diff options
| -rw-r--r-- | src/pkg/compress/lzw/reader.go | 21 |
1 files changed, 11 insertions, 10 deletions
diff --git a/src/pkg/compress/lzw/reader.go b/src/pkg/compress/lzw/reader.go index ccd882f88b..21231c8e51 100644 --- a/src/pkg/compress/lzw/reader.go +++ b/src/pkg/compress/lzw/reader.go @@ -64,13 +64,14 @@ type decoder struct { // The c == hi case is a special case. suffix [1 << maxWidth]uint8 prefix [1 << maxWidth]uint16 - // buf is a scratch buffer for reconstituting the bytes that a code expands to. - // Code suffixes are written right-to-left from the end of the buffer. - buf [1 << maxWidth]byte // output is the temporary output buffer. + // Literal codes are accumulated from the start of the buffer. + // Non-literal codes decode to a sequence of suffixes that are first + // written right-to-left from the end of the buffer before being copied + // to the start of the buffer. // It is flushed when it contains >= 1<<maxWidth bytes, - // so that there is always room to copy buf into it while decoding. + // so that there is always room to decode an entire code. output [2 * 1 << maxWidth]byte o int // write index into output toRead []byte // bytes to return from Read @@ -158,7 +159,7 @@ func (d *decoder) decode() { d.err = os.EOF return case code <= d.hi: - c, i := code, len(d.buf)-1 + c, i := code, len(d.output)-1 if code == d.hi { // code == hi is a special case which expands to the last expansion // followed by the head of the last expansion. To find the head, we walk @@ -167,18 +168,18 @@ func (d *decoder) decode() { for c >= d.clear { c = d.prefix[c] } - d.buf[i] = uint8(c) + d.output[i] = uint8(c) i-- c = d.last } - // Copy the suffix chain into buf and then write that to w. + // Copy the suffix chain into output and then write that to w. for c >= d.clear { - d.buf[i] = d.suffix[c] + d.output[i] = d.suffix[c] i-- c = d.prefix[c] } - d.buf[i] = uint8(c) - d.o += copy(d.output[d.o:], d.buf[i:]) + d.output[i] = uint8(c) + d.o += copy(d.output[d.o:], d.output[i:]) if d.last != decoderInvalidCode { // Save what the hi code expands to. d.suffix[d.hi] = uint8(c) |