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compress/gzip, compress/zlib: add HuffmanOnly as compression levels. 

This exposes HuffmanOnly in zlib and gzip packages, which is currently
unavailable.

Change-Id: If5d103bbc8b5fce2f5d740fd103a235c5d1ed7cd
Reviewed-on: https://go-review.googlesource.com/31186
Reviewed-by: Nigel Tao <nigeltao@golang.org>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Klaus Post 2016-10-16 22:18:01 +02:00 committed by Nigel Tao
parent 7ea5829717
commit c9517b1ffe
3 changed files with 16 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
src/compress/gzip/gzip.go
View File

@ -19,6 +19,7 @@ const (
BestSpeed = flate.BestSpeed
BestCompression = flate.BestCompression
DefaultCompression = flate.DefaultCompression
HuffmanOnly = flate.HuffmanOnly
)
// A Writer is an io.WriteCloser.
@ -52,11 +53,11 @@ func NewWriter(w io.Writer) *Writer {
// NewWriterLevel is like NewWriter but specifies the compression level instead
// of assuming DefaultCompression.
//
// The compression level can be DefaultCompression, NoCompression, or any
// integer value between BestSpeed and BestCompression inclusive. The error
// returned will be nil if the level is valid.
// The compression level can be DefaultCompression, NoCompression, HuffmanOnly
// or any integer value between BestSpeed and BestCompression inclusive.
// The error returned will be nil if the level is valid.
func NewWriterLevel(w io.Writer, level int) (*Writer, error) {
if level < DefaultCompression || level > BestCompression {
if level < HuffmanOnly || level > BestCompression {
return nil, fmt.Errorf("gzip: invalid compression level: %d", level)
}
z := new(Writer)

11
src/compress/zlib/writer.go
View File

@ -19,6 +19,7 @@ const (
BestSpeed = flate.BestSpeed
BestCompression = flate.BestCompression
DefaultCompression = flate.DefaultCompression
HuffmanOnly = flate.HuffmanOnly
)
// A Writer takes data written to it and writes the compressed
@ -47,9 +48,9 @@ func NewWriter(w io.Writer) *Writer {
// NewWriterLevel is like NewWriter but specifies the compression level instead
// of assuming DefaultCompression.
//
// The compression level can be DefaultCompression, NoCompression, or any
// integer value between BestSpeed and BestCompression inclusive. The error
// returned will be nil if the level is valid.
// The compression level can be DefaultCompression, NoCompression, HuffmanOnly
// or any integer value between BestSpeed and BestCompression inclusive.
// The error returned will be nil if the level is valid.
func NewWriterLevel(w io.Writer, level int) (*Writer, error) {
return NewWriterLevelDict(w, level, nil)
}
@ -60,7 +61,7 @@ func NewWriterLevel(w io.Writer, level int) (*Writer, error) {
// The dictionary may be nil. If not, its contents should not be modified until
// the Writer is closed.
func NewWriterLevelDict(w io.Writer, level int, dict []byte) (*Writer, error) {
if level < DefaultCompression || level > BestCompression {
if level < HuffmanOnly || level > BestCompression {
return nil, fmt.Errorf("zlib: invalid compression level: %d", level)
}
return &Writer{
@ -99,7 +100,7 @@ func (z *Writer) writeHeader() (err error) {
// The next bit, FDICT, is set if a dictionary is given.
// The final five FCHECK bits form a mod-31 checksum.
switch z.level {
case 0, 1:
case -2, 0, 1:
z.scratch[1] = 0 << 6
case 2, 3, 4, 5:
z.scratch[1] = 1 << 6

5
src/compress/zlib/writer_test.go
View File

@ -147,6 +147,7 @@ func TestWriter(t *testing.T) {
tag := fmt.Sprintf("#%d", i)
testLevelDict(t, tag, b, DefaultCompression, "")
testLevelDict(t, tag, b, NoCompression, "")
testLevelDict(t, tag, b, HuffmanOnly, "")
for level := BestSpeed; level <= BestCompression; level++ {
testLevelDict(t, tag, b, level, "")
}
@ -157,6 +158,7 @@ func TestWriterBig(t *testing.T) {
for i, fn := range filenames {
testFileLevelDict(t, fn, DefaultCompression, "")
testFileLevelDict(t, fn, NoCompression, "")
testFileLevelDict(t, fn, HuffmanOnly, "")
for level := BestSpeed; level <= BestCompression; level++ {
testFileLevelDict(t, fn, level, "")
if level >= 1 && testing.Short() && testenv.Builder() == "" {
@ -174,6 +176,7 @@ func TestWriterDict(t *testing.T) {
for i, fn := range filenames {
testFileLevelDict(t, fn, DefaultCompression, dictionary)
testFileLevelDict(t, fn, NoCompression, dictionary)
testFileLevelDict(t, fn, HuffmanOnly, dictionary)
for level := BestSpeed; level <= BestCompression; level++ {
testFileLevelDict(t, fn, level, dictionary)
if level >= 1 && testing.Short() && testenv.Builder() == "" {
@ -191,8 +194,10 @@ func TestWriterReset(t *testing.T) {
for _, fn := range filenames {
testFileLevelDictReset(t, fn, NoCompression, nil)
testFileLevelDictReset(t, fn, DefaultCompression, nil)
testFileLevelDictReset(t, fn, HuffmanOnly, nil)
testFileLevelDictReset(t, fn, NoCompression, []byte(dictionary))
testFileLevelDictReset(t, fn, DefaultCompression, []byte(dictionary))
testFileLevelDictReset(t, fn, HuffmanOnly, []byte(dictionary))
if testing.Short() {
break
}