chromium/v8/src/bigint/digit-arithmetic.h

// Copyright 2021 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// Helper functions that operate on individual digits.

#ifndef V8_BIGINT_DIGIT_ARITHMETIC_H_
#define V8_BIGINT_DIGIT_ARITHMETIC_H_

#include "src/bigint/bigint.h"
#include "src/bigint/util.h"

namespace v8 {
namespace bigint {

static constexpr int kHalfDigitBits = …;
static constexpr digit_t kHalfDigitBase = …;
static constexpr digit_t kHalfDigitMask = …;

constexpr bool digit_ismax(digit_t x) { … }

// {carry} will be set to 0 or 1.
inline digit_t digit_add2(digit_t a, digit_t b, digit_t* carry) { … }

// This compiles to slightly better machine code than repeated invocations
// of {digit_add2}.
inline digit_t digit_add3(digit_t a, digit_t b, digit_t c, digit_t* carry) { … }

// {borrow} will be set to 0 or 1.
inline digit_t digit_sub(digit_t a, digit_t b, digit_t* borrow) { … }

// {borrow_out} will be set to 0 or 1.
inline digit_t digit_sub2(digit_t a, digit_t b, digit_t borrow_in,
                          digit_t* borrow_out) { … }

// Returns the low half of the result. High half is in {high}.
inline digit_t digit_mul(digit_t a, digit_t b, digit_t* high) { … }

// Returns the quotient.
// quotient = (high << kDigitBits + low - remainder) / divisor
static inline digit_t digit_div(digit_t high, digit_t low, digit_t divisor,
                                digit_t* remainder) { … }

}  // namespace bigint
}  // namespace v8

#endif  // V8_BIGINT_DIGIT_ARITHMETIC_H_