mirror of
https://github.com/fumiama/unibase2n.git
synced 2026-06-20 02:15:08 +08:00
finish decode
This commit is contained in:
源文雨
226
decode.go
226
decode.go
@@ -2,14 +2,58 @@ package unibase2n
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import (
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"encoding/binary"
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"math/bits"
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)
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func (bs Base) Decode(data []byte) []byte {
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return nil
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func (bs Base) Decode(data []byte) (out []byte) {
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if len(data) == 0 || len(data)%2 != 0 {
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return nil
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}
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if bits.OnesCount8(bs.bit) == 1 { // 2的幂永无offset, 无需管til (1/2/4/8)
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out = make([]byte, bs.DecodeLen(len(data), 0))
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switch bs.bit {
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case 8:
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dec16blk8(bs.off, data, out)
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case 4:
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mask := uint32(bs.off) | uint32(bs.off)<<16
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dec32blk4(mask, data, out)
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case 2:
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mask := uint64(bs.off) | uint64(bs.off)<<16 | uint64(bs.off)<<32 | uint64(bs.off)<<48
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dec64blk2(mask, data, out)
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case 1:
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mask64 := uint64(bs.off) | uint64(bs.off)<<16 | uint64(bs.off)<<32 | uint64(bs.off)<<48
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mask := uint128be{a: mask64, b: mask64}
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dec128blk1(mask, data, out)
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}
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return
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}
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offset := 0
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tile := uint32(bs.til) // [til, tile)
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if bs.bit > 4 && bs.bit%2 == 0 {
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tile += uint32(bs.bit / 2) // 6 10 12 14
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} else {
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tile += uint32(bs.bit) // 3 5 7 9 11 13 15
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}
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realtail := binary.BigEndian.Uint16(data[len(data)-2:])
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if realtail >= bs.til && uint32(realtail) < tile {
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offset = int(realtail - bs.til)
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}
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out = make([]byte, bs.DecodeLen(len(data), offset))
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switch bs.bit {
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case 3, 5, 7, 9, 11, 13, 15:
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mask64 := uint64(bs.off) | uint64(bs.off)<<16 | uint64(bs.off)<<32 | uint64(bs.off)<<48
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mask := uint128be{a: mask64, b: mask64}
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dec128blk(mask, bs.bit, data, out)
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case 6, 10, 12, 14:
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mask := uint64(bs.off) | uint64(bs.off)<<16 | uint64(bs.off)<<32 | uint64(bs.off)<<48
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dec64blk(mask, bs.bit, data, out)
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}
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return
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}
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// dec128blk1 for bit 1
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// len(in)>0, len(in)%16==0, len(out)==len(in)/16
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//go:nosplit
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func dec128blk1(mask uint128be, in, out []byte) {
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for i := range out {
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c := i * 16
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@@ -43,21 +87,183 @@ func dec128blk1(mask uint128be, in, out []byte) {
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}
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// dec64blk2 for bit 2
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// len(in)!=0, len(out)==len(in)/8
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// len(in)>0, len(in)%8==0, len(out)==len(in)/8
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//go:nosplit
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func dec64blk2(mask uint64, in, out []byte) {
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for i, n := range in {
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for i := range out {
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c := i * 8
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x := (uint64(n)<<42 | uint64(n)<<28 | uint64(n)<<14 | uint64(n)) & 0x00030003_00030003
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binary.BigEndian.PutUint64(out[c:c+8], x+mask)
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n := binary.BigEndian.Uint64(in[c:c+8]) - mask
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sum := n & 0x03
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n >>= 16 - 2
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sum |= n & 0x0c
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n >>= 16 - 2
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sum |= n & 0x30
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n >>= 16 - 2
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sum |= n & 0xc0
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out[i] = uint8(sum)
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}
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}
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// dec32blk4 for bit 4
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// len(in)!=0, len(out)==len(in)/4
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// len(in)>0, len(in)%4==0, len(out)==len(in)/4
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//go:nosplit
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func dec32blk4(mask uint32, in, out []byte) {
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for i, n := range in {
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for i := range out {
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c := i * 4
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x := (uint32(n)<<12 | uint32(n)) & 0x000f000f
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binary.BigEndian.PutUint32(out[c:c+4], x+mask)
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n := binary.BigEndian.Uint32(in[c:c+4]) - mask
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sum := n & 0x0f
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n >>= 16 - 4
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sum |= n & 0xf0
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out[i] = uint8(sum)
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}
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}
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// dec16blk8 for bit 8
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// len(in)>0, len(in)%2==0, len(out)==len(in)/2
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//go:nosplit
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func dec16blk8(mask uint16, in, out []byte) {
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for i := range out {
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c := i * 2
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n := binary.BigEndian.Uint16(in[c:c+2]) - mask
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out[i] = uint8(n)
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}
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}
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// dec128blk for bit 3 5 6 7 9 11 13 15
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// len(in)>0, len(in)%2==0, len(out)==len(in)/16*bit+offset
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//go:nosplit
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func dec128blk(mask uint128be, bit uint8, in, out []byte) {
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var tmp [16]byte
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i := 0
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n := 0
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c := 16 - bit
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for ; i <= len(out)-int(bit); n += 16 {
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m := uint128be{a: (uint64(1)<<bit - 1) << (64 - bit)}
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shift := readuint128be(in[n:]).sub(mask)
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shift.shleq(c)
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sum := shift.and(m)
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shift.shleq(c)
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m.shreq(bit)
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sum.oreq(shift.and(m))
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shift.shleq(c)
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m.shreq(bit)
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sum.oreq(shift.and(m))
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shift.shleq(c)
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m.shreq(bit)
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sum.oreq(shift.and(m))
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shift.shleq(c)
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m.shreq(bit)
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sum.oreq(shift.and(m))
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shift.shleq(c)
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m.shreq(bit)
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sum.oreq(shift.and(m))
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shift.shleq(c)
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m.shreq(bit)
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sum.oreq(shift.and(m))
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shift.shleq(c)
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m.shreq(bit)
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sum.oreq(shift.and(m))
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if len(out[i:]) < 16 {
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sum.write(tmp[:])
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copy(out[i:], tmp[:])
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} else {
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sum.write(out[i:])
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}
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i += int(bit)
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}
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if n < len(in)-2 {
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m := uint128be{a: (uint64(1)<<bit - 1) << (64 - bit)}
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copy(tmp[:], in[n:])
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msk := uint16(mask.a & 0xffff)
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for j := 0; j < 8; j++ {
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x := binary.BigEndian.Uint16(tmp[j*2:])
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if x < msk {
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binary.BigEndian.PutUint16(tmp[j*2:], msk)
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}
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}
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shift := readuint128be(tmp[:]).sub(mask)
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shift.shleq(c)
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sum := shift.and(m)
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shift.shleq(c)
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m.shreq(bit)
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sum.oreq(shift.and(m))
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shift.shleq(c)
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m.shreq(bit)
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sum.oreq(shift.and(m))
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shift.shleq(c)
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m.shreq(bit)
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sum.oreq(shift.and(m))
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shift.shleq(c)
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m.shreq(bit)
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sum.oreq(shift.and(m))
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shift.shleq(c)
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m.shreq(bit)
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sum.oreq(shift.and(m))
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shift.shleq(c)
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m.shreq(bit)
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sum.oreq(shift.and(m))
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shift.shleq(c)
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m.shreq(bit)
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sum.oreq(shift.and(m))
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sum.write(tmp[:])
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copy(out[i:], tmp[:])
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}
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}
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// dec64blk for bit 6 10 12 14
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// len(in)>0, len(in)%2==0, len(out)==len(in)/16*bit+offset
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//go:nosplit
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func dec64blk(mask uint64, bit uint8, in, out []byte) {
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var tmp [8]byte
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i := 0
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s := int(bit) >> 1
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n := 0
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c := 16 - bit
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for ; i <= len(out)-s; n += 8 {
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m := (uint64(1)<<bit - 1) << (64 - bit)
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shift := binary.BigEndian.Uint64(in[n:]) - mask
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shift <<= c
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sum := shift & m
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shift <<= c
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m >>= bit
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sum |= shift & m
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shift <<= c
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m >>= bit
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sum |= shift & m
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shift <<= c
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m >>= bit
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sum |= shift & m
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if len(out[i:]) < 8 {
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binary.BigEndian.PutUint64(tmp[:], sum)
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copy(out[i:], tmp[:])
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} else {
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binary.BigEndian.PutUint64(out[i:], sum)
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}
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i += s
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}
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if n < len(in)-2 {
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m := (uint64(1)<<bit - 1) << (64 - bit)
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copy(tmp[:], in[n:])
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msk := uint16(mask & 0xffff)
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for j := 0; j < 4; j++ {
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x := binary.BigEndian.Uint16(tmp[j*2:])
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if x < msk {
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binary.BigEndian.PutUint16(tmp[j*2:], msk)
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}
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}
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shift := binary.BigEndian.Uint64(tmp[:]) - mask
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shift <<= c
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sum := shift & m
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shift <<= c
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m >>= bit
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sum |= shift & m
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shift <<= c
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m >>= bit
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sum |= shift & m
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shift <<= c
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m >>= bit
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sum |= shift & m
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binary.BigEndian.PutUint64(tmp[:], sum)
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copy(out[i:], tmp[:])
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}
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}
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