mirror of
https://github.com/ApfelTeeSaft/reactos.git
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141 lines
2.8 KiB
C
141 lines
2.8 KiB
C
#ifndef _I386_BITOPS_H
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#define _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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* Reused for the ReactOS kernel by David Welch (1998)
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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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#ifdef __SMP__
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#define LOCK_PREFIX "lock ; "
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#define SMPVOL volatile
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#else
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#define LOCK_PREFIX ""
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#define SMPVOL
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#endif
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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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#define CONST_ADDR (*(const struct __dummy *) addr)
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extern __inline__ int set_bit(int nr, SMPVOL void * addr)
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{
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int oldbit;
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__asm__ __volatile__(LOCK_PREFIX
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"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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extern __inline__ int clear_bit(int nr, SMPVOL void * addr)
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{
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int oldbit;
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__asm__ __volatile__(LOCK_PREFIX
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"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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extern __inline__ int change_bit(int nr, SMPVOL void * addr)
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{
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int oldbit;
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__asm__ __volatile__(LOCK_PREFIX
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"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.
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*/
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extern __inline__ int test_bit(int nr, const SMPVOL void * addr)
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{
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return ((1UL << (nr & 31)) & (((const unsigned int *) addr)[nr >> 5])) != 0;
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}
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/*
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* Find-bit routines..
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*/
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extern __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__("cld\n\t"
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"movl $-1,%%eax\n\t"
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"xorl %%edx,%%edx\n\t"
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"repe; scasl\n\t"
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"je 1f\n\t"
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"xorl -4(%%edi),%%eax\n\t"
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"subl $4,%%edi\n\t"
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"bsfl %%eax,%%edx\n"
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"1:\tsubl %%ebx,%%edi\n\t"
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"shll $3,%%edi\n\t"
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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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extern __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__("bsfl %1,%0\n\t"
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"jne 1f\n\t"
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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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extern __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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#endif /* _I386_BITOPS_H */
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