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GIF extractor for GIF89a

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This commit is contained in:
n1073645 2019-11-07 15:06:30 +00:00
parent b83f6591bb
commit 4f5e0c007d
1 changed files with 32 additions and 2 deletions
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34
src/core/lib/FileSignatures.mjs
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@ -40,7 +40,7 @@ export const FILE_SIGNATURES = {
4: [0x37, 0x39], // 7|9
5: 0x61 // a
},
extractor: null
extractor: extractGIF
},
{
name: "Portable Network Graphics image",
@ -2440,6 +2440,36 @@ export function extractJPEG(bytes, offset) {
}
/**
* GIF extractor.
*
* @param {Uint8Array} bytes
* @param {Number} offset
* @returns {Uint8Array}
*/
export function extractGIF(bytes, offset) {
const stream = new Stream(bytes.slice(offset));
stream.continueUntil([0x21, 0xff]);
stream.continueUntil([0x21, 0xf9]);
while (stream.hasMore()) {
stream.continueUntil(0x2c);
stream.moveForwardsBy(11);
while (stream.getBytes(2) !== [0x21, 0xf9]) {
stream.moveBackwardsBy(2);
stream.moveForwardsBy(stream.getBytes(1)[0]);
if (!stream.getBytes(1)[0])
break;
stream.moveBackwardsBy(1);
}
if (stream.getBytes(1)[0] === 0x3b)
break;
stream.moveBackwardsBy(1);
}
stream.moveBackwardsBy(10);
return stream.carve();
}
/**
* Portable executable extractor.
* Assumes that the offset refers to an MZ header.
@ -2809,7 +2839,7 @@ export function extractZlib(bytes, offset) {
/**
* XZ extractor
* XZ extractor.
*
* @param {Uint8Array} bytes
* @param {Number} offset