[linux.git] / lib / div64.c

/*
 * Copyright (C) 2003 Bernardo Innocenti <[email protected]>
 *
 * Based on former do_div() implementation from asm-parisc/div64.h:
 *	Copyright (C) 1999 Hewlett-Packard Co
 *	Copyright (C) 1999 David Mosberger-Tang <[email protected]>
 *
 *
 * Generic C version of 64bit/32bit division and modulo, with
 * 64bit result and 32bit remainder.
 *
 * The fast case for (n>>32 == 0) is handled inline by do_div(). 
 *
 * Code generated for this function might be very inefficient
 * for some CPUs. __div64_32() can be overridden by linking arch-specific
 * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S.
 */

#include <linux/module.h>
#include <linux/math64.h>

/* Not needed on 64bit architectures */
#if BITS_PER_LONG == 32

uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
{
	uint64_t rem = *n;
	uint64_t b = base;
	uint64_t res, d = 1;
	uint32_t high = rem >> 32;

	/* Reduce the thing a bit first */
	res = 0;
	if (high >= base) {
		high /= base;
		res = (uint64_t) high << 32;
		rem -= (uint64_t) (high*base) << 32;
	}

	while ((int64_t)b > 0 && b < rem) {
		b = b+b;
		d = d+d;
	}

	do {
		if (rem >= b) {
			rem -= b;
			res += d;
		}
		b >>= 1;
		d >>= 1;
	} while (d);

	*n = res;
	return rem;
}

EXPORT_SYMBOL(__div64_32);

#ifndef div_s64_rem
s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
{
	u64 quotient;

	if (dividend < 0) {
		quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
		*remainder = -*remainder;
		if (divisor > 0)
			quotient = -quotient;
	} else {
		quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
		if (divisor < 0)
			quotient = -quotient;
	}
	return quotient;
}
EXPORT_SYMBOL(div_s64_rem);
#endif

/**
 * div64_u64 - unsigned 64bit divide with 64bit divisor
 * @dividend:	64bit dividend
 * @divisor:	64bit divisor
 *
 * This implementation is a modified version of the algorithm proposed
 * by the book 'Hacker's Delight'.  The original source and full proof
 * can be found here and is available for use without restriction.
 *
 * 'http://www.hackersdelight.org/HDcode/newCode/divDouble.c'
 */
#ifndef div64_u64
u64 div64_u64(u64 dividend, u64 divisor)
{
	u32 high = divisor >> 32;
	u64 quot;

	if (high == 0) {
		quot = div_u64(dividend, divisor);
	} else {
		int n = 1 + fls(high);
		quot = div_u64(dividend >> n, divisor >> n);

		if (quot != 0)
			quot--;
		if ((dividend - quot * divisor) >= divisor)
			quot++;
	}

	return quot;
}
EXPORT_SYMBOL(div64_u64);
#endif

/**
 * div64_s64 - signed 64bit divide with 64bit divisor
 * @dividend:	64bit dividend
 * @divisor:	64bit divisor
 */
#ifndef div64_s64
s64 div64_s64(s64 dividend, s64 divisor)
{
	s64 quot, t;

	quot = div64_u64(abs64(dividend), abs64(divisor));
	t = (dividend ^ divisor) >> 63;

	return (quot ^ t) - t;
}
EXPORT_SYMBOL(div64_s64);
#endif

#endif /* BITS_PER_LONG == 32 */

/*
 * Iterative div/mod for use when dividend is not expected to be much
 * bigger than divisor.
 */
u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
{
	return __iter_div_u64_rem(dividend, divisor, remainder);
}
EXPORT_SYMBOL(iter_div_u64_rem);
Commit	Line	Data
1da177e4 LT	1	/*
	2	* Copyright (C) 2003 Bernardo Innocenti <[email protected]>
	3	*
	4	* Based on former do_div() implementation from asm-parisc/div64.h:
	5	* Copyright (C) 1999 Hewlett-Packard Co
	6	* Copyright (C) 1999 David Mosberger-Tang <[email protected]>
	7	*
	8	*
	9	* Generic C version of 64bit/32bit division and modulo, with
	10	* 64bit result and 32bit remainder.
	11	*
	12	* The fast case for (n>>32 == 0) is handled inline by do_div().
	13	*
	14	* Code generated for this function might be very inefficient
	15	* for some CPUs. __div64_32() can be overridden by linking arch-specific
	16	* assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S.
	17	*/
	18
1da177e4	19	#include <linux/module.h>
2418f4f2	20	#include <linux/math64.h>
1da177e4 LT	21
	22	/* Not needed on 64bit architectures */
	23	#if BITS_PER_LONG == 32
	24
cb8c181f	25	uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
1da177e4 LT	26	{
	27	uint64_t rem = *n;
	28	uint64_t b = base;
	29	uint64_t res, d = 1;
	30	uint32_t high = rem >> 32;
	31
	32	/* Reduce the thing a bit first */
	33	res = 0;
	34	if (high >= base) {
	35	high /= base;
	36	res = (uint64_t) high << 32;
	37	rem -= (uint64_t) (high*base) << 32;
	38	}
	39
	40	while ((int64_t)b > 0 && b < rem) {
	41	b = b+b;
	42	d = d+d;
	43	}
	44
	45	do {
	46	if (rem >= b) {
	47	rem -= b;
	48	res += d;
	49	}
	50	b >>= 1;
	51	d >>= 1;
	52	} while (d);
	53
	54	*n = res;
	55	return rem;
	56	}
	57
	58	EXPORT_SYMBOL(__div64_32);
	59
2418f4f2 RZ	60	#ifndef div_s64_rem
	61	s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
	62	{
	63	u64 quotient;
	64
	65	if (dividend < 0) {
	66	quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
	67	remainder = -remainder;
	68	if (divisor > 0)
	69	quotient = -quotient;
	70	} else {
	71	quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
	72	if (divisor < 0)
	73	quotient = -quotient;
	74	}
	75	return quotient;
	76	}
	77	EXPORT_SYMBOL(div_s64_rem);
	78	#endif
	79
658716d1 BB	80	/**
	81	* div64_u64 - unsigned 64bit divide with 64bit divisor
	82	* @dividend: 64bit dividend
	83	* @divisor: 64bit divisor
	84	*
	85	* This implementation is a modified version of the algorithm proposed
	86	* by the book 'Hacker's Delight'. The original source and full proof
	87	* can be found here and is available for use without restriction.
	88	*
	89	* 'http://www.hackersdelight.org/HDcode/newCode/divDouble.c'
	90	*/
6f6d6a1a RZ	91	#ifndef div64_u64
6f6d6a1a RZ	92	u64 div64_u64(u64 dividend, u64 divisor)
3927f2e8	93	{
658716d1 BB	94	u32 high = divisor >> 32;
658716d1 BB	95	u64 quot;
3927f2e8	96
658716d1 BB	97	if (high == 0) {
	98	quot = div_u64(dividend, divisor);
	99	} else {
	100	int n = 1 + fls(high);
	101	quot = div_u64(dividend >> n, divisor >> n);
3927f2e8	102
658716d1 BB	103	if (quot != 0)
	104	quot--;
	105	if ((dividend - quot * divisor) >= divisor)
	106	quot++;
	107	}
3927f2e8	108
658716d1	109	return quot;
3927f2e8	110	}
6f6d6a1a RZ	111	EXPORT_SYMBOL(div64_u64);
6f6d6a1a RZ	112	#endif
3927f2e8	113
658716d1 BB	114	/**
	115	* div64_s64 - signed 64bit divide with 64bit divisor
	116	* @dividend: 64bit dividend
	117	* @divisor: 64bit divisor
	118	*/
	119	#ifndef div64_s64
	120	s64 div64_s64(s64 dividend, s64 divisor)
	121	{
	122	s64 quot, t;
	123
	124	quot = div64_u64(abs64(dividend), abs64(divisor));
	125	t = (dividend ^ divisor) >> 63;
	126
	127	return (quot ^ t) - t;
	128	}
	129	EXPORT_SYMBOL(div64_s64);
	130	#endif
	131
1da177e4	132	#endif /* BITS_PER_LONG == 32 */
f595ec96 JF	133
	134	/*
	135	* Iterative div/mod for use when dividend is not expected to be much
	136	* bigger than divisor.
	137	*/
	138	u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
	139	{
d5e181f7	140	return __iter_div_u64_rem(dividend, divisor, remainder);
f595ec96 JF	141	}
f595ec96 JF	142	EXPORT_SYMBOL(iter_div_u64_rem);