19a21ec41a2007f01ba18cf5fa48f7987e40e5109ulan@chromium.org// Copyright 2012 the V8 project authors. All rights reserved. 23484964a86451e86dcf04be9bd8c0d76ee04f081rossberg@chromium.org// Use of this source code is governed by a BSD-style license that can be 33484964a86451e86dcf04be9bd8c0d76ee04f081rossberg@chromium.org// found in the LICENSE file. 4b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 5b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org#include <stdarg.h> 677ca49ac05d25684c89442029c22f5b2bce94395ulan@chromium.org#include <cmath> 7b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 8196eb601290dc49c3754da728dc58700dff2de1bmachenbach@chromium.org#include "src/globals.h" 9196eb601290dc49c3754da728dc58700dff2de1bmachenbach@chromium.org#include "src/utils.h" 10196eb601290dc49c3754da728dc58700dff2de1bmachenbach@chromium.org#include "src/strtod.h" 11196eb601290dc49c3754da728dc58700dff2de1bmachenbach@chromium.org#include "src/bignum.h" 12196eb601290dc49c3754da728dc58700dff2de1bmachenbach@chromium.org#include "src/cached-powers.h" 13196eb601290dc49c3754da728dc58700dff2de1bmachenbach@chromium.org#include "src/double.h" 14b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 15b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.orgnamespace v8 { 16b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.orgnamespace internal { 17b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 18b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org// 2^53 = 9007199254740992. 19b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org// Any integer with at most 15 decimal digits will hence fit into a double 20b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org// (which has a 53bit significand) without loss of precision. 21b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.orgstatic const int kMaxExactDoubleIntegerDecimalDigits = 15; 22303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org// 2^64 = 18446744073709551616 > 10^19 23b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.orgstatic const int kMaxUint64DecimalDigits = 19; 24303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 2542841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.org// Max double: 1.7976931348623157 x 10^308 2642841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.org// Min non-zero double: 4.9406564584124654 x 10^-324 2742841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.org// Any x >= 10^309 is interpreted as +infinity. 2842841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.org// Any x <= 10^-324 is interpreted as 0. 2942841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.org// Note that 2.5e-324 (despite being smaller than the min double) will be read 3042841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.org// as non-zero (equal to the min non-zero double). 3142841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.orgstatic const int kMaxDecimalPower = 309; 3242841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.orgstatic const int kMinDecimalPower = -324; 33b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 34303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org// 2^64 = 18446744073709551616 35303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.orgstatic const uint64_t kMaxUint64 = V8_2PART_UINT64_C(0xFFFFFFFF, FFFFFFFF); 36303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 37303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 38b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.orgstatic const double exact_powers_of_ten[] = { 39b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 1.0, // 10^0 40b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 10.0, 41b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 100.0, 42b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 1000.0, 43b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 10000.0, 44b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 100000.0, 45b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 1000000.0, 46b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 10000000.0, 47b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 100000000.0, 48b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 1000000000.0, 49b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 10000000000.0, // 10^10 50b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 100000000000.0, 51b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 1000000000000.0, 52b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 10000000000000.0, 53b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 100000000000000.0, 54b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 1000000000000000.0, 55b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 10000000000000000.0, 56b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 100000000000000000.0, 57b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 1000000000000000000.0, 58b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 10000000000000000000.0, 59b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 100000000000000000000.0, // 10^20 60b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 1000000000000000000000.0, 61b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org // 10^22 = 0x21e19e0c9bab2400000 = 0x878678326eac9 * 2^22 62b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 10000000000000000000000.0 63b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org}; 64b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.orgstatic const int kExactPowersOfTenSize = ARRAY_SIZE(exact_powers_of_ten); 65b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 6601fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org// Maximum number of significant digits in the decimal representation. 6701fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org// In fact the value is 772 (see conversions.cc), but to give us some margin 6801fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org// we round up to 780. 6901fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.orgstatic const int kMaxSignificantDecimalDigits = 780; 70b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 7142841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.orgstatic Vector<const char> TrimLeadingZeros(Vector<const char> buffer) { 7242841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.org for (int i = 0; i < buffer.length(); i++) { 7342841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.org if (buffer[i] != '0') { 74303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org return buffer.SubVector(i, buffer.length()); 7542841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.org } 7642841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.org } 7742841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.org return Vector<const char>(buffer.start(), 0); 7842841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.org} 7942841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.org 8042841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.org 8142841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.orgstatic Vector<const char> TrimTrailingZeros(Vector<const char> buffer) { 82b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org for (int i = buffer.length() - 1; i >= 0; --i) { 83b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org if (buffer[i] != '0') { 84303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org return buffer.SubVector(0, i + 1); 85b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org } 86b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org } 8742841968c3c92e3b07bcd67e79eb6ba3f83032c1vegorov@chromium.org return Vector<const char>(buffer.start(), 0); 88b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org} 89b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 90b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 9101fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.orgstatic void TrimToMaxSignificantDigits(Vector<const char> buffer, 9201fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org int exponent, 9301fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org char* significant_buffer, 9401fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org int* significant_exponent) { 9501fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org for (int i = 0; i < kMaxSignificantDecimalDigits - 1; ++i) { 9601fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org significant_buffer[i] = buffer[i]; 9701fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org } 9801fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org // The input buffer has been trimmed. Therefore the last digit must be 9901fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org // different from '0'. 10001fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org ASSERT(buffer[buffer.length() - 1] != '0'); 10101fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org // Set the last digit to be non-zero. This is sufficient to guarantee 10201fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org // correct rounding. 10301fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org significant_buffer[kMaxSignificantDecimalDigits - 1] = '1'; 10401fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org *significant_exponent = 10501fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org exponent + (buffer.length() - kMaxSignificantDecimalDigits); 10601fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org} 10701fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org 108e0e1b0d3e70c933d36ed381d511e9fda39f2a751mstarzinger@chromium.org 109303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org// Reads digits from the buffer and converts them to a uint64. 110303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org// Reads in as many digits as fit into a uint64. 111303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org// When the string starts with "1844674407370955161" no further digit is read. 112303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org// Since 2^64 = 18446744073709551616 it would still be possible read another 113303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org// digit if it was less or equal than 6, but this would complicate the code. 114303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.orgstatic uint64_t ReadUint64(Vector<const char> buffer, 115303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int* number_of_read_digits) { 116b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org uint64_t result = 0; 117303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int i = 0; 118303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org while (i < buffer.length() && result <= (kMaxUint64 / 10 - 1)) { 119303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int digit = buffer[i++] - '0'; 120b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org ASSERT(0 <= digit && digit <= 9); 121b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org result = 10 * result + digit; 122b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org } 123303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org *number_of_read_digits = i; 124b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org return result; 125b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org} 126b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 127b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 128303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org// Reads a DiyFp from the buffer. 129303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org// The returned DiyFp is not necessarily normalized. 130303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org// If remaining_decimals is zero then the returned DiyFp is accurate. 131303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org// Otherwise it has been rounded and has error of at most 1/2 ulp. 132303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.orgstatic void ReadDiyFp(Vector<const char> buffer, 133303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org DiyFp* result, 134303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int* remaining_decimals) { 135303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int read_digits; 136303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org uint64_t significand = ReadUint64(buffer, &read_digits); 137303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org if (buffer.length() == read_digits) { 138303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org *result = DiyFp(significand, 0); 139303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org *remaining_decimals = 0; 140303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org } else { 141303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // Round the significand. 142303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org if (buffer[read_digits] >= '5') { 143303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org significand++; 144303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org } 145303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // Compute the binary exponent. 146303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int exponent = 0; 147303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org *result = DiyFp(significand, exponent); 148303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org *remaining_decimals = buffer.length() - read_digits; 149303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org } 150303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org} 151303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 152303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 1534a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.orgstatic bool DoubleStrtod(Vector<const char> trimmed, 1544a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org int exponent, 1554a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org double* result) { 156864abd7677f434b5aef191e3388e71cd4dd1e6c8machenbach@chromium.org#if (V8_TARGET_ARCH_IA32 || V8_TARGET_ARCH_X87 || defined(USE_SIMULATOR)) && \ 157864abd7677f434b5aef191e3388e71cd4dd1e6c8machenbach@chromium.org !defined(_MSC_VER) 1584a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org // On x86 the floating-point stack can be 64 or 80 bits wide. If it is 1594a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org // 80 bits wide (as is the case on Linux) then double-rounding occurs and the 1604a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org // result is not accurate. 1619a21ec41a2007f01ba18cf5fa48f7987e40e5109ulan@chromium.org // We know that Windows32 with MSVC, unlike with MinGW32, uses 64 bits and is 1629a21ec41a2007f01ba18cf5fa48f7987e40e5109ulan@chromium.org // therefore accurate. 1639a21ec41a2007f01ba18cf5fa48f7987e40e5109ulan@chromium.org // Note that the ARM and MIPS simulators are compiled for 32bits. They 1649a21ec41a2007f01ba18cf5fa48f7987e40e5109ulan@chromium.org // therefore exhibit the same problem. 1654a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org return false; 1664a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org#endif 167b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org if (trimmed.length() <= kMaxExactDoubleIntegerDecimalDigits) { 168303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int read_digits; 169b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org // The trimmed input fits into a double. 170b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org // If the 10^exponent (resp. 10^-exponent) fits into a double too then we 171b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org // can compute the result-double simply by multiplying (resp. dividing) the 172b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org // two numbers. 173b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org // This is possible because IEEE guarantees that floating-point operations 174b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org // return the best possible approximation. 175b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org if (exponent < 0 && -exponent < kExactPowersOfTenSize) { 176b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org // 10^-exponent fits into a double. 177303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org *result = static_cast<double>(ReadUint64(trimmed, &read_digits)); 178303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org ASSERT(read_digits == trimmed.length()); 1794a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org *result /= exact_powers_of_ten[-exponent]; 1804a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org return true; 181b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org } 182b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org if (0 <= exponent && exponent < kExactPowersOfTenSize) { 183b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org // 10^exponent fits into a double. 184303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org *result = static_cast<double>(ReadUint64(trimmed, &read_digits)); 185303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org ASSERT(read_digits == trimmed.length()); 1864a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org *result *= exact_powers_of_ten[exponent]; 1874a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org return true; 188b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org } 189b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org int remaining_digits = 190b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org kMaxExactDoubleIntegerDecimalDigits - trimmed.length(); 191b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org if ((0 <= exponent) && 192b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org (exponent - remaining_digits < kExactPowersOfTenSize)) { 193b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org // The trimmed string was short and we can multiply it with 194b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org // 10^remaining_digits. As a result the remaining exponent now fits 195b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org // into a double too. 196303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org *result = static_cast<double>(ReadUint64(trimmed, &read_digits)); 197303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org ASSERT(read_digits == trimmed.length()); 1984a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org *result *= exact_powers_of_ten[remaining_digits]; 1994a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org *result *= exact_powers_of_ten[exponent - remaining_digits]; 2004a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org return true; 201b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org } 202b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org } 2034a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org return false; 2044a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org} 2054a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org 2064a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org 207303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org// Returns 10^exponent as an exact DiyFp. 208303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org// The given exponent must be in the range [1; kDecimalExponentDistance[. 209303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.orgstatic DiyFp AdjustmentPowerOfTen(int exponent) { 210303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org ASSERT(0 < exponent); 211303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org ASSERT(exponent < PowersOfTenCache::kDecimalExponentDistance); 212303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // Simply hardcode the remaining powers for the given decimal exponent 213303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // distance. 214303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org ASSERT(PowersOfTenCache::kDecimalExponentDistance == 8); 215303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org switch (exponent) { 216303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org case 1: return DiyFp(V8_2PART_UINT64_C(0xa0000000, 00000000), -60); 217303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org case 2: return DiyFp(V8_2PART_UINT64_C(0xc8000000, 00000000), -57); 218303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org case 3: return DiyFp(V8_2PART_UINT64_C(0xfa000000, 00000000), -54); 219303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org case 4: return DiyFp(V8_2PART_UINT64_C(0x9c400000, 00000000), -50); 220303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org case 5: return DiyFp(V8_2PART_UINT64_C(0xc3500000, 00000000), -47); 221303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org case 6: return DiyFp(V8_2PART_UINT64_C(0xf4240000, 00000000), -44); 222303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org case 7: return DiyFp(V8_2PART_UINT64_C(0x98968000, 00000000), -40); 223303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org default: 224303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org UNREACHABLE(); 225303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org return DiyFp(0, 0); 226303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org } 227303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org} 228303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 229303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 230303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org// If the function returns true then the result is the correct double. 231303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org// Otherwise it is either the correct double or the double that is just below 232303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org// the correct double. 233303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.orgstatic bool DiyFpStrtod(Vector<const char> buffer, 234303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int exponent, 235303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org double* result) { 236303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org DiyFp input; 237303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int remaining_decimals; 238303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org ReadDiyFp(buffer, &input, &remaining_decimals); 239303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // Since we may have dropped some digits the input is not accurate. 240303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // If remaining_decimals is different than 0 than the error is at most 241303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // .5 ulp (unit in the last place). 242303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // We don't want to deal with fractions and therefore keep a common 243303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // denominator. 244303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org const int kDenominatorLog = 3; 245303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org const int kDenominator = 1 << kDenominatorLog; 246303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // Move the remaining decimals into the exponent. 247303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org exponent += remaining_decimals; 248303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int error = (remaining_decimals == 0 ? 0 : kDenominator / 2); 249303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 250303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int old_e = input.e(); 251303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org input.Normalize(); 252303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org error <<= old_e - input.e(); 253303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 254303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org ASSERT(exponent <= PowersOfTenCache::kMaxDecimalExponent); 255303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org if (exponent < PowersOfTenCache::kMinDecimalExponent) { 256303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org *result = 0.0; 257303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org return true; 258303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org } 259303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org DiyFp cached_power; 260303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int cached_decimal_exponent; 261303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org PowersOfTenCache::GetCachedPowerForDecimalExponent(exponent, 262303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org &cached_power, 263303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org &cached_decimal_exponent); 264303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 265303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org if (cached_decimal_exponent != exponent) { 266303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int adjustment_exponent = exponent - cached_decimal_exponent; 267303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org DiyFp adjustment_power = AdjustmentPowerOfTen(adjustment_exponent); 268303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org input.Multiply(adjustment_power); 269303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org if (kMaxUint64DecimalDigits - buffer.length() >= adjustment_exponent) { 270303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // The product of input with the adjustment power fits into a 64 bit 271303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // integer. 272303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org ASSERT(DiyFp::kSignificandSize == 64); 273303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org } else { 274303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // The adjustment power is exact. There is hence only an error of 0.5. 275303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org error += kDenominator / 2; 276303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org } 277303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org } 278303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 279303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org input.Multiply(cached_power); 280303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // The error introduced by a multiplication of a*b equals 281303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // error_a + error_b + error_a*error_b/2^64 + 0.5 282303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // Substituting a with 'input' and b with 'cached_power' we have 283303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // error_b = 0.5 (all cached powers have an error of less than 0.5 ulp), 284303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // error_ab = 0 or 1 / kDenominator > error_a*error_b/ 2^64 285303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int error_b = kDenominator / 2; 286303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int error_ab = (error == 0 ? 0 : 1); // We round up to 1. 287303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int fixed_error = kDenominator / 2; 288303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org error += error_b + error_ab + fixed_error; 289303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 290303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org old_e = input.e(); 291303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org input.Normalize(); 292303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org error <<= old_e - input.e(); 293303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 294303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // See if the double's significand changes if we add/subtract the error. 295303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int order_of_magnitude = DiyFp::kSignificandSize + input.e(); 296303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int effective_significand_size = 297303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org Double::SignificandSizeForOrderOfMagnitude(order_of_magnitude); 298303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int precision_digits_count = 299303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org DiyFp::kSignificandSize - effective_significand_size; 300303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org if (precision_digits_count + kDenominatorLog >= DiyFp::kSignificandSize) { 301303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // This can only happen for very small denormals. In this case the 302303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // half-way multiplied by the denominator exceeds the range of an uint64. 303303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // Simply shift everything to the right. 304303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org int shift_amount = (precision_digits_count + kDenominatorLog) - 305303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org DiyFp::kSignificandSize + 1; 306303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org input.set_f(input.f() >> shift_amount); 307303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org input.set_e(input.e() + shift_amount); 308303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // We add 1 for the lost precision of error, and kDenominator for 309303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // the lost precision of input.f(). 310303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org error = (error >> shift_amount) + 1 + kDenominator; 311303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org precision_digits_count -= shift_amount; 312303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org } 313303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // We use uint64_ts now. This only works if the DiyFp uses uint64_ts too. 314303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org ASSERT(DiyFp::kSignificandSize == 64); 315303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org ASSERT(precision_digits_count < 64); 316303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org uint64_t one64 = 1; 317303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org uint64_t precision_bits_mask = (one64 << precision_digits_count) - 1; 318303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org uint64_t precision_bits = input.f() & precision_bits_mask; 319303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org uint64_t half_way = one64 << (precision_digits_count - 1); 320303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org precision_bits *= kDenominator; 321303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org half_way *= kDenominator; 322303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org DiyFp rounded_input(input.f() >> precision_digits_count, 323303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org input.e() + precision_digits_count); 324303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org if (precision_bits >= half_way + error) { 325303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org rounded_input.set_f(rounded_input.f() + 1); 326303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org } 327303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // If the last_bits are too close to the half-way case than we are too 328303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // inaccurate and round down. In this case we return false so that we can 329303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // fall back to a more precise algorithm. 330303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 331303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org *result = Double(rounded_input).value(); 332303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org if (half_way - error < precision_bits && precision_bits < half_way + error) { 333303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // Too imprecise. The caller will have to fall back to a slower version. 334303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // However the returned number is guaranteed to be either the correct 335303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org // double, or the next-lower double. 336303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org return false; 337303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org } else { 338303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org return true; 339303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org } 340303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org} 341303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 342303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 34301fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org// Returns the correct double for the buffer*10^exponent. 34401fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org// The variable guess should be a close guess that is either the correct double 34501fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org// or its lower neighbor (the nearest double less than the correct one). 34601fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org// Preconditions: 34701fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org// buffer.length() + exponent <= kMaxDecimalPower + 1 34801fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org// buffer.length() + exponent > kMinDecimalPower 34901fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org// buffer.length() <= kMaxDecimalSignificantDigits 35001fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.orgstatic double BignumStrtod(Vector<const char> buffer, 35101fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org int exponent, 35201fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org double guess) { 35301fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org if (guess == V8_INFINITY) { 35401fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org return guess; 35501fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org } 35601fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org 35701fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org DiyFp upper_boundary = Double(guess).UpperBoundary(); 35801fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org 35901fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org ASSERT(buffer.length() + exponent <= kMaxDecimalPower + 1); 36001fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org ASSERT(buffer.length() + exponent > kMinDecimalPower); 36101fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org ASSERT(buffer.length() <= kMaxSignificantDecimalDigits); 36201fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org // Make sure that the Bignum will be able to hold all our numbers. 36301fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org // Our Bignum implementation has a separate field for exponents. Shifts will 36401fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org // consume at most one bigit (< 64 bits). 36501fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org // ln(10) == 3.3219... 36601fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org ASSERT(((kMaxDecimalPower + 1) * 333 / 100) < Bignum::kMaxSignificantBits); 36701fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org Bignum input; 36801fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org Bignum boundary; 36901fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org input.AssignDecimalString(buffer); 37001fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org boundary.AssignUInt64(upper_boundary.f()); 37101fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org if (exponent >= 0) { 37201fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org input.MultiplyByPowerOfTen(exponent); 37301fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org } else { 37401fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org boundary.MultiplyByPowerOfTen(-exponent); 37501fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org } 37601fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org if (upper_boundary.e() > 0) { 37701fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org boundary.ShiftLeft(upper_boundary.e()); 37801fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org } else { 37901fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org input.ShiftLeft(-upper_boundary.e()); 38001fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org } 38101fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org int comparison = Bignum::Compare(input, boundary); 38201fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org if (comparison < 0) { 38301fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org return guess; 38401fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org } else if (comparison > 0) { 38501fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org return Double(guess).NextDouble(); 38601fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org } else if ((Double(guess).Significand() & 1) == 0) { 38701fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org // Round towards even. 38801fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org return guess; 38901fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org } else { 39001fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org return Double(guess).NextDouble(); 39101fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org } 39201fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org} 39301fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org 39401fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org 3954a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.orgdouble Strtod(Vector<const char> buffer, int exponent) { 3964a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org Vector<const char> left_trimmed = TrimLeadingZeros(buffer); 3974a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org Vector<const char> trimmed = TrimTrailingZeros(left_trimmed); 3984a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org exponent += left_trimmed.length() - trimmed.length(); 3994a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org if (trimmed.length() == 0) return 0.0; 40001fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org if (trimmed.length() > kMaxSignificantDecimalDigits) { 40101fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org char significant_buffer[kMaxSignificantDecimalDigits]; 40201fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org int significant_exponent; 40301fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org TrimToMaxSignificantDigits(trimmed, exponent, 40401fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org significant_buffer, &significant_exponent); 4054a6c3279070e8f133607a74c08d8c08ac394ab98erik.corry@gmail.com return Strtod(Vector<const char>(significant_buffer, 4064a6c3279070e8f133607a74c08d8c08ac394ab98erik.corry@gmail.com kMaxSignificantDecimalDigits), 4074a6c3279070e8f133607a74c08d8c08ac394ab98erik.corry@gmail.com significant_exponent); 40801fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org } 4094a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org if (exponent + trimmed.length() - 1 >= kMaxDecimalPower) return V8_INFINITY; 4104a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org if (exponent + trimmed.length() <= kMinDecimalPower) return 0.0; 411303ada708275d2d425b846fb237f1ba7598ee239lrn@chromium.org 41201fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org double guess; 41301fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org if (DoubleStrtod(trimmed, exponent, &guess) || 41401fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org DiyFpStrtod(trimmed, exponent, &guess)) { 41501fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org return guess; 4164a5224e84636d192e82f288bfab0d308bdae5c37whesse@chromium.org } 41701fe7df37ce9858e3d0069ec6a2d7c667256b95aager@chromium.org return BignumStrtod(trimmed, exponent, guess); 418b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org} 419b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org 420b61a0d13e9690ef4c2de424bbe82a38884d981a6ager@chromium.org} } // namespace v8::internal 421