Sakurai/pdf.js
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Extract the "scanning for endstream command" part of Parser.makeStream into a helper method

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With this code now living in a separate method, it can be simplified slightly (e.g. by using early returns).
This commit is contained in:
Jonas Jenwald 2018-08-26 01:33:56 +02:00
parent 436d2efa8a
commit c81cbe113c
1 changed files with 43 additions and 41 deletions
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84
src/core/parser.js
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@ -471,13 +471,45 @@ var Parser = (function ParserClosure() {
return imageStream;
},
_findStreamLength(startPos, signature) {
const { stream, } = this.lexer;
stream.pos = startPos;
const SCAN_BLOCK_LENGTH = 2048;
const signatureLength = signature.length;
while (stream.pos < stream.end) {
const scanBytes = stream.peekBytes(SCAN_BLOCK_LENGTH);
const scanLength = scanBytes.length - signatureLength;
if (scanLength <= 0) {
break;
}
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 (stream.pos - startPos);
}
pos++;
}
stream.pos += scanLength;
}
return -1;
},
makeStream: function Parser_makeStream(dict, cipherTransform) {
var lexer = this.lexer;
var stream = lexer.stream;
// get stream start position
lexer.skipToNextLine();
var pos = stream.pos - 1;
const startPos = stream.pos - 1;
// get length
var length = dict.get('Length');
@ -487,52 +519,22 @@ var Parser = (function ParserClosure() {
}
// skip over the stream data
stream.pos = pos + length;
stream.pos = startPos + length;
lexer.nextChar();
// Shift '>>' and check whether the new object marks the end of the stream
if (this.tryShift() && isCmd(this.buf2, 'endstream')) {
this.shift(); // 'stream'
} else {
// bad stream length, scanning for endstream
stream.pos = pos;
var SCAN_BLOCK_SIZE = 2048;
var ENDSTREAM_SIGNATURE_LENGTH = 9;
var ENDSTREAM_SIGNATURE = [0x65, 0x6E, 0x64, 0x73, 0x74, 0x72, 0x65,
0x61, 0x6D];
var skipped = 0, found = false, i, j;
while (stream.pos < stream.end) {
var scanBytes = stream.peekBytes(SCAN_BLOCK_SIZE);
var scanLength = scanBytes.length - ENDSTREAM_SIGNATURE_LENGTH;
if (scanLength <= 0) {
break;
}
found = false;
i = 0;
while (i < scanLength) {
j = 0;
while (j < ENDSTREAM_SIGNATURE_LENGTH &&
scanBytes[i + j] === ENDSTREAM_SIGNATURE[j]) {
j++;
}
if (j >= ENDSTREAM_SIGNATURE_LENGTH) {
found = true;
break;
}
i++;
}
if (found) {
skipped += i;
stream.pos += i;
break;
}
skipped += scanLength;
stream.pos += scanLength;
// Bad stream length, scanning for endstream command.
const ENDSTREAM_SIGNATURE = new Uint8Array([
0x65, 0x6E, 0x64, 0x73, 0x74, 0x72, 0x65, 0x61, 0x6D]);
let actualLength = this._findStreamLength(startPos,
ENDSTREAM_SIGNATURE);
if (actualLength < 0) {
throw new FormatError('Missing endstream command.');
}
if (!found) {
throw new FormatError('Missing endstream');
}
length = skipped;
length = actualLength;
lexer.nextChar();
this.shift();
@ -540,7 +542,7 @@ var Parser = (function ParserClosure() {
}
this.shift(); // 'endstream'
stream = stream.makeSubStream(pos, length, dict);
stream = stream.makeSubStream(startPos, length, dict);
if (cipherTransform) {
stream = cipherTransform.createStream(stream, length);
}