1//===--- StringRef.h - Constant String Reference Wrapper --------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef LLVM_ADT_STRINGREF_H
11#define LLVM_ADT_STRINGREF_H
12
13#include "llvm/Support/type_traits.h"
14#include <algorithm>
15#include <cassert>
16#include <cstring>
17#include <limits>
18#include <string>
19#include <utility>
20
21namespace llvm {
22  template <typename T>
23  class SmallVectorImpl;
24  class APInt;
25  class hash_code;
26  class StringRef;
27
28  /// Helper functions for StringRef::getAsInteger.
29  bool getAsUnsignedInteger(StringRef Str, unsigned Radix,
30                            unsigned long long &Result);
31
32  bool getAsSignedInteger(StringRef Str, unsigned Radix, long long &Result);
33
34  /// StringRef - Represent a constant reference to a string, i.e. a character
35  /// array and a length, which need not be null terminated.
36  ///
37  /// This class does not own the string data, it is expected to be used in
38  /// situations where the character data resides in some other buffer, whose
39  /// lifetime extends past that of the StringRef. For this reason, it is not in
40  /// general safe to store a StringRef.
41  class StringRef {
42  public:
43    typedef const char *iterator;
44    typedef const char *const_iterator;
45    static const size_t npos = ~size_t(0);
46    typedef size_t size_type;
47
48  private:
49    /// The start of the string, in an external buffer.
50    const char *Data;
51
52    /// The length of the string.
53    size_t Length;
54
55    // Workaround PR5482: nearly all gcc 4.x miscompile StringRef and std::min()
56    // Changing the arg of min to be an integer, instead of a reference to an
57    // integer works around this bug.
58    static size_t min(size_t a, size_t b) { return a < b ? a : b; }
59    static size_t max(size_t a, size_t b) { return a > b ? a : b; }
60
61    // Workaround memcmp issue with null pointers (undefined behavior)
62    // by providing a specialized version
63    static int compareMemory(const char *Lhs, const char *Rhs, size_t Length) {
64      if (Length == 0) { return 0; }
65      return ::memcmp(Lhs,Rhs,Length);
66    }
67
68  public:
69    /// @name Constructors
70    /// @{
71
72    /// Construct an empty string ref.
73    /*implicit*/ StringRef() : Data(0), Length(0) {}
74
75    /// Construct a string ref from a cstring.
76    /*implicit*/ StringRef(const char *Str)
77      : Data(Str) {
78        assert(Str && "StringRef cannot be built from a NULL argument");
79        Length = ::strlen(Str); // invoking strlen(NULL) is undefined behavior
80      }
81
82    /// Construct a string ref from a pointer and length.
83    /*implicit*/ StringRef(const char *data, size_t length)
84      : Data(data), Length(length) {
85        assert((data || length == 0) &&
86        "StringRef cannot be built from a NULL argument with non-null length");
87      }
88
89    /// Construct a string ref from an std::string.
90    /*implicit*/ StringRef(const std::string &Str)
91      : Data(Str.data()), Length(Str.length()) {}
92
93    /// @}
94    /// @name Iterators
95    /// @{
96
97    iterator begin() const { return Data; }
98
99    iterator end() const { return Data + Length; }
100
101    /// @}
102    /// @name String Operations
103    /// @{
104
105    /// data - Get a pointer to the start of the string (which may not be null
106    /// terminated).
107    const char *data() const { return Data; }
108
109    /// empty - Check if the string is empty.
110    bool empty() const { return Length == 0; }
111
112    /// size - Get the string size.
113    size_t size() const { return Length; }
114
115    /// front - Get the first character in the string.
116    char front() const {
117      assert(!empty());
118      return Data[0];
119    }
120
121    /// back - Get the last character in the string.
122    char back() const {
123      assert(!empty());
124      return Data[Length-1];
125    }
126
127    /// equals - Check for string equality, this is more efficient than
128    /// compare() when the relative ordering of inequal strings isn't needed.
129    bool equals(StringRef RHS) const {
130      return (Length == RHS.Length &&
131              compareMemory(Data, RHS.Data, RHS.Length) == 0);
132    }
133
134    /// equals_lower - Check for string equality, ignoring case.
135    bool equals_lower(StringRef RHS) const {
136      return Length == RHS.Length && compare_lower(RHS) == 0;
137    }
138
139    /// compare - Compare two strings; the result is -1, 0, or 1 if this string
140    /// is lexicographically less than, equal to, or greater than the \p RHS.
141    int compare(StringRef RHS) const {
142      // Check the prefix for a mismatch.
143      if (int Res = compareMemory(Data, RHS.Data, min(Length, RHS.Length)))
144        return Res < 0 ? -1 : 1;
145
146      // Otherwise the prefixes match, so we only need to check the lengths.
147      if (Length == RHS.Length)
148        return 0;
149      return Length < RHS.Length ? -1 : 1;
150    }
151
152    /// compare_lower - Compare two strings, ignoring case.
153    int compare_lower(StringRef RHS) const;
154
155    /// compare_numeric - Compare two strings, treating sequences of digits as
156    /// numbers.
157    int compare_numeric(StringRef RHS) const;
158
159    /// \brief Determine the edit distance between this string and another
160    /// string.
161    ///
162    /// \param Other the string to compare this string against.
163    ///
164    /// \param AllowReplacements whether to allow character
165    /// replacements (change one character into another) as a single
166    /// operation, rather than as two operations (an insertion and a
167    /// removal).
168    ///
169    /// \param MaxEditDistance If non-zero, the maximum edit distance that
170    /// this routine is allowed to compute. If the edit distance will exceed
171    /// that maximum, returns \c MaxEditDistance+1.
172    ///
173    /// \returns the minimum number of character insertions, removals,
174    /// or (if \p AllowReplacements is \c true) replacements needed to
175    /// transform one of the given strings into the other. If zero,
176    /// the strings are identical.
177    unsigned edit_distance(StringRef Other, bool AllowReplacements = true,
178                           unsigned MaxEditDistance = 0);
179
180    /// str - Get the contents as an std::string.
181    std::string str() const {
182      if (Data == 0) return std::string();
183      return std::string(Data, Length);
184    }
185
186    /// @}
187    /// @name Operator Overloads
188    /// @{
189
190    char operator[](size_t Index) const {
191      assert(Index < Length && "Invalid index!");
192      return Data[Index];
193    }
194
195    /// @}
196    /// @name Type Conversions
197    /// @{
198
199    operator std::string() const {
200      return str();
201    }
202
203    /// @}
204    /// @name String Predicates
205    /// @{
206
207    /// Check if this string starts with the given \p Prefix.
208    bool startswith(StringRef Prefix) const {
209      return Length >= Prefix.Length &&
210             compareMemory(Data, Prefix.Data, Prefix.Length) == 0;
211    }
212
213    /// Check if this string ends with the given \p Suffix.
214    bool endswith(StringRef Suffix) const {
215      return Length >= Suffix.Length &&
216        compareMemory(end() - Suffix.Length, Suffix.Data, Suffix.Length) == 0;
217    }
218
219    /// @}
220    /// @name String Searching
221    /// @{
222
223    /// Search for the first character \p C in the string.
224    ///
225    /// \returns The index of the first occurrence of \p C, or npos if not
226    /// found.
227    size_t find(char C, size_t From = 0) const {
228      for (size_t i = min(From, Length), e = Length; i != e; ++i)
229        if (Data[i] == C)
230          return i;
231      return npos;
232    }
233
234    /// Search for the first string \p Str in the string.
235    ///
236    /// \returns The index of the first occurrence of \p Str, or npos if not
237    /// found.
238    size_t find(StringRef Str, size_t From = 0) const;
239
240    /// Search for the last character \p C in the string.
241    ///
242    /// \returns The index of the last occurrence of \p C, or npos if not
243    /// found.
244    size_t rfind(char C, size_t From = npos) const {
245      From = min(From, Length);
246      size_t i = From;
247      while (i != 0) {
248        --i;
249        if (Data[i] == C)
250          return i;
251      }
252      return npos;
253    }
254
255    /// Search for the last string \p Str in the string.
256    ///
257    /// \returns The index of the last occurrence of \p Str, or npos if not
258    /// found.
259    size_t rfind(StringRef Str) const;
260
261    /// Find the first character in the string that is \p C, or npos if not
262    /// found. Same as find.
263    size_t find_first_of(char C, size_t From = 0) const {
264      return find(C, From);
265    }
266
267    /// Find the first character in the string that is in \p Chars, or npos if
268    /// not found.
269    ///
270    /// Complexity: O(size() + Chars.size())
271    size_t find_first_of(StringRef Chars, size_t From = 0) const;
272
273    /// Find the first character in the string that is not \p C or npos if not
274    /// found.
275    size_t find_first_not_of(char C, size_t From = 0) const;
276
277    /// Find the first character in the string that is not in the string
278    /// \p Chars, or npos if not found.
279    ///
280    /// Complexity: O(size() + Chars.size())
281    size_t find_first_not_of(StringRef Chars, size_t From = 0) const;
282
283    /// Find the last character in the string that is \p C, or npos if not
284    /// found.
285    size_t find_last_of(char C, size_t From = npos) const {
286      return rfind(C, From);
287    }
288
289    /// Find the last character in the string that is in \p C, or npos if not
290    /// found.
291    ///
292    /// Complexity: O(size() + Chars.size())
293    size_t find_last_of(StringRef Chars, size_t From = npos) const;
294
295    /// Find the last character in the string that is not \p C, or npos if not
296    /// found.
297    size_t find_last_not_of(char C, size_t From = npos) const;
298
299    /// Find the last character in the string that is not in \p Chars, or
300    /// npos if not found.
301    ///
302    /// Complexity: O(size() + Chars.size())
303    size_t find_last_not_of(StringRef Chars, size_t From = npos) const;
304
305    /// @}
306    /// @name Helpful Algorithms
307    /// @{
308
309    /// Return the number of occurrences of \p C in the string.
310    size_t count(char C) const {
311      size_t Count = 0;
312      for (size_t i = 0, e = Length; i != e; ++i)
313        if (Data[i] == C)
314          ++Count;
315      return Count;
316    }
317
318    /// Return the number of non-overlapped occurrences of \p Str in
319    /// the string.
320    size_t count(StringRef Str) const;
321
322    /// Parse the current string as an integer of the specified radix.  If
323    /// \p Radix is specified as zero, this does radix autosensing using
324    /// extended C rules: 0 is octal, 0x is hex, 0b is binary.
325    ///
326    /// If the string is invalid or if only a subset of the string is valid,
327    /// this returns true to signify the error.  The string is considered
328    /// erroneous if empty or if it overflows T.
329    template <typename T>
330    typename enable_if_c<std::numeric_limits<T>::is_signed, bool>::type
331    getAsInteger(unsigned Radix, T &Result) const {
332      long long LLVal;
333      if (getAsSignedInteger(*this, Radix, LLVal) ||
334            static_cast<T>(LLVal) != LLVal)
335        return true;
336      Result = LLVal;
337      return false;
338    }
339
340    template <typename T>
341    typename enable_if_c<!std::numeric_limits<T>::is_signed, bool>::type
342    getAsInteger(unsigned Radix, T &Result) const {
343      unsigned long long ULLVal;
344      if (getAsUnsignedInteger(*this, Radix, ULLVal) ||
345            static_cast<T>(ULLVal) != ULLVal)
346        return true;
347      Result = ULLVal;
348      return false;
349    }
350
351    /// Parse the current string as an integer of the specified \p Radix, or of
352    /// an autosensed radix if the \p Radix given is 0.  The current value in
353    /// \p Result is discarded, and the storage is changed to be wide enough to
354    /// store the parsed integer.
355    ///
356    /// \returns true if the string does not solely consist of a valid
357    /// non-empty number in the appropriate base.
358    ///
359    /// APInt::fromString is superficially similar but assumes the
360    /// string is well-formed in the given radix.
361    bool getAsInteger(unsigned Radix, APInt &Result) const;
362
363    /// @}
364    /// @name String Operations
365    /// @{
366
367    // Convert the given ASCII string to lowercase.
368    std::string lower() const;
369
370    /// Convert the given ASCII string to uppercase.
371    std::string upper() const;
372
373    /// @}
374    /// @name Substring Operations
375    /// @{
376
377    /// Return a reference to the substring from [Start, Start + N).
378    ///
379    /// \param Start The index of the starting character in the substring; if
380    /// the index is npos or greater than the length of the string then the
381    /// empty substring will be returned.
382    ///
383    /// \param N The number of characters to included in the substring. If N
384    /// exceeds the number of characters remaining in the string, the string
385    /// suffix (starting with \p Start) will be returned.
386    StringRef substr(size_t Start, size_t N = npos) const {
387      Start = min(Start, Length);
388      return StringRef(Data + Start, min(N, Length - Start));
389    }
390
391    /// Return a StringRef equal to 'this' but with the first \p N elements
392    /// dropped.
393    StringRef drop_front(size_t N = 1) const {
394      assert(size() >= N && "Dropping more elements than exist");
395      return substr(N);
396    }
397
398    /// Return a StringRef equal to 'this' but with the last \p N elements
399    /// dropped.
400    StringRef drop_back(size_t N = 1) const {
401      assert(size() >= N && "Dropping more elements than exist");
402      return substr(0, size()-N);
403    }
404
405    /// Return a reference to the substring from [Start, End).
406    ///
407    /// \param Start The index of the starting character in the substring; if
408    /// the index is npos or greater than the length of the string then the
409    /// empty substring will be returned.
410    ///
411    /// \param End The index following the last character to include in the
412    /// substring. If this is npos, or less than \p Start, or exceeds the
413    /// number of characters remaining in the string, the string suffix
414    /// (starting with \p Start) will be returned.
415    StringRef slice(size_t Start, size_t End) const {
416      Start = min(Start, Length);
417      End = min(max(Start, End), Length);
418      return StringRef(Data + Start, End - Start);
419    }
420
421    /// Split into two substrings around the first occurrence of a separator
422    /// character.
423    ///
424    /// If \p Separator is in the string, then the result is a pair (LHS, RHS)
425    /// such that (*this == LHS + Separator + RHS) is true and RHS is
426    /// maximal. If \p Separator is not in the string, then the result is a
427    /// pair (LHS, RHS) where (*this == LHS) and (RHS == "").
428    ///
429    /// \param Separator The character to split on.
430    /// \returns The split substrings.
431    std::pair<StringRef, StringRef> split(char Separator) const {
432      size_t Idx = find(Separator);
433      if (Idx == npos)
434        return std::make_pair(*this, StringRef());
435      return std::make_pair(slice(0, Idx), slice(Idx+1, npos));
436    }
437
438    /// Split into two substrings around the first occurrence of a separator
439    /// string.
440    ///
441    /// If \p Separator is in the string, then the result is a pair (LHS, RHS)
442    /// such that (*this == LHS + Separator + RHS) is true and RHS is
443    /// maximal. If \p Separator is not in the string, then the result is a
444    /// pair (LHS, RHS) where (*this == LHS) and (RHS == "").
445    ///
446    /// \param Separator - The string to split on.
447    /// \return - The split substrings.
448    std::pair<StringRef, StringRef> split(StringRef Separator) const {
449      size_t Idx = find(Separator);
450      if (Idx == npos)
451        return std::make_pair(*this, StringRef());
452      return std::make_pair(slice(0, Idx), slice(Idx + Separator.size(), npos));
453    }
454
455    /// Split into substrings around the occurrences of a separator string.
456    ///
457    /// Each substring is stored in \p A. If \p MaxSplit is >= 0, at most
458    /// \p MaxSplit splits are done and consequently <= \p MaxSplit
459    /// elements are added to A.
460    /// If \p KeepEmpty is false, empty strings are not added to \p A. They
461    /// still count when considering \p MaxSplit
462    /// An useful invariant is that
463    /// Separator.join(A) == *this if MaxSplit == -1 and KeepEmpty == true
464    ///
465    /// \param A - Where to put the substrings.
466    /// \param Separator - The string to split on.
467    /// \param MaxSplit - The maximum number of times the string is split.
468    /// \param KeepEmpty - True if empty substring should be added.
469    void split(SmallVectorImpl<StringRef> &A,
470               StringRef Separator, int MaxSplit = -1,
471               bool KeepEmpty = true) const;
472
473    /// Split into two substrings around the last occurrence of a separator
474    /// character.
475    ///
476    /// If \p Separator is in the string, then the result is a pair (LHS, RHS)
477    /// such that (*this == LHS + Separator + RHS) is true and RHS is
478    /// minimal. If \p Separator is not in the string, then the result is a
479    /// pair (LHS, RHS) where (*this == LHS) and (RHS == "").
480    ///
481    /// \param Separator - The character to split on.
482    /// \return - The split substrings.
483    std::pair<StringRef, StringRef> rsplit(char Separator) const {
484      size_t Idx = rfind(Separator);
485      if (Idx == npos)
486        return std::make_pair(*this, StringRef());
487      return std::make_pair(slice(0, Idx), slice(Idx+1, npos));
488    }
489
490    /// Return string with consecutive characters in \p Chars starting from
491    /// the left removed.
492    StringRef ltrim(StringRef Chars = " \t\n\v\f\r") const {
493      return drop_front(std::min(Length, find_first_not_of(Chars)));
494    }
495
496    /// Return string with consecutive characters in \p Chars starting from
497    /// the right removed.
498    StringRef rtrim(StringRef Chars = " \t\n\v\f\r") const {
499      return drop_back(Length - std::min(Length, find_last_not_of(Chars) + 1));
500    }
501
502    /// Return string with consecutive characters in \p Chars starting from
503    /// the left and right removed.
504    StringRef trim(StringRef Chars = " \t\n\v\f\r") const {
505      return ltrim(Chars).rtrim(Chars);
506    }
507
508    /// @}
509  };
510
511  /// @name StringRef Comparison Operators
512  /// @{
513
514  inline bool operator==(StringRef LHS, StringRef RHS) {
515    return LHS.equals(RHS);
516  }
517
518  inline bool operator!=(StringRef LHS, StringRef RHS) {
519    return !(LHS == RHS);
520  }
521
522  inline bool operator<(StringRef LHS, StringRef RHS) {
523    return LHS.compare(RHS) == -1;
524  }
525
526  inline bool operator<=(StringRef LHS, StringRef RHS) {
527    return LHS.compare(RHS) != 1;
528  }
529
530  inline bool operator>(StringRef LHS, StringRef RHS) {
531    return LHS.compare(RHS) == 1;
532  }
533
534  inline bool operator>=(StringRef LHS, StringRef RHS) {
535    return LHS.compare(RHS) != -1;
536  }
537
538  inline std::string &operator+=(std::string &buffer, StringRef string) {
539    return buffer.append(string.data(), string.size());
540  }
541
542  /// @}
543
544  /// \brief Compute a hash_code for a StringRef.
545  hash_code hash_value(StringRef S);
546
547  // StringRefs can be treated like a POD type.
548  template <typename T> struct isPodLike;
549  template <> struct isPodLike<StringRef> { static const bool value = true; };
550
551  /// Construct a string ref from a boolean.
552  inline StringRef toStringRef(bool B) {
553    return StringRef(B ? "true" : "false");
554  }
555}
556
557#endif
558