161 lines
3.3 KiB
C
161 lines
3.3 KiB
C
/*
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* this is mixture of i386/bitops.h and asm/string.h
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* taken from the Linux source tree
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*
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* XXX replace with Mach routines or reprogram in C
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*/
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#ifndef _SYS_GNU_EXT2FS_I386_BITOPS_H_
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#define _SYS_GNU_EXT2FS_I386_BITOPS_H_
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/*
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* Copyright 1992, Linus Torvalds.
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*/
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/*
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* These have to be done with inline assembly: that way the bit-setting
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* is guaranteed to be atomic. All bit operations return 0 if the bit
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* was cleared before the operation and != 0 if it was not.
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*
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* bit 0 is the LSB of addr; bit 32 is the LSB of (addr+1).
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*/
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/*
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* Some hacks to defeat gcc over-optimizations..
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*/
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struct __dummy { unsigned long a[100]; };
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#define ADDR (*(struct __dummy *) addr)
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static __inline__ int set_bit(int nr, void * addr)
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{
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int oldbit;
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__asm__ __volatile__("btsl %2,%1\n\tsbbl %0,%0"
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:"=r" (oldbit),"=m" (ADDR)
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:"ir" (nr));
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return oldbit;
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}
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static __inline__ int clear_bit(int nr, void * addr)
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{
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int oldbit;
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__asm__ __volatile__("btrl %2,%1\n\tsbbl %0,%0"
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:"=r" (oldbit),"=m" (ADDR)
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:"ir" (nr));
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return oldbit;
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}
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static __inline__ int change_bit(int nr, void * addr)
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{
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int oldbit;
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__asm__ __volatile__("btcl %2,%1\n\tsbbl %0,%0"
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:"=r" (oldbit),"=m" (ADDR)
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:"ir" (nr));
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return oldbit;
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}
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/*
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* This routine doesn't need to be atomic, but it's faster to code it
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* this way.
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*/
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static __inline__ int test_bit(int nr, void * addr)
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{
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int oldbit;
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__asm__ __volatile__("btl %2,%1\n\tsbbl %0,%0"
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:"=r" (oldbit)
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:"m" (ADDR),"ir" (nr));
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return oldbit;
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}
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/*
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* Find-bit routines..
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*/
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static __inline__ int find_first_zero_bit(void * addr, unsigned size)
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{
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int res;
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if (!size)
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return 0;
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__asm__(" \n\
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cld \n\
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movl $-1,%%eax \n\
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xorl %%edx,%%edx \n\
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repe; scasl \n\
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je 1f \n\
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xorl -4(%%edi),%%eax \n\
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subl $4,%%edi \n\
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bsfl %%eax,%%edx \n\
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1: subl %%ebx,%%edi \n\
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shll $3,%%edi \n\
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addl %%edi,%%edx"
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:"=d" (res)
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:"c" ((size + 31) >> 5), "D" (addr), "b" (addr)
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:"ax", "cx", "di");
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return res;
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}
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static __inline__ int find_next_zero_bit (void * addr, int size, int offset)
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{
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unsigned long * p = ((unsigned long *) addr) + (offset >> 5);
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int set = 0, bit = offset & 31, res;
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if (bit) {
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/*
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* Look for zero in first byte
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*/
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__asm__(" \n\
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bsfl %1,%0 \n\
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jne 1f \n\
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movl $32, %0 \n\
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1: "
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: "=r" (set)
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: "r" (~(*p >> bit)));
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if (set < (32 - bit))
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return set + offset;
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set = 32 - bit;
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p++;
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}
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/*
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* No zero yet, search remaining full bytes for a zero
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*/
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res = find_first_zero_bit (p, size - 32 * (p - (unsigned long *) addr));
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return (offset + set + res);
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}
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/*
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* ffz = Find First Zero in word. Undefined if no zero exists,
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* so code should check against ~0UL first..
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*/
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static __inline__ unsigned long ffz(unsigned long word)
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{
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__asm__("bsfl %1,%0"
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:"=r" (word)
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:"r" (~word));
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return word;
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}
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/*
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* memscan() taken from linux asm/string.h
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*/
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/*
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* find the first occurrence of byte 'c', or 1 past the area if none
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*/
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static __inline__ char * memscan(void * addr, unsigned char c, int size)
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{
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if (!size)
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return addr;
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__asm__(" \n\
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cld \n\
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repnz; scasb \n\
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jnz 1f \n\
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dec %%edi \n\
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1: "
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: "=D" (addr), "=c" (size)
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: "0" (addr), "1" (size), "a" (c));
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return addr;
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}
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#endif /* !_SYS_GNU_EXT2FS_I386_BITOPS_H_ */
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