mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-11-30 07:32:45 +00:00
316 lines
7.9 KiB
Go
316 lines
7.9 KiB
Go
package flate
|
|
|
|
import "fmt"
|
|
|
|
type fastEncL6 struct {
|
|
fastGen
|
|
table [tableSize]tableEntry
|
|
bTable [tableSize]tableEntryPrev
|
|
}
|
|
|
|
func (e *fastEncL6) Encode(dst *tokens, src []byte) {
|
|
const (
|
|
inputMargin = 12 - 1
|
|
minNonLiteralBlockSize = 1 + 1 + inputMargin
|
|
)
|
|
if debugDeflate && e.cur < 0 {
|
|
panic(fmt.Sprint("e.cur < 0: ", e.cur))
|
|
}
|
|
|
|
// Protect against e.cur wraparound.
|
|
for e.cur >= bufferReset {
|
|
if len(e.hist) == 0 {
|
|
for i := range e.table[:] {
|
|
e.table[i] = tableEntry{}
|
|
}
|
|
for i := range e.bTable[:] {
|
|
e.bTable[i] = tableEntryPrev{}
|
|
}
|
|
e.cur = maxMatchOffset
|
|
break
|
|
}
|
|
// Shift down everything in the table that isn't already too far away.
|
|
minOff := e.cur + int32(len(e.hist)) - maxMatchOffset
|
|
for i := range e.table[:] {
|
|
v := e.table[i].offset
|
|
if v <= minOff {
|
|
v = 0
|
|
} else {
|
|
v = v - e.cur + maxMatchOffset
|
|
}
|
|
e.table[i].offset = v
|
|
}
|
|
for i := range e.bTable[:] {
|
|
v := e.bTable[i]
|
|
if v.Cur.offset <= minOff {
|
|
v.Cur.offset = 0
|
|
v.Prev.offset = 0
|
|
} else {
|
|
v.Cur.offset = v.Cur.offset - e.cur + maxMatchOffset
|
|
if v.Prev.offset <= minOff {
|
|
v.Prev.offset = 0
|
|
} else {
|
|
v.Prev.offset = v.Prev.offset - e.cur + maxMatchOffset
|
|
}
|
|
}
|
|
e.bTable[i] = v
|
|
}
|
|
e.cur = maxMatchOffset
|
|
}
|
|
|
|
s := e.addBlock(src)
|
|
|
|
// This check isn't in the Snappy implementation, but there, the caller
|
|
// instead of the callee handles this case.
|
|
if len(src) < minNonLiteralBlockSize {
|
|
// We do not fill the token table.
|
|
// This will be picked up by caller.
|
|
dst.n = uint16(len(src))
|
|
return
|
|
}
|
|
|
|
// Override src
|
|
src = e.hist
|
|
nextEmit := s
|
|
|
|
// sLimit is when to stop looking for offset/length copies. The inputMargin
|
|
// lets us use a fast path for emitLiteral in the main loop, while we are
|
|
// looking for copies.
|
|
sLimit := int32(len(src) - inputMargin)
|
|
|
|
// nextEmit is where in src the next emitLiteral should start from.
|
|
cv := load6432(src, s)
|
|
// Repeat MUST be > 1 and within range
|
|
repeat := int32(1)
|
|
for {
|
|
const skipLog = 7
|
|
const doEvery = 1
|
|
|
|
nextS := s
|
|
var l int32
|
|
var t int32
|
|
for {
|
|
nextHashS := hash4x64(cv, tableBits)
|
|
nextHashL := hash7(cv, tableBits)
|
|
s = nextS
|
|
nextS = s + doEvery + (s-nextEmit)>>skipLog
|
|
if nextS > sLimit {
|
|
goto emitRemainder
|
|
}
|
|
// Fetch a short+long candidate
|
|
sCandidate := e.table[nextHashS]
|
|
lCandidate := e.bTable[nextHashL]
|
|
next := load6432(src, nextS)
|
|
entry := tableEntry{offset: s + e.cur}
|
|
e.table[nextHashS] = entry
|
|
eLong := &e.bTable[nextHashL]
|
|
eLong.Cur, eLong.Prev = entry, eLong.Cur
|
|
|
|
// Calculate hashes of 'next'
|
|
nextHashS = hash4x64(next, tableBits)
|
|
nextHashL = hash7(next, tableBits)
|
|
|
|
t = lCandidate.Cur.offset - e.cur
|
|
if s-t < maxMatchOffset {
|
|
if uint32(cv) == load3232(src, lCandidate.Cur.offset-e.cur) {
|
|
// Long candidate matches at least 4 bytes.
|
|
|
|
// Store the next match
|
|
e.table[nextHashS] = tableEntry{offset: nextS + e.cur}
|
|
eLong := &e.bTable[nextHashL]
|
|
eLong.Cur, eLong.Prev = tableEntry{offset: nextS + e.cur}, eLong.Cur
|
|
|
|
// Check the previous long candidate as well.
|
|
t2 := lCandidate.Prev.offset - e.cur
|
|
if s-t2 < maxMatchOffset && uint32(cv) == load3232(src, lCandidate.Prev.offset-e.cur) {
|
|
l = e.matchlen(s+4, t+4, src) + 4
|
|
ml1 := e.matchlen(s+4, t2+4, src) + 4
|
|
if ml1 > l {
|
|
t = t2
|
|
l = ml1
|
|
break
|
|
}
|
|
}
|
|
break
|
|
}
|
|
// Current value did not match, but check if previous long value does.
|
|
t = lCandidate.Prev.offset - e.cur
|
|
if s-t < maxMatchOffset && uint32(cv) == load3232(src, lCandidate.Prev.offset-e.cur) {
|
|
// Store the next match
|
|
e.table[nextHashS] = tableEntry{offset: nextS + e.cur}
|
|
eLong := &e.bTable[nextHashL]
|
|
eLong.Cur, eLong.Prev = tableEntry{offset: nextS + e.cur}, eLong.Cur
|
|
break
|
|
}
|
|
}
|
|
|
|
t = sCandidate.offset - e.cur
|
|
if s-t < maxMatchOffset && uint32(cv) == load3232(src, sCandidate.offset-e.cur) {
|
|
// Found a 4 match...
|
|
l = e.matchlen(s+4, t+4, src) + 4
|
|
|
|
// Look up next long candidate (at nextS)
|
|
lCandidate = e.bTable[nextHashL]
|
|
|
|
// Store the next match
|
|
e.table[nextHashS] = tableEntry{offset: nextS + e.cur}
|
|
eLong := &e.bTable[nextHashL]
|
|
eLong.Cur, eLong.Prev = tableEntry{offset: nextS + e.cur}, eLong.Cur
|
|
|
|
// Check repeat at s + repOff
|
|
const repOff = 1
|
|
t2 := s - repeat + repOff
|
|
if load3232(src, t2) == uint32(cv>>(8*repOff)) {
|
|
ml := e.matchlen(s+4+repOff, t2+4, src) + 4
|
|
if ml > l {
|
|
t = t2
|
|
l = ml
|
|
s += repOff
|
|
// Not worth checking more.
|
|
break
|
|
}
|
|
}
|
|
|
|
// If the next long is a candidate, use that...
|
|
t2 = lCandidate.Cur.offset - e.cur
|
|
if nextS-t2 < maxMatchOffset {
|
|
if load3232(src, lCandidate.Cur.offset-e.cur) == uint32(next) {
|
|
ml := e.matchlen(nextS+4, t2+4, src) + 4
|
|
if ml > l {
|
|
t = t2
|
|
s = nextS
|
|
l = ml
|
|
// This is ok, but check previous as well.
|
|
}
|
|
}
|
|
// If the previous long is a candidate, use that...
|
|
t2 = lCandidate.Prev.offset - e.cur
|
|
if nextS-t2 < maxMatchOffset && load3232(src, lCandidate.Prev.offset-e.cur) == uint32(next) {
|
|
ml := e.matchlen(nextS+4, t2+4, src) + 4
|
|
if ml > l {
|
|
t = t2
|
|
s = nextS
|
|
l = ml
|
|
break
|
|
}
|
|
}
|
|
}
|
|
break
|
|
}
|
|
cv = next
|
|
}
|
|
|
|
// 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.
|
|
|
|
// Extend the 4-byte match as long as possible.
|
|
if l == 0 {
|
|
l = e.matchlenLong(s+4, t+4, src) + 4
|
|
} else if l == maxMatchLength {
|
|
l += e.matchlenLong(s+l, t+l, src)
|
|
}
|
|
|
|
// Try to locate a better match by checking the end-of-match...
|
|
if sAt := s + l; sAt < sLimit {
|
|
eLong := &e.bTable[hash7(load6432(src, sAt), tableBits)]
|
|
// Test current
|
|
t2 := eLong.Cur.offset - e.cur - l
|
|
off := s - t2
|
|
if off < maxMatchOffset {
|
|
if off > 0 && t2 >= 0 {
|
|
if l2 := e.matchlenLong(s, t2, src); l2 > l {
|
|
t = t2
|
|
l = l2
|
|
}
|
|
}
|
|
// Test next:
|
|
t2 = eLong.Prev.offset - e.cur - l
|
|
off := s - t2
|
|
if off > 0 && off < maxMatchOffset && t2 >= 0 {
|
|
if l2 := e.matchlenLong(s, t2, src); l2 > l {
|
|
t = t2
|
|
l = l2
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// Extend backwards
|
|
for t > 0 && s > nextEmit && src[t-1] == src[s-1] {
|
|
s--
|
|
t--
|
|
l++
|
|
}
|
|
if nextEmit < s {
|
|
if false {
|
|
emitLiteral(dst, src[nextEmit:s])
|
|
} else {
|
|
for _, v := range src[nextEmit:s] {
|
|
dst.tokens[dst.n] = token(v)
|
|
dst.litHist[v]++
|
|
dst.n++
|
|
}
|
|
}
|
|
}
|
|
if false {
|
|
if t >= s {
|
|
panic(fmt.Sprintln("s-t", s, t))
|
|
}
|
|
if (s - t) > maxMatchOffset {
|
|
panic(fmt.Sprintln("mmo", s-t))
|
|
}
|
|
if l < baseMatchLength {
|
|
panic("bml")
|
|
}
|
|
}
|
|
|
|
dst.AddMatchLong(l, uint32(s-t-baseMatchOffset))
|
|
repeat = s - t
|
|
s += l
|
|
nextEmit = s
|
|
if nextS >= s {
|
|
s = nextS + 1
|
|
}
|
|
|
|
if s >= sLimit {
|
|
// Index after match end.
|
|
for i := nextS + 1; i < int32(len(src))-8; i += 2 {
|
|
cv := load6432(src, i)
|
|
e.table[hash4x64(cv, tableBits)] = tableEntry{offset: i + e.cur}
|
|
eLong := &e.bTable[hash7(cv, tableBits)]
|
|
eLong.Cur, eLong.Prev = tableEntry{offset: i + e.cur}, eLong.Cur
|
|
}
|
|
goto emitRemainder
|
|
}
|
|
|
|
// Store every long hash in-between and every second short.
|
|
if true {
|
|
for i := nextS + 1; i < s-1; i += 2 {
|
|
cv := load6432(src, i)
|
|
t := tableEntry{offset: i + e.cur}
|
|
t2 := tableEntry{offset: t.offset + 1}
|
|
eLong := &e.bTable[hash7(cv, tableBits)]
|
|
eLong2 := &e.bTable[hash7(cv>>8, tableBits)]
|
|
e.table[hash4x64(cv, tableBits)] = t
|
|
eLong.Cur, eLong.Prev = t, eLong.Cur
|
|
eLong2.Cur, eLong2.Prev = t2, eLong2.Cur
|
|
}
|
|
}
|
|
|
|
// We could immediately start working at s now, but to improve
|
|
// compression we first update the hash table at s-1 and at s.
|
|
cv = load6432(src, s)
|
|
}
|
|
|
|
emitRemainder:
|
|
if int(nextEmit) < len(src) {
|
|
// If nothing was added, don't encode literals.
|
|
if dst.n == 0 {
|
|
return
|
|
}
|
|
|
|
emitLiteral(dst, src[nextEmit:])
|
|
}
|
|
}
|