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image/jpeg: ignore an incorrect but harmless trailing restart marker.

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Fixes #4084.

R=r
CC=golang-dev
https://golang.org/cl/6526043
This commit is contained in:
Nigel Tao 2012-09-18 21:57:33 +10:00
parent 6e4d24999f
commit 648c9eb0b5
1 changed files with 10 additions and 1 deletions
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11
src/pkg/image/jpeg/reader.go
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@ -403,6 +403,15 @@ func (d *decoder) decode(r io.Reader, configOnly bool) (image.Image, error) {
if marker == eoiMarker { // End Of Image.
break
}
if rst0Marker <= marker && marker <= rst7Marker {
// Figures B.2 and B.16 of the specification suggest that restart markers should
// only occur between Entropy Coded Segments and not after the final ECS.
// However, some encoders may generate incorrect JPEGs with a final restart
// marker. That restart marker will be seen here instead of inside the processSOS
// method, and is ignored as a harmless error. Restart markers have no extra data,
// so we check for this before we read the 16-bit length of the segment.
continue
}
// Read the 16-bit length of the segment. The value includes the 2 bytes for the
// length itself, so we subtract 2 to get the number of remaining bytes.
@ -431,7 +440,7 @@ func (d *decoder) decode(r io.Reader, configOnly bool) (image.Image, error) {
err = d.processSOS(n)
case marker == driMarker: // Define Restart Interval.
err = d.processDRI(n)
case marker >= app0Marker && marker <= app15Marker || marker == comMarker: // APPlication specific, or COMment.
case app0Marker <= marker && marker <= app15Marker || marker == comMarker: // APPlication specific, or COMment.
err = d.ignore(n)
default:
err = UnsupportedError("unknown marker")