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Commit	Line	Data
	1	/*
	2	* $FreeBSD: src/sys/gnu/ext2fs/i386-bitops.h,v 1.5 1999/11/15 23:16:06 obrien Exp $
	3	*/
	4	/*
	5	* this is mixture of i386/bitops.h and asm/string.h
	6	* taken from the Linux source tree
	7	*
	8	* XXX replace with Mach routines or reprogram in C
	9	*/
	10	#ifndef _VFS_GNU_EXT2FS_I386_BITOPS_H_
	11	#define _VFS_GNU_EXT2FS_I386_BITOPS_H_
	12
	13	/*
	14	* Copyright 1992, Linus Torvalds.
	15	*/
	16
	17	/*
	18	* These have to be done with inline assembly: that way the bit-setting
	19	* is guaranteed to be atomic. All bit operations return 0 if the bit
	20	* was cleared before the operation and != 0 if it was not.
	21	*
	22	* bit 0 is the LSB of addr; bit 32 is the LSB of (addr+1).
	23	*/
	24
	25	/*
	26	* Some hacks to defeat gcc over-optimizations..
	27	*/
	28	struct __dummy { unsigned long a[100]; };
	29	#define ADDR ((struct __dummy ) addr)
	30
	31	static __inline__ int
	32	set_bit(int nr, void *addr)
	33	{
	34	int oldbit;
	35
	36	__asm__ __volatile__("btsl %2,%1\n\tsbbl %0,%0"
	37	:"=r" (oldbit),"=m" (ADDR)
	38	:"ir" (nr));
	39	return oldbit;
	40	}
	41
	42	static __inline__ int
	43	clear_bit(int nr, void *addr)
	44	{
	45	int oldbit;
	46
	47	__asm__ __volatile__("btrl %2,%1\n\tsbbl %0,%0"
	48	:"=r" (oldbit),"=m" (ADDR)
	49	:"ir" (nr));
	50	return oldbit;
	51	}
	52
	53	static __inline__ int
	54	change_bit(int nr, void *addr)
	55	{
	56	int oldbit;
	57
	58	__asm__ __volatile__("btcl %2,%1\n\tsbbl %0,%0"
	59	:"=r" (oldbit),"=m" (ADDR)
	60	:"ir" (nr));
	61	return oldbit;
	62	}
	63
	64	/*
	65	* This routine doesn't need to be atomic, but it's faster to code it
	66	* this way.
	67	*/
	68	static __inline__ int
	69	test_bit(int nr, void *addr)
	70	{
	71	int oldbit;
	72
	73	__asm__ __volatile__("btl %2,%1\n\tsbbl %0,%0"
	74	:"=r" (oldbit)
	75	:"m" (ADDR),"ir" (nr));
	76	return oldbit;
	77	}
	78
	79	/*
	80	* Find-bit routines..
	81	*/
	82	static __inline__ int
	83	find_first_zero_bit(void *addr, unsigned size)
	84	{
	85	int res;
	86	int _count = (size + 31) >> 5;
	87
	88	if (!size)
	89	return 0;
	90	__asm__(" \n\
	91	cld \n\
	92	movl $-1,%%eax \n\
	93	xorl %%edx,%%edx \n\
	94	repe; scasl \n\
	95	je 1f \n\
	96	xorl -4(%%edi),%%eax \n\
	97	subl $4,%%edi \n\
	98	bsfl %%eax,%%edx \n\
	99	1: subl %%ebx,%%edi \n\
	100	shll $3,%%edi \n\
	101	addl %%edi,%%edx"
	102	: "=c" (_count), "=D" (addr), "=d" (res)
	103	: "0" (_count), "1" (addr), "b" (addr)
	104	: "ax");
	105	return res;
	106	}
	107
	108	static __inline__ int
	109	find_next_zero_bit(void *addr, int size, int offset)
	110	{
	111	unsigned long * p = ((unsigned long *) addr) + (offset >> 5);
	112	int set = 0, bit = offset & 31, res;
	113
	114	if (bit) {
	115	/*
	116	* Look for zero in first byte
	117	*/
	118	__asm__(" \n\
	119	bsfl %1,%0 \n\
	120	jne 1f \n\
	121	movl $32, %0 \n\
	122	1: "
	123	: "=r" (set)
	124	: "r" (~(*p >> bit)));
	125	if (set < (32 - bit))
	126	return set + offset;
	127	set = 32 - bit;
	128	p++;
	129	}
	130	/*
	131	* No zero yet, search remaining full bytes for a zero
	132	*/
	133	res = find_first_zero_bit (p, size - 32 * (p - (unsigned long *) addr));
	134	return (offset + set + res);
	135	}
	136
	137	/*
	138	* ffz = Find First Zero in word. Undefined if no zero exists,
	139	* so code should check against ~0UL first..
	140	*/
	141	static __inline__ unsigned long
	142	ffz(unsigned long word)
	143	{
	144	__asm__("bsfl %1,%0"
	145	:"=r" (word)
	146	:"r" (~word));
	147	return word;
	148	}
	149
	150	/*
	151	* memscan() taken from linux asm/string.h
	152	*/
	153	/*
	154	* find the first occurrence of byte 'c', or 1 past the area if none
	155	*/
	156	static __inline__ char *
	157	memscan(void *addr, unsigned char c, int size)
	158	{
	159	if (!size)
	160	return addr;
	161	__asm__(" \n\
	162	cld \n\
	163	repnz; scasb \n\
	164	jnz 1f \n\
	165	dec %%edi \n\
	166	1: "
	167	: "=D" (addr), "=c" (size)
	168	: "0" (addr), "1" (size), "a" (c));
	169	return addr;
	170	}
	171
	172	#endif /* _VFS_GNU_EXT2FS_I386_BITOPS_H_ */