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comparison: mfbt/double-conversion/fast-dtoa.h
mfbt/double-conversion/fast-dtoa.h
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| 1 // Copyright 2010 the V8 project authors. All rights reserved. | |
| 2 // Redistribution and use in source and binary forms, with or without | |
| 3 // modification, are permitted provided that the following conditions are | |
| 4 // met: | |
| 5 // | |
| 6 // * Redistributions of source code must retain the above copyright | |
| 7 // notice, this list of conditions and the following disclaimer. | |
| 8 // * Redistributions in binary form must reproduce the above | |
| 9 // copyright notice, this list of conditions and the following | |
| 10 // disclaimer in the documentation and/or other materials provided | |
| 11 // with the distribution. | |
| 12 // * Neither the name of Google Inc. nor the names of its | |
| 13 // contributors may be used to endorse or promote products derived | |
| 14 // from this software without specific prior written permission. | |
| 15 // | |
| 16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
| 17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
| 18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | |
| 19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | |
| 20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
| 21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | |
| 22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
| 23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
| 24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
| 25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |
| 26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| 27 | |
| 28 #ifndef DOUBLE_CONVERSION_FAST_DTOA_H_ | |
| 29 #define DOUBLE_CONVERSION_FAST_DTOA_H_ | |
| 30 | |
| 31 #include "utils.h" | |
| 32 | |
| 33 namespace double_conversion { | |
| 34 | |
| 35 enum FastDtoaMode { | |
| 36 // Computes the shortest representation of the given input. The returned | |
| 37 // result will be the most accurate number of this length. Longer | |
| 38 // representations might be more accurate. | |
| 39 FAST_DTOA_SHORTEST, | |
| 40 // Same as FAST_DTOA_SHORTEST but for single-precision floats. | |
| 41 FAST_DTOA_SHORTEST_SINGLE, | |
| 42 // Computes a representation where the precision (number of digits) is | |
| 43 // given as input. The precision is independent of the decimal point. | |
| 44 FAST_DTOA_PRECISION | |
| 45 }; | |
| 46 | |
| 47 // FastDtoa will produce at most kFastDtoaMaximalLength digits. This does not | |
| 48 // include the terminating '\0' character. | |
| 49 static const int kFastDtoaMaximalLength = 17; | |
| 50 // Same for single-precision numbers. | |
| 51 static const int kFastDtoaMaximalSingleLength = 9; | |
| 52 | |
| 53 // Provides a decimal representation of v. | |
| 54 // The result should be interpreted as buffer * 10^(point - length). | |
| 55 // | |
| 56 // Precondition: | |
| 57 // * v must be a strictly positive finite double. | |
| 58 // | |
| 59 // Returns true if it succeeds, otherwise the result can not be trusted. | |
| 60 // There will be *length digits inside the buffer followed by a null terminator. | |
| 61 // If the function returns true and mode equals | |
| 62 // - FAST_DTOA_SHORTEST, then | |
| 63 // the parameter requested_digits is ignored. | |
| 64 // The result satisfies | |
| 65 // v == (double) (buffer * 10^(point - length)). | |
| 66 // The digits in the buffer are the shortest representation possible. E.g. | |
| 67 // if 0.099999999999 and 0.1 represent the same double then "1" is returned | |
| 68 // with point = 0. | |
| 69 // The last digit will be closest to the actual v. That is, even if several | |
| 70 // digits might correctly yield 'v' when read again, the buffer will contain | |
| 71 // the one closest to v. | |
| 72 // - FAST_DTOA_PRECISION, then | |
| 73 // the buffer contains requested_digits digits. | |
| 74 // the difference v - (buffer * 10^(point-length)) is closest to zero for | |
| 75 // all possible representations of requested_digits digits. | |
| 76 // If there are two values that are equally close, then FastDtoa returns | |
| 77 // false. | |
| 78 // For both modes the buffer must be large enough to hold the result. | |
| 79 bool FastDtoa(double d, | |
| 80 FastDtoaMode mode, | |
| 81 int requested_digits, | |
| 82 Vector<char> buffer, | |
| 83 int* length, | |
| 84 int* decimal_point); | |
| 85 | |
| 86 } // namespace double_conversion | |
| 87 | |
| 88 #endif // DOUBLE_CONVERSION_FAST_DTOA_H_ |
