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[src/core/jpg.js] Remove some redundant marker validation during the MCU parsing in the decodeScan function

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Some of the code in `src/core/jpg.js` is fairly old, and has with time become unnecessary when the surrounding code has been updated to handle various types of JPEG corruption.
In particular the `if (!marker || marker <= 0xff00) { ... }` branch is now dead code, since:

 - The `!marker` case can no longer happen, since we would already have broken out of the loop thanks to the `!fileMarker` branch a handful of lines above.

 - The `marker <= 0xff00` case can also no longer happen, since the `findNextFileMarker` function validate markers much more thoroughly (by checking `marker >= 0xffc0 && marker <= 0xfffe`). Hence we'd again have broken out of the loop via the `!fileMarker` branch above when no valid marker was found.
This commit is contained in:
Jonas Jenwald 2020-04-11 15:49:25 +02:00
parent 50bc4a18e8
commit 26cffd03b0
1 changed files with 6 additions and 13 deletions
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19
src/core/jpg.js
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@ -429,23 +429,17 @@ var JpegImage = (function JpegImageClosure() {
bitsCount = 0;
fileMarker = findNextFileMarker(data, offset);
if (!fileMarker) {
// Reached the end of the image data without finding an EOI marker.
break;
} else if (fileMarker.invalid) {
break; // Reached the end of the image data without finding any marker.
}
if (fileMarker.invalid) {
// Some bad images seem to pad Scan blocks with e.g. zero bytes, skip
// past those to attempt to find a valid marker (fixes issue4090.pdf).
warn(
"decodeScan - unexpected MCU data, current marker is: " +
fileMarker.invalid
`decodeScan - unexpected MCU data, current marker is: ${fileMarker.invalid}`
);
offset = fileMarker.offset;
}
var marker = fileMarker && fileMarker.marker;
if (!marker || marker <= 0xff00) {
throw new JpegError("decodeScan - a valid marker was not found.");
}
if (marker >= 0xffd0 && marker <= 0xffd7) {
if (fileMarker.marker >= 0xffd0 && fileMarker.marker <= 0xffd7) {
// RSTx
offset += 2;
} else {
@ -458,8 +452,7 @@ var JpegImage = (function JpegImageClosure() {
// attempt to find the next valid marker (fixes issue8182.pdf).
if (fileMarker && fileMarker.invalid) {
warn(
"decodeScan - unexpected Scan data, current marker is: " +
fileMarker.invalid
`decodeScan - unexpected Scan data, current marker is: ${fileMarker.invalid}`
);
offset = fileMarker.offset;
}