Ben Murdoch | 3ef787d | 2012-04-12 10:51:47 +0100 | [diff] [blame] | 1 | // Copyright 2011 the V8 project authors. All rights reserved. |
Ben Murdoch | b8a8cc1 | 2014-11-26 15:28:44 +0000 | [diff] [blame] | 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
Kristian Monsen | 25f6136 | 2010-05-21 11:50:48 +0100 | [diff] [blame] | 4 | |
| 5 | #ifndef V8_DTOA_H_ |
| 6 | #define V8_DTOA_H_ |
| 7 | |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 8 | #include "src/vector.h" |
| 9 | |
Kristian Monsen | 25f6136 | 2010-05-21 11:50:48 +0100 | [diff] [blame] | 10 | namespace v8 { |
| 11 | namespace internal { |
| 12 | |
| 13 | enum DtoaMode { |
Shimeng (Simon) Wang | 8a31eba | 2010-12-06 19:01:33 -0800 | [diff] [blame] | 14 | // Return the shortest correct representation. |
| 15 | // For example the output of 0.299999999999999988897 is (the less accurate but |
| 16 | // correct) 0.3. |
Kristian Monsen | 25f6136 | 2010-05-21 11:50:48 +0100 | [diff] [blame] | 17 | DTOA_SHORTEST, |
Shimeng (Simon) Wang | 8a31eba | 2010-12-06 19:01:33 -0800 | [diff] [blame] | 18 | // Return a fixed number of digits after the decimal point. |
Kristian Monsen | 25f6136 | 2010-05-21 11:50:48 +0100 | [diff] [blame] | 19 | // For instance fixed(0.1, 4) becomes 0.1000 |
| 20 | // If the input number is big, the output will be big. |
| 21 | DTOA_FIXED, |
Shimeng (Simon) Wang | 8a31eba | 2010-12-06 19:01:33 -0800 | [diff] [blame] | 22 | // Return a fixed number of digits, no matter what the exponent is. |
Kristian Monsen | 25f6136 | 2010-05-21 11:50:48 +0100 | [diff] [blame] | 23 | DTOA_PRECISION |
| 24 | }; |
| 25 | |
| 26 | // The maximal length of digits a double can have in base 10. |
| 27 | // Note that DoubleToAscii null-terminates its input. So the given buffer should |
| 28 | // be at least kBase10MaximalLength + 1 characters long. |
Ben Murdoch | 3ef787d | 2012-04-12 10:51:47 +0100 | [diff] [blame] | 29 | const int kBase10MaximalLength = 17; |
Kristian Monsen | 25f6136 | 2010-05-21 11:50:48 +0100 | [diff] [blame] | 30 | |
Ben Murdoch | 3ef787d | 2012-04-12 10:51:47 +0100 | [diff] [blame] | 31 | // Converts the given double 'v' to ASCII. |
Kristian Monsen | 25f6136 | 2010-05-21 11:50:48 +0100 | [diff] [blame] | 32 | // The result should be interpreted as buffer * 10^(point-length). |
| 33 | // |
| 34 | // The output depends on the given mode: |
| 35 | // - SHORTEST: produce the least amount of digits for which the internal |
| 36 | // identity requirement is still satisfied. If the digits are printed |
| 37 | // (together with the correct exponent) then reading this number will give |
| 38 | // 'v' again. The buffer will choose the representation that is closest to |
| 39 | // 'v'. If there are two at the same distance, than the one farther away |
| 40 | // from 0 is chosen (halfway cases - ending with 5 - are rounded up). |
| 41 | // In this mode the 'requested_digits' parameter is ignored. |
| 42 | // - FIXED: produces digits necessary to print a given number with |
| 43 | // 'requested_digits' digits after the decimal point. The produced digits |
| 44 | // might be too short in which case the caller has to fill the gaps with '0's. |
| 45 | // Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2. |
| 46 | // Halfway cases are rounded towards +/-Infinity (away from 0). The call |
| 47 | // toFixed(0.15, 2) thus returns buffer="2", point=0. |
| 48 | // The returned buffer may contain digits that would be truncated from the |
| 49 | // shortest representation of the input. |
| 50 | // - PRECISION: produces 'requested_digits' where the first digit is not '0'. |
| 51 | // Even though the length of produced digits usually equals |
| 52 | // 'requested_digits', the function is allowed to return fewer digits, in |
| 53 | // which case the caller has to fill the missing digits with '0's. |
| 54 | // Halfway cases are again rounded away from 0. |
| 55 | // 'DoubleToAscii' expects the given buffer to be big enough to hold all digits |
Shimeng (Simon) Wang | 8a31eba | 2010-12-06 19:01:33 -0800 | [diff] [blame] | 56 | // and a terminating null-character. In SHORTEST-mode it expects a buffer of |
| 57 | // at least kBase10MaximalLength + 1. Otherwise, the size of the output is |
| 58 | // limited to requested_digits digits plus the null terminator. |
| 59 | void DoubleToAscii(double v, DtoaMode mode, int requested_digits, |
Kristian Monsen | 25f6136 | 2010-05-21 11:50:48 +0100 | [diff] [blame] | 60 | Vector<char> buffer, int* sign, int* length, int* point); |
| 61 | |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 62 | } // namespace internal |
| 63 | } // namespace v8 |
Kristian Monsen | 25f6136 | 2010-05-21 11:50:48 +0100 | [diff] [blame] | 64 | |
| 65 | #endif // V8_DTOA_H_ |