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1 // Copyright 2010 the V8 project authors. All rights reserved. | 1 // Copyright 2010 the V8 project authors. All rights reserved. |
2 // Redistribution and use in source and binary forms, with or without | 2 // Redistribution and use in source and binary forms, with or without |
3 // modification, are permitted provided that the following conditions are | 3 // modification, are permitted provided that the following conditions are |
4 // met: | 4 // met: |
5 // | 5 // |
6 // * Redistributions of source code must retain the above copyright | 6 // * Redistributions of source code must retain the above copyright |
7 // notice, this list of conditions and the following disclaimer. | 7 // notice, this list of conditions and the following disclaimer. |
8 // * Redistributions in binary form must reproduce the above | 8 // * Redistributions in binary form must reproduce the above |
9 // copyright notice, this list of conditions and the following | 9 // copyright notice, this list of conditions and the following |
10 // disclaimer in the documentation and/or other materials provided | 10 // disclaimer in the documentation and/or other materials provided |
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24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | 24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | 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. | 26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
27 | 27 |
28 #ifndef V8_FAST_DTOA_H_ | 28 #ifndef V8_FAST_DTOA_H_ |
29 #define V8_FAST_DTOA_H_ | 29 #define V8_FAST_DTOA_H_ |
30 | 30 |
31 namespace v8 { | 31 namespace v8 { |
32 namespace internal { | 32 namespace internal { |
33 | 33 |
| 34 enum FastDtoaMode { |
| 35 // Computes the shortest representation of the given input. The returned |
| 36 // result will be the most accurate number of this length. Longer |
| 37 // representations might be more accurate. |
| 38 FAST_DTOA_SHORTEST, |
| 39 // Computes a representation where the precision (number of digits) is |
| 40 // given as input. The precision is independent of the decimal point. |
| 41 FAST_DTOA_PRECISION |
| 42 }; |
| 43 |
34 // FastDtoa will produce at most kFastDtoaMaximalLength digits. This does not | 44 // FastDtoa will produce at most kFastDtoaMaximalLength digits. This does not |
35 // include the terminating '\0' character. | 45 // include the terminating '\0' character. |
36 static const int kFastDtoaMaximalLength = 17; | 46 static const int kFastDtoaMaximalLength = 17; |
37 | 47 |
38 // Provides a decimal representation of v. | 48 // Provides a decimal representation of v. |
39 // v must be a strictly positive finite double. | 49 // The result should be interpreted as buffer * 10^(point - length). |
| 50 // |
| 51 // Precondition: |
| 52 // * v must be a strictly positive finite double. |
| 53 // |
40 // Returns true if it succeeds, otherwise the result can not be trusted. | 54 // Returns true if it succeeds, otherwise the result can not be trusted. |
41 // There will be *length digits inside the buffer followed by a null terminator. | 55 // There will be *length digits inside the buffer followed by a null terminator. |
42 // If the function returns true then | 56 // If the function returns true and mode equals |
43 // v == (double) (buffer * 10^(point - length)). | 57 // - FAST_DTOA_SHORTEST, then |
44 // The digits in the buffer are the shortest representation possible: no | 58 // the parameter requested_digits is ignored. |
45 // 0.099999999999 instead of 0.1. | 59 // The result satisfies |
46 // The last digit will be closest to the actual v. That is, even if several | 60 // v == (double) (buffer * 10^(point - length)). |
47 // digits might correctly yield 'v' when read again, the buffer will contain the | 61 // The digits in the buffer are the shortest representation possible. E.g. |
48 // one closest to v. | 62 // if 0.099999999999 and 0.1 represent the same double then "1" is returned |
49 // The variable 'sign' will be '0' if the given number is positive, and '1' | 63 // with point = 0. |
50 // otherwise. | 64 // The last digit will be closest to the actual v. That is, even if several |
| 65 // digits might correctly yield 'v' when read again, the buffer will contain |
| 66 // the one closest to v. |
| 67 // - FAST_DTOA_PRECISION, then |
| 68 // the buffer contains requested_digits digits. |
| 69 // the difference v - (buffer * 10^(point-length)) is closest to zero for |
| 70 // all possible representations of requested_digits digits. |
| 71 // If there are two values that are equally close, then FastDtoa returns |
| 72 // false. |
| 73 // For both modes the buffer must be large enough to hold the result. |
51 bool FastDtoa(double d, | 74 bool FastDtoa(double d, |
| 75 FastDtoaMode mode, |
| 76 int requested_digits, |
52 Vector<char> buffer, | 77 Vector<char> buffer, |
53 int* length, | 78 int* length, |
54 int* point); | 79 int* decimal_point); |
55 | 80 |
56 } } // namespace v8::internal | 81 } } // namespace v8::internal |
57 | 82 |
58 #endif // V8_FAST_DTOA_H_ | 83 #endif // V8_FAST_DTOA_H_ |
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