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Diffstat (limited to 'vendor/github.com/ulikunitz/xz/lzma/literalcodec.go')
-rw-r--r--vendor/github.com/ulikunitz/xz/lzma/literalcodec.go132
1 files changed, 132 insertions, 0 deletions
diff --git a/vendor/github.com/ulikunitz/xz/lzma/literalcodec.go b/vendor/github.com/ulikunitz/xz/lzma/literalcodec.go
new file mode 100644
index 000000000..c949d6ebd
--- /dev/null
+++ b/vendor/github.com/ulikunitz/xz/lzma/literalcodec.go
@@ -0,0 +1,132 @@
+// Copyright 2014-2017 Ulrich Kunitz. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package lzma
+
+// literalCodec supports the encoding of literal. It provides 768 probability
+// values per literal state. The upper 512 probabilities are used with the
+// context of a match bit.
+type literalCodec struct {
+ probs []prob
+}
+
+// deepcopy initializes literal codec c as a deep copy of the source.
+func (c *literalCodec) deepcopy(src *literalCodec) {
+ if c == src {
+ return
+ }
+ c.probs = make([]prob, len(src.probs))
+ copy(c.probs, src.probs)
+}
+
+// init initializes the literal codec.
+func (c *literalCodec) init(lc, lp int) {
+ switch {
+ case !(minLC <= lc && lc <= maxLC):
+ panic("lc out of range")
+ case !(minLP <= lp && lp <= maxLP):
+ panic("lp out of range")
+ }
+ c.probs = make([]prob, 0x300<<uint(lc+lp))
+ for i := range c.probs {
+ c.probs[i] = probInit
+ }
+}
+
+// Encode encodes the byte s using a range encoder as well as the current LZMA
+// encoder state, a match byte and the literal state.
+func (c *literalCodec) Encode(e *rangeEncoder, s byte,
+ state uint32, match byte, litState uint32,
+) (err error) {
+ k := litState * 0x300
+ probs := c.probs[k : k+0x300]
+ symbol := uint32(1)
+ r := uint32(s)
+ if state >= 7 {
+ m := uint32(match)
+ for {
+ matchBit := (m >> 7) & 1
+ m <<= 1
+ bit := (r >> 7) & 1
+ r <<= 1
+ i := ((1 + matchBit) << 8) | symbol
+ if err = probs[i].Encode(e, bit); err != nil {
+ return
+ }
+ symbol = (symbol << 1) | bit
+ if matchBit != bit {
+ break
+ }
+ if symbol >= 0x100 {
+ break
+ }
+ }
+ }
+ for symbol < 0x100 {
+ bit := (r >> 7) & 1
+ r <<= 1
+ if err = probs[symbol].Encode(e, bit); err != nil {
+ return
+ }
+ symbol = (symbol << 1) | bit
+ }
+ return nil
+}
+
+// Decode decodes a literal byte using the range decoder as well as the LZMA
+// state, a match byte, and the literal state.
+func (c *literalCodec) Decode(d *rangeDecoder,
+ state uint32, match byte, litState uint32,
+) (s byte, err error) {
+ k := litState * 0x300
+ probs := c.probs[k : k+0x300]
+ symbol := uint32(1)
+ if state >= 7 {
+ m := uint32(match)
+ for {
+ matchBit := (m >> 7) & 1
+ m <<= 1
+ i := ((1 + matchBit) << 8) | symbol
+ bit, err := d.DecodeBit(&probs[i])
+ if err != nil {
+ return 0, err
+ }
+ symbol = (symbol << 1) | bit
+ if matchBit != bit {
+ break
+ }
+ if symbol >= 0x100 {
+ break
+ }
+ }
+ }
+ for symbol < 0x100 {
+ bit, err := d.DecodeBit(&probs[symbol])
+ if err != nil {
+ return 0, err
+ }
+ symbol = (symbol << 1) | bit
+ }
+ s = byte(symbol - 0x100)
+ return s, nil
+}
+
+// minLC and maxLC define the range for LC values.
+const (
+ minLC = 0
+ maxLC = 8
+)
+
+// minLC and maxLC define the range for LP values.
+const (
+ minLP = 0
+ maxLP = 4
+)
+
+// minState and maxState define a range for the state values stored in
+// the State values.
+const (
+ minState = 0
+ maxState = 11
+)