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Simplify the PDFDocument.fingerprint method slightly

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The way that this method handles documents without an `ID` entry in the Trailer dictionary feels overly complicated to me. Hence this patch adds `getByteRange` methods to the various Stream implementations[1], and utilize that rather than manually calling `ensureRange` when computing a fallback `fingerprint`.

---
[1] Note that `PDFDocument` is only ever initialized with either a `Stream` or a `ChunkedStream`, hence why the `DecodeStream.getByteRange` method isn't implemented.
This commit is contained in:
Jonas Jenwald 2019-07-15 11:26:07 +02:00
parent c7de6dbe41
commit bea15b6ce5
3 changed files with 30 additions and 10 deletions
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14
src/core/document.js
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@ -598,20 +598,16 @@ class PDFDocument {
idArray[0] !== EMPTY_FINGERPRINT) {
hash = stringToBytes(idArray[0]);
} else {
if (this.stream.ensureRange) {
this.stream.ensureRange(0,
Math.min(FINGERPRINT_FIRST_BYTES, this.stream.end));
}
hash = calculateMD5(this.stream.bytes.subarray(0,
FINGERPRINT_FIRST_BYTES), 0, FINGERPRINT_FIRST_BYTES);
hash = calculateMD5(this.stream.getByteRange(0, FINGERPRINT_FIRST_BYTES),
0, FINGERPRINT_FIRST_BYTES);
}
let fingerprint = '';
const fingerprintBuf = [];
for (let i = 0, ii = hash.length; i < ii; i++) {
const hex = hash[i].toString(16);
fingerprint += (hex.length === 1 ? '0' + hex : hex);
fingerprintBuf.push(hex.padStart(2, '0'));
}
return shadow(this, 'fingerprint', fingerprint);
return shadow(this, 'fingerprint', fingerprintBuf.join(''));
}
_getLinearizationPage(pageIndex) {