64 lines
878 B
Go
64 lines
878 B
Go
package rlepluslazy
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type rbitvec struct {
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index int
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bits uint64
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bitCap byte
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vec []byte
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}
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func readBitvec(vec []byte) *rbitvec {
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bv := &rbitvec{vec: vec}
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for n := 7; n >= 0; n-- {
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var o uint64
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if len(bv.vec) > n {
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o = uint64(bv.vec[n])
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}
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bv.bits = bv.bits<<8 | o
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bv.index++
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}
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bv.bitCap = 64
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return bv
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}
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const (
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minCap = 8
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)
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var bitMasks = [9]byte{
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0x0,
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0x1,
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0x3,
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0x7,
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0xF,
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0x1F,
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0x3F,
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0x7F,
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0xFF,
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}
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func (bv *rbitvec) Get(count byte) byte {
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res := byte(bv.bits) & bitMasks[count]
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bv.bits = bv.bits >> count
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bv.bitCap = bv.bitCap - count
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if bv.bitCap < minCap {
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var add uint64
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for n := 6; n >= 0; n-- {
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var o uint64
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if len(bv.vec) > bv.index+n {
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o = uint64(bv.vec[bv.index+n])
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}
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add = add<<8 | o
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}
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bv.index = bv.index + 7
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bv.bits = bv.bits | add<<(bv.bitCap)
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bv.bitCap = bv.bitCap + 7*8
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}
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return res
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}
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