path: root/contrib/libs/double-conversion/double-conversion.h

// Copyright 2012 the V8 project authors. All rights reserved. 
// Redistribution and use in source and binary forms, with or without 
// modification, are permitted provided that the following conditions are 
// met: 
// 
//     * Redistributions of source code must retain the above copyright 
//       notice, this list of conditions and the following disclaimer. 
//     * Redistributions in binary form must reproduce the above 
//       copyright notice, this list of conditions and the following 
//       disclaimer in the documentation and/or other materials provided 
//       with the distribution. 
//     * Neither the name of Google Inc. nor the names of its 
//       contributors may be used to endorse or promote products derived 
//       from this software without specific prior written permission. 
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 
#ifndef DOUBLE_CONVERSION_DOUBLE_CONVERSION_H_ 
#define DOUBLE_CONVERSION_DOUBLE_CONVERSION_H_ 
 
#include "utils.h" 
 
namespace double_conversion { 
 
class DoubleToStringConverter { 
 public: 
  // When calling ToFixed with a double > 10^kMaxFixedDigitsBeforePoint 
  // or a requested_digits parameter > kMaxFixedDigitsAfterPoint then the 
  // function returns false. 
  static const int kMaxFixedDigitsBeforePoint = 60; 
  static const int kMaxFixedDigitsAfterPoint = 60; 
 
  // When calling ToExponential with a requested_digits 
  // parameter > kMaxExponentialDigits then the function returns false. 
  static const int kMaxExponentialDigits = 120; 
 
  // When calling ToPrecision with a requested_digits 
  // parameter < kMinPrecisionDigits or requested_digits > kMaxPrecisionDigits 
  // then the function returns false. 
  static const int kMinPrecisionDigits = 1; 
  static const int kMaxPrecisionDigits = 120; 
 
  enum Flags { 
    NO_FLAGS = 0, 
    EMIT_POSITIVE_EXPONENT_SIGN = 1, 
    EMIT_TRAILING_DECIMAL_POINT = 2, 
    EMIT_TRAILING_ZERO_AFTER_POINT = 4, 
    UNIQUE_ZERO = 8 
  }; 
 
  // Flags should be a bit-or combination of the possible Flags-enum. 
  //  - NO_FLAGS: no special flags. 
  //  - EMIT_POSITIVE_EXPONENT_SIGN: when the number is converted into exponent 
  //    form, emits a '+' for positive exponents. Example: 1.2e+2. 
  //  - EMIT_TRAILING_DECIMAL_POINT: when the input number is an integer and is 
  //    converted into decimal format then a trailing decimal point is appended. 
  //    Example: 2345.0 is converted to "2345.". 
  //  - EMIT_TRAILING_ZERO_AFTER_POINT: in addition to a trailing decimal point 
  //    emits a trailing '0'-character. This flag requires the 
  //    EXMIT_TRAILING_DECIMAL_POINT flag. 
  //    Example: 2345.0 is converted to "2345.0". 
  //  - UNIQUE_ZERO: "-0.0" is converted to "0.0". 
  // 
  // Infinity symbol and nan_symbol provide the string representation for these 
  // special values. If the string is NULL and the special value is encountered 
  // then the conversion functions return false. 
  // 
  // The exponent_character is used in exponential representations. It is 
  // usually 'e' or 'E'. 
  // 
  // When converting to the shortest representation the converter will 
  // represent input numbers in decimal format if they are in the interval 
  // [10^decimal_in_shortest_low; 10^decimal_in_shortest_high[ 
  //    (lower boundary included, greater boundary excluded). 
  // Example: with decimal_in_shortest_low = -6 and 
  //               decimal_in_shortest_high = 21: 
  //   ToShortest(0.000001)  -> "0.000001" 
  //   ToShortest(0.0000001) -> "1e-7" 
  //   ToShortest(111111111111111111111.0)  -> "111111111111111110000" 
  //   ToShortest(100000000000000000000.0)  -> "100000000000000000000" 
  //   ToShortest(1111111111111111111111.0) -> "1.1111111111111111e+21" 
  // 
  // When converting to precision mode the converter may add 
  // max_leading_padding_zeroes before returning the number in exponential 
  // format. 
  // Example with max_leading_padding_zeroes_in_precision_mode = 6. 
  //   ToPrecision(0.0000012345, 2) -> "0.0000012" 
  //   ToPrecision(0.00000012345, 2) -> "1.2e-7" 
  // Similarily the converter may add up to 
  // max_trailing_padding_zeroes_in_precision_mode in precision mode to avoid 
  // returning an exponential representation. A zero added by the 
  // EMIT_TRAILING_ZERO_AFTER_POINT flag is counted for this limit. 
  // Examples for max_trailing_padding_zeroes_in_precision_mode = 1: 
  //   ToPrecision(230.0, 2) -> "230" 
  //   ToPrecision(230.0, 2) -> "230."  with EMIT_TRAILING_DECIMAL_POINT. 
  //   ToPrecision(230.0, 2) -> "2.3e2" with EMIT_TRAILING_ZERO_AFTER_POINT. 
  DoubleToStringConverter(int flags, 
                          const char* infinity_symbol, 
                          const char* nan_symbol, 
                          char exponent_character, 
                          int decimal_in_shortest_low, 
                          int decimal_in_shortest_high, 
                          int max_leading_padding_zeroes_in_precision_mode, 
                          int max_trailing_padding_zeroes_in_precision_mode) 
      : flags_(flags), 
        infinity_symbol_(infinity_symbol), 
        nan_symbol_(nan_symbol), 
        exponent_character_(exponent_character), 
        decimal_in_shortest_low_(decimal_in_shortest_low), 
        decimal_in_shortest_high_(decimal_in_shortest_high), 
        max_leading_padding_zeroes_in_precision_mode_( 
            max_leading_padding_zeroes_in_precision_mode), 
        max_trailing_padding_zeroes_in_precision_mode_( 
            max_trailing_padding_zeroes_in_precision_mode) { 
    // When 'trailing zero after the point' is set, then 'trailing point' 
    // must be set too. 
    ASSERT(((flags & EMIT_TRAILING_DECIMAL_POINT) != 0) || 
        !((flags & EMIT_TRAILING_ZERO_AFTER_POINT) != 0)); 
  } 
 
  // Returns a converter following the EcmaScript specification. 
  static const DoubleToStringConverter& EcmaScriptConverter(); 
 
  // Computes the shortest string of digits that correctly represent the input 
  // number. Depending on decimal_in_shortest_low and decimal_in_shortest_high 
  // (see constructor) it then either returns a decimal representation, or an 
  // exponential representation. 
  // Example with decimal_in_shortest_low = -6, 
  //              decimal_in_shortest_high = 21, 
  //              EMIT_POSITIVE_EXPONENT_SIGN activated, and 
  //              EMIT_TRAILING_DECIMAL_POINT deactived: 
  //   ToShortest(0.000001)  -> "0.000001" 
  //   ToShortest(0.0000001) -> "1e-7" 
  //   ToShortest(111111111111111111111.0)  -> "111111111111111110000" 
  //   ToShortest(100000000000000000000.0)  -> "100000000000000000000" 
  //   ToShortest(1111111111111111111111.0) -> "1.1111111111111111e+21" 
  // 
  // Note: the conversion may round the output if the returned string 
  // is accurate enough to uniquely identify the input-number. 
  // For example the most precise representation of the double 9e59 equals 
  // "899999999999999918767229449717619953810131273674690656206848", but 
  // the converter will return the shorter (but still correct) "9e59". 
  // 
  // Returns true if the conversion succeeds. The conversion always succeeds 
  // except when the input value is special and no infinity_symbol or 
  // nan_symbol has been given to the constructor. 
  bool ToShortest(double value, StringBuilder* result_builder) const { 
    return ToShortestIeeeNumber(value, result_builder, SHORTEST); 
  } 
 
  // Same as ToShortest, but for single-precision floats. 
  bool ToShortestSingle(float value, StringBuilder* result_builder) const { 
    return ToShortestIeeeNumber(value, result_builder, SHORTEST_SINGLE); 
  } 
 
 
  // Computes a decimal representation with a fixed number of digits after the 
  // decimal point. The last emitted digit is rounded. 
  // 
  // Examples: 
  //   ToFixed(3.12, 1) -> "3.1" 
  //   ToFixed(3.1415, 3) -> "3.142" 
  //   ToFixed(1234.56789, 4) -> "1234.5679" 
  //   ToFixed(1.23, 5) -> "1.23000" 
  //   ToFixed(0.1, 4) -> "0.1000" 
  //   ToFixed(1e30, 2) -> "1000000000000000019884624838656.00" 
  //   ToFixed(0.1, 30) -> "0.100000000000000005551115123126" 
  //   ToFixed(0.1, 17) -> "0.10000000000000001" 
  // 
  // If requested_digits equals 0, then the tail of the result depends on 
  // the EMIT_TRAILING_DECIMAL_POINT and EMIT_TRAILING_ZERO_AFTER_POINT. 
  // Examples, for requested_digits == 0, 
  //   let EMIT_TRAILING_DECIMAL_POINT and EMIT_TRAILING_ZERO_AFTER_POINT be 
  //    - false and false: then 123.45 -> 123 
  //                             0.678 -> 1 
  //    - true and false: then 123.45 -> 123. 
  //                            0.678 -> 1. 
  //    - true and true: then 123.45 -> 123.0 
  //                           0.678 -> 1.0 
  // 
  // Returns true if the conversion succeeds. The conversion always succeeds 
  // except for the following cases: 
  //   - the input value is special and no infinity_symbol or nan_symbol has 
  //     been provided to the constructor, 
  //   - 'value' > 10^kMaxFixedDigitsBeforePoint, or 
  //   - 'requested_digits' > kMaxFixedDigitsAfterPoint. 
  // The last two conditions imply that the result will never contain more than 
  // 1 + kMaxFixedDigitsBeforePoint + 1 + kMaxFixedDigitsAfterPoint characters 
  // (one additional character for the sign, and one for the decimal point). 
  bool ToFixed(double value, 
               int requested_digits, 
               StringBuilder* result_builder) const; 
 
  // Computes a representation in exponential format with requested_digits 
  // after the decimal point. The last emitted digit is rounded. 
  // If requested_digits equals -1, then the shortest exponential representation 
  // is computed. 
  // 
  // Examples with EMIT_POSITIVE_EXPONENT_SIGN deactivated, and 
  //               exponent_character set to 'e'. 
  //   ToExponential(3.12, 1) -> "3.1e0" 
  //   ToExponential(5.0, 3) -> "5.000e0" 
  //   ToExponential(0.001, 2) -> "1.00e-3" 
  //   ToExponential(3.1415, -1) -> "3.1415e0" 
  //   ToExponential(3.1415, 4) -> "3.1415e0" 
  //   ToExponential(3.1415, 3) -> "3.142e0" 
  //   ToExponential(123456789000000, 3) -> "1.235e14" 
  //   ToExponential(1000000000000000019884624838656.0, -1) -> "1e30" 
  //   ToExponential(1000000000000000019884624838656.0, 32) -> 
  //                     "1.00000000000000001988462483865600e30" 
  //   ToExponential(1234, 0) -> "1e3" 
  // 
  // Returns true if the conversion succeeds. The conversion always succeeds 
  // except for the following cases: 
  //   - the input value is special and no infinity_symbol or nan_symbol has 
  //     been provided to the constructor, 
  //   - 'requested_digits' > kMaxExponentialDigits. 
  // The last condition implies that the result will never contain more than 
  // kMaxExponentialDigits + 8 characters (the sign, the digit before the 
  // decimal point, the decimal point, the exponent character, the 
  // exponent's sign, and at most 3 exponent digits). 
  bool ToExponential(double value, 
                     int requested_digits, 
                     StringBuilder* result_builder) const; 
 
  // Computes 'precision' leading digits of the given 'value' and returns them 
  // either in exponential or decimal format, depending on 
  // max_{leading|trailing}_padding_zeroes_in_precision_mode (given to the 
  // constructor). 
  // The last computed digit is rounded. 
  // 
  // Example with max_leading_padding_zeroes_in_precision_mode = 6. 
  //   ToPrecision(0.0000012345, 2) -> "0.0000012" 
  //   ToPrecision(0.00000012345, 2) -> "1.2e-7" 
  // Similarily the converter may add up to 
  // max_trailing_padding_zeroes_in_precision_mode in precision mode to avoid 
  // returning an exponential representation. A zero added by the 
  // EMIT_TRAILING_ZERO_AFTER_POINT flag is counted for this limit. 
  // Examples for max_trailing_padding_zeroes_in_precision_mode = 1: 
  //   ToPrecision(230.0, 2) -> "230" 
  //   ToPrecision(230.0, 2) -> "230."  with EMIT_TRAILING_DECIMAL_POINT. 
  //   ToPrecision(230.0, 2) -> "2.3e2" with EMIT_TRAILING_ZERO_AFTER_POINT. 
  // Examples for max_trailing_padding_zeroes_in_precision_mode = 3, and no 
  //    EMIT_TRAILING_ZERO_AFTER_POINT: 
  //   ToPrecision(123450.0, 6) -> "123450" 
  //   ToPrecision(123450.0, 5) -> "123450" 
  //   ToPrecision(123450.0, 4) -> "123500" 
  //   ToPrecision(123450.0, 3) -> "123000" 
  //   ToPrecision(123450.0, 2) -> "1.2e5" 
  // 
  // Returns true if the conversion succeeds. The conversion always succeeds 
  // except for the following cases: 
  //   - the input value is special and no infinity_symbol or nan_symbol has 
  //     been provided to the constructor, 
  //   - precision < kMinPericisionDigits 
  //   - precision > kMaxPrecisionDigits 
  // The last condition implies that the result will never contain more than 
  // kMaxPrecisionDigits + 7 characters (the sign, the decimal point, the 
  // exponent character, the exponent's sign, and at most 3 exponent digits). 
  bool ToPrecision(double value, 
                   int precision, 
                   StringBuilder* result_builder) const; 
 
  enum DtoaMode { 
    // Produce the shortest correct representation. 
    // For example the output of 0.299999999999999988897 is (the less accurate 
    // but correct) 0.3. 
    SHORTEST, 
    // Same as SHORTEST, but for single-precision floats. 
    SHORTEST_SINGLE, 
    // Produce a fixed number of digits after the decimal point. 
    // For instance fixed(0.1, 4) becomes 0.1000 
    // If the input number is big, the output will be big. 
    FIXED, 
    // Fixed number of digits (independent of the decimal point). 
    PRECISION 
  }; 
 
  // The maximal number of digits that are needed to emit a double in base 10. 
  // A higher precision can be achieved by using more digits, but the shortest 
  // accurate representation of any double will never use more digits than 
  // kBase10MaximalLength. 
  // Note that DoubleToAscii null-terminates its input. So the given buffer 
  // should be at least kBase10MaximalLength + 1 characters long. 
  static const int kBase10MaximalLength = 17; 
 
  // Converts the given double 'v' to digit characters. 'v' must not be NaN,
  // +Infinity, or -Infinity. In SHORTEST_SINGLE-mode this restriction also
  // applies to 'v' after it has been casted to a single-precision float. That
  // is, in this mode static_cast<float>(v) must not be NaN, +Infinity or
  // -Infinity.
  // 
  // The result should be interpreted as buffer * 10^(point-length). 
  // 
  // The digits are written to the buffer in the platform's charset, which is
  // often UTF-8 (with ASCII-range digits) but may be another charset, such
  // as EBCDIC.
  //
  // The output depends on the given mode: 
  //  - SHORTEST: produce the least amount of digits for which the internal 
  //   identity requirement is still satisfied. If the digits are printed 
  //   (together with the correct exponent) then reading this number will give 
  //   'v' again. The buffer will choose the representation that is closest to 
  //   'v'. If there are two at the same distance, than the one farther away 
  //   from 0 is chosen (halfway cases - ending with 5 - are rounded up). 
  //   In this mode the 'requested_digits' parameter is ignored. 
  //  - SHORTEST_SINGLE: same as SHORTEST but with single-precision. 
  //  - FIXED: produces digits necessary to print a given number with 
  //   'requested_digits' digits after the decimal point. The produced digits 
  //   might be too short in which case the caller has to fill the remainder 
  //   with '0's. 
  //   Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2. 
  //   Halfway cases are rounded towards +/-Infinity (away from 0). The call 
  //   toFixed(0.15, 2) thus returns buffer="2", point=0. 
  //   The returned buffer may contain digits that would be truncated from the 
  //   shortest representation of the input. 
  //  - PRECISION: produces 'requested_digits' where the first digit is not '0'. 
  //   Even though the length of produced digits usually equals 
  //   'requested_digits', the function is allowed to return fewer digits, in 
  //   which case the caller has to fill the missing digits with '0's. 
  //   Halfway cases are again rounded away from 0. 
  // DoubleToAscii expects the given buffer to be big enough to hold all 
  // digits and a terminating null-character. In SHORTEST-mode it expects a 
  // buffer of at least kBase10MaximalLength + 1. In all other modes the 
  // requested_digits parameter and the padding-zeroes limit the size of the 
  // output. Don't forget the decimal point, the exponent character and the 
  // terminating null-character when computing the maximal output size. 
  // The given length is only used in debug mode to ensure the buffer is big 
  // enough. 
  static void DoubleToAscii(double v, 
                            DtoaMode mode, 
                            int requested_digits, 
                            char* buffer, 
                            int buffer_length, 
                            bool* sign, 
                            int* length, 
                            int* point); 
 
 private: 
  // Implementation for ToShortest and ToShortestSingle. 
  bool ToShortestIeeeNumber(double value, 
                            StringBuilder* result_builder, 
                            DtoaMode mode) const; 
 
  // If the value is a special value (NaN or Infinity) constructs the 
  // corresponding string using the configured infinity/nan-symbol. 
  // If either of them is NULL or the value is not special then the 
  // function returns false. 
  bool HandleSpecialValues(double value, StringBuilder* result_builder) const; 
  // Constructs an exponential representation (i.e. 1.234e56). 
  // The given exponent assumes a decimal point after the first decimal digit. 
  void CreateExponentialRepresentation(const char* decimal_digits, 
                                       int length, 
                                       int exponent, 
                                       StringBuilder* result_builder) const; 
  // Creates a decimal representation (i.e 1234.5678). 
  void CreateDecimalRepresentation(const char* decimal_digits, 
                                   int length, 
                                   int decimal_point, 
                                   int digits_after_point, 
                                   StringBuilder* result_builder) const; 
 
  const int flags_; 
  const char* const infinity_symbol_; 
  const char* const nan_symbol_; 
  const char exponent_character_; 
  const int decimal_in_shortest_low_; 
  const int decimal_in_shortest_high_; 
  const int max_leading_padding_zeroes_in_precision_mode_; 
  const int max_trailing_padding_zeroes_in_precision_mode_; 
 
  DC_DISALLOW_IMPLICIT_CONSTRUCTORS(DoubleToStringConverter);
}; 
 
 
class StringToDoubleConverter { 
 public: 
  // Enumeration for allowing octals and ignoring junk when converting 
  // strings to numbers. 
  enum Flags { 
    NO_FLAGS = 0, 
    ALLOW_HEX = 1, 
    ALLOW_OCTALS = 2, 
    ALLOW_TRAILING_JUNK = 4, 
    ALLOW_LEADING_SPACES = 8, 
    ALLOW_TRAILING_SPACES = 16, 
    ALLOW_SPACES_AFTER_SIGN = 32,
    ALLOW_CASE_INSENSIBILITY = 64,
    ALLOW_HEX_FLOATS = 128,
  }; 
 
  static const uc16 kNoSeparator = '\0';

  // Flags should be a bit-or combination of the possible Flags-enum. 
  //  - NO_FLAGS: no special flags. 
  //  - ALLOW_HEX: recognizes the prefix "0x". Hex numbers may only be integers. 
  //      Ex: StringToDouble("0x1234") -> 4660.0 
  //          In StringToDouble("0x1234.56") the characters ".56" are trailing 
  //          junk. The result of the call is hence dependent on 
  //          the ALLOW_TRAILING_JUNK flag and/or the junk value. 
  //      With this flag "0x" is a junk-string. Even with ALLOW_TRAILING_JUNK, 
  //      the string will not be parsed as "0" followed by junk. 
  // 
  //  - ALLOW_OCTALS: recognizes the prefix "0" for octals: 
  //      If a sequence of octal digits starts with '0', then the number is 
  //      read as octal integer. Octal numbers may only be integers. 
  //      Ex: StringToDouble("01234") -> 668.0 
  //          StringToDouble("012349") -> 12349.0  // Not a sequence of octal 
  //                                               // digits. 
  //          In StringToDouble("01234.56") the characters ".56" are trailing 
  //          junk. The result of the call is hence dependent on 
  //          the ALLOW_TRAILING_JUNK flag and/or the junk value. 
  //          In StringToDouble("01234e56") the characters "e56" are trailing 
  //          junk, too. 
  //  - ALLOW_TRAILING_JUNK: ignore trailing characters that are not part of 
  //      a double literal. 
  //  - ALLOW_LEADING_SPACES: skip over leading whitespace, including spaces, 
  //                          new-lines, and tabs. 
  //  - ALLOW_TRAILING_SPACES: ignore trailing whitespace. 
  //  - ALLOW_SPACES_AFTER_SIGN: ignore whitespace after the sign. 
  //       Ex: StringToDouble("-   123.2") -> -123.2. 
  //           StringToDouble("+   123.2") -> 123.2 
  //  - ALLOW_CASE_INSENSIBILITY: ignore case of characters for special values:
  //      infinity and nan.
  //  - ALLOW_HEX_FLOATS: allows hexadecimal float literals.
  //      This *must* start with "0x" and separate the exponent with "p".
  //      Examples: 0x1.2p3 == 9.0
  //                0x10.1p0 == 16.0625
  //      ALLOW_HEX and ALLOW_HEX_FLOATS are indendent.
  // 
  // empty_string_value is returned when an empty string is given as input. 
  // If ALLOW_LEADING_SPACES or ALLOW_TRAILING_SPACES are set, then a string 
  // containing only spaces is converted to the 'empty_string_value', too. 
  // 
  // junk_string_value is returned when 
  //  a) ALLOW_TRAILING_JUNK is not set, and a junk character (a character not 
  //     part of a double-literal) is found. 
  //  b) ALLOW_TRAILING_JUNK is set, but the string does not start with a 
  //     double literal. 
  // 
  // infinity_symbol and nan_symbol are strings that are used to detect 
  // inputs that represent infinity and NaN. They can be null, in which case 
  // they are ignored. 
  // The conversion routine first reads any possible signs. Then it compares the 
  // following character of the input-string with the first character of 
  // the infinity, and nan-symbol. If either matches, the function assumes, that 
  // a match has been found, and expects the following input characters to match 
  // the remaining characters of the special-value symbol. 
  // This means that the following restrictions apply to special-value symbols: 
  //  - they must not start with signs ('+', or '-'), 
  //  - they must not have the same first character. 
  //  - they must not start with digits. 
  // 
  // If the separator character is not kNoSeparator, then that specific
  // character is ignored when in between two valid digits of the significant.
  // It is not allowed to appear in the exponent.
  // It is not allowed to lead or trail the number.
  // It is not allowed to appear twice next to each other.
  //
  // Examples: 
  //  flags = ALLOW_HEX | ALLOW_TRAILING_JUNK, 
  //  empty_string_value = 0.0, 
  //  junk_string_value = NaN, 
  //  infinity_symbol = "infinity", 
  //  nan_symbol = "nan": 
  //    StringToDouble("0x1234") -> 4660.0. 
  //    StringToDouble("0x1234K") -> 4660.0. 
  //    StringToDouble("") -> 0.0  // empty_string_value. 
  //    StringToDouble(" ") -> NaN  // junk_string_value. 
  //    StringToDouble(" 1") -> NaN  // junk_string_value. 
  //    StringToDouble("0x") -> NaN  // junk_string_value. 
  //    StringToDouble("-123.45") -> -123.45. 
  //    StringToDouble("--123.45") -> NaN  // junk_string_value. 
  //    StringToDouble("123e45") -> 123e45. 
  //    StringToDouble("123E45") -> 123e45. 
  //    StringToDouble("123e+45") -> 123e45. 
  //    StringToDouble("123E-45") -> 123e-45. 
  //    StringToDouble("123e") -> 123.0  // trailing junk ignored. 
  //    StringToDouble("123e-") -> 123.0  // trailing junk ignored. 
  //    StringToDouble("+NaN") -> NaN  // NaN string literal. 
  //    StringToDouble("-infinity") -> -inf.  // infinity literal. 
  //    StringToDouble("Infinity") -> NaN  // junk_string_value. 
  // 
  //  flags = ALLOW_OCTAL | ALLOW_LEADING_SPACES, 
  //  empty_string_value = 0.0, 
  //  junk_string_value = NaN, 
  //  infinity_symbol = NULL, 
  //  nan_symbol = NULL: 
  //    StringToDouble("0x1234") -> NaN  // junk_string_value. 
  //    StringToDouble("01234") -> 668.0. 
  //    StringToDouble("") -> 0.0  // empty_string_value. 
  //    StringToDouble(" ") -> 0.0  // empty_string_value. 
  //    StringToDouble(" 1") -> 1.0 
  //    StringToDouble("0x") -> NaN  // junk_string_value. 
  //    StringToDouble("0123e45") -> NaN  // junk_string_value. 
  //    StringToDouble("01239E45") -> 1239e45. 
  //    StringToDouble("-infinity") -> NaN  // junk_string_value. 
  //    StringToDouble("NaN") -> NaN  // junk_string_value. 
  //
  //  flags = NO_FLAGS,
  //  separator = ' ':
  //    StringToDouble("1 2 3 4") -> 1234.0
  //    StringToDouble("1  2") -> NaN // junk_string_value
  //    StringToDouble("1 000 000.0") -> 1000000.0
  //    StringToDouble("1.000 000") -> 1.0
  //    StringToDouble("1.0e1 000") -> NaN // junk_string_value
  StringToDoubleConverter(int flags, 
                          double empty_string_value, 
                          double junk_string_value, 
                          const char* infinity_symbol, 
                          const char* nan_symbol,
                          uc16 separator = kNoSeparator)
      : flags_(flags), 
        empty_string_value_(empty_string_value), 
        junk_string_value_(junk_string_value), 
        infinity_symbol_(infinity_symbol), 
        nan_symbol_(nan_symbol),
        separator_(separator) {
  } 
 
  // Performs the conversion. 
  // The output parameter 'processed_characters_count' is set to the number 
  // of characters that have been processed to read the number. 
  // Spaces than are processed with ALLOW_{LEADING|TRAILING}_SPACES are included 
  // in the 'processed_characters_count'. Trailing junk is never included. 
  double StringToDouble(const char* buffer, 
                        int length, 
                        int* processed_characters_count) const; 
 
  // Same as StringToDouble above but for 16 bit characters. 
  double StringToDouble(const uc16* buffer, 
                        int length, 
                        int* processed_characters_count) const; 
 
  // Same as StringToDouble but reads a float. 
  // Note that this is not equivalent to static_cast<float>(StringToDouble(...)) 
  // due to potential double-rounding. 
  float StringToFloat(const char* buffer, 
                      int length, 
                      int* processed_characters_count) const; 
 
  // Same as StringToFloat above but for 16 bit characters. 
  float StringToFloat(const uc16* buffer, 
                      int length, 
                      int* processed_characters_count) const; 
 
 private: 
  const int flags_; 
  const double empty_string_value_; 
  const double junk_string_value_; 
  const char* const infinity_symbol_; 
  const char* const nan_symbol_; 
  const uc16 separator_;
 
  template <class Iterator> 
  double StringToIeee(Iterator start_pointer, 
                      int length, 
                      bool read_as_double, 
                      int* processed_characters_count) const; 
 
  DC_DISALLOW_IMPLICIT_CONSTRUCTORS(StringToDoubleConverter);
}; 
 
}  // namespace double_conversion 
 
#endif  // DOUBLE_CONVERSION_DOUBLE_CONVERSION_H_