tiff/lzw: sync with the stdlib compress/lzw.
As noted at the top of reader.go, this package is a fork of the standard
library's LZW package, due to an "off by one" in the TIFF format. Grep
for "NOTE" in the Go code for more details.
This commit picks up an upstream change:
https://go-review.googlesource.com/14410 "tidy up some flush calls"
Picking up the more recent change:
https://go-review.googlesource.com/42032 "fix hi code overflow"
will be a follow-up commit, separate from this straightforward commit,
since it has a non-trivial interaction with that off by one.
Change-Id: Iaf795d11590b3e3e0891e3ea3f04b696de4243c9
Reviewed-on: https://go-review.googlesource.com/42191
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/tiff/lzw/reader.go b/tiff/lzw/reader.go
index ad35819..51ae39f 100644
--- a/tiff/lzw/reader.go
+++ b/tiff/lzw/reader.go
@@ -147,6 +147,7 @@
// litWidth is the width in bits of literal codes.
func (d *decoder) decode() {
// Loop over the code stream, converting codes into decompressed bytes.
+loop:
for {
code, err := d.read(d)
if err != nil {
@@ -154,8 +155,7 @@
err = io.ErrUnexpectedEOF
}
d.err = err
- d.flush()
- return
+ break
}
switch {
case code < d.clear:
@@ -174,9 +174,8 @@
d.last = decoderInvalidCode
continue
case code == d.eof:
- d.flush()
d.err = io.EOF
- return
+ break loop
case code <= d.hi:
c, i := code, len(d.output)-1
if code == d.hi {
@@ -206,8 +205,7 @@
}
default:
d.err = errors.New("lzw: invalid code")
- d.flush()
- return
+ break loop
}
d.last, d.hi = code, d.hi+1
if d.hi+1 >= d.overflow { // NOTE: the "+1" is where TIFF's LZW differs from the standard algorithm.
@@ -219,13 +217,10 @@
}
}
if d.o >= flushBuffer {
- d.flush()
- return
+ break
}
}
-}
-
-func (d *decoder) flush() {
+ // Flush pending output.
d.toRead = d.output[:d.o]
d.o = 0
}
