1// Copyright 2011 the V8 project authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5#ifndef V8_DTOA_H_ 6#define V8_DTOA_H_ 7 8#include "src/vector.h" 9 10namespace v8 { 11namespace internal { 12 13enum DtoaMode { 14 // Return the shortest correct representation. 15 // For example the output of 0.299999999999999988897 is (the less accurate but 16 // correct) 0.3. 17 DTOA_SHORTEST, 18 // Return a fixed number of digits after the decimal point. 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, 22 // Return a fixed number of digits, no matter what the exponent is. 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. 29const int kBase10MaximalLength = 17; 30 31// Converts the given double 'v' to ASCII. 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 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. 59void DoubleToAscii(double v, DtoaMode mode, int requested_digits, 60 Vector<char> buffer, int* sign, int* length, int* point); 61 62} // namespace internal 63} // namespace v8 64 65#endif // V8_DTOA_H_ 66