Linux Kernel  3.7.1
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word-at-a-time.h
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1 #ifndef _ASM_WORD_AT_A_TIME_H
2 #define _ASM_WORD_AT_A_TIME_H
3 
4 /*
5  * This says "generic", but it's actually big-endian only.
6  * Little-endian can use more efficient versions of these
7  * interfaces, see for example
8  * arch/x86/include/asm/word-at-a-time.h
9  * for those.
10  */
11 
12 #include <linux/kernel.h>
13 
14 struct word_at_a_time {
15  const unsigned long high_bits, low_bits;
16 };
17 
18 #define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0xfe) + 1, REPEAT_BYTE(0x7f) }
19 
20 /* Bit set in the bytes that have a zero */
21 static inline long prep_zero_mask(unsigned long val, unsigned long rhs, const struct word_at_a_time *c)
22 {
23  unsigned long mask = (val & c->low_bits) + c->low_bits;
24  return ~(mask | rhs);
25 }
26 
27 #define create_zero_mask(mask) (mask)
28 
29 static inline long find_zero(unsigned long mask)
30 {
31  long byte = 0;
32 #ifdef CONFIG_64BIT
33  if (mask >> 32)
34  mask >>= 32;
35  else
36  byte = 4;
37 #endif
38  if (mask >> 16)
39  mask >>= 16;
40  else
41  byte += 2;
42  return (mask >> 8) ? byte : byte + 1;
43 }
44 
45 static inline bool has_zero(unsigned long val, unsigned long *data, const struct word_at_a_time *c)
46 {
47  unsigned long rhs = val | c->low_bits;
48  *data = rhs;
49  return (val + c->high_bits) & ~rhs;
50 }
51 
52 #endif /* _ASM_WORD_AT_A_TIME_H */