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Tidied up GIF and BZIP2 extractors

This commit is contained in:
n1474335 2019-11-08 13:49:39 +00:00
parent 8d660e53b2
commit 04f1fa06ad
1 changed files with 18 additions and 16 deletions
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34
src/core/lib/FileSignatures.mjs
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@ -2450,31 +2450,33 @@ export function extractJPEG(bytes, offset) {
export function extractGIF(bytes, offset) {
const stream = new Stream(bytes.slice(offset));
//Move to application extension block.
// Move to application extension block.
stream.continueUntil([0x21, 0xff]);
//Move to Graphic Control Extension for frame #1.
// Move to Graphic Control Extension for frame #1.
stream.continueUntil([0x21, 0xf9]);
stream.moveForwardsBy(2);
while (stream.hasMore()) {
// Move to Image descriptor.
stream.moveForwardsBy(stream.readInt(1) + 1);
//Move to Image descriptor.
stream.moveForwardsBy(stream.getBytes(1)[0]+1);
//Move past Image descriptor to the image data.
// Move past Image descriptor to the image data.
stream.moveForwardsBy(11);
//Loop until next Graphic Control Extension.
// Loop until next Graphic Control Extension.
while (stream.getBytes(2) !== [0x21, 0xf9]) {
stream.moveBackwardsBy(2);
stream.moveForwardsBy(stream.getBytes(1)[0]);
if (!stream.getBytes(1)[0])
stream.moveForwardsBy(stream.readInt(1));
if (!stream.readInt(1))
break;
stream.moveBackwardsBy(1);
}
//When the end of the file is [0x00, 0x3b], end.
if (stream.getBytes(1)[0] === 0x3b)
// When the end of the file is [0x00, 0x3b], end.
if (stream.readInt(1) === 0x3b)
break;
stream.moveForwardsBy(1);
}
return stream.carve();
@ -2828,7 +2830,7 @@ export function extractGZIP(bytes, offset) {
export function extractBZIP2(bytes, offset) {
const stream = new Stream(bytes.slice(offset));
//The EOFs shifted between all possible combinations.
// The EOFs shifted between all possible combinations.
const lookingfor = [
[0x77, 0x24, 0x53, 0x85, 0x09],
[0xee, 0x48, 0xa7, 0x0a, 0x12],
@ -2838,16 +2840,16 @@ export function extractBZIP2(bytes, offset) {
[0xbb, 0x92, 0x29, 0xc2, 0x84],
[0x5d, 0xc9, 0x14, 0xe1, 0x42],
[0x2e, 0xe4, 0x8a, 0x70, 0xa1],
[0x17, 0x72, 0x45, 0x38, 0x50]];
[0x17, 0x72, 0x45, 0x38, 0x50]
];
for (let i = 0; i < lookingfor.length; i++) {
//Continue until an EOF.
// Continue until an EOF.
stream.continueUntil(lookingfor[i]);
if (stream.getBytes(5).join("") === lookingfor[i].join(""))
break;
//Jump back to the start if invalid EOF.
// Jump back to the start if invalid EOF.
stream.moveTo(0);
}
stream.moveForwardsBy(4);