1 #ifndef _ASM_WORD_AT_A_TIME_H
2 #define _ASM_WORD_AT_A_TIME_H
4 #include <linux/kernel.h>
5 #include <asm/byteorder.h>
9 struct word_at_a_time {
10 const unsigned long high_bits, low_bits;
13 #define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0xfe) + 1, REPEAT_BYTE(0x7f) }
15 /* Bit set in the bytes that have a zero */
16 static inline long prep_zero_mask(unsigned long val, unsigned long rhs, const struct word_at_a_time *c)
18 unsigned long mask = (val & c->low_bits) + c->low_bits;
22 #define create_zero_mask(mask) (mask)
24 static inline long find_zero(unsigned long mask)
37 return (mask >> 8) ? byte : byte + 1;
40 static inline bool has_zero(unsigned long val, unsigned long *data, const struct word_at_a_time *c)
42 unsigned long rhs = val | c->low_bits;
44 return (val + c->high_bits) & ~rhs;
48 #define zero_bytemask(mask) (~1ul << __fls(mask))
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.
59 struct word_at_a_time {
60 const unsigned long one_bits, high_bits;
63 #define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }
68 * Jan Achrenius on G+: microoptimized version of
69 * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
70 * that works for the bytemasks without having to
73 static inline long count_masked_bytes(unsigned long mask)
75 return mask*0x0001020304050608ul >> 56;
78 #else /* 32-bit case */
80 /* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
81 static inline long count_masked_bytes(long mask)
83 /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
84 long a = (0x0ff0001+mask) >> 23;
85 /* Fix the 1 for 00 case */
91 /* Return nonzero if it has a zero */
92 static inline unsigned long has_zero(unsigned long a, unsigned long *bits, const struct word_at_a_time *c)
94 unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
99 static inline unsigned long prep_zero_mask(unsigned long a, unsigned long bits, const struct word_at_a_time *c)
104 static inline unsigned long create_zero_mask(unsigned long bits)
106 bits = (bits - 1) & ~bits;
110 /* The mask we created is directly usable as a bytemask */
111 #define zero_bytemask(mask) (mask)
113 static inline unsigned long find_zero(unsigned long mask)
115 return count_masked_bytes(mask);
118 #endif /* __BIG_ENDIAN */
120 #endif /* _ASM_WORD_AT_A_TIME_H */