| // Copyright 2011 the V8 project authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef V8_FAST_DTOA_H_ |
| #define V8_FAST_DTOA_H_ |
| |
| #include "src/vector.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| enum FastDtoaMode { |
| // Computes the shortest representation of the given input. The returned |
| // result will be the most accurate number of this length. Longer |
| // representations might be more accurate. |
| FAST_DTOA_SHORTEST, |
| // Computes a representation where the precision (number of digits) is |
| // given as input. The precision is independent of the decimal point. |
| FAST_DTOA_PRECISION |
| }; |
| |
| // FastDtoa will produce at most kFastDtoaMaximalLength digits. This does not |
| // include the terminating '\0' character. |
| const int kFastDtoaMaximalLength = 17; |
| |
| // Provides a decimal representation of v. |
| // The result should be interpreted as buffer * 10^(point - length). |
| // |
| // Precondition: |
| // * v must be a strictly positive finite double. |
| // |
| // Returns true if it succeeds, otherwise the result can not be trusted. |
| // There will be *length digits inside the buffer followed by a null terminator. |
| // If the function returns true and mode equals |
| // - FAST_DTOA_SHORTEST, then |
| // the parameter requested_digits is ignored. |
| // The result satisfies |
| // v == (double) (buffer * 10^(point - length)). |
| // The digits in the buffer are the shortest representation possible. E.g. |
| // if 0.099999999999 and 0.1 represent the same double then "1" is returned |
| // with point = 0. |
| // The last digit will be closest to the actual v. That is, even if several |
| // digits might correctly yield 'v' when read again, the buffer will contain |
| // the one closest to v. |
| // - FAST_DTOA_PRECISION, then |
| // the buffer contains requested_digits digits. |
| // the difference v - (buffer * 10^(point-length)) is closest to zero for |
| // all possible representations of requested_digits digits. |
| // If there are two values that are equally close, then FastDtoa returns |
| // false. |
| // For both modes the buffer must be large enough to hold the result. |
| bool FastDtoa(double d, |
| FastDtoaMode mode, |
| int requested_digits, |
| Vector<char> buffer, |
| int* length, |
| int* decimal_point); |
| |
| } // namespace internal |
| } // namespace v8 |
| |
| #endif // V8_FAST_DTOA_H_ |