obs-studio/libobs/util/util_uint64.h

/*
 * Copyright (c) 2020 Hans Petter Selasky <[email protected]>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#pragma once

#if defined(_MSC_VER) && defined(_M_X64)
#include <intrin.h>
#endif

static inline uint64_t util_mul_div64(uint64_t num, uint64_t mul, uint64_t div)
{
#if defined(_MSC_VER) && defined(_M_X64)
	unsigned __int64 high;
	const unsigned __int64 low = _umul128(num, mul, &high);
	unsigned __int64 rem;
	return _udiv128(high, low, div, &rem);
#else
	const uint64_t rem = num % div;
	return (num / div) * mul + (rem * mul) / div;
#endif
}