base/strings/string_number_conversions.cc - mirrors/engine - Git at Google

 // 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) {
       if (value >= 0) {
         return value;
       } else {
         // Avoid integer overflow when negating INT_MIN.
         return static_cast<UINT2>(-(value + 1)) + 1;
       }
     }
   };

   // 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 = static_cast<uint8>(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 IsUnicodeWhitespace 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 SizeTToString(size_t value) {
   return IntToStringT<std::string, size_t, size_t, false>::IntToString(value);
 }

 string16 SizeTToString16(size_t value) {
   return IntToStringT<string16, size_t, size_t, 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
	// 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) {
	if (value >= 0) {
	return value;
	} else {
	// Avoid integer overflow when negating INT_MIN.
	return static_cast<UINT2>(-(value + 1)) + 1;
	}
	}
	};

	// 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 = static_cast<uint8>(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 IsUnicodeWhitespace 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 SizeTToString(size_t value) {
	return IntToStringT<std::string, size_t, size_t, false>::IntToString(value);
	}

	string16 SizeTToString16(size_t value) {
	return IntToStringT<string16, size_t, size_t, 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