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authorOpenShift Merge Robot <openshift-merge-robot@users.noreply.github.com>2019-11-22 16:21:19 +0100
committerGitHub <noreply@github.com>2019-11-22 16:21:19 +0100
commite4b805441b84017bdd313d412a4138e4fb41f3d3 (patch)
treebf4088f29a62893822c2696a43f2bebac52d8168 /vendor/github.com/klauspost/compress/flate/level1.go
parent22e7d7d86f945620bbc1bdd3aa9c4a9d3248fa1f (diff)
parent866391bb574f885549f5cf3cec965dc224cb84b3 (diff)
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Merge pull request #4538 from containers/dependabot/go_modules/github.com/containers/storage-1.14.0
build(deps): bump github.com/containers/storage from 1.13.5 to 1.14.0
Diffstat (limited to 'vendor/github.com/klauspost/compress/flate/level1.go')
-rw-r--r--vendor/github.com/klauspost/compress/flate/level1.go174
1 files changed, 174 insertions, 0 deletions
diff --git a/vendor/github.com/klauspost/compress/flate/level1.go b/vendor/github.com/klauspost/compress/flate/level1.go
new file mode 100644
index 000000000..20de8f11f
--- /dev/null
+++ b/vendor/github.com/klauspost/compress/flate/level1.go
@@ -0,0 +1,174 @@
+package flate
+
+// fastGen maintains the table for matches,
+// and the previous byte block for level 2.
+// This is the generic implementation.
+type fastEncL1 struct {
+ fastGen
+ table [tableSize]tableEntry
+}
+
+// EncodeL1 uses a similar algorithm to level 1
+func (e *fastEncL1) Encode(dst *tokens, src []byte) {
+ const (
+ inputMargin = 12 - 1
+ minNonLiteralBlockSize = 1 + 1 + inputMargin
+ )
+
+ // Protect against e.cur wraparound.
+ for e.cur >= bufferReset {
+ if len(e.hist) == 0 {
+ for i := range e.table[:] {
+ e.table[i] = tableEntry{}
+ }
+ 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
+ }
+ 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 := load3232(src, s)
+
+ for {
+ const skipLog = 5
+ const doEvery = 2
+
+ nextS := s
+ var candidate tableEntry
+ for {
+ nextHash := hash(cv)
+ candidate = e.table[nextHash]
+ nextS = s + doEvery + (s-nextEmit)>>skipLog
+ if nextS > sLimit {
+ goto emitRemainder
+ }
+
+ now := load6432(src, nextS)
+ e.table[nextHash] = tableEntry{offset: s + e.cur, val: cv}
+ nextHash = hash(uint32(now))
+
+ offset := s - (candidate.offset - e.cur)
+ if offset < maxMatchOffset && cv == candidate.val {
+ e.table[nextHash] = tableEntry{offset: nextS + e.cur, val: uint32(now)}
+ break
+ }
+
+ // Do one right away...
+ cv = uint32(now)
+ s = nextS
+ nextS++
+ candidate = e.table[nextHash]
+ now >>= 8
+ e.table[nextHash] = tableEntry{offset: s + e.cur, val: cv}
+
+ offset = s - (candidate.offset - e.cur)
+ if offset < maxMatchOffset && cv == candidate.val {
+ e.table[nextHash] = tableEntry{offset: nextS + e.cur, val: uint32(now)}
+ break
+ }
+ cv = uint32(now)
+ s = nextS
+ }
+
+ // 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.
+ for {
+ // Invariant: we have a 4-byte match at s, and no need to emit any
+ // literal bytes prior to s.
+
+ // Extend the 4-byte match as long as possible.
+ t := candidate.offset - e.cur
+ l := e.matchlenLong(s+4, t+4, src) + 4
+
+ // Extend backwards
+ for t > 0 && s > nextEmit && src[t-1] == src[s-1] {
+ s--
+ t--
+ l++
+ }
+ if nextEmit < s {
+ emitLiteral(dst, src[nextEmit:s])
+ }
+
+ // Save the match found
+ dst.AddMatchLong(l, uint32(s-t-baseMatchOffset))
+ s += l
+ nextEmit = s
+ if nextS >= s {
+ s = nextS + 1
+ }
+ if s >= sLimit {
+ // Index first pair after match end.
+ if int(s+l+4) < len(src) {
+ cv := load3232(src, s)
+ e.table[hash(cv)] = tableEntry{offset: s + e.cur, val: cv}
+ }
+ goto emitRemainder
+ }
+
+ // We could immediately start working at s now, but to improve
+ // compression we first update the hash table at s-2 and at s. If
+ // another emitCopy is not our next move, also calculate nextHash
+ // at s+1. At least on GOARCH=amd64, these three hash calculations
+ // are faster as one load64 call (with some shifts) instead of
+ // three load32 calls.
+ x := load6432(src, s-2)
+ o := e.cur + s - 2
+ prevHash := hash(uint32(x))
+ e.table[prevHash] = tableEntry{offset: o, val: uint32(x)}
+ x >>= 16
+ currHash := hash(uint32(x))
+ candidate = e.table[currHash]
+ e.table[currHash] = tableEntry{offset: o + 2, val: uint32(x)}
+
+ offset := s - (candidate.offset - e.cur)
+ if offset > maxMatchOffset || uint32(x) != candidate.val {
+ cv = uint32(x >> 8)
+ s++
+ break
+ }
+ }
+ }
+
+emitRemainder:
+ if int(nextEmit) < len(src) {
+ // If nothing was added, don't encode literals.
+ if dst.n == 0 {
+ return
+ }
+ emitLiteral(dst, src[nextEmit:])
+ }
+}