mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-05-20 09:18:13 +00:00
730 lines
18 KiB
Go
730 lines
18 KiB
Go
//go:build !amd64 || appengine || !gc || noasm
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// +build !amd64 appengine !gc noasm
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package s2
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import (
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"bytes"
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"math/bits"
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)
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const hasAmd64Asm = false
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// encodeBlock encodes a non-empty src to a guaranteed-large-enough dst. It
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// assumes that the varint-encoded length of the decompressed bytes has already
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// been written.
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//
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// It also assumes that:
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//
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// len(dst) >= MaxEncodedLen(len(src))
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func encodeBlock(dst, src []byte) (d int) {
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if len(src) < minNonLiteralBlockSize {
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return 0
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}
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return encodeBlockGo(dst, src)
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}
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// encodeBlockBetter encodes a non-empty src to a guaranteed-large-enough dst. It
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// assumes that the varint-encoded length of the decompressed bytes has already
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// been written.
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//
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// It also assumes that:
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//
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// len(dst) >= MaxEncodedLen(len(src))
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func encodeBlockBetter(dst, src []byte) (d int) {
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return encodeBlockBetterGo(dst, src)
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}
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// encodeBlockBetter encodes a non-empty src to a guaranteed-large-enough dst. It
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// assumes that the varint-encoded length of the decompressed bytes has already
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// been written.
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//
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// It also assumes that:
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//
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// len(dst) >= MaxEncodedLen(len(src))
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func encodeBlockBetterSnappy(dst, src []byte) (d int) {
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return encodeBlockBetterSnappyGo(dst, src)
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}
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// encodeBlock encodes a non-empty src to a guaranteed-large-enough dst. It
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// assumes that the varint-encoded length of the decompressed bytes has already
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// been written.
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//
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// It also assumes that:
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//
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// len(dst) >= MaxEncodedLen(len(src))
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func encodeBlockSnappy(dst, src []byte) (d int) {
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if len(src) < minNonLiteralBlockSize {
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return 0
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}
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return encodeBlockSnappyGo(dst, src)
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}
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// emitLiteral writes a literal chunk and returns the number of bytes written.
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//
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// It assumes that:
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//
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// dst is long enough to hold the encoded bytes
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// 0 <= len(lit) && len(lit) <= math.MaxUint32
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func emitLiteral(dst, lit []byte) int {
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if len(lit) == 0 {
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return 0
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}
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const num = 63<<2 | tagLiteral
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i, n := 0, uint(len(lit)-1)
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switch {
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case n < 60:
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dst[0] = uint8(n)<<2 | tagLiteral
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i = 1
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case n < 1<<8:
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dst[1] = uint8(n)
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dst[0] = 60<<2 | tagLiteral
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i = 2
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case n < 1<<16:
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dst[2] = uint8(n >> 8)
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dst[1] = uint8(n)
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dst[0] = 61<<2 | tagLiteral
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i = 3
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case n < 1<<24:
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dst[3] = uint8(n >> 16)
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dst[2] = uint8(n >> 8)
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dst[1] = uint8(n)
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dst[0] = 62<<2 | tagLiteral
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i = 4
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default:
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dst[4] = uint8(n >> 24)
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dst[3] = uint8(n >> 16)
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dst[2] = uint8(n >> 8)
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dst[1] = uint8(n)
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dst[0] = 63<<2 | tagLiteral
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i = 5
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}
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return i + copy(dst[i:], lit)
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}
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// emitRepeat writes a repeat chunk and returns the number of bytes written.
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// Length must be at least 4 and < 1<<24
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func emitRepeat(dst []byte, offset, length int) int {
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// Repeat offset, make length cheaper
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length -= 4
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if length <= 4 {
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dst[0] = uint8(length)<<2 | tagCopy1
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dst[1] = 0
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return 2
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}
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if length < 8 && offset < 2048 {
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// Encode WITH offset
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dst[1] = uint8(offset)
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dst[0] = uint8(offset>>8)<<5 | uint8(length)<<2 | tagCopy1
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return 2
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}
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if length < (1<<8)+4 {
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length -= 4
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dst[2] = uint8(length)
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dst[1] = 0
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dst[0] = 5<<2 | tagCopy1
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return 3
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}
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if length < (1<<16)+(1<<8) {
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length -= 1 << 8
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dst[3] = uint8(length >> 8)
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dst[2] = uint8(length >> 0)
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dst[1] = 0
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dst[0] = 6<<2 | tagCopy1
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return 4
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}
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const maxRepeat = (1 << 24) - 1
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length -= 1 << 16
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left := 0
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if length > maxRepeat {
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left = length - maxRepeat + 4
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length = maxRepeat - 4
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}
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dst[4] = uint8(length >> 16)
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dst[3] = uint8(length >> 8)
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dst[2] = uint8(length >> 0)
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dst[1] = 0
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dst[0] = 7<<2 | tagCopy1
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if left > 0 {
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return 5 + emitRepeat(dst[5:], offset, left)
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}
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return 5
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}
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// emitCopy writes a copy chunk and returns the number of bytes written.
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//
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// It assumes that:
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//
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// dst is long enough to hold the encoded bytes
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// 1 <= offset && offset <= math.MaxUint32
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// 4 <= length && length <= 1 << 24
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func emitCopy(dst []byte, offset, length int) int {
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if offset >= 65536 {
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i := 0
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if length > 64 {
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// Emit a length 64 copy, encoded as 5 bytes.
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dst[4] = uint8(offset >> 24)
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dst[3] = uint8(offset >> 16)
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dst[2] = uint8(offset >> 8)
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dst[1] = uint8(offset)
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dst[0] = 63<<2 | tagCopy4
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length -= 64
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if length >= 4 {
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// Emit remaining as repeats
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return 5 + emitRepeat(dst[5:], offset, length)
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}
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i = 5
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}
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if length == 0 {
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return i
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}
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// Emit a copy, offset encoded as 4 bytes.
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dst[i+0] = uint8(length-1)<<2 | tagCopy4
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dst[i+1] = uint8(offset)
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dst[i+2] = uint8(offset >> 8)
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dst[i+3] = uint8(offset >> 16)
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dst[i+4] = uint8(offset >> 24)
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return i + 5
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}
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// Offset no more than 2 bytes.
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if length > 64 {
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off := 3
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if offset < 2048 {
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// emit 8 bytes as tagCopy1, rest as repeats.
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dst[1] = uint8(offset)
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dst[0] = uint8(offset>>8)<<5 | uint8(8-4)<<2 | tagCopy1
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length -= 8
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off = 2
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} else {
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// Emit a length 60 copy, encoded as 3 bytes.
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// Emit remaining as repeat value (minimum 4 bytes).
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dst[2] = uint8(offset >> 8)
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dst[1] = uint8(offset)
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dst[0] = 59<<2 | tagCopy2
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length -= 60
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}
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// Emit remaining as repeats, at least 4 bytes remain.
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return off + emitRepeat(dst[off:], offset, length)
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}
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if length >= 12 || offset >= 2048 {
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// Emit the remaining copy, encoded as 3 bytes.
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dst[2] = uint8(offset >> 8)
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dst[1] = uint8(offset)
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dst[0] = uint8(length-1)<<2 | tagCopy2
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return 3
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}
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// Emit the remaining copy, encoded as 2 bytes.
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dst[1] = uint8(offset)
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dst[0] = uint8(offset>>8)<<5 | uint8(length-4)<<2 | tagCopy1
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return 2
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}
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// emitCopyNoRepeat writes a copy chunk and returns the number of bytes written.
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//
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// It assumes that:
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//
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// dst is long enough to hold the encoded bytes
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// 1 <= offset && offset <= math.MaxUint32
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// 4 <= length && length <= 1 << 24
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func emitCopyNoRepeat(dst []byte, offset, length int) int {
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if offset >= 65536 {
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i := 0
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if length > 64 {
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// Emit a length 64 copy, encoded as 5 bytes.
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dst[4] = uint8(offset >> 24)
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dst[3] = uint8(offset >> 16)
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dst[2] = uint8(offset >> 8)
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dst[1] = uint8(offset)
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dst[0] = 63<<2 | tagCopy4
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length -= 64
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if length >= 4 {
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// Emit remaining as repeats
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return 5 + emitCopyNoRepeat(dst[5:], offset, length)
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}
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i = 5
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}
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if length == 0 {
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return i
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}
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// Emit a copy, offset encoded as 4 bytes.
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dst[i+0] = uint8(length-1)<<2 | tagCopy4
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dst[i+1] = uint8(offset)
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dst[i+2] = uint8(offset >> 8)
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dst[i+3] = uint8(offset >> 16)
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dst[i+4] = uint8(offset >> 24)
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return i + 5
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}
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// Offset no more than 2 bytes.
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if length > 64 {
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// Emit a length 60 copy, encoded as 3 bytes.
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// Emit remaining as repeat value (minimum 4 bytes).
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dst[2] = uint8(offset >> 8)
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dst[1] = uint8(offset)
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dst[0] = 59<<2 | tagCopy2
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length -= 60
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// Emit remaining as repeats, at least 4 bytes remain.
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return 3 + emitCopyNoRepeat(dst[3:], offset, length)
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}
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if length >= 12 || offset >= 2048 {
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// Emit the remaining copy, encoded as 3 bytes.
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dst[2] = uint8(offset >> 8)
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dst[1] = uint8(offset)
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dst[0] = uint8(length-1)<<2 | tagCopy2
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return 3
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}
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// Emit the remaining copy, encoded as 2 bytes.
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dst[1] = uint8(offset)
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dst[0] = uint8(offset>>8)<<5 | uint8(length-4)<<2 | tagCopy1
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return 2
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}
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// matchLen returns how many bytes match in a and b
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//
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// It assumes that:
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//
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// len(a) <= len(b)
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func matchLen(a []byte, b []byte) int {
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b = b[:len(a)]
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var checked int
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if len(a) > 4 {
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// Try 4 bytes first
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if diff := load32(a, 0) ^ load32(b, 0); diff != 0 {
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return bits.TrailingZeros32(diff) >> 3
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}
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// Switch to 8 byte matching.
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checked = 4
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a = a[4:]
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b = b[4:]
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for len(a) >= 8 {
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b = b[:len(a)]
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if diff := load64(a, 0) ^ load64(b, 0); diff != 0 {
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return checked + (bits.TrailingZeros64(diff) >> 3)
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}
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checked += 8
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a = a[8:]
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b = b[8:]
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}
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}
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b = b[:len(a)]
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for i := range a {
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if a[i] != b[i] {
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return int(i) + checked
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}
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}
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return len(a) + checked
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}
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// input must be > inputMargin
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func calcBlockSize(src []byte) (d int) {
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// Initialize the hash table.
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const (
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tableBits = 13
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maxTableSize = 1 << tableBits
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)
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var table [maxTableSize]uint32
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// sLimit is when to stop looking for offset/length copies. The inputMargin
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// lets us use a fast path for emitLiteral in the main loop, while we are
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// looking for copies.
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sLimit := len(src) - inputMargin
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// Bail if we can't compress to at least this.
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dstLimit := len(src) - len(src)>>5 - 5
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// nextEmit is where in src the next emitLiteral should start from.
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nextEmit := 0
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// The encoded form must start with a literal, as there are no previous
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// bytes to copy, so we start looking for hash matches at s == 1.
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s := 1
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cv := load64(src, s)
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// We search for a repeat at -1, but don't output repeats when nextEmit == 0
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repeat := 1
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for {
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candidate := 0
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for {
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// Next src position to check
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nextS := s + (s-nextEmit)>>6 + 4
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if nextS > sLimit {
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goto emitRemainder
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}
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hash0 := hash6(cv, tableBits)
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hash1 := hash6(cv>>8, tableBits)
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candidate = int(table[hash0])
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candidate2 := int(table[hash1])
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table[hash0] = uint32(s)
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table[hash1] = uint32(s + 1)
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hash2 := hash6(cv>>16, tableBits)
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// Check repeat at offset checkRep.
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const checkRep = 1
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if uint32(cv>>(checkRep*8)) == load32(src, s-repeat+checkRep) {
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base := s + checkRep
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// Extend back
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for i := base - repeat; base > nextEmit && i > 0 && src[i-1] == src[base-1]; {
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i--
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base--
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}
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d += emitLiteralSize(src[nextEmit:base])
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// Extend forward
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candidate := s - repeat + 4 + checkRep
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s += 4 + checkRep
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for s <= sLimit {
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if diff := load64(src, s) ^ load64(src, candidate); diff != 0 {
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s += bits.TrailingZeros64(diff) >> 3
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break
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}
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s += 8
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candidate += 8
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}
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d += emitCopyNoRepeatSize(repeat, s-base)
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nextEmit = s
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if s >= sLimit {
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goto emitRemainder
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}
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cv = load64(src, s)
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continue
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}
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if uint32(cv) == load32(src, candidate) {
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break
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}
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candidate = int(table[hash2])
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if uint32(cv>>8) == load32(src, candidate2) {
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table[hash2] = uint32(s + 2)
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candidate = candidate2
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s++
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break
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}
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table[hash2] = uint32(s + 2)
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if uint32(cv>>16) == load32(src, candidate) {
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s += 2
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break
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}
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cv = load64(src, nextS)
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s = nextS
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}
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// Extend backwards
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for candidate > 0 && s > nextEmit && src[candidate-1] == src[s-1] {
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candidate--
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s--
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}
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// Bail if we exceed the maximum size.
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if d+(s-nextEmit) > dstLimit {
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return 0
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}
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// A 4-byte match has been found. We'll later see if more than 4 bytes
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// match. But, prior to the match, src[nextEmit:s] are unmatched. Emit
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// them as literal bytes.
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d += emitLiteralSize(src[nextEmit:s])
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// Call emitCopy, and then see if another emitCopy could be our next
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// move. Repeat until we find no match for the input immediately after
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// what was consumed by the last emitCopy call.
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//
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// If we exit this loop normally then we need to call emitLiteral next,
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// though we don't yet know how big the literal will be. We handle that
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// by proceeding to the next iteration of the main loop. We also can
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// exit this loop via goto if we get close to exhausting the input.
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for {
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// Invariant: we have a 4-byte match at s, and no need to emit any
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// literal bytes prior to s.
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base := s
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repeat = base - candidate
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// Extend the 4-byte match as long as possible.
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s += 4
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candidate += 4
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for s <= len(src)-8 {
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if diff := load64(src, s) ^ load64(src, candidate); diff != 0 {
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s += bits.TrailingZeros64(diff) >> 3
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break
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}
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s += 8
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candidate += 8
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}
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d += emitCopyNoRepeatSize(repeat, s-base)
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if false {
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// Validate match.
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a := src[base:s]
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b := src[base-repeat : base-repeat+(s-base)]
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if !bytes.Equal(a, b) {
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panic("mismatch")
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}
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}
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nextEmit = s
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if s >= sLimit {
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goto emitRemainder
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}
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if d > dstLimit {
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// Do we have space for more, if not bail.
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return 0
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}
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// Check for an immediate match, otherwise start search at s+1
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x := load64(src, s-2)
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m2Hash := hash6(x, tableBits)
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currHash := hash6(x>>16, tableBits)
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candidate = int(table[currHash])
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table[m2Hash] = uint32(s - 2)
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table[currHash] = uint32(s)
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if uint32(x>>16) != load32(src, candidate) {
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cv = load64(src, s+1)
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s++
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break
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}
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}
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}
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emitRemainder:
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if nextEmit < len(src) {
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// Bail if we exceed the maximum size.
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if d+len(src)-nextEmit > dstLimit {
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return 0
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}
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d += emitLiteralSize(src[nextEmit:])
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}
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return d
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}
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// length must be > inputMargin.
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func calcBlockSizeSmall(src []byte) (d int) {
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// Initialize the hash table.
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const (
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tableBits = 9
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maxTableSize = 1 << tableBits
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)
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|
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var table [maxTableSize]uint32
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|
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// sLimit is when to stop looking for offset/length copies. The inputMargin
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// lets us use a fast path for emitLiteral in the main loop, while we are
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// looking for copies.
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sLimit := len(src) - inputMargin
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|
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// Bail if we can't compress to at least this.
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dstLimit := len(src) - len(src)>>5 - 5
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|
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// nextEmit is where in src the next emitLiteral should start from.
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nextEmit := 0
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|
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// The encoded form must start with a literal, as there are no previous
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// bytes to copy, so we start looking for hash matches at s == 1.
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s := 1
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cv := load64(src, s)
|
|
|
|
// We search for a repeat at -1, but don't output repeats when nextEmit == 0
|
|
repeat := 1
|
|
|
|
for {
|
|
candidate := 0
|
|
for {
|
|
// Next src position to check
|
|
nextS := s + (s-nextEmit)>>6 + 4
|
|
if nextS > sLimit {
|
|
goto emitRemainder
|
|
}
|
|
hash0 := hash6(cv, tableBits)
|
|
hash1 := hash6(cv>>8, tableBits)
|
|
candidate = int(table[hash0])
|
|
candidate2 := int(table[hash1])
|
|
table[hash0] = uint32(s)
|
|
table[hash1] = uint32(s + 1)
|
|
hash2 := hash6(cv>>16, tableBits)
|
|
|
|
// Check repeat at offset checkRep.
|
|
const checkRep = 1
|
|
if uint32(cv>>(checkRep*8)) == load32(src, s-repeat+checkRep) {
|
|
base := s + checkRep
|
|
// Extend back
|
|
for i := base - repeat; base > nextEmit && i > 0 && src[i-1] == src[base-1]; {
|
|
i--
|
|
base--
|
|
}
|
|
d += emitLiteralSize(src[nextEmit:base])
|
|
|
|
// Extend forward
|
|
candidate := s - repeat + 4 + checkRep
|
|
s += 4 + checkRep
|
|
for s <= sLimit {
|
|
if diff := load64(src, s) ^ load64(src, candidate); diff != 0 {
|
|
s += bits.TrailingZeros64(diff) >> 3
|
|
break
|
|
}
|
|
s += 8
|
|
candidate += 8
|
|
}
|
|
|
|
d += emitCopyNoRepeatSize(repeat, s-base)
|
|
nextEmit = s
|
|
if s >= sLimit {
|
|
goto emitRemainder
|
|
}
|
|
|
|
cv = load64(src, s)
|
|
continue
|
|
}
|
|
|
|
if uint32(cv) == load32(src, candidate) {
|
|
break
|
|
}
|
|
candidate = int(table[hash2])
|
|
if uint32(cv>>8) == load32(src, candidate2) {
|
|
table[hash2] = uint32(s + 2)
|
|
candidate = candidate2
|
|
s++
|
|
break
|
|
}
|
|
table[hash2] = uint32(s + 2)
|
|
if uint32(cv>>16) == load32(src, candidate) {
|
|
s += 2
|
|
break
|
|
}
|
|
|
|
cv = load64(src, nextS)
|
|
s = nextS
|
|
}
|
|
|
|
// Extend backwards
|
|
for candidate > 0 && s > nextEmit && src[candidate-1] == src[s-1] {
|
|
candidate--
|
|
s--
|
|
}
|
|
|
|
// Bail if we exceed the maximum size.
|
|
if d+(s-nextEmit) > dstLimit {
|
|
return 0
|
|
}
|
|
|
|
// A 4-byte match has been found. We'll later see if more than 4 bytes
|
|
// match. But, prior to the match, src[nextEmit:s] are unmatched. Emit
|
|
// them as literal bytes.
|
|
|
|
d += emitLiteralSize(src[nextEmit:s])
|
|
|
|
// Call emitCopy, and then see if another emitCopy could be our next
|
|
// move. Repeat until we find no match for the input immediately after
|
|
// what was consumed by the last emitCopy call.
|
|
//
|
|
// If we exit this loop normally then we need to call emitLiteral next,
|
|
// though we don't yet know how big the literal will be. We handle that
|
|
// by proceeding to the next iteration of the main loop. We also can
|
|
// exit this loop via goto if we get close to exhausting the input.
|
|
for {
|
|
// Invariant: we have a 4-byte match at s, and no need to emit any
|
|
// literal bytes prior to s.
|
|
base := s
|
|
repeat = base - candidate
|
|
|
|
// Extend the 4-byte match as long as possible.
|
|
s += 4
|
|
candidate += 4
|
|
for s <= len(src)-8 {
|
|
if diff := load64(src, s) ^ load64(src, candidate); diff != 0 {
|
|
s += bits.TrailingZeros64(diff) >> 3
|
|
break
|
|
}
|
|
s += 8
|
|
candidate += 8
|
|
}
|
|
|
|
d += emitCopyNoRepeatSize(repeat, s-base)
|
|
if false {
|
|
// Validate match.
|
|
a := src[base:s]
|
|
b := src[base-repeat : base-repeat+(s-base)]
|
|
if !bytes.Equal(a, b) {
|
|
panic("mismatch")
|
|
}
|
|
}
|
|
|
|
nextEmit = s
|
|
if s >= sLimit {
|
|
goto emitRemainder
|
|
}
|
|
|
|
if d > dstLimit {
|
|
// Do we have space for more, if not bail.
|
|
return 0
|
|
}
|
|
// Check for an immediate match, otherwise start search at s+1
|
|
x := load64(src, s-2)
|
|
m2Hash := hash6(x, tableBits)
|
|
currHash := hash6(x>>16, tableBits)
|
|
candidate = int(table[currHash])
|
|
table[m2Hash] = uint32(s - 2)
|
|
table[currHash] = uint32(s)
|
|
if uint32(x>>16) != load32(src, candidate) {
|
|
cv = load64(src, s+1)
|
|
s++
|
|
break
|
|
}
|
|
}
|
|
}
|
|
|
|
emitRemainder:
|
|
if nextEmit < len(src) {
|
|
// Bail if we exceed the maximum size.
|
|
if d+len(src)-nextEmit > dstLimit {
|
|
return 0
|
|
}
|
|
d += emitLiteralSize(src[nextEmit:])
|
|
}
|
|
return d
|
|
}
|
|
|
|
// emitLiteral writes a literal chunk and returns the number of bytes written.
|
|
//
|
|
// It assumes that:
|
|
//
|
|
// dst is long enough to hold the encoded bytes
|
|
// 0 <= len(lit) && len(lit) <= math.MaxUint32
|
|
func emitLiteralSize(lit []byte) int {
|
|
if len(lit) == 0 {
|
|
return 0
|
|
}
|
|
switch {
|
|
case len(lit) <= 60:
|
|
return len(lit) + 1
|
|
case len(lit) <= 1<<8:
|
|
return len(lit) + 2
|
|
case len(lit) <= 1<<16:
|
|
return len(lit) + 3
|
|
case len(lit) <= 1<<24:
|
|
return len(lit) + 4
|
|
default:
|
|
return len(lit) + 5
|
|
}
|
|
}
|
|
|
|
func cvtLZ4BlockAsm(dst []byte, src []byte) (uncompressed int, dstUsed int) {
|
|
panic("cvtLZ4BlockAsm should be unreachable")
|
|
}
|
|
|
|
func cvtLZ4BlockSnappyAsm(dst []byte, src []byte) (uncompressed int, dstUsed int) {
|
|
panic("cvtLZ4BlockSnappyAsm should be unreachable")
|
|
}
|
|
|
|
func cvtLZ4sBlockAsm(dst []byte, src []byte) (uncompressed int, dstUsed int) {
|
|
panic("cvtLZ4sBlockAsm should be unreachable")
|
|
}
|
|
|
|
func cvtLZ4sBlockSnappyAsm(dst []byte, src []byte) (uncompressed int, dstUsed int) {
|
|
panic("cvtLZ4sBlockSnappyAsm should be unreachable")
|
|
}
|