
12*                           of existing methods in UnicodeString.
13**************************************************************************
14*/
15
16#ifndef REP_H
17#define REP_H
18
19#include "unicode/uobject.h"
20
21/**
22 * \file
23 * \brief C++ API: Replaceable String
24 */
25
26U_NAMESPACE_BEGIN
27
28class UnicodeString;
29
30/**
31 * <code>Replaceable</code> is an abstract base class representing a
32 * string of characters that supports the replacement of a range of
33 * itself with a new string of characters.  It is used by APIs that
34 * change a piece of text while retaining metadata.  Metadata is data
35 * other than the Unicode characters returned by char32At().  One
36 * example of metadata is style attributes; another is an edit
37 * history, marking each character with an author and revision number.
38 *
39 * <p>An implicit aspect of the <code>Replaceable</code> API is that
40 * during a replace operation, new characters take on the metadata of
41 * the old characters.  For example, if the string "the <b>bold</b>
42 * font" has range (4, 8) replaced with "strong", then it becomes "the
43 * <b>strong</b> font".
44 *
45 * <p><code>Replaceable</code> specifies ranges using a start
46 * offset and a limit offset.  The range of characters thus specified
47 * includes the characters at offset start..limit-1.  That is, the
48 * start offset is inclusive, and the limit offset is exclusive.
49 *
50 * <p><code>Replaceable</code> also includes API to access characters
51 * in the string: <code>length()</code>, <code>charAt()</code>,
52 * <code>char32At()</code>, and <code>extractBetween()</code>.
53 *
54 * <p>For a subclass to support metadata, typical behavior of
55 * <code>replace()</code> is the following:
56 * <ul>
57 *   <li>Set the metadata of the new text to the metadata of the first
58 *   character replaced</li>
59 *   <li>If no characters are replaced, use the metadata of the
60 *   previous character</li>
61 *   <li>If there is no previous character (i.e. start == 0), use the
62 *   following character</li>
63 *   <li>If there is no following character (i.e. the replaceable was
64 *   empty), use default metadata.<br>
65 *   <li>If the code point U+FFFF is seen, it should be interpreted as
66 *   a special marker having no metadata<li>
67 *   </li>
68 * </ul>
69 * If this is not the behavior, the subclass should document any differences.
70 * @author Alan Liu
71 * @stable ICU 2.0
72 */
73class U_COMMON_API Replaceable : public UObject {
74
75public:
76    /**
77     * Destructor.
78     * @stable ICU 2.0
79     */
80    virtual ~Replaceable();
81
82    /**
83     * Returns the number of 16-bit code units in the text.
84     * @return number of 16-bit code units in text
85     * @stable ICU 1.8
86     */
87    inline int32_t length() const;
88
89    /**
90     * Returns the 16-bit code unit at the given offset into the text.
91     * @param offset an integer between 0 and <code>length()</code>-1
92     * inclusive
93     * @return 16-bit code unit of text at given offset
94     * @stable ICU 1.8
95     */
96    inline char16_t charAt(int32_t offset) const;
97
98    /**
99     * Returns the 32-bit code point at the given 16-bit offset into
100     * the text.  This assumes the text is stored as 16-bit code units
101     * with surrogate pairs intermixed.  If the offset of a leading or
102     * trailing code unit of a surrogate pair is given, return the
103     * code point of the surrogate pair.
104     *
105     * @param offset an integer between 0 and <code>length()</code>-1
106     * inclusive
107     * @return 32-bit code point of text at given offset
108     * @stable ICU 1.8
109     */
110    inline UChar32 char32At(int32_t offset) const;
111
112    /**
113     * Copies characters in the range [<tt>start</tt>, <tt>limit</tt>)
114     * into the UnicodeString <tt>target</tt>.
115     * @param start offset of first character which will be copied
116     * @param limit offset immediately following the last character to
117     * be copied
118     * @param target UnicodeString into which to copy characters.
119     * @return A reference to <TT>target</TT>
120     * @stable ICU 2.1
121     */
122    virtual void extractBetween(int32_t start,
123                                int32_t limit,
124                                UnicodeString& target) const = 0;
125
126    /**
127     * Replaces a substring of this object with the given text.  If the
128     * characters being replaced have metadata, the new characters
129     * that replace them should be given the same metadata.
130     *
131     * <p>Subclasses must ensure that if the text between start and
132     * limit is equal to the replacement text, that replace has no
133     * effect. That is, any metadata
134     * should be unaffected. In addition, subclasses are encouraged to
135     * check for initial and trailing identical characters, and make a
136     * smaller replacement if possible. This will preserve as much
137     * metadata as possible.
138     * @param start the beginning index, inclusive; <code>0 <= start
139     * <= limit</code>.
140     * @param limit the ending index, exclusive; <code>start <= limit
141     * <= length()</code>.
142     * @param text the text to replace characters <code>start</code>
143     * to <code>limit - 1</code>
144     * @stable ICU 2.0
145     */
146    virtual void handleReplaceBetween(int32_t start,
147                                      int32_t limit,
148                                      const UnicodeString& text) = 0;
149    // Note: All other methods in this class take the names of
150    // existing UnicodeString methods.  This method is the exception.
151    // It is named differently because all replace methods of
152    // UnicodeString return a UnicodeString&.  The 'between' is
153    // required in order to conform to the UnicodeString naming
154    // convention; API taking start/length are named <operation>, and
155    // those taking start/limit are named <operationBetween>.  The
156    // 'handle' is added because 'replaceBetween' and
157    // 'doReplaceBetween' are already taken.
158
159    /**
160     * Copies a substring of this object, retaining metadata.
161     * This method is used to duplicate or reorder substrings.
162     * The destination index must not overlap the source range.
163     *
164     * @param start the beginning index, inclusive; <code>0 <= start <=
165     * limit</code>.
166     * @param limit the ending index, exclusive; <code>start <= limit <=
167     * length()</code>.
168     * @param dest the destination index.  The characters from
169     * <code>start..limit-1</code> will be copied to <code>dest</code>.
170     * Implementations of this method may assume that <code>dest <= start ||
171     * dest >= limit</code>.
172     * @stable ICU 2.0
173     */
174    virtual void copy(int32_t start, int32_t limit, int32_t dest) = 0;
175
176    /**
177     * Returns true if this object contains metadata.  If a
178     * Replaceable object has metadata, calls to the Replaceable API
179     * must be made so as to preserve metadata.  If it does not, calls
180     * to the Replaceable API may be optimized to improve performance.
181     * The default implementation returns true.
182     * @return true if this object contains metadata
183     * @stable ICU 2.2
184     */
185    virtual UBool hasMetaData() const;
186
187    /**
188     * Clone this object, an instance of a subclass of Replaceable.
189     * Clones can be used concurrently in multiple threads.
190     * If a subclass does not implement clone(), or if an error occurs,
191     * then NULL is returned.
192     * The clone functions in all subclasses return a pointer to a Replaceable
193     * because some compilers do not support covariant (same-as-this)
194     * return types; cast to the appropriate subclass if necessary.
195     * The caller must delete the clone.
196     *
197     * @return a clone of this object
198     *
199     * @see getDynamicClassID
200     * @stable ICU 2.6
201     */
202    virtual Replaceable *clone() const;
203
204protected:
205
206    /**
207     * Default constructor.
208     * @stable ICU 2.4
209     */
210    inline Replaceable();
211
212    /*
213     * Assignment operator not declared. The compiler will provide one
214     * which does nothing since this class does not contain any data members.
215     * API/code coverage may show the assignment operator as present and
216     * untested - ignore.
217     * Subclasses need this assignment operator if they use compiler-provided
218     * assignment operators of their own. An alternative to not declaring one
219     * here would be to declare and empty-implement a protected or public one.
220    Replaceable &Replaceable::operator=(const Replaceable &);
221     */
222
223    /**
224     * Virtual version of length().
225     * @stable ICU 2.4
226     */
227    virtual int32_t getLength() const = 0;
228
229    /**
230     * Virtual version of charAt().
231     * @stable ICU 2.4
232     */
233    virtual char16_t getCharAt(int32_t offset) const = 0;
234
235    /**
236     * Virtual version of char32At().
237     * @stable ICU 2.4
238     */
239    virtual UChar32 getChar32At(int32_t offset) const = 0;
240};
241
242inline Replaceable::Replaceable() {}
243
244inline int32_t
245Replaceable::length() const {
246    return getLength();
247}
248
249inline char16_t
250Replaceable::charAt(int32_t offset) const {
251    return getCharAt(offset);
252}
253
254inline UChar32
255Replaceable::char32At(int32_t offset) const {
256    return getChar32At(offset);
257}
258
259// There is no rep.cpp, see unistr.cpp for Replaceable function implementations.
260
261U_NAMESPACE_END
262
263#endif
264