| // 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_DTOA_H_ |
| #define V8_DTOA_H_ |
| |
| #include "src/vector.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| enum DtoaMode { |
| // Return the shortest correct representation. |
| // For example the output of 0.299999999999999988897 is (the less accurate but |
| // correct) 0.3. |
| DTOA_SHORTEST, |
| // Return a fixed number of digits after the decimal point. |
| // For instance fixed(0.1, 4) becomes 0.1000 |
| // If the input number is big, the output will be big. |
| DTOA_FIXED, |
| // Return a fixed number of digits, no matter what the exponent is. |
| DTOA_PRECISION |
| }; |
| |
| // The maximal length of digits a double can have in base 10. |
| // Note that DoubleToAscii null-terminates its input. So the given buffer should |
| // be at least kBase10MaximalLength + 1 characters long. |
| const int kBase10MaximalLength = 17; |
| |
| // Converts the given double 'v' to ASCII. |
| // The result should be interpreted as buffer * 10^(point-length). |
| // |
| // The output depends on the given mode: |
| // - SHORTEST: produce the least amount of digits for which the internal |
| // identity requirement is still satisfied. If the digits are printed |
| // (together with the correct exponent) then reading this number will give |
| // 'v' again. The buffer will choose the representation that is closest to |
| // 'v'. If there are two at the same distance, than the one farther away |
| // from 0 is chosen (halfway cases - ending with 5 - are rounded up). |
| // In this mode the 'requested_digits' parameter is ignored. |
| // - FIXED: produces digits necessary to print a given number with |
| // 'requested_digits' digits after the decimal point. The produced digits |
| // might be too short in which case the caller has to fill the gaps with '0's. |
| // Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2. |
| // Halfway cases are rounded towards +/-Infinity (away from 0). The call |
| // toFixed(0.15, 2) thus returns buffer="2", point=0. |
| // The returned buffer may contain digits that would be truncated from the |
| // shortest representation of the input. |
| // - PRECISION: produces 'requested_digits' where the first digit is not '0'. |
| // Even though the length of produced digits usually equals |
| // 'requested_digits', the function is allowed to return fewer digits, in |
| // which case the caller has to fill the missing digits with '0's. |
| // Halfway cases are again rounded away from 0. |
| // 'DoubleToAscii' expects the given buffer to be big enough to hold all digits |
| // and a terminating null-character. In SHORTEST-mode it expects a buffer of |
| // at least kBase10MaximalLength + 1. Otherwise, the size of the output is |
| // limited to requested_digits digits plus the null terminator. |
| void DoubleToAscii(double v, DtoaMode mode, int requested_digits, |
| Vector<char> buffer, int* sign, int* length, int* point); |
| |
| } // namespace internal |
| } // namespace v8 |
| |
| #endif // V8_DTOA_H_ |