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11 package sys
12
13
14
15 const deBruijn64ctz = 0x0218a392cd3d5dbf
16
17 var deBruijnIdx64ctz = [64]byte{
18 0, 1, 2, 7, 3, 13, 8, 19,
19 4, 25, 14, 28, 9, 34, 20, 40,
20 5, 17, 26, 38, 15, 46, 29, 48,
21 10, 31, 35, 54, 21, 50, 41, 57,
22 63, 6, 12, 18, 24, 27, 33, 39,
23 16, 37, 45, 47, 30, 53, 49, 56,
24 62, 11, 23, 32, 36, 44, 52, 55,
25 61, 22, 43, 51, 60, 42, 59, 58,
26 }
27
28 const deBruijn32ctz = 0x04653adf
29
30 var deBruijnIdx32ctz = [32]byte{
31 0, 1, 2, 6, 3, 11, 7, 16,
32 4, 14, 12, 21, 8, 23, 17, 26,
33 31, 5, 10, 15, 13, 20, 22, 25,
34 30, 9, 19, 24, 29, 18, 28, 27,
35 }
36
37
38
39 func Ctz64(x uint64) int {
40 x &= -x
41 y := x * deBruijn64ctz >> 58
42 i := int(deBruijnIdx64ctz[y])
43 z := int((x - 1) >> 57 & 64)
44 return i + z
45 }
46
47
48
49 func Ctz32(x uint32) int {
50 x &= -x
51 y := x * deBruijn32ctz >> 27
52 i := int(deBruijnIdx32ctz[y])
53 z := int((x - 1) >> 26 & 32)
54 return i + z
55 }
56
57
58 func Ctz8(x uint8) int {
59 return int(ntz8tab[x])
60 }
61
62
63
64 func Bswap64(x uint64) uint64 {
65 c8 := uint64(0x00ff00ff00ff00ff)
66 a := x >> 8 & c8
67 b := (x & c8) << 8
68 x = a | b
69 c16 := uint64(0x0000ffff0000ffff)
70 a = x >> 16 & c16
71 b = (x & c16) << 16
72 x = a | b
73 c32 := uint64(0x00000000ffffffff)
74 a = x >> 32 & c32
75 b = (x & c32) << 32
76 x = a | b
77 return x
78 }
79
80
81
82 func Bswap32(x uint32) uint32 {
83 c8 := uint32(0x00ff00ff)
84 a := x >> 8 & c8
85 b := (x & c8) << 8
86 x = a | b
87 c16 := uint32(0x0000ffff)
88 a = x >> 16 & c16
89 b = (x & c16) << 16
90 x = a | b
91 return x
92 }
93
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