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47 lines
1.2 KiB
C
47 lines
1.2 KiB
C
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#ifndef _ASM_WORD_AT_A_TIME_H
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#define _ASM_WORD_AT_A_TIME_H
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/*
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* This is largely generic for little-endian machines, but the
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* optimal byte mask counting is probably going to be something
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* that is architecture-specific. If you have a reliably fast
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* bit count instruction, that might be better than the multiply
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* and shift, for example.
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*/
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#ifdef CONFIG_64BIT
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/*
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* Jan Achrenius on G+: microoptimized version of
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* the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
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* that works for the bytemasks without having to
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* mask them first.
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*/
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static inline long count_masked_bytes(unsigned long mask)
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{
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return mask*0x0001020304050608ul >> 56;
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}
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#else /* 32-bit case */
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/* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
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static inline long count_masked_bytes(long mask)
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{
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/* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
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long a = (0x0ff0001+mask) >> 23;
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/* Fix the 1 for 00 case */
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return a & mask;
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}
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#endif
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#define REPEAT_BYTE(x) ((~0ul / 0xff) * (x))
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/* Return the high bit set in the first byte that is a zero */
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static inline unsigned long has_zero(unsigned long a)
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{
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return ((a - REPEAT_BYTE(0x01)) & ~a) & REPEAT_BYTE(0x80);
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}
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#endif /* _ASM_WORD_AT_A_TIME_H */
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