LXR linux/include/asm-generic/word-at-a-time.h

   1#ifndef _ASM_WORD_AT_A_TIME_H
   2#define _ASM_WORD_AT_A_TIME_H
   3
   4#include <linux/kernel.h>
   5#include <asm/byteorder.h>
   6
   7#ifdef __BIG_ENDIAN
   8
   9struct word_at_a_time {
  10        const unsigned long high_bits, low_bits;
  11};
  12
  13#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0xfe) + 1, REPEAT_BYTE(0x7f) }
  14
  15/* Bit set in the bytes that have a zero */
  16static inline long prep_zero_mask(unsigned long val, unsigned long rhs, const struct word_at_a_time *c)
  17{
  18        unsigned long mask = (val & c->low_bits) + c->low_bits;
  19        return ~(mask | rhs);
  20}
  21
  22#define create_zero_mask(mask) (mask)
  23
  24static inline long find_zero(unsigned long mask)
  25{
  26        long byte = 0;
  27#ifdef CONFIG_64BIT
  28        if (mask >> 32)
  29                mask >>= 32;
  30        else
  31                byte = 4;
  32#endif
  33        if (mask >> 16)
  34                mask >>= 16;
  35        else
  36                byte += 2;
  37        return (mask >> 8) ? byte : byte + 1;
  38}
  39
  40static inline bool has_zero(unsigned long val, unsigned long *data, const struct word_at_a_time *c)
  41{
  42        unsigned long rhs = val | c->low_bits;
  43        *data = rhs;
  44        return (val + c->high_bits) & ~rhs;
  45}
  46
  47#ifndef zero_bytemask
  48#define zero_bytemask(mask) (~1ul << __fls(mask))
  49#endif
  50
  51#else
  52
  53/*
  54 * The optimal byte mask counting is probably going to be something
  55 * that is architecture-specific. If you have a reliably fast
  56 * bit count instruction, that might be better than the multiply
  57 * and shift, for example.
  58 */
  59struct word_at_a_time {
  60        const unsigned long one_bits, high_bits;
  61};
  62
  63#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }
  64
  65#ifdef CONFIG_64BIT
  66
  67/*
  68 * Jan Achrenius on G+: microoptimized version of
  69 * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
  70 * that works for the bytemasks without having to
  71 * mask them first.
  72 */
  73static inline long count_masked_bytes(unsigned long mask)
  74{
  75        return mask*0x0001020304050608ul >> 56;
  76}
  77
  78#else   /* 32-bit case */
  79
  80/* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
  81static inline long count_masked_bytes(long mask)
  82{
  83        /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
  84        long a = (0x0ff0001+mask) >> 23;
  85        /* Fix the 1 for 00 case */
  86        return a & mask;
  87}
  88
  89#endif
  90
  91/* Return nonzero if it has a zero */
  92static inline unsigned long has_zero(unsigned long a, unsigned long *bits, const struct word_at_a_time *c)
  93{
  94        unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
  95        *bits = mask;
  96        return mask;
  97}
  98
  99static inline unsigned long prep_zero_mask(unsigned long a, unsigned long bits, const struct word_at_a_time *c)
 100{
 101        return bits;
 102}
 103
 104static inline unsigned long create_zero_mask(unsigned long bits)
 105{
 106        bits = (bits - 1) & ~bits;
 107        return bits >> 7;
 108}
 109
 110/* The mask we created is directly usable as a bytemask */
 111#define zero_bytemask(mask) (mask)
 112
 113static inline unsigned long find_zero(unsigned long mask)
 114{
 115        return count_masked_bytes(mask);
 116}
 117
 118#endif /* __BIG_ENDIAN */
 119
 120#endif /* _ASM_WORD_AT_A_TIME_H */
 121