1 // Copyright 2011 the V8 project 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 #ifndef V8_FAST_DTOA_H_ 6 #define V8_FAST_DTOA_H_ 7 8 #include "src/vector.h" 9 10 namespace v8 { 11 namespace internal { 12 13 enum FastDtoaMode { 14 // Computes the shortest representation of the given input. The returned 15 // result will be the most accurate number of this length. Longer 16 // representations might be more accurate. 17 FAST_DTOA_SHORTEST, 18 // Computes a representation where the precision (number of digits) is 19 // given as input. The precision is independent of the decimal point. 20 FAST_DTOA_PRECISION 21 }; 22 23 // FastDtoa will produce at most kFastDtoaMaximalLength digits. This does not 24 // include the terminating '\0' character. 25 const int kFastDtoaMaximalLength = 17; 26 27 // Provides a decimal representation of v. 28 // The result should be interpreted as buffer * 10^(point - length). 29 // 30 // Precondition: 31 // * v must be a strictly positive finite double. 32 // 33 // Returns true if it succeeds, otherwise the result can not be trusted. 34 // There will be *length digits inside the buffer followed by a null terminator. 35 // If the function returns true and mode equals 36 // - FAST_DTOA_SHORTEST, then 37 // the parameter requested_digits is ignored. 38 // The result satisfies 39 // v == (double) (buffer * 10^(point - length)). 40 // The digits in the buffer are the shortest representation possible. E.g. 41 // if 0.099999999999 and 0.1 represent the same double then "1" is returned 42 // with point = 0. 43 // The last digit will be closest to the actual v. That is, even if several 44 // digits might correctly yield 'v' when read again, the buffer will contain 45 // the one closest to v. 46 // - FAST_DTOA_PRECISION, then 47 // the buffer contains requested_digits digits. 48 // the difference v - (buffer * 10^(point-length)) is closest to zero for 49 // all possible representations of requested_digits digits. 50 // If there are two values that are equally close, then FastDtoa returns 51 // false. 52 // For both modes the buffer must be large enough to hold the result. 53 bool FastDtoa(double d, 54 FastDtoaMode mode, 55 int requested_digits, 56 Vector<char> buffer, 57 int* length, 58 int* decimal_point); 59 60 } // namespace internal 61 } // namespace v8 62 63 #endif // V8_FAST_DTOA_H_ 64
