mirror of
https://codeberg.org/forgejo/forgejo.git
synced 2024-11-23 08:47:42 -05:00
44 lines
1.5 KiB
Go
44 lines
1.5 KiB
Go
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package numeric
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var interleaveMagic = []uint64{
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0x5555555555555555,
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0x3333333333333333,
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0x0F0F0F0F0F0F0F0F,
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0x00FF00FF00FF00FF,
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0x0000FFFF0000FFFF,
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0x00000000FFFFFFFF,
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0xAAAAAAAAAAAAAAAA,
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}
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var interleaveShift = []uint{1, 2, 4, 8, 16}
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// Interleave the first 32 bits of each uint64
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// apdated from org.apache.lucene.util.BitUtil
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// whcih was adapted from:
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// http://graphics.stanford.edu/~seander/bithacks.html#InterleaveBMN
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func Interleave(v1, v2 uint64) uint64 {
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v1 = (v1 | (v1 << interleaveShift[4])) & interleaveMagic[4]
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v1 = (v1 | (v1 << interleaveShift[3])) & interleaveMagic[3]
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v1 = (v1 | (v1 << interleaveShift[2])) & interleaveMagic[2]
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v1 = (v1 | (v1 << interleaveShift[1])) & interleaveMagic[1]
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v1 = (v1 | (v1 << interleaveShift[0])) & interleaveMagic[0]
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v2 = (v2 | (v2 << interleaveShift[4])) & interleaveMagic[4]
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v2 = (v2 | (v2 << interleaveShift[3])) & interleaveMagic[3]
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v2 = (v2 | (v2 << interleaveShift[2])) & interleaveMagic[2]
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v2 = (v2 | (v2 << interleaveShift[1])) & interleaveMagic[1]
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v2 = (v2 | (v2 << interleaveShift[0])) & interleaveMagic[0]
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return (v2 << 1) | v1
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}
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// Deinterleave the 32-bit value starting at position 0
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// to get the other 32-bit value, shift it by 1 first
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func Deinterleave(b uint64) uint64 {
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b &= interleaveMagic[0]
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b = (b ^ (b >> interleaveShift[0])) & interleaveMagic[1]
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b = (b ^ (b >> interleaveShift[1])) & interleaveMagic[2]
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b = (b ^ (b >> interleaveShift[2])) & interleaveMagic[3]
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b = (b ^ (b >> interleaveShift[3])) & interleaveMagic[4]
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b = (b ^ (b >> interleaveShift[4])) & interleaveMagic[5]
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return b
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}
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