code review 4209043: compress/lzw: implement an encoder.

compress/lzw: implement an encoder.

[nigeltao, 2011-02-24 00:23:45]

Hello rsc (cc: golang-dev@googlegroups.com),

I'd like you to review this change to
https://go.googlecode.com/hg/

[nigeltao_gnome, 2011-02-24 00:26:05]

compress/lzw/writer_test.go has a lot in common with
compress/zlib/writer_test.go.

I'll cook up a separate CL to move that stuff into testing/iotest.

[rsc, 2011-02-24 13:39:17]

LGTM

writer_test.go is so short that trying to share
code with zlib is probably not worth your while.
if nothing else you can give more specific error
messages in the duplicated code.

http://codereview.appspot.com/4209043/diff/5001/src/pkg/compress/lzw/writer.go
File src/pkg/compress/lzw/writer.go (right):

http://codereview.appspot.com/4209043/diff/5001/src/pkg/compress/lzw/writer.g...
src/pkg/compress/lzw/writer.go:25: func (e errWriteCloser) Write([]byte) (int,
os.Error) {
s/e /e */
next one too

http://codereview.appspot.com/4209043/diff/5001/src/pkg/compress/lzw/writer.g...
src/pkg/compress/lzw/writer.go:34: // Codes are a 12 bit value, stored as a
uint32 when encoding to avoid
s/Codes are/A code is/

http://codereview.appspot.com/4209043/diff/5001/src/pkg/compress/lzw/writer.g...
src/pkg/compress/lzw/writer.go:42: // Hash table entries are a uint32. Zero is
an invalid entry since the
// A hash table entry is

http://codereview.appspot.com/4209043/diff/5001/src/pkg/compress/lzw/writer.g...
src/pkg/compress/lzw/writer.go:108: // unused codes. In the latter case, a clear
code is sent, the encoder state
say who does what.

In the latter case, incHi sends a clear code, resets the
encoder state, and returns errOutOfCodes.

http://codereview.appspot.com/4209043/diff/5001/src/pkg/compress/lzw/writer.g...
src/pkg/compress/lzw/writer.go:132: // Write writes compressed bytes to e's
underlying writer.
s/compressed bytes/a compressed representation of p/

to make it clear that p is not already compressed

http://codereview.appspot.com/4209043/diff/5001/src/pkg/compress/lzw/writer.g...
src/pkg/compress/lzw/writer.go:229: // order is either LSB or MSB for Least or
Most Significant Bits first packing
first sentence doesn't make it clear that the writecloser
is doing the compressing.  start sentences with capital letters.  leave the LSB
and MSB comments to describe them.

// NewWriter creates a new io.WriteCloser that satisfies writes
// by compressing the data and writing it to w.
// It is the caller's responsibility ...
// The number of bits to use for literal codes, litWidth,
// must be in the range [2,8] and is typically 8.

[nigeltao, 2011-02-24 22:20:16]

*** Submitted as http://code.google.com/p/go/source/detail?r=0d7c59b3e418 ***

compress/lzw: implement an encoder.

R=rsc, nigeltao_gnome
CC=golang-dev
http://codereview.appspot.com/4209043