| Index: src/fixed-dtoa.cc
|
| ===================================================================
|
| --- src/fixed-dtoa.cc (revision 4591)
|
| +++ src/fixed-dtoa.cc (working copy)
|
| @@ -1,404 +0,0 @@
|
| -// Copyright 2010 the V8 project authors. All rights reserved.
|
| -// Redistribution and use in source and binary forms, with or without
|
| -// modification, are permitted provided that the following conditions are
|
| -// met:
|
| -//
|
| -// * Redistributions of source code must retain the above copyright
|
| -// notice, this list of conditions and the following disclaimer.
|
| -// * Redistributions in binary form must reproduce the above
|
| -// copyright notice, this list of conditions and the following
|
| -// disclaimer in the documentation and/or other materials provided
|
| -// with the distribution.
|
| -// * Neither the name of Google Inc. nor the names of its
|
| -// contributors may be used to endorse or promote products derived
|
| -// from this software without specific prior written permission.
|
| -//
|
| -// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
| -// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
| -// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
|
| -// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
|
| -// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
| -// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
| -// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
| -// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
| -// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
| -// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
|
| -// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
| -
|
| -#include <math.h>
|
| -
|
| -#include "v8.h"
|
| -
|
| -#include "double.h"
|
| -#include "fixed-dtoa.h"
|
| -
|
| -namespace v8 {
|
| -namespace internal {
|
| -
|
| -// Represents a 128bit type. This class should be replaced by a native type on
|
| -// platforms that support 128bit integers.
|
| -class UInt128 {
|
| - public:
|
| - UInt128() : high_bits_(0), low_bits_(0) { }
|
| - UInt128(uint64_t high, uint64_t low) : high_bits_(high), low_bits_(low) { }
|
| -
|
| - void Multiply(uint32_t multiplicand) {
|
| - uint64_t accumulator;
|
| -
|
| - accumulator = (low_bits_ & kMask32) * multiplicand;
|
| - uint32_t part = static_cast<uint32_t>(accumulator & kMask32);
|
| - accumulator >>= 32;
|
| - accumulator = accumulator + (low_bits_ >> 32) * multiplicand;
|
| - low_bits_ = (accumulator << 32) + part;
|
| - accumulator >>= 32;
|
| - accumulator = accumulator + (high_bits_ & kMask32) * multiplicand;
|
| - part = static_cast<uint32_t>(accumulator & kMask32);
|
| - accumulator >>= 32;
|
| - accumulator = accumulator + (high_bits_ >> 32) * multiplicand;
|
| - high_bits_ = (accumulator << 32) + part;
|
| - ASSERT((accumulator >> 32) == 0);
|
| - }
|
| -
|
| - void Shift(int shift_amount) {
|
| - ASSERT(-64 <= shift_amount && shift_amount <= 64);
|
| - if (shift_amount == 0) {
|
| - return;
|
| - } else if (shift_amount == -64) {
|
| - high_bits_ = low_bits_;
|
| - low_bits_ = 0;
|
| - } else if (shift_amount == 64) {
|
| - low_bits_ = high_bits_;
|
| - high_bits_ = 0;
|
| - } else if (shift_amount <= 0) {
|
| - high_bits_ <<= -shift_amount;
|
| - high_bits_ += low_bits_ >> (64 + shift_amount);
|
| - low_bits_ <<= -shift_amount;
|
| - } else {
|
| - low_bits_ >>= shift_amount;
|
| - low_bits_ += high_bits_ << (64 - shift_amount);
|
| - high_bits_ >>= shift_amount;
|
| - }
|
| - }
|
| -
|
| - // Modifies *this to *this MOD (2^power).
|
| - // Returns *this DIV (2^power).
|
| - int DivModPowerOf2(int power) {
|
| - if (power >= 64) {
|
| - int result = static_cast<int>(high_bits_ >> (power - 64));
|
| - high_bits_ -= static_cast<uint64_t>(result) << (power - 64);
|
| - return result;
|
| - } else {
|
| - uint64_t part_low = low_bits_ >> power;
|
| - uint64_t part_high = high_bits_ << (64 - power);
|
| - int result = static_cast<int>(part_low + part_high);
|
| - high_bits_ = 0;
|
| - low_bits_ -= part_low << power;
|
| - return result;
|
| - }
|
| - }
|
| -
|
| - bool IsZero() const {
|
| - return high_bits_ == 0 && low_bits_ == 0;
|
| - }
|
| -
|
| - int BitAt(int position) {
|
| - if (position >= 64) {
|
| - return (high_bits_ >> (position - 64)) & 1;
|
| - } else {
|
| - return (low_bits_ >> position) & 1;
|
| - }
|
| - }
|
| -
|
| - private:
|
| - static const uint64_t kMask32 = 0xFFFFFFFF;
|
| - // Value == (high_bits_ << 64) + low_bits_
|
| - uint64_t high_bits_;
|
| - uint64_t low_bits_;
|
| -};
|
| -
|
| -
|
| -static const int kDoubleSignificandSize = 53; // Includes the hidden bit.
|
| -
|
| -
|
| -static void FillDigits32FixedLength(uint32_t number, int requested_length,
|
| - Vector<char> buffer, int* length) {
|
| - for (int i = requested_length - 1; i >= 0; --i) {
|
| - buffer[(*length) + i] = '0' + number % 10;
|
| - number /= 10;
|
| - }
|
| - *length += requested_length;
|
| -}
|
| -
|
| -
|
| -static void FillDigits32(uint32_t number, Vector<char> buffer, int* length) {
|
| - int number_length = 0;
|
| - // We fill the digits in reverse order and exchange them afterwards.
|
| - while (number != 0) {
|
| - int digit = number % 10;
|
| - number /= 10;
|
| - buffer[(*length) + number_length] = '0' + digit;
|
| - number_length++;
|
| - }
|
| - // Exchange the digits.
|
| - int i = *length;
|
| - int j = *length + number_length - 1;
|
| - while (i < j) {
|
| - char tmp = buffer[i];
|
| - buffer[i] = buffer[j];
|
| - buffer[j] = tmp;
|
| - i++; j--;
|
| - }
|
| - *length += number_length;
|
| -}
|
| -
|
| -
|
| -static void FillDigits64FixedLength(uint64_t number, int requested_length,
|
| - Vector<char> buffer, int* length) {
|
| - const uint32_t kTen7 = 10000000;
|
| - // For efficiency cut the number into 3 uint32_t parts, and print those.
|
| - uint32_t part2 = number % kTen7;
|
| - number /= kTen7;
|
| - uint32_t part1 = number % kTen7;
|
| - uint32_t part0 = number / kTen7;
|
| -
|
| - FillDigits32FixedLength(part0, 3, buffer, length);
|
| - FillDigits32FixedLength(part1, 7, buffer, length);
|
| - FillDigits32FixedLength(part2, 7, buffer, length);
|
| -}
|
| -
|
| -
|
| -static void FillDigits64(uint64_t number, Vector<char> buffer, int* length) {
|
| - const uint32_t kTen7 = 10000000;
|
| - // For efficiency cut the number into 3 uint32_t parts, and print those.
|
| - uint32_t part2 = number % kTen7;
|
| - number /= kTen7;
|
| - uint32_t part1 = number % kTen7;
|
| - uint32_t part0 = number / kTen7;
|
| -
|
| - if (part0 != 0) {
|
| - FillDigits32(part0, buffer, length);
|
| - FillDigits32FixedLength(part1, 7, buffer, length);
|
| - FillDigits32FixedLength(part2, 7, buffer, length);
|
| - } else if (part1 != 0) {
|
| - FillDigits32(part1, buffer, length);
|
| - FillDigits32FixedLength(part2, 7, buffer, length);
|
| - } else {
|
| - FillDigits32(part2, buffer, length);
|
| - }
|
| -}
|
| -
|
| -
|
| -static void RoundUp(Vector<char> buffer, int* length, int* decimal_point) {
|
| - // An empty buffer represents 0.
|
| - if (*length == 0) {
|
| - buffer[0] = '1';
|
| - *decimal_point = 1;
|
| - *length = 1;
|
| - return;
|
| - }
|
| - // Round the last digit until we either have a digit that was not '9' or until
|
| - // we reached the first digit.
|
| - buffer[(*length) - 1]++;
|
| - for (int i = (*length) - 1; i > 0; --i) {
|
| - if (buffer[i] != '0' + 10) {
|
| - return;
|
| - }
|
| - buffer[i] = '0';
|
| - buffer[i - 1]++;
|
| - }
|
| - // If the first digit is now '0' + 10, we would need to set it to '0' and add
|
| - // a '1' in front. However we reach the first digit only if all following
|
| - // digits had been '9' before rounding up. Now all trailing digits are '0' and
|
| - // we simply switch the first digit to '1' and update the decimal-point
|
| - // (indicating that the point is now one digit to the right).
|
| - if (buffer[0] == '0' + 10) {
|
| - buffer[0] = '1';
|
| - (*decimal_point)++;
|
| - }
|
| -}
|
| -
|
| -
|
| -// The given fractionals number represents a fixed-point number with binary
|
| -// point at bit (-exponent).
|
| -// Preconditions:
|
| -// -128 <= exponent <= 0.
|
| -// 0 <= fractionals * 2^exponent < 1
|
| -// The buffer holds the result.
|
| -// The function will round its result. During the rounding-process digits not
|
| -// generated by this function might be updated, and the decimal-point variable
|
| -// might be updated. If this function generates the digits 99 and the buffer
|
| -// already contained "199" (thus yielding a buffer of "19999") then a
|
| -// rounding-up will change the contents of the buffer to "20000".
|
| -static void FillFractionals(uint64_t fractionals, int exponent,
|
| - int fractional_count, Vector<char> buffer,
|
| - int* length, int* decimal_point) {
|
| - ASSERT(-128 <= exponent && exponent <= 0);
|
| - // 'fractionals' is a fixed-point number, with binary point at bit
|
| - // (-exponent). Inside the function the non-converted remainder of fractionals
|
| - // is a fixed-point number, with binary point at bit 'point'.
|
| - if (-exponent <= 64) {
|
| - // One 64 bit number is sufficient.
|
| - ASSERT(fractionals >> 56 == 0);
|
| - int point = -exponent;
|
| - for (int i = 0; i < fractional_count; ++i) {
|
| - if (fractionals == 0) break;
|
| - // Instead of multiplying by 10 we multiply by 5 and adjust the point
|
| - // location. This way the fractionals variable will not overflow.
|
| - // Invariant at the beginning of the loop: fractionals < 2^point.
|
| - // Initially we have: point <= 64 and fractionals < 2^56
|
| - // After each iteration the point is decremented by one.
|
| - // Note that 5^3 = 125 < 128 = 2^7.
|
| - // Therefore three iterations of this loop will not overflow fractionals
|
| - // (even without the subtraction at the end of the loop body). At this time
|
| - // point will satisfy point <= 61 and therefore fractionals < 2^point and
|
| - // any further multiplication of fractionals by 5 will not overflow.
|
| - fractionals *= 5;
|
| - point--;
|
| - int digit = static_cast<int>(fractionals >> point);
|
| - buffer[*length] = '0' + digit;
|
| - (*length)++;
|
| - fractionals -= static_cast<uint64_t>(digit) << point;
|
| - }
|
| - // If the first bit after the point is set we have to round up.
|
| - if (((fractionals >> (point - 1)) & 1) == 1) {
|
| - RoundUp(buffer, length, decimal_point);
|
| - }
|
| - } else { // We need 128 bits.
|
| - ASSERT(64 < -exponent && -exponent <= 128);
|
| - UInt128 fractionals128 = UInt128(fractionals, 0);
|
| - fractionals128.Shift(-exponent - 64);
|
| - int point = 128;
|
| - for (int i = 0; i < fractional_count; ++i) {
|
| - if (fractionals128.IsZero()) break;
|
| - // As before: instead of multiplying by 10 we multiply by 5 and adjust the
|
| - // point location.
|
| - // This multiplication will not overflow for the same reasons as before.
|
| - fractionals128.Multiply(5);
|
| - point--;
|
| - int digit = fractionals128.DivModPowerOf2(point);
|
| - buffer[*length] = '0' + digit;
|
| - (*length)++;
|
| - }
|
| - if (fractionals128.BitAt(point - 1) == 1) {
|
| - RoundUp(buffer, length, decimal_point);
|
| - }
|
| - }
|
| -}
|
| -
|
| -
|
| -// Removes leading and trailing zeros.
|
| -// If leading zeros are removed then the decimal point position is adjusted.
|
| -static void TrimZeros(Vector<char> buffer, int* length, int* decimal_point) {
|
| - while (*length > 0 && buffer[(*length) - 1] == '0') {
|
| - (*length)--;
|
| - }
|
| - int first_non_zero = 0;
|
| - while (first_non_zero < *length && buffer[first_non_zero] == '0') {
|
| - first_non_zero++;
|
| - }
|
| - if (first_non_zero != 0) {
|
| - for (int i = first_non_zero; i < *length; ++i) {
|
| - buffer[i - first_non_zero] = buffer[i];
|
| - }
|
| - *length -= first_non_zero;
|
| - *decimal_point -= first_non_zero;
|
| - }
|
| -}
|
| -
|
| -
|
| -bool FastFixedDtoa(double v,
|
| - int fractional_count,
|
| - Vector<char> buffer,
|
| - int* length,
|
| - int* decimal_point) {
|
| - const uint32_t kMaxUInt32 = 0xFFFFFFFF;
|
| - uint64_t significand = Double(v).Significand();
|
| - int exponent = Double(v).Exponent();
|
| - // v = significand * 2^exponent (with significand a 53bit integer).
|
| - // If the exponent is larger than 20 (i.e. we may have a 73bit number) then we
|
| - // don't know how to compute the representation. 2^73 ~= 9.5*10^21.
|
| - // If necessary this limit could probably be increased, but we don't need
|
| - // more.
|
| - if (exponent > 20) return false;
|
| - if (fractional_count > 20) return false;
|
| - *length = 0;
|
| - // At most kDoubleSignificandSize bits of the significand are non-zero.
|
| - // Given a 64 bit integer we have 11 0s followed by 53 potentially non-zero
|
| - // bits: 0..11*..0xxx..53*..xx
|
| - if (exponent + kDoubleSignificandSize > 64) {
|
| - // The exponent must be > 11.
|
| - //
|
| - // We know that v = significand * 2^exponent.
|
| - // And the exponent > 11.
|
| - // We simplify the task by dividing v by 10^17.
|
| - // The quotient delivers the first digits, and the remainder fits into a 64
|
| - // bit number.
|
| - // Dividing by 10^17 is equivalent to dividing by 5^17*2^17.
|
| - const uint64_t kFive17 = V8_2PART_UINT64_C(0xB1, A2BC2EC5); // 5^17
|
| - uint64_t divisor = kFive17;
|
| - int divisor_power = 17;
|
| - uint64_t dividend = significand;
|
| - uint64_t quotient;
|
| - uint64_t remainder;
|
| - // Let v = f * 2^e with f == significand and e == exponent.
|
| - // Then need q (quotient) and r (remainder) as follows:
|
| - // v = q * 10^17 + r
|
| - // f * 2^e = q * 10^17 + r
|
| - // f * 2^e = q * 5^17 * 2^17 + r
|
| - // If e > 17 then
|
| - // f * 2^(e-17) = q * 5^17 + r/2^17
|
| - // else
|
| - // f = q * 5^17 * 2^(17-e) + r/2^e
|
| - if (exponent > divisor_power) {
|
| - // We only allow exponents of up to 20 and therefore (17 - e) <= 3
|
| - dividend <<= exponent - divisor_power;
|
| - quotient = dividend / divisor;
|
| - remainder = (dividend % divisor) << divisor_power;
|
| - } else {
|
| - divisor <<= divisor_power - exponent;
|
| - quotient = dividend / divisor;
|
| - remainder = (dividend % divisor) << exponent;
|
| - }
|
| - FillDigits32(quotient, buffer, length);
|
| - FillDigits64FixedLength(remainder, divisor_power, buffer, length);
|
| - *decimal_point = *length;
|
| - } else if (exponent >= 0) {
|
| - // 0 <= exponent <= 11
|
| - significand <<= exponent;
|
| - FillDigits64(significand, buffer, length);
|
| - *decimal_point = *length;
|
| - } else if (exponent > -kDoubleSignificandSize) {
|
| - // We have to cut the number.
|
| - uint64_t integrals = significand >> -exponent;
|
| - uint64_t fractionals = significand - (integrals << -exponent);
|
| - if (integrals > kMaxUInt32) {
|
| - FillDigits64(integrals, buffer, length);
|
| - } else {
|
| - FillDigits32(static_cast<uint32_t>(integrals), buffer, length);
|
| - }
|
| - *decimal_point = *length;
|
| - FillFractionals(fractionals, exponent, fractional_count,
|
| - buffer, length, decimal_point);
|
| - } else if (exponent < -128) {
|
| - // This configuration (with at most 20 digits) means that all digits must be
|
| - // 0.
|
| - ASSERT(fractional_count <= 20);
|
| - buffer[0] = '\0';
|
| - *length = 0;
|
| - *decimal_point = -fractional_count;
|
| - } else {
|
| - *decimal_point = 0;
|
| - FillFractionals(significand, exponent, fractional_count,
|
| - buffer, length, decimal_point);
|
| - }
|
| - TrimZeros(buffer, length, decimal_point);
|
| - buffer[*length] = '\0';
|
| - if ((*length) == 0) {
|
| - // The string is empty and the decimal_point thus has no importance. Mimick
|
| - // Gay's dtoa and and set it to -fractional_count.
|
| - *decimal_point = -fractional_count;
|
| - }
|
| - return true;
|
| -}
|
| -
|
| -} } // namespace v8::internal
|
|
|
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