summaryrefslogtreecommitdiffstats
path: root/base/string_number_conversions.cc
blob: e80b6499f2e04c0787a48d08f87b306e9fc3e468 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/string_number_conversions.h"

#include <ctype.h>
#include <errno.h>
#include <stdlib.h>
#include <wctype.h>

#include <limits>

#include "base/logging.h"
#include "base/third_party/dmg_fp/dmg_fp.h"
#include "base/utf_string_conversions.h"

namespace base {

namespace {

template <typename STR, typename INT, typename UINT, bool NEG>
struct IntToStringT {
  // This is to avoid a compiler warning about unary minus on unsigned type.
  // For example, say you had the following code:
  //   template <typename INT>
  //   INT abs(INT value) { return value < 0 ? -value : value; }
  // Even though if INT is unsigned, it's impossible for value < 0, so the
  // unary minus will never be taken, the compiler will still generate a
  // warning.  We do a little specialization dance...
  template <typename INT2, typename UINT2, bool NEG2>
  struct ToUnsignedT {};

  template <typename INT2, typename UINT2>
  struct ToUnsignedT<INT2, UINT2, false> {
    static UINT2 ToUnsigned(INT2 value) {
      return static_cast<UINT2>(value);
    }
  };

  template <typename INT2, typename UINT2>
  struct ToUnsignedT<INT2, UINT2, true> {
    static UINT2 ToUnsigned(INT2 value) {
      return static_cast<UINT2>(value < 0 ? -value : value);
    }
  };

  // This set of templates is very similar to the above templates, but
  // for testing whether an integer is negative.
  template <typename INT2, bool NEG2>
  struct TestNegT {};
  template <typename INT2>
  struct TestNegT<INT2, false> {
    static bool TestNeg(INT2 value) {
      // value is unsigned, and can never be negative.
      return false;
    }
  };
  template <typename INT2>
  struct TestNegT<INT2, true> {
    static bool TestNeg(INT2 value) {
      return value < 0;
    }
  };

  static STR IntToString(INT value) {
    // log10(2) ~= 0.3 bytes needed per bit or per byte log10(2**8) ~= 2.4.
    // So round up to allocate 3 output characters per byte, plus 1 for '-'.
    const int kOutputBufSize = 3 * sizeof(INT) + 1;

    // Allocate the whole string right away, we will right back to front, and
    // then return the substr of what we ended up using.
    STR outbuf(kOutputBufSize, 0);

    bool is_neg = TestNegT<INT, NEG>::TestNeg(value);
    // Even though is_neg will never be true when INT is parameterized as
    // unsigned, even the presence of the unary operation causes a warning.
    UINT res = ToUnsignedT<INT, UINT, NEG>::ToUnsigned(value);

    for (typename STR::iterator it = outbuf.end();;) {
      --it;
      DCHECK(it != outbuf.begin());
      *it = static_cast<typename STR::value_type>((res % 10) + '0');
      res /= 10;

      // We're done..
      if (res == 0) {
        if (is_neg) {
          --it;
          DCHECK(it != outbuf.begin());
          *it = static_cast<typename STR::value_type>('-');
        }
        return STR(it, outbuf.end());
      }
    }
    NOTREACHED();
    return STR();
  }
};

// Utility to convert a character to a digit in a given base
template<typename CHAR, int BASE, bool BASE_LTE_10> class BaseCharToDigit {
};

// Faster specialization for bases <= 10
template<typename CHAR, int BASE> class BaseCharToDigit<CHAR, BASE, true> {
 public:
  static bool Convert(CHAR c, uint8* digit) {
    if (c >= '0' && c < '0' + BASE) {
      *digit = c - '0';
      return true;
    }
    return false;
  }
};

// Specialization for bases where 10 < base <= 36
template<typename CHAR, int BASE> class BaseCharToDigit<CHAR, BASE, false> {
 public:
  static bool Convert(CHAR c, uint8* digit) {
    if (c >= '0' && c <= '9') {
      *digit = c - '0';
    } else if (c >= 'a' && c < 'a' + BASE - 10) {
      *digit = c - 'a' + 10;
    } else if (c >= 'A' && c < 'A' + BASE - 10) {
      *digit = c - 'A' + 10;
    } else {
      return false;
    }
    return true;
  }
};

template<int BASE, typename CHAR> bool CharToDigit(CHAR c, uint8* digit) {
  return BaseCharToDigit<CHAR, BASE, BASE <= 10>::Convert(c, digit);
}

// There is an IsWhitespace for wchars defined in string_util.h, but it is
// locale independent, whereas the functions we are replacing were
// locale-dependent. TBD what is desired, but for the moment let's not introduce
// a change in behaviour.
template<typename CHAR> class WhitespaceHelper {
};

template<> class WhitespaceHelper<char> {
 public:
  static bool Invoke(char c) {
    return 0 != isspace(static_cast<unsigned char>(c));
  }
};

template<> class WhitespaceHelper<char16> {
 public:
  static bool Invoke(char16 c) {
    return 0 != iswspace(c);
  }
};

template<typename CHAR> bool LocalIsWhitespace(CHAR c) {
  return WhitespaceHelper<CHAR>::Invoke(c);
}

// IteratorRangeToNumberTraits should provide:
//  - a typedef for iterator_type, the iterator type used as input.
//  - a typedef for value_type, the target numeric type.
//  - static functions min, max (returning the minimum and maximum permitted
//    values)
//  - constant kBase, the base in which to interpret the input
template<typename IteratorRangeToNumberTraits>
class IteratorRangeToNumber {
 public:
  typedef IteratorRangeToNumberTraits traits;
  typedef typename traits::iterator_type const_iterator;
  typedef typename traits::value_type value_type;

  // Generalized iterator-range-to-number conversion.
  //
  static bool Invoke(const_iterator begin,
                     const_iterator end,
                     value_type* output) {
    bool valid = true;

    while (begin != end && LocalIsWhitespace(*begin)) {
      valid = false;
      ++begin;
    }

    if (begin != end && *begin == '-') {
      if (!Negative::Invoke(begin + 1, end, output)) {
        valid = false;
      }
    } else {
      if (begin != end && *begin == '+') {
        ++begin;
      }
      if (!Positive::Invoke(begin, end, output)) {
        valid = false;
      }
    }

    return valid;
  }

 private:
  // Sign provides:
  //  - a static function, CheckBounds, that determines whether the next digit
  //    causes an overflow/underflow
  //  - a static function, Increment, that appends the next digit appropriately
  //    according to the sign of the number being parsed.
  template<typename Sign>
  class Base {
   public:
    static bool Invoke(const_iterator begin, const_iterator end,
                       typename traits::value_type* output) {
      *output = 0;

      if (begin == end) {
        return false;
      }

      // Note: no performance difference was found when using template
      // specialization to remove this check in bases other than 16
      if (traits::kBase == 16 && end - begin > 2 && *begin == '0' &&
          (*(begin + 1) == 'x' || *(begin + 1) == 'X')) {
        begin += 2;
      }

      for (const_iterator current = begin; current != end; ++current) {
        uint8 new_digit = 0;

        if (!CharToDigit<traits::kBase>(*current, &new_digit)) {
          return false;
        }

        if (current != begin) {
          if (!Sign::CheckBounds(output, new_digit)) {
            return false;
          }
          *output *= traits::kBase;
        }

        Sign::Increment(new_digit, output);
      }
      return true;
    }
  };

  class Positive : public Base<Positive> {
   public:
    static bool CheckBounds(value_type* output, uint8 new_digit) {
      if (*output > static_cast<value_type>(traits::max() / traits::kBase) ||
          (*output == static_cast<value_type>(traits::max() / traits::kBase) &&
           new_digit > traits::max() % traits::kBase)) {
        *output = traits::max();
        return false;
      }
      return true;
    }
    static void Increment(uint8 increment, value_type* output) {
      *output += increment;
    }
  };

  class Negative : public Base<Negative> {
   public:
    static bool CheckBounds(value_type* output, uint8 new_digit) {
      if (*output < traits::min() / traits::kBase ||
          (*output == traits::min() / traits::kBase &&
           new_digit > 0 - traits::min() % traits::kBase)) {
        *output = traits::min();
        return false;
      }
      return true;
    }
    static void Increment(uint8 increment, value_type* output) {
      *output -= increment;
    }
  };
};

template<typename ITERATOR, typename VALUE, int BASE>
class BaseIteratorRangeToNumberTraits {
 public:
  typedef ITERATOR iterator_type;
  typedef VALUE value_type;
  static value_type min() {
    return std::numeric_limits<value_type>::min();
  }
  static value_type max() {
    return std::numeric_limits<value_type>::max();
  }
  static const int kBase = BASE;
};

template<typename ITERATOR>
class BaseHexIteratorRangeToIntTraits
    : public BaseIteratorRangeToNumberTraits<ITERATOR, int, 16> {
 public:
  // Allow parsing of 0xFFFFFFFF, which is technically an overflow
  static unsigned int max() {
    return std::numeric_limits<unsigned int>::max();
  }
};

typedef BaseHexIteratorRangeToIntTraits<StringPiece::const_iterator>
    HexIteratorRangeToIntTraits;

template<typename STR>
bool HexStringToBytesT(const STR& input, std::vector<uint8>* output) {
  DCHECK_EQ(output->size(), 0u);
  size_t count = input.size();
  if (count == 0 || (count % 2) != 0)
    return false;
  for (uintptr_t i = 0; i < count / 2; ++i) {
    uint8 msb = 0;  // most significant 4 bits
    uint8 lsb = 0;  // least significant 4 bits
    if (!CharToDigit<16>(input[i * 2], &msb) ||
        !CharToDigit<16>(input[i * 2 + 1], &lsb))
      return false;
    output->push_back((msb << 4) | lsb);
  }
  return true;
}

template <typename VALUE, int BASE>
class StringPieceToNumberTraits
    : public BaseIteratorRangeToNumberTraits<StringPiece::const_iterator,
                                             VALUE,
                                             BASE> {};

template <typename VALUE>
bool StringToIntImpl(const StringPiece& input, VALUE* output) {
  return IteratorRangeToNumber<StringPieceToNumberTraits<VALUE, 10> >::Invoke(
      input.begin(), input.end(), output);
}

template <typename VALUE, int BASE>
class StringPiece16ToNumberTraits
    : public BaseIteratorRangeToNumberTraits<StringPiece16::const_iterator,
                                             VALUE,
                                             BASE> {};

template <typename VALUE>
bool String16ToIntImpl(const StringPiece16& input, VALUE* output) {
  return IteratorRangeToNumber<StringPiece16ToNumberTraits<VALUE, 10> >::Invoke(
      input.begin(), input.end(), output);
}

}  // namespace

std::string IntToString(int value) {
  return IntToStringT<std::string, int, unsigned int, true>::
      IntToString(value);
}

string16 IntToString16(int value) {
  return IntToStringT<string16, int, unsigned int, true>::
      IntToString(value);
}

std::string UintToString(unsigned int value) {
  return IntToStringT<std::string, unsigned int, unsigned int, false>::
      IntToString(value);
}

string16 UintToString16(unsigned int value) {
  return IntToStringT<string16, unsigned int, unsigned int, false>::
      IntToString(value);
}

std::string Int64ToString(int64 value) {
  return IntToStringT<std::string, int64, uint64, true>::
      IntToString(value);
}

string16 Int64ToString16(int64 value) {
  return IntToStringT<string16, int64, uint64, true>::IntToString(value);
}

std::string Uint64ToString(uint64 value) {
  return IntToStringT<std::string, uint64, uint64, false>::
      IntToString(value);
}

string16 Uint64ToString16(uint64 value) {
  return IntToStringT<string16, uint64, uint64, false>::
      IntToString(value);
}

std::string DoubleToString(double value) {
  // According to g_fmt.cc, it is sufficient to declare a buffer of size 32.
  char buffer[32];
  dmg_fp::g_fmt(buffer, value);
  return std::string(buffer);
}

bool StringToInt(const StringPiece& input, int* output) {
  return StringToIntImpl(input, output);
}

bool StringToInt(const StringPiece16& input, int* output) {
  return String16ToIntImpl(input, output);
}

bool StringToUint(const StringPiece& input, unsigned* output) {
  return StringToIntImpl(input, output);
}

bool StringToUint(const StringPiece16& input, unsigned* output) {
  return String16ToIntImpl(input, output);
}

bool StringToInt64(const StringPiece& input, int64* output) {
  return StringToIntImpl(input, output);
}

bool StringToInt64(const StringPiece16& input, int64* output) {
  return String16ToIntImpl(input, output);
}

bool StringToUint64(const StringPiece& input, uint64* output) {
  return StringToIntImpl(input, output);
}

bool StringToUint64(const StringPiece16& input, uint64* output) {
  return String16ToIntImpl(input, output);
}

bool StringToSizeT(const StringPiece& input, size_t* output) {
  return StringToIntImpl(input, output);
}

bool StringToSizeT(const StringPiece16& input, size_t* output) {
  return String16ToIntImpl(input, output);
}

bool StringToDouble(const std::string& input, double* output) {
  errno = 0;  // Thread-safe?  It is on at least Mac, Linux, and Windows.
  char* endptr = NULL;
  *output = dmg_fp::strtod(input.c_str(), &endptr);

  // Cases to return false:
  //  - If errno is ERANGE, there was an overflow or underflow.
  //  - If the input string is empty, there was nothing to parse.
  //  - If endptr does not point to the end of the string, there are either
  //    characters remaining in the string after a parsed number, or the string
  //    does not begin with a parseable number.  endptr is compared to the
  //    expected end given the string's stated length to correctly catch cases
  //    where the string contains embedded NUL characters.
  //  - If the first character is a space, there was leading whitespace
  return errno == 0 &&
         !input.empty() &&
         input.c_str() + input.length() == endptr &&
         !isspace(input[0]);
}

// Note: if you need to add String16ToDouble, first ask yourself if it's
// really necessary. If it is, probably the best implementation here is to
// convert to 8-bit and then use the 8-bit version.

// Note: if you need to add an iterator range version of StringToDouble, first
// ask yourself if it's really necessary. If it is, probably the best
// implementation here is to instantiate a string and use the string version.

std::string HexEncode(const void* bytes, size_t size) {
  static const char kHexChars[] = "0123456789ABCDEF";

  // Each input byte creates two output hex characters.
  std::string ret(size * 2, '\0');

  for (size_t i = 0; i < size; ++i) {
    char b = reinterpret_cast<const char*>(bytes)[i];
    ret[(i * 2)] = kHexChars[(b >> 4) & 0xf];
    ret[(i * 2) + 1] = kHexChars[b & 0xf];
  }
  return ret;
}

bool HexStringToInt(const StringPiece& input, int* output) {
  return IteratorRangeToNumber<HexIteratorRangeToIntTraits>::Invoke(
    input.begin(), input.end(), output);
}

bool HexStringToBytes(const std::string& input, std::vector<uint8>* output) {
  return HexStringToBytesT(input, output);
}

}  // namespace base