base/strings/string_number_conversions.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/strings/string_number_conversions.h"
   6
   7 #include <ctype.h>
   8 #include <errno.h>
   9 #include <stdlib.h>
  10 #include <wctype.h>
  11
  12 #include <limits>
  13
  14 #include "base/logging.h"
  15 #include "base/scoped_clear_errno.h"
  16 #include "base/strings/utf_string_conversions.h"
  17 #include "base/third_party/dmg_fp/dmg_fp.h"
  18
  19 namespace base {
  20
  21 namespace {
  22
  23 template <typename STR, typename INT, typename UINT, bool NEG>
  24 struct IntToStringT {
  25   // This is to avoid a compiler warning about unary minus on unsigned type.
  26   // For example, say you had the following code:
  27   //   template <typename INT>
  28   //   INT abs(INT value) { return value < 0 ? -value : value; }
  29   // Even though if INT is unsigned, it's impossible for value < 0, so the
  30   // unary minus will never be taken, the compiler will still generate a
  31   // warning.  We do a little specialization dance...
  32   template <typename INT2, typename UINT2, bool NEG2>
  33   struct ToUnsignedT {};
  34
  35   template <typename INT2, typename UINT2>
  36   struct ToUnsignedT<INT2, UINT2, false> {
  37     static UINT2 ToUnsigned(INT2 value) {
  38       return static_cast<UINT2>(value);
  39     }
  40   };
  41
  42   template <typename INT2, typename UINT2>
  43   struct ToUnsignedT<INT2, UINT2, true> {
  44     static UINT2 ToUnsigned(INT2 value) {
  45       if (value >= 0) {
  46         return value;
  47       } else {
  48         // Avoid integer overflow when negating INT_MIN.
  49         return static_cast<UINT2>(-(value + 1)) + 1;
  50       }
  51     }
  52   };
  53
  54   // This set of templates is very similar to the above templates, but
  55   // for testing whether an integer is negative.
  56   template <typename INT2, bool NEG2>
  57   struct TestNegT {};
  58   template <typename INT2>
  59   struct TestNegT<INT2, false> {
  60     static bool TestNeg(INT2 value) {
  61       // value is unsigned, and can never be negative.
  62       return false;
  63     }
  64   };
  65   template <typename INT2>
  66   struct TestNegT<INT2, true> {
  67     static bool TestNeg(INT2 value) {
  68       return value < 0;
  69     }
  70   };
  71
  72   static STR IntToString(INT value) {
  73     // log10(2) ~= 0.3 bytes needed per bit or per byte log10(2**8) ~= 2.4.
  74     // So round up to allocate 3 output characters per byte, plus 1 for '-'.
  75     const int kOutputBufSize = 3 * sizeof(INT) + 1;
  76
  77     // Allocate the whole string right away, we will right back to front, and
  78     // then return the substr of what we ended up using.
  79     STR outbuf(kOutputBufSize, 0);
  80
  81     bool is_neg = TestNegT<INT, NEG>::TestNeg(value);
  82     // Even though is_neg will never be true when INT is parameterized as
  83     // unsigned, even the presence of the unary operation causes a warning.
  84     UINT res = ToUnsignedT<INT, UINT, NEG>::ToUnsigned(value);
  85
  86     typename STR::iterator it(outbuf.end());
  87     do {
  88       --it;
  89       DCHECK(it != outbuf.begin());
  90       *it = static_cast<typename STR::value_type>((res % 10) + '0');
  91       res /= 10;
  92     } while (res != 0);
  93     if (is_neg) {
  94       --it;
  95       DCHECK(it != outbuf.begin());
  96       *it = static_cast<typename STR::value_type>('-');
  97     }
  98     return STR(it, outbuf.end());
  99   }
 100 };
 101
 102 // Utility to convert a character to a digit in a given base
 103 template<typename CHAR, int BASE, bool BASE_LTE_10> class BaseCharToDigit {
 104 };
 105
 106 // Faster specialization for bases <= 10
 107 template<typename CHAR, int BASE> class BaseCharToDigit<CHAR, BASE, true> {
 108  public:
 109   static bool Convert(CHAR c, uint8* digit) {
 110     if (c >= '0' && c < '0' + BASE) {
 111       *digit = static_cast<uint8>(c - '0');
 112       return true;
 113     }
 114     return false;
 115   }
 116 };
 117
 118 // Specialization for bases where 10 < base <= 36
 119 template<typename CHAR, int BASE> class BaseCharToDigit<CHAR, BASE, false> {
 120  public:
 121   static bool Convert(CHAR c, uint8* digit) {
 122     if (c >= '0' && c <= '9') {
 123       *digit = c - '0';
 124     } else if (c >= 'a' && c < 'a' + BASE - 10) {
 125       *digit = c - 'a' + 10;
 126     } else if (c >= 'A' && c < 'A' + BASE - 10) {
 127       *digit = c - 'A' + 10;
 128     } else {
 129       return false;
 130     }
 131     return true;
 132   }
 133 };
 134
 135 template<int BASE, typename CHAR> bool CharToDigit(CHAR c, uint8* digit) {
 136   return BaseCharToDigit<CHAR, BASE, BASE <= 10>::Convert(c, digit);
 137 }
 138
 139 // There is an IsUnicodeWhitespace for wchars defined in string_util.h, but it
 140 // is locale independent, whereas the functions we are replacing were
 141 // locale-dependent. TBD what is desired, but for the moment let's not
 142 // introduce a change in behaviour.
 143 template<typename CHAR> class WhitespaceHelper {
 144 };
 145
 146 template<> class WhitespaceHelper<char> {
 147  public:
 148   static bool Invoke(char c) {
 149     return 0 != isspace(static_cast<unsigned char>(c));
 150   }
 151 };
 152
 153 template<> class WhitespaceHelper<char16> {
 154  public:
 155   static bool Invoke(char16 c) {
 156     return 0 != iswspace(c);
 157   }
 158 };
 159
 160 template<typename CHAR> bool LocalIsWhitespace(CHAR c) {
 161   return WhitespaceHelper<CHAR>::Invoke(c);
 162 }
 163
 164 // IteratorRangeToNumberTraits should provide:
 165 //  - a typedef for iterator_type, the iterator type used as input.
 166 //  - a typedef for value_type, the target numeric type.
 167 //  - static functions min, max (returning the minimum and maximum permitted
 168 //    values)
 169 //  - constant kBase, the base in which to interpret the input
 170 template<typename IteratorRangeToNumberTraits>
 171 class IteratorRangeToNumber {
 172  public:
 173   typedef IteratorRangeToNumberTraits traits;
 174   typedef typename traits::iterator_type const_iterator;
 175   typedef typename traits::value_type value_type;
 176
 177   // Generalized iterator-range-to-number conversion.
 178   //
 179   static bool Invoke(const_iterator begin,
 180                      const_iterator end,
 181                      value_type* output) {
 182     bool valid = true;
 183
 184     while (begin != end && LocalIsWhitespace(*begin)) {
 185       valid = false;
 186       ++begin;
 187     }
 188
 189     if (begin != end && *begin == '-') {
 190       if (!std::numeric_limits<value_type>::is_signed) {
 191         valid = false;
 192       } else if (!Negative::Invoke(begin + 1, end, output)) {
 193         valid = false;
 194       }
 195     } else {
 196       if (begin != end && *begin == '+') {
 197         ++begin;
 198       }
 199       if (!Positive::Invoke(begin, end, output)) {
 200         valid = false;
 201       }
 202     }
 203
 204     return valid;
 205   }
 206
 207  private:
 208   // Sign provides:
 209   //  - a static function, CheckBounds, that determines whether the next digit
 210   //    causes an overflow/underflow
 211   //  - a static function, Increment, that appends the next digit appropriately
 212   //    according to the sign of the number being parsed.
 213   template<typename Sign>
 214   class Base {
 215    public:
 216     static bool Invoke(const_iterator begin, const_iterator end,
 217                        typename traits::value_type* output) {
 218       *output = 0;
 219
 220       if (begin == end) {
 221         return false;
 222       }
 223
 224       // Note: no performance difference was found when using template
 225       // specialization to remove this check in bases other than 16
 226       if (traits::kBase == 16 && end - begin > 2 && *begin == '0' &&
 227           (*(begin + 1) == 'x' || *(begin + 1) == 'X')) {
 228         begin += 2;
 229       }
 230
 231       for (const_iterator current = begin; current != end; ++current) {
 232         uint8 new_digit = 0;
 233
 234         if (!CharToDigit<traits::kBase>(*current, &new_digit)) {
 235           return false;
 236         }
 237
 238         if (current != begin) {
 239           if (!Sign::CheckBounds(output, new_digit)) {
 240             return false;
 241           }
 242           *output *= traits::kBase;
 243         }
 244
 245         Sign::Increment(new_digit, output);
 246       }
 247       return true;
 248     }
 249   };
 250
 251   class Positive : public Base<Positive> {
 252    public:
 253     static bool CheckBounds(value_type* output, uint8 new_digit) {
 254       if (*output > static_cast<value_type>(traits::max() / traits::kBase) ||
 255           (*output == static_cast<value_type>(traits::max() / traits::kBase) &&
 256            new_digit > traits::max() % traits::kBase)) {
 257         *output = traits::max();
 258         return false;
 259       }
 260       return true;
 261     }
 262     static void Increment(uint8 increment, value_type* output) {
 263       *output += increment;
 264     }
 265   };
 266
 267   class Negative : public Base<Negative> {
 268    public:
 269     static bool CheckBounds(value_type* output, uint8 new_digit) {
 270       if (*output < traits::min() / traits::kBase ||
 271           (*output == traits::min() / traits::kBase &&
 272            new_digit > 0 - traits::min() % traits::kBase)) {
 273         *output = traits::min();
 274         return false;
 275       }
 276       return true;
 277     }
 278     static void Increment(uint8 increment, value_type* output) {
 279       *output -= increment;
 280     }
 281   };
 282 };
 283
 284 template<typename ITERATOR, typename VALUE, int BASE>
 285 class BaseIteratorRangeToNumberTraits {
 286  public:
 287   typedef ITERATOR iterator_type;
 288   typedef VALUE value_type;
 289   static value_type min() {
 290     return std::numeric_limits<value_type>::min();
 291   }
 292   static value_type max() {
 293     return std::numeric_limits<value_type>::max();
 294   }
 295   static const int kBase = BASE;
 296 };
 297
 298 template<typename ITERATOR>
 299 class BaseHexIteratorRangeToIntTraits
 300     : public BaseIteratorRangeToNumberTraits<ITERATOR, int, 16> {
 301 };
 302
 303 template<typename ITERATOR>
 304 class BaseHexIteratorRangeToUIntTraits
 305     : public BaseIteratorRangeToNumberTraits<ITERATOR, uint32, 16> {
 306 };
 307
 308 template<typename ITERATOR>
 309 class BaseHexIteratorRangeToInt64Traits
 310     : public BaseIteratorRangeToNumberTraits<ITERATOR, int64, 16> {
 311 };
 312
 313 template<typename ITERATOR>
 314 class BaseHexIteratorRangeToUInt64Traits
 315     : public BaseIteratorRangeToNumberTraits<ITERATOR, uint64, 16> {
 316 };
 317
 318 typedef BaseHexIteratorRangeToIntTraits<StringPiece::const_iterator>
 319     HexIteratorRangeToIntTraits;
 320
 321 typedef BaseHexIteratorRangeToUIntTraits<StringPiece::const_iterator>
 322     HexIteratorRangeToUIntTraits;
 323
 324 typedef BaseHexIteratorRangeToInt64Traits<StringPiece::const_iterator>
 325     HexIteratorRangeToInt64Traits;
 326
 327 typedef BaseHexIteratorRangeToUInt64Traits<StringPiece::const_iterator>
 328     HexIteratorRangeToUInt64Traits;
 329
 330 template<typename STR>
 331 bool HexStringToBytesT(const STR& input, std::vector<uint8>* output) {
 332   DCHECK_EQ(output->size(), 0u);
 333   size_t count = input.size();
 334   if (count == 0 || (count % 2) != 0)
 335     return false;
 336   for (uintptr_t i = 0; i < count / 2; ++i) {
 337     uint8 msb = 0;  // most significant 4 bits
 338     uint8 lsb = 0;  // least significant 4 bits
 339     if (!CharToDigit<16>(input[i * 2], &msb) ||
 340         !CharToDigit<16>(input[i * 2 + 1], &lsb))
 341       return false;
 342     output->push_back((msb << 4) | lsb);
 343   }
 344   return true;
 345 }
 346
 347 template <typename VALUE, int BASE>
 348 class StringPieceToNumberTraits
 349     : public BaseIteratorRangeToNumberTraits<StringPiece::const_iterator,
 350                                              VALUE,
 351                                              BASE> {
 352 };
 353
 354 template <typename VALUE>
 355 bool StringToIntImpl(const StringPiece& input, VALUE* output) {
 356   return IteratorRangeToNumber<StringPieceToNumberTraits<VALUE, 10> >::Invoke(
 357       input.begin(), input.end(), output);
 358 }
 359
 360 template <typename VALUE, int BASE>
 361 class StringPiece16ToNumberTraits
 362     : public BaseIteratorRangeToNumberTraits<StringPiece16::const_iterator,
 363                                              VALUE,
 364                                              BASE> {
 365 };
 366
 367 template <typename VALUE>
 368 bool String16ToIntImpl(const StringPiece16& input, VALUE* output) {
 369   return IteratorRangeToNumber<StringPiece16ToNumberTraits<VALUE, 10> >::Invoke(
 370       input.begin(), input.end(), output);
 371 }
 372
 373 }  // namespace
 374
 375 std::string IntToString(int value) {
 376   return IntToStringT<std::string, int, unsigned int, true>::
 377       IntToString(value);
 378 }
 379
 380 string16 IntToString16(int value) {
 381   return IntToStringT<string16, int, unsigned int, true>::
 382       IntToString(value);
 383 }
 384
 385 std::string UintToString(unsigned int value) {
 386   return IntToStringT<std::string, unsigned int, unsigned int, false>::
 387       IntToString(value);
 388 }
 389
 390 string16 UintToString16(unsigned int value) {
 391   return IntToStringT<string16, unsigned int, unsigned int, false>::
 392       IntToString(value);
 393 }
 394
 395 std::string Int64ToString(int64 value) {
 396   return IntToStringT<std::string, int64, uint64, true>::IntToString(value);
 397 }
 398
 399 string16 Int64ToString16(int64 value) {
 400   return IntToStringT<string16, int64, uint64, true>::IntToString(value);
 401 }
 402
 403 std::string Uint64ToString(uint64 value) {
 404   return IntToStringT<std::string, uint64, uint64, false>::IntToString(value);
 405 }
 406
 407 string16 Uint64ToString16(uint64 value) {
 408   return IntToStringT<string16, uint64, uint64, false>::IntToString(value);
 409 }
 410
 411 std::string SizeTToString(size_t value) {
 412   return IntToStringT<std::string, size_t, size_t, false>::IntToString(value);
 413 }
 414
 415 string16 SizeTToString16(size_t value) {
 416   return IntToStringT<string16, size_t, size_t, false>::IntToString(value);
 417 }
 418
 419 std::string DoubleToString(double value) {
 420   // According to g_fmt.cc, it is sufficient to declare a buffer of size 32.
 421   char buffer[32];
 422   dmg_fp::g_fmt(buffer, value);
 423   return std::string(buffer);
 424 }
 425
 426 bool StringToInt(const StringPiece& input, int* output) {
 427   return StringToIntImpl(input, output);
 428 }
 429
 430 bool StringToInt(const StringPiece16& input, int* output) {
 431   return String16ToIntImpl(input, output);
 432 }
 433
 434 bool StringToUint(const StringPiece& input, unsigned* output) {
 435   return StringToIntImpl(input, output);
 436 }
 437
 438 bool StringToUint(const StringPiece16& input, unsigned* output) {
 439   return String16ToIntImpl(input, output);
 440 }
 441
 442 bool StringToInt64(const StringPiece& input, int64* output) {
 443   return StringToIntImpl(input, output);
 444 }
 445
 446 bool StringToInt64(const StringPiece16& input, int64* output) {
 447   return String16ToIntImpl(input, output);
 448 }
 449
 450 bool StringToUint64(const StringPiece& input, uint64* output) {
 451   return StringToIntImpl(input, output);
 452 }
 453
 454 bool StringToUint64(const StringPiece16& input, uint64* output) {
 455   return String16ToIntImpl(input, output);
 456 }
 457
 458 bool StringToSizeT(const StringPiece& input, size_t* output) {
 459   return StringToIntImpl(input, output);
 460 }
 461
 462 bool StringToSizeT(const StringPiece16& input, size_t* output) {
 463   return String16ToIntImpl(input, output);
 464 }
 465
 466 bool StringToDouble(const std::string& input, double* output) {
 467   // Thread-safe?  It is on at least Mac, Linux, and Windows.
 468   ScopedClearErrno clear_errno;
 469
 470   char* endptr = NULL;
 471   *output = dmg_fp::strtod(input.c_str(), &endptr);
 472
 473   // Cases to return false:
 474   //  - If errno is ERANGE, there was an overflow or underflow.
 475   //  - If the input string is empty, there was nothing to parse.
 476   //  - If endptr does not point to the end of the string, there are either
 477   //    characters remaining in the string after a parsed number, or the string
 478   //    does not begin with a parseable number.  endptr is compared to the
 479   //    expected end given the string's stated length to correctly catch cases
 480   //    where the string contains embedded NUL characters.
 481   //  - If the first character is a space, there was leading whitespace
 482   return errno == 0 &&
 483          !input.empty() &&
 484          input.c_str() + input.length() == endptr &&
 485          !isspace(input[0]);
 486 }
 487
 488 // Note: if you need to add String16ToDouble, first ask yourself if it's
 489 // really necessary. If it is, probably the best implementation here is to
 490 // convert to 8-bit and then use the 8-bit version.
 491
 492 // Note: if you need to add an iterator range version of StringToDouble, first
 493 // ask yourself if it's really necessary. If it is, probably the best
 494 // implementation here is to instantiate a string and use the string version.
 495
 496 std::string HexEncode(const void* bytes, size_t size) {
 497   static const char kHexChars[] = "0123456789ABCDEF";
 498
 499   // Each input byte creates two output hex characters.
 500   std::string ret(size * 2, '\0');
 501
 502   for (size_t i = 0; i < size; ++i) {
 503     char b = reinterpret_cast<const char*>(bytes)[i];
 504     ret[(i * 2)] = kHexChars[(b >> 4) & 0xf];
 505     ret[(i * 2) + 1] = kHexChars[b & 0xf];
 506   }
 507   return ret;
 508 }
 509
 510 bool HexStringToInt(const StringPiece& input, int* output) {
 511   return IteratorRangeToNumber<HexIteratorRangeToIntTraits>::Invoke(
 512     input.begin(), input.end(), output);
 513 }
 514
 515 bool HexStringToUInt(const StringPiece& input, uint32* output) {
 516   return IteratorRangeToNumber<HexIteratorRangeToUIntTraits>::Invoke(
 517       input.begin(), input.end(), output);
 518 }
 519
 520 bool HexStringToInt64(const StringPiece& input, int64* output) {
 521   return IteratorRangeToNumber<HexIteratorRangeToInt64Traits>::Invoke(
 522     input.begin(), input.end(), output);
 523 }
 524
 525 bool HexStringToUInt64(const StringPiece& input, uint64* output) {
 526   return IteratorRangeToNumber<HexIteratorRangeToUInt64Traits>::Invoke(
 527       input.begin(), input.end(), output);
 528 }
 529
 530 bool HexStringToBytes(const std::string& input, std::vector<uint8>* output) {
 531   return HexStringToBytesT(input, output);
 532 }
 533
 534 }  // namespace base