conversions.h revision 589d6979ff2ef66fca2d8fa51404c369ca5e9250
1// Copyright 2011 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_CONVERSIONS_H_ 29#define V8_CONVERSIONS_H_ 30 31#include <limits> 32 33#include "utils.h" 34 35namespace v8 { 36namespace internal { 37 38class UnicodeCache; 39 40// Maximum number of significant digits in decimal representation. 41// The longest possible double in decimal representation is 42// (2^53 - 1) * 2 ^ -1074 that is (2 ^ 53 - 1) * 5 ^ 1074 / 10 ^ 1074 43// (768 digits). If we parse a number whose first digits are equal to a 44// mean of 2 adjacent doubles (that could have up to 769 digits) the result 45// must be rounded to the bigger one unless the tail consists of zeros, so 46// we don't need to preserve all the digits. 47const int kMaxSignificantDigits = 772; 48 49 50static inline bool isDigit(int x, int radix) { 51 return (x >= '0' && x <= '9' && x < '0' + radix) 52 || (radix > 10 && x >= 'a' && x < 'a' + radix - 10) 53 || (radix > 10 && x >= 'A' && x < 'A' + radix - 10); 54} 55 56 57static inline double SignedZero(bool negative) { 58 return negative ? -0.0 : 0.0; 59} 60 61 62// The fast double-to-(unsigned-)int conversion routine does not guarantee 63// rounding towards zero. 64// The result is unspecified if x is infinite or NaN, or if the rounded 65// integer value is outside the range of type int. 66static inline int FastD2I(double x) { 67 // The static_cast convertion from double to int used to be slow, but 68 // as new benchmarks show, now it is much faster than lrint(). 69 return static_cast<int>(x); 70} 71 72static inline unsigned int FastD2UI(double x); 73 74 75static inline double FastI2D(int x) { 76 // There is no rounding involved in converting an integer to a 77 // double, so this code should compile to a few instructions without 78 // any FPU pipeline stalls. 79 return static_cast<double>(x); 80} 81 82 83static inline double FastUI2D(unsigned x) { 84 // There is no rounding involved in converting an unsigned integer to a 85 // double, so this code should compile to a few instructions without 86 // any FPU pipeline stalls. 87 return static_cast<double>(x); 88} 89 90 91// This function should match the exact semantics of ECMA-262 9.4. 92static inline double DoubleToInteger(double x); 93 94 95// This function should match the exact semantics of ECMA-262 9.5. 96static inline int32_t DoubleToInt32(double x); 97 98 99// This function should match the exact semantics of ECMA-262 9.6. 100static inline uint32_t DoubleToUint32(double x) { 101 return static_cast<uint32_t>(DoubleToInt32(x)); 102} 103 104 105// Enumeration for allowing octals and ignoring junk when converting 106// strings to numbers. 107enum ConversionFlags { 108 NO_FLAGS = 0, 109 ALLOW_HEX = 1, 110 ALLOW_OCTALS = 2, 111 ALLOW_TRAILING_JUNK = 4 112}; 113 114 115// Converts a string into a double value according to ECMA-262 9.3.1 116double StringToDouble(UnicodeCache* unicode_cache, 117 Vector<const char> str, 118 int flags, 119 double empty_string_val = 0); 120double StringToDouble(UnicodeCache* unicode_cache, 121 Vector<const uc16> str, 122 int flags, 123 double empty_string_val = 0); 124// This version expects a zero-terminated character array. 125double StringToDouble(UnicodeCache* unicode_cache, 126 const char* str, 127 int flags, 128 double empty_string_val = 0); 129 130const int kDoubleToCStringMinBufferSize = 100; 131 132// Converts a double to a string value according to ECMA-262 9.8.1. 133// The buffer should be large enough for any floating point number. 134// 100 characters is enough. 135const char* DoubleToCString(double value, Vector<char> buffer); 136 137// Convert an int to a null-terminated string. The returned string is 138// located inside the buffer, but not necessarily at the start. 139const char* IntToCString(int n, Vector<char> buffer); 140 141// Additional number to string conversions for the number type. 142// The caller is responsible for calling free on the returned pointer. 143char* DoubleToFixedCString(double value, int f); 144char* DoubleToExponentialCString(double value, int f); 145char* DoubleToPrecisionCString(double value, int f); 146char* DoubleToRadixCString(double value, int radix); 147 148} } // namespace v8::internal 149 150#endif // V8_CONVERSIONS_H_ 151