WebKit/Source/JavaScriptCore/runtime/BigInteger.h at main · WebKit/WebKit · GitHub

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* 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>

#include <wtf/Vector.h>

WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN

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

WTF_ALLOW_UNSAFE_BUFFER_USAGE_END

WebKit/Source/JavaScriptCore/runtime/BigInteger.h at main · WebKit/WebKit · GitHub

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