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