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Merge pull request #11406 from Snuffleupagus/find-scanBytes

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Re-factor the `find` helper function, in `src/core/document.js`, to search through the raw bytes rather than a string
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Tim van der Meij 2019-12-15 16:26:42 +01:00 committed by GitHub
commit e09fe7226d
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1 changed files with 53 additions and 15 deletions
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src/core/document.js
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@ -15,8 +15,8 @@
/* eslint no-var: error */
import {
assert, bytesToString, FormatError, info, InvalidPDFException, isArrayBuffer,
isArrayEqual, isBool, isNum, isSpace, isString, OPS, shadow, stringToBytes,
assert, FormatError, info, InvalidPDFException, isArrayBuffer, isArrayEqual,
isBool, isNum, isSpace, isString, OPS, shadow, stringToBytes,
stringToPDFString, Util, warn
} from '../shared/util';
import { Catalog, ObjectLoader, XRef } from './obj';
@ -344,21 +344,59 @@ class Page {
}
}
const PDF_HEADER_SIGNATURE = new Uint8Array([0x25, 0x50, 0x44, 0x46, 0x2D]);
const STARTXREF_SIGNATURE = new Uint8Array([
0x73, 0x74, 0x61, 0x72, 0x74, 0x78, 0x72, 0x65, 0x66]);
const ENDOBJ_SIGNATURE = new Uint8Array([0x65, 0x6E, 0x64, 0x6F, 0x62, 0x6A]);
const FINGERPRINT_FIRST_BYTES = 1024;
const EMPTY_FINGERPRINT = '\x00\x00\x00\x00\x00\x00\x00' +
'\x00\x00\x00\x00\x00\x00\x00\x00\x00';
const EMPTY_FINGERPRINT =
'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00';
function find(stream, needle, limit, backwards = false) {
assert(limit > 0, 'The "limit" must be a positive integer.');
function find(stream, signature, limit = 1024, backwards = false) {
if (typeof PDFJSDev === 'undefined' ||
PDFJSDev.test('!PRODUCTION || TESTING')) {
assert(limit > 0, 'The "limit" must be a positive integer.');
}
const signatureLength = signature.length;
const str = bytesToString(stream.peekBytes(limit));
const scanBytes = stream.peekBytes(limit);
const scanLength = scanBytes.length - signatureLength;
const index = backwards ? str.lastIndexOf(needle) : str.indexOf(needle);
if (index === -1) {
if (scanLength <= 0) {
return false;
}
stream.pos += index;
return true;
if (backwards) {
const signatureEnd = signatureLength - 1;
let pos = scanBytes.length - 1;
while (pos >= signatureEnd) {
let j = 0;
while (j < signatureLength &&
scanBytes[pos - j] === signature[signatureEnd - j]) {
j++;
}
if (j >= signatureLength) { // `signature` found.
stream.pos += (pos - signatureEnd);
return true;
}
pos--;
}
} else { // forwards
let pos = 0;
while (pos <= scanLength) {
let j = 0;
while (j < signatureLength && scanBytes[pos + j] === signature[j]) {
j++;
}
if (j >= signatureLength) { // `signature` found.
stream.pos += pos;
return true;
}
pos++;
}
}
return false;
}
/**
@ -450,13 +488,13 @@ class PDFDocument {
if (this.linearization) {
// Find the end of the first object.
stream.reset();
if (find(stream, 'endobj', 1024)) {
if (find(stream, ENDOBJ_SIGNATURE)) {
startXRef = (stream.pos + 6) - stream.start;
}
} else {
// Find `startxref` by checking backwards from the end of the file.
const step = 1024;
const startXRefLength = 'startxref'.length;
const startXRefLength = STARTXREF_SIGNATURE.length;
let found = false, pos = stream.end;
while (!found && pos > 0) {
@ -465,7 +503,7 @@ class PDFDocument {
pos = 0;
}
stream.pos = pos;
found = find(stream, 'startxref', step, true);
found = find(stream, STARTXREF_SIGNATURE, step, true);
}
if (found) {
@ -494,7 +532,7 @@ class PDFDocument {
const stream = this.stream;
stream.reset();
if (!find(stream, '%PDF-', 1024)) {
if (!find(stream, PDF_HEADER_SIGNATURE)) {
// May not be a PDF file, but don't throw an error and let
// parsing continue.
return;