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 V8_DTOA_H_ 29 #define V8_DTOA_H_ 30 31 namespace v8 { 32 namespace internal { 33 34 enum DtoaMode { 35 // Return the shortest correct representation. 36 // For example the output of 0.299999999999999988897 is (the less accurate but 37 // correct) 0.3. 38 DTOA_SHORTEST, 39 // Return a fixed number of digits after the decimal point. 40 // For instance fixed(0.1, 4) becomes 0.1000 41 // If the input number is big, the output will be big. 42 DTOA_FIXED, 43 // Return a fixed number of digits, no matter what the exponent is. 44 DTOA_PRECISION 45 }; 46 47 // The maximal length of digits a double can have in base 10. 48 // Note that DoubleToAscii null-terminates its input. So the given buffer should 49 // be at least kBase10MaximalLength + 1 characters long. 50 static const int kBase10MaximalLength = 17; 51 52 // Converts the given double 'v' to ascii. 53 // The result should be interpreted as buffer * 10^(point-length). 54 // 55 // The output depends on the given mode: 56 // - SHORTEST: produce the least amount of digits for which the internal 57 // identity requirement is still satisfied. If the digits are printed 58 // (together with the correct exponent) then reading this number will give 59 // 'v' again. The buffer will choose the representation that is closest to 60 // 'v'. If there are two at the same distance, than the one farther away 61 // from 0 is chosen (halfway cases - ending with 5 - are rounded up). 62 // In this mode the 'requested_digits' parameter is ignored. 63 // - FIXED: produces digits necessary to print a given number with 64 // 'requested_digits' digits after the decimal point. The produced digits 65 // might be too short in which case the caller has to fill the gaps with '0's. 66 // Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2. 67 // Halfway cases are rounded towards +/-Infinity (away from 0). The call 68 // toFixed(0.15, 2) thus returns buffer="2", point=0. 69 // The returned buffer may contain digits that would be truncated from the 70 // shortest representation of the input. 71 // - PRECISION: produces 'requested_digits' where the first digit is not '0'. 72 // Even though the length of produced digits usually equals 73 // 'requested_digits', the function is allowed to return fewer digits, in 74 // which case the caller has to fill the missing digits with '0's. 75 // Halfway cases are again rounded away from 0. 76 // 'DoubleToAscii' expects the given buffer to be big enough to hold all digits 77 // and a terminating null-character. In SHORTEST-mode it expects a buffer of 78 // at least kBase10MaximalLength + 1. Otherwise, the size of the output is 79 // limited to requested_digits digits plus the null terminator. 80 void DoubleToAscii(double v, DtoaMode mode, int requested_digits, 81 Vector<char> buffer, int* sign, int* length, int* point); 82 83 } } // namespace v8::internal 84 85 #endif // V8_DTOA_H_ 86
