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BigInteger.h
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108 lines (89 loc) · 3.67 KB
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/*
* Copyright (C) 2011 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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 APPLE INC. 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.
*/
#pragma once
#include <wtf/MathExtras.h>
namespace JSC {
// This is used in converting the integer part of a number to a string.
class BigInteger {
public:
BigInteger(double number)
{
ASSERT(std::isfinite(number) && !std::signbit(number));
ASSERT(number == floor(number));
bool sign;
int32_t exponent;
uint64_t mantissa;
decomposeDouble(number, sign, exponent, mantissa);
ASSERT(!sign && exponent >= 0);
int32_t zeroBits = exponent - 52;
if (zeroBits < 0) {
mantissa >>= -zeroBits;
zeroBits = 0;
}
while (zeroBits >= 32) {
m_values.append(0);
zeroBits -= 32;
}
// Left align the 53 bits of the mantissa within 96 bits.
uint32_t values[3];
values[0] = static_cast<uint32_t>(mantissa);
values[1] = static_cast<uint32_t>(mantissa >> 32);
values[2] = 0;
// Shift based on the remainder of the exponent.
if (zeroBits) {
values[2] = values[1] >> (32 - zeroBits);
values[1] = (values[1] << zeroBits) | (values[0] >> (32 - zeroBits));
values[0] = (values[0] << zeroBits);
}
m_values.append(values[0]);
m_values.append(values[1]);
m_values.append(values[2]);
// Canonicalize; remove all trailing zeros.
while (m_values.size() && !m_values.last())
m_values.removeLast();
}
uint32_t divide(uint32_t divisor)
{
uint32_t carry = 0;
for (size_t i = m_values.size(); i; ) {
--i;
uint64_t dividend = (static_cast<uint64_t>(carry) << 32) + static_cast<uint64_t>(m_values[i]);
uint64_t result = dividend / static_cast<uint64_t>(divisor);
ASSERT(result == static_cast<uint32_t>(result));
uint64_t remainder = dividend % static_cast<uint64_t>(divisor);
ASSERT(remainder == static_cast<uint32_t>(remainder));
m_values[i] = static_cast<uint32_t>(result);
carry = static_cast<uint32_t>(remainder);
}
// Canonicalize; remove all trailing zeros.
while (m_values.size() && !m_values.last())
m_values.removeLast();
return carry;
}
bool operator!() { return !m_values.size(); }
private:
Vector<uint32_t, 36> m_values;
};
} // namespace JSC