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