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compress/flate: document HuffmanOnly 

Fixes #16489

Change-Id: I13e2ed6de59102f977566de637d8d09b4e541980
Reviewed-on: https://go-review.googlesource.com/25200
Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Joe Tsai 2016-07-25 15:49:35 -07:00 committed by Joe Tsai
parent 10538a8f9e
commit d0256118de
1 changed files with 11 additions and 2 deletions
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13
src/compress/flate/deflate.go
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@ -15,7 +15,17 @@ const (
BestSpeed = 1 BestSpeed = 1
BestCompression = 9 BestCompression = 9
DefaultCompression = -1 DefaultCompression = -1
HuffmanOnly = -2 // Disables match search and only does Huffman entropy reduction.
// HuffmanOnly disables Lempel-Ziv match searching and only performs Huffman
// entropy encoding. This mode is useful in compressing data that has
// already been compressed with an LZ style algorithm (e.g. Snappy or LZ4)
// that lacks an entropy encoder. Compression gains are achieved when
// certain bytes in the input stream occur more frequently than others.
//
// Note that HuffmanOnly produces a compressed output that is
// RFC 1951 compliant. That is, any valid DEFLATE decompressor will
// continue to be able to decompress this output.
HuffmanOnly = -2
) )
const ( const (
@ -644,7 +654,6 @@ func (d *compressor) close() error {
// a very fast compression for all types of input, but sacrificing considerable // a very fast compression for all types of input, but sacrificing considerable
// compression efficiency. // compression efficiency.
// //
//
// If level is in the range [-2, 9] then the error returned will be nil. // If level is in the range [-2, 9] then the error returned will be nil.
// Otherwise the error returned will be non-nil. // Otherwise the error returned will be non-nil.
func NewWriter(w io.Writer, level int) (*Writer, error) { func NewWriter(w io.Writer, level int) (*Writer, error) {