/*-
 * Copyright (c) 2007 Cisco Systems, Inc.  All rights reserved.
 * Copyright (c) 2014-2015 Mellanox Technologies, Ltd. All rights reserved.
 * 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 unmodified, 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 THE AUTHOR ``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 AUTHOR 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.
 */

#ifndef _LINUXKPI_LINUX_MATH64_H
#define	_LINUXKPI_LINUX_MATH64_H

#include <sys/stdint.h>
#include <sys/systm.h>

#define	do_div(n, base) ({			\
	uint32_t __base = (base);		\
	uint32_t __rem;				\
	__rem = ((uint64_t)(n)) % __base;	\
	(n) = ((uint64_t)(n)) / __base;		\
	__rem;					\
})

static inline uint64_t
div64_u64_rem(uint64_t dividend, uint64_t divisor, uint64_t *remainder)
{

	*remainder = dividend % divisor;
	return (dividend / divisor);
}

static inline int64_t
div64_s64(int64_t dividend, int64_t divisor)
{

	return (dividend / divisor);
}

static inline uint64_t
div64_u64(uint64_t dividend, uint64_t divisor)
{

	return (dividend / divisor);
}

static inline uint64_t
div_u64_rem(uint64_t dividend, uint32_t divisor, uint32_t *remainder)
{

	*remainder = dividend % divisor;
	return (dividend / divisor);
}

static inline int64_t
div_s64(int64_t dividend, int32_t divisor)
{

	return (dividend / divisor);
}

static inline uint64_t
div_u64(uint64_t dividend, uint32_t divisor)
{

	return (dividend / divisor);
}

static inline uint64_t
mul_u32_u32(uint32_t a, uint32_t b)
{

	return ((uint64_t)a * b);
}

static inline uint64_t
div64_u64_round_up(uint64_t dividend, uint64_t divisor)
{
	return ((dividend + divisor - 1) / divisor);
}

#define	DIV64_U64_ROUND_UP(...) \
	div64_u64_round_up(__VA_ARGS__)

static inline uint64_t
mul_u64_u32_div(uint64_t x, uint32_t y, uint32_t div)
{
	const uint64_t rem = x % div;

	return ((x / div) * y + (rem * y) / div);
}

static inline uint64_t
mul_u64_u64_div_u64(uint64_t x, uint64_t y, uint64_t z)
{
	uint64_t res, rem;
	uint64_t x1, y1, y1z;

	res = rem = 0;
	x1 = x;
	y1z = y / z;
	y1 = y - y1z * z;

	/*
	 * INVARIANT: x * y = res * z + rem + (y1 + y1z * z) * x1
	 * INVARIANT: y1 < z
	 * INVARIANT: rem < z
	 */
	while (x1 > 0) {
		/* Handle low bit. */
		if (x1 & 1) {
			x1 &= ~1;
			res += y1z;
			rem += y1;
			if ((rem < y1) || (rem >= z)) {
				res += 1;
				rem -= z;
			}
		}

		/* Shift x1 right and (y1 + y1z * z) left */
		x1 >>= 1;
		if ((y1 * 2 < y1) || (y1 * 2 >= z)) {
			y1z = y1z * 2 + 1;
			y1 = y1 * 2 - z;
		} else {
			y1z *= 2;
			y1 *= 2;
		}
	}

	KASSERT(res * z + rem == x * y, ("%s: res %ju * z %ju + rem %ju != "
	    "x %ju * y %ju", __func__, (uintmax_t)res, (uintmax_t)z,
	    (uintmax_t)rem, (uintmax_t)x, (uintmax_t)y));
	KASSERT(rem < z, ("%s: rem %ju >= z %ju\n", __func__,
	    (uintmax_t)rem, (uintmax_t)z));

	return (res);
}

static inline uint64_t
mul_u64_u32_shr(uint64_t x, uint32_t y, unsigned int shift)
{
	uint32_t hi, lo;
	hi = x >> 32;
	lo = x & 0xffffffff;

	return (mul_u32_u32(lo, y) >> shift) +
		(mul_u32_u32(hi, y) << (32 - shift));
}

#endif /* _LINUXKPI_LINUX_MATH64_H */