root/base/strings/string_number_conversions.cc

DEFINITIONS

1. Convert
2. Convert
3. CharToDigit
4. Invoke
5. Invoke
6. LocalIsWhitespace
7. Invoke
8. Invoke
9. CheckBounds
10. Increment
11. CheckBounds
12. Increment
13. min
14. max
15. HexStringToBytesT
16. StringToIntImpl
17. String16ToIntImpl
18. IntToString
19. IntToString16
20. UintToString
21. UintToString16
22. Int64ToString
23. Int64ToString16
24. Uint64ToString
25. Uint64ToString16
26. DoubleToString
27. StringToInt
28. StringToInt
29. StringToUint
30. StringToUint
31. StringToInt64
32. StringToInt64
33. StringToUint64
34. StringToUint64
35. StringToSizeT
36. StringToSizeT
37. StringToDouble
38. HexEncode
39. HexStringToInt
40. HexStringToUInt
41. HexStringToInt64
42. HexStringToUInt64
43. HexStringToBytes

// 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/strings/string_number_conversions.h"

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

#include <limits>

#include "base/logging.h"
#include "base/scoped_clear_errno.h"
#include "base/strings/utf_string_conversions.h"
#include "base/third_party/dmg_fp/dmg_fp.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);

    typename STR::iterator it(outbuf.end());
    do {
      --it;
      DCHECK(it != outbuf.begin());
      *it = static_cast<typename STR::value_type>((res % 10) + '0');
      res /= 10;
    } while (res != 0);
    if (is_neg) {
      --it;
      DCHECK(it != outbuf.begin());
      *it = static_cast<typename STR::value_type>('-');
    }
    return STR(it, outbuf.end());
  }
};

// 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 (!std::numeric_limits<value_type>::is_signed) {
        valid = false;
      } else 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> {
};

template<typename ITERATOR>
class BaseHexIteratorRangeToUIntTraits
    : public BaseIteratorRangeToNumberTraits<ITERATOR, uint32, 16> {
};

template<typename ITERATOR>
class BaseHexIteratorRangeToInt64Traits
    : public BaseIteratorRangeToNumberTraits<ITERATOR, int64, 16> {
};

template<typename ITERATOR>
class BaseHexIteratorRangeToUInt64Traits
    : public BaseIteratorRangeToNumberTraits<ITERATOR, uint64, 16> {
};

typedef BaseHexIteratorRangeToIntTraits<StringPiece::const_iterator>
    HexIteratorRangeToIntTraits;

typedef BaseHexIteratorRangeToUIntTraits<StringPiece::const_iterator>
    HexIteratorRangeToUIntTraits;

typedef BaseHexIteratorRangeToInt64Traits<StringPiece::const_iterator>
    HexIteratorRangeToInt64Traits;

typedef BaseHexIteratorRangeToUInt64Traits<StringPiece::const_iterator>
    HexIteratorRangeToUInt64Traits;

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) {
  // Thread-safe?  It is on at least Mac, Linux, and Windows.
  ScopedClearErrno clear_errno;

  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 HexStringToUInt(const StringPiece& input, uint32* output) {
  return IteratorRangeToNumber<HexIteratorRangeToUIntTraits>::Invoke(
      input.begin(), input.end(), output);
}

bool HexStringToInt64(const StringPiece& input, int64* output) {
  return IteratorRangeToNumber<HexIteratorRangeToInt64Traits>::Invoke(
    input.begin(), input.end(), output);
}

bool HexStringToUInt64(const StringPiece& input, uint64* output) {
  return IteratorRangeToNumber<HexIteratorRangeToUInt64Traits>::Invoke(
      input.begin(), input.end(), output);
}

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

}  // namespace base