934 lines
28 KiB
JavaScript
934 lines
28 KiB
JavaScript
/* Copyright 2021 Mozilla Foundation
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*/
|
|
|
|
import {
|
|
assert,
|
|
bytesToString,
|
|
FormatError,
|
|
info,
|
|
InvalidPDFException,
|
|
warn,
|
|
} from "../shared/util.js";
|
|
import { CIRCULAR_REF, Cmd, Dict, isCmd, Ref, RefSet } from "./primitives.js";
|
|
import {
|
|
DocStats,
|
|
MissingDataException,
|
|
ParserEOFException,
|
|
XRefEntryException,
|
|
XRefParseException,
|
|
} from "./core_utils.js";
|
|
import { Lexer, Parser } from "./parser.js";
|
|
import { BaseStream } from "./base_stream.js";
|
|
import { CipherTransformFactory } from "./crypto.js";
|
|
|
|
class XRef {
|
|
constructor(stream, pdfManager) {
|
|
this.stream = stream;
|
|
this.pdfManager = pdfManager;
|
|
this.entries = [];
|
|
this.xrefstms = Object.create(null);
|
|
this._cacheMap = new Map(); // Prepare the XRef cache.
|
|
this._pendingRefs = new RefSet();
|
|
this.stats = new DocStats(pdfManager.msgHandler);
|
|
this._newRefNum = null;
|
|
}
|
|
|
|
getNewRef() {
|
|
if (this._newRefNum === null) {
|
|
this._newRefNum = this.entries.length || 1;
|
|
}
|
|
return Ref.get(this._newRefNum++, 0);
|
|
}
|
|
|
|
resetNewRef() {
|
|
this._newRefNum = null;
|
|
}
|
|
|
|
setStartXRef(startXRef) {
|
|
// Store the starting positions of xref tables as we process them
|
|
// so we can recover from missing data errors
|
|
this.startXRefQueue = [startXRef];
|
|
}
|
|
|
|
parse(recoveryMode = false) {
|
|
let trailerDict;
|
|
if (!recoveryMode) {
|
|
trailerDict = this.readXRef();
|
|
} else {
|
|
warn("Indexing all PDF objects");
|
|
trailerDict = this.indexObjects();
|
|
}
|
|
trailerDict.assignXref(this);
|
|
this.trailer = trailerDict;
|
|
|
|
let encrypt;
|
|
try {
|
|
encrypt = trailerDict.get("Encrypt");
|
|
} catch (ex) {
|
|
if (ex instanceof MissingDataException) {
|
|
throw ex;
|
|
}
|
|
warn(`XRef.parse - Invalid "Encrypt" reference: "${ex}".`);
|
|
}
|
|
if (encrypt instanceof Dict) {
|
|
const ids = trailerDict.get("ID");
|
|
const fileId = ids && ids.length ? ids[0] : "";
|
|
// The 'Encrypt' dictionary itself should not be encrypted, and by
|
|
// setting `suppressEncryption` we can prevent an infinite loop inside
|
|
// of `XRef_fetchUncompressed` if the dictionary contains indirect
|
|
// objects (fixes issue7665.pdf).
|
|
encrypt.suppressEncryption = true;
|
|
this.encrypt = new CipherTransformFactory(
|
|
encrypt,
|
|
fileId,
|
|
this.pdfManager.password
|
|
);
|
|
}
|
|
|
|
// Get the root dictionary (catalog) object, and do some basic validation.
|
|
let root;
|
|
try {
|
|
root = trailerDict.get("Root");
|
|
} catch (ex) {
|
|
if (ex instanceof MissingDataException) {
|
|
throw ex;
|
|
}
|
|
warn(`XRef.parse - Invalid "Root" reference: "${ex}".`);
|
|
}
|
|
if (root instanceof Dict) {
|
|
try {
|
|
const pages = root.get("Pages");
|
|
if (pages instanceof Dict) {
|
|
this.root = root;
|
|
return;
|
|
}
|
|
} catch (ex) {
|
|
if (ex instanceof MissingDataException) {
|
|
throw ex;
|
|
}
|
|
warn(`XRef.parse - Invalid "Pages" reference: "${ex}".`);
|
|
}
|
|
}
|
|
|
|
if (!recoveryMode) {
|
|
throw new XRefParseException();
|
|
}
|
|
// Even recovery failed, there's nothing more we can do here.
|
|
throw new InvalidPDFException("Invalid Root reference.");
|
|
}
|
|
|
|
processXRefTable(parser) {
|
|
if (!("tableState" in this)) {
|
|
// Stores state of the table as we process it so we can resume
|
|
// from middle of table in case of missing data error
|
|
this.tableState = {
|
|
entryNum: 0,
|
|
streamPos: parser.lexer.stream.pos,
|
|
parserBuf1: parser.buf1,
|
|
parserBuf2: parser.buf2,
|
|
};
|
|
}
|
|
|
|
const obj = this.readXRefTable(parser);
|
|
|
|
// Sanity check
|
|
if (!isCmd(obj, "trailer")) {
|
|
throw new FormatError(
|
|
"Invalid XRef table: could not find trailer dictionary"
|
|
);
|
|
}
|
|
// Read trailer dictionary, e.g.
|
|
// trailer
|
|
// << /Size 22
|
|
// /Root 20R
|
|
// /Info 10R
|
|
// /ID [ <81b14aafa313db63dbd6f981e49f94f4> ]
|
|
// >>
|
|
// The parser goes through the entire stream << ... >> and provides
|
|
// a getter interface for the key-value table
|
|
let dict = parser.getObj();
|
|
|
|
// The pdflib PDF generator can generate a nested trailer dictionary
|
|
if (!(dict instanceof Dict) && dict.dict) {
|
|
dict = dict.dict;
|
|
}
|
|
if (!(dict instanceof Dict)) {
|
|
throw new FormatError(
|
|
"Invalid XRef table: could not parse trailer dictionary"
|
|
);
|
|
}
|
|
delete this.tableState;
|
|
|
|
return dict;
|
|
}
|
|
|
|
readXRefTable(parser) {
|
|
// Example of cross-reference table:
|
|
// xref
|
|
// 0 1 <-- subsection header (first obj #, obj count)
|
|
// 0000000000 65535 f <-- actual object (offset, generation #, f/n)
|
|
// 23 2 <-- subsection header ... and so on ...
|
|
// 0000025518 00002 n
|
|
// 0000025635 00000 n
|
|
// trailer
|
|
// ...
|
|
|
|
const stream = parser.lexer.stream;
|
|
const tableState = this.tableState;
|
|
stream.pos = tableState.streamPos;
|
|
parser.buf1 = tableState.parserBuf1;
|
|
parser.buf2 = tableState.parserBuf2;
|
|
|
|
// Outer loop is over subsection headers
|
|
let obj;
|
|
|
|
while (true) {
|
|
if (!("firstEntryNum" in tableState) || !("entryCount" in tableState)) {
|
|
if (isCmd((obj = parser.getObj()), "trailer")) {
|
|
break;
|
|
}
|
|
tableState.firstEntryNum = obj;
|
|
tableState.entryCount = parser.getObj();
|
|
}
|
|
|
|
let first = tableState.firstEntryNum;
|
|
const count = tableState.entryCount;
|
|
if (!Number.isInteger(first) || !Number.isInteger(count)) {
|
|
throw new FormatError(
|
|
"Invalid XRef table: wrong types in subsection header"
|
|
);
|
|
}
|
|
// Inner loop is over objects themselves
|
|
for (let i = tableState.entryNum; i < count; i++) {
|
|
tableState.streamPos = stream.pos;
|
|
tableState.entryNum = i;
|
|
tableState.parserBuf1 = parser.buf1;
|
|
tableState.parserBuf2 = parser.buf2;
|
|
|
|
const entry = {};
|
|
entry.offset = parser.getObj();
|
|
entry.gen = parser.getObj();
|
|
const type = parser.getObj();
|
|
|
|
if (type instanceof Cmd) {
|
|
switch (type.cmd) {
|
|
case "f":
|
|
entry.free = true;
|
|
break;
|
|
case "n":
|
|
entry.uncompressed = true;
|
|
break;
|
|
}
|
|
}
|
|
|
|
// Validate entry obj
|
|
if (
|
|
!Number.isInteger(entry.offset) ||
|
|
!Number.isInteger(entry.gen) ||
|
|
!(entry.free || entry.uncompressed)
|
|
) {
|
|
throw new FormatError(
|
|
`Invalid entry in XRef subsection: ${first}, ${count}`
|
|
);
|
|
}
|
|
|
|
// The first xref table entry, i.e. obj 0, should be free. Attempting
|
|
// to adjust an incorrect first obj # (fixes issue 3248 and 7229).
|
|
if (i === 0 && entry.free && first === 1) {
|
|
first = 0;
|
|
}
|
|
|
|
if (!this.entries[i + first]) {
|
|
this.entries[i + first] = entry;
|
|
}
|
|
}
|
|
|
|
tableState.entryNum = 0;
|
|
tableState.streamPos = stream.pos;
|
|
tableState.parserBuf1 = parser.buf1;
|
|
tableState.parserBuf2 = parser.buf2;
|
|
delete tableState.firstEntryNum;
|
|
delete tableState.entryCount;
|
|
}
|
|
|
|
// Sanity check: as per spec, first object must be free
|
|
if (this.entries[0] && !this.entries[0].free) {
|
|
throw new FormatError("Invalid XRef table: unexpected first object");
|
|
}
|
|
return obj;
|
|
}
|
|
|
|
processXRefStream(stream) {
|
|
if (!("streamState" in this)) {
|
|
// Stores state of the stream as we process it so we can resume
|
|
// from middle of stream in case of missing data error
|
|
const streamParameters = stream.dict;
|
|
const byteWidths = streamParameters.get("W");
|
|
let range = streamParameters.get("Index");
|
|
if (!range) {
|
|
range = [0, streamParameters.get("Size")];
|
|
}
|
|
|
|
this.streamState = {
|
|
entryRanges: range,
|
|
byteWidths,
|
|
entryNum: 0,
|
|
streamPos: stream.pos,
|
|
};
|
|
}
|
|
this.readXRefStream(stream);
|
|
delete this.streamState;
|
|
|
|
return stream.dict;
|
|
}
|
|
|
|
readXRefStream(stream) {
|
|
const streamState = this.streamState;
|
|
stream.pos = streamState.streamPos;
|
|
|
|
const [typeFieldWidth, offsetFieldWidth, generationFieldWidth] =
|
|
streamState.byteWidths;
|
|
|
|
const entryRanges = streamState.entryRanges;
|
|
while (entryRanges.length > 0) {
|
|
const [first, n] = entryRanges;
|
|
|
|
if (!Number.isInteger(first) || !Number.isInteger(n)) {
|
|
throw new FormatError(`Invalid XRef range fields: ${first}, ${n}`);
|
|
}
|
|
if (
|
|
!Number.isInteger(typeFieldWidth) ||
|
|
!Number.isInteger(offsetFieldWidth) ||
|
|
!Number.isInteger(generationFieldWidth)
|
|
) {
|
|
throw new FormatError(
|
|
`Invalid XRef entry fields length: ${first}, ${n}`
|
|
);
|
|
}
|
|
for (let i = streamState.entryNum; i < n; ++i) {
|
|
streamState.entryNum = i;
|
|
streamState.streamPos = stream.pos;
|
|
|
|
let type = 0,
|
|
offset = 0,
|
|
generation = 0;
|
|
for (let j = 0; j < typeFieldWidth; ++j) {
|
|
const typeByte = stream.getByte();
|
|
if (typeByte === -1) {
|
|
throw new FormatError("Invalid XRef byteWidths 'type'.");
|
|
}
|
|
type = (type << 8) | typeByte;
|
|
}
|
|
// if type field is absent, its default value is 1
|
|
if (typeFieldWidth === 0) {
|
|
type = 1;
|
|
}
|
|
for (let j = 0; j < offsetFieldWidth; ++j) {
|
|
const offsetByte = stream.getByte();
|
|
if (offsetByte === -1) {
|
|
throw new FormatError("Invalid XRef byteWidths 'offset'.");
|
|
}
|
|
offset = (offset << 8) | offsetByte;
|
|
}
|
|
for (let j = 0; j < generationFieldWidth; ++j) {
|
|
const generationByte = stream.getByte();
|
|
if (generationByte === -1) {
|
|
throw new FormatError("Invalid XRef byteWidths 'generation'.");
|
|
}
|
|
generation = (generation << 8) | generationByte;
|
|
}
|
|
const entry = {};
|
|
entry.offset = offset;
|
|
entry.gen = generation;
|
|
switch (type) {
|
|
case 0:
|
|
entry.free = true;
|
|
break;
|
|
case 1:
|
|
entry.uncompressed = true;
|
|
break;
|
|
case 2:
|
|
break;
|
|
default:
|
|
throw new FormatError(`Invalid XRef entry type: ${type}`);
|
|
}
|
|
if (!this.entries[first + i]) {
|
|
this.entries[first + i] = entry;
|
|
}
|
|
}
|
|
|
|
streamState.entryNum = 0;
|
|
streamState.streamPos = stream.pos;
|
|
entryRanges.splice(0, 2);
|
|
}
|
|
}
|
|
|
|
indexObjects() {
|
|
// Simple scan through the PDF content to find objects,
|
|
// trailers and XRef streams.
|
|
const TAB = 0x9,
|
|
LF = 0xa,
|
|
CR = 0xd,
|
|
SPACE = 0x20;
|
|
const PERCENT = 0x25,
|
|
LT = 0x3c;
|
|
|
|
function readToken(data, offset) {
|
|
let token = "",
|
|
ch = data[offset];
|
|
while (ch !== LF && ch !== CR && ch !== LT) {
|
|
if (++offset >= data.length) {
|
|
break;
|
|
}
|
|
token += String.fromCharCode(ch);
|
|
ch = data[offset];
|
|
}
|
|
return token;
|
|
}
|
|
function skipUntil(data, offset, what) {
|
|
const length = what.length,
|
|
dataLength = data.length;
|
|
let skipped = 0;
|
|
// finding byte sequence
|
|
while (offset < dataLength) {
|
|
let i = 0;
|
|
while (i < length && data[offset + i] === what[i]) {
|
|
++i;
|
|
}
|
|
if (i >= length) {
|
|
break; // sequence found
|
|
}
|
|
offset++;
|
|
skipped++;
|
|
}
|
|
return skipped;
|
|
}
|
|
const objRegExp = /^(\d+)\s+(\d+)\s+obj\b/;
|
|
const endobjRegExp = /\bendobj[\b\s]$/;
|
|
const nestedObjRegExp = /\s+(\d+\s+\d+\s+obj[\b\s<])$/;
|
|
const CHECK_CONTENT_LENGTH = 25;
|
|
|
|
const trailerBytes = new Uint8Array([116, 114, 97, 105, 108, 101, 114]);
|
|
const startxrefBytes = new Uint8Array([
|
|
115, 116, 97, 114, 116, 120, 114, 101, 102,
|
|
]);
|
|
const objBytes = new Uint8Array([111, 98, 106]);
|
|
const xrefBytes = new Uint8Array([47, 88, 82, 101, 102]);
|
|
|
|
// Clear out any existing entries, since they may be bogus.
|
|
this.entries.length = 0;
|
|
this._cacheMap.clear();
|
|
|
|
const stream = this.stream;
|
|
stream.pos = 0;
|
|
const buffer = stream.getBytes(),
|
|
length = buffer.length;
|
|
let position = stream.start;
|
|
const trailers = [],
|
|
xrefStms = [];
|
|
while (position < length) {
|
|
let ch = buffer[position];
|
|
if (ch === TAB || ch === LF || ch === CR || ch === SPACE) {
|
|
++position;
|
|
continue;
|
|
}
|
|
if (ch === PERCENT) {
|
|
// %-comment
|
|
do {
|
|
++position;
|
|
if (position >= length) {
|
|
break;
|
|
}
|
|
ch = buffer[position];
|
|
} while (ch !== LF && ch !== CR);
|
|
continue;
|
|
}
|
|
const token = readToken(buffer, position);
|
|
let m;
|
|
if (
|
|
token.startsWith("xref") &&
|
|
(token.length === 4 || /\s/.test(token[4]))
|
|
) {
|
|
position += skipUntil(buffer, position, trailerBytes);
|
|
trailers.push(position);
|
|
position += skipUntil(buffer, position, startxrefBytes);
|
|
} else if ((m = objRegExp.exec(token))) {
|
|
const num = m[1] | 0,
|
|
gen = m[2] | 0;
|
|
|
|
let contentLength,
|
|
startPos = position + token.length,
|
|
updateEntries = false;
|
|
if (!this.entries[num]) {
|
|
updateEntries = true;
|
|
} else if (this.entries[num].gen === gen) {
|
|
// Before overwriting an existing entry, ensure that the new one won't
|
|
// cause *immediate* errors when it's accessed (fixes issue13783.pdf).
|
|
try {
|
|
const parser = new Parser({
|
|
lexer: new Lexer(stream.makeSubStream(startPos)),
|
|
});
|
|
parser.getObj();
|
|
updateEntries = true;
|
|
} catch (ex) {
|
|
if (ex instanceof ParserEOFException) {
|
|
warn(`indexObjects -- checking object (${token}): "${ex}".`);
|
|
} else {
|
|
// The error may come from the `Parser`-instance being initialized
|
|
// without an `XRef`-instance (we don't have a usable one yet).
|
|
updateEntries = true;
|
|
}
|
|
}
|
|
}
|
|
if (updateEntries) {
|
|
this.entries[num] = {
|
|
offset: position - stream.start,
|
|
gen,
|
|
uncompressed: true,
|
|
};
|
|
}
|
|
|
|
// Find the next "obj" string, rather than "endobj", to ensure that
|
|
// we won't skip over a new 'obj' operator in corrupt files where
|
|
// 'endobj' operators are missing (fixes issue9105_reduced.pdf).
|
|
while (startPos < buffer.length) {
|
|
const endPos = startPos + skipUntil(buffer, startPos, objBytes) + 4;
|
|
contentLength = endPos - position;
|
|
|
|
const checkPos = Math.max(endPos - CHECK_CONTENT_LENGTH, startPos);
|
|
const tokenStr = bytesToString(buffer.subarray(checkPos, endPos));
|
|
|
|
// Check if the current object ends with an 'endobj' operator.
|
|
if (endobjRegExp.test(tokenStr)) {
|
|
break;
|
|
} else {
|
|
// Check if an "obj" occurrence is actually a new object,
|
|
// i.e. the current object is missing the 'endobj' operator.
|
|
const objToken = nestedObjRegExp.exec(tokenStr);
|
|
|
|
if (objToken && objToken[1]) {
|
|
warn(
|
|
'indexObjects: Found new "obj" inside of another "obj", ' +
|
|
'caused by missing "endobj" -- trying to recover.'
|
|
);
|
|
contentLength -= objToken[1].length;
|
|
break;
|
|
}
|
|
}
|
|
startPos = endPos;
|
|
}
|
|
const content = buffer.subarray(position, position + contentLength);
|
|
|
|
// checking XRef stream suspect
|
|
// (it shall have '/XRef' and next char is not a letter)
|
|
const xrefTagOffset = skipUntil(content, 0, xrefBytes);
|
|
if (xrefTagOffset < contentLength && content[xrefTagOffset + 5] < 64) {
|
|
xrefStms.push(position - stream.start);
|
|
this.xrefstms[position - stream.start] = 1; // Avoid recursion
|
|
}
|
|
|
|
position += contentLength;
|
|
} else if (
|
|
token.startsWith("trailer") &&
|
|
(token.length === 7 || /\s/.test(token[7]))
|
|
) {
|
|
trailers.push(position);
|
|
position += skipUntil(buffer, position, startxrefBytes);
|
|
} else {
|
|
position += token.length + 1;
|
|
}
|
|
}
|
|
// reading XRef streams
|
|
for (let i = 0, ii = xrefStms.length; i < ii; ++i) {
|
|
this.startXRefQueue.push(xrefStms[i]);
|
|
this.readXRef(/* recoveryMode */ true);
|
|
}
|
|
// finding main trailer
|
|
let trailerDict;
|
|
for (let i = 0, ii = trailers.length; i < ii; ++i) {
|
|
stream.pos = trailers[i];
|
|
const parser = new Parser({
|
|
lexer: new Lexer(stream),
|
|
xref: this,
|
|
allowStreams: true,
|
|
recoveryMode: true,
|
|
});
|
|
const obj = parser.getObj();
|
|
if (!isCmd(obj, "trailer")) {
|
|
continue;
|
|
}
|
|
// read the trailer dictionary
|
|
const dict = parser.getObj();
|
|
if (!(dict instanceof Dict)) {
|
|
continue;
|
|
}
|
|
// Do some basic validation of the trailer/root dictionary candidate.
|
|
try {
|
|
const rootDict = dict.get("Root");
|
|
if (!(rootDict instanceof Dict)) {
|
|
continue;
|
|
}
|
|
const pagesDict = rootDict.get("Pages");
|
|
if (!(pagesDict instanceof Dict)) {
|
|
continue;
|
|
}
|
|
const pagesCount = pagesDict.get("Count");
|
|
if (!Number.isInteger(pagesCount)) {
|
|
continue;
|
|
}
|
|
// The top-level /Pages dictionary isn't obviously corrupt.
|
|
} catch (ex) {
|
|
continue;
|
|
}
|
|
// taking the first one with 'ID'
|
|
if (dict.has("ID")) {
|
|
return dict;
|
|
}
|
|
// The current dictionary is a candidate, but continue searching.
|
|
trailerDict = dict;
|
|
}
|
|
// No trailer with 'ID', taking last one (if exists).
|
|
if (trailerDict) {
|
|
return trailerDict;
|
|
}
|
|
// No trailer dictionary found, taking the "top"-dictionary (if exists).
|
|
if (this.topDict) {
|
|
return this.topDict;
|
|
}
|
|
// nothing helps
|
|
throw new InvalidPDFException("Invalid PDF structure.");
|
|
}
|
|
|
|
readXRef(recoveryMode = false) {
|
|
const stream = this.stream;
|
|
// Keep track of already parsed XRef tables, to prevent an infinite loop
|
|
// when parsing corrupt PDF files where e.g. the /Prev entries create a
|
|
// circular dependency between tables (fixes bug1393476.pdf).
|
|
const startXRefParsedCache = new Set();
|
|
|
|
try {
|
|
while (this.startXRefQueue.length) {
|
|
const startXRef = this.startXRefQueue[0];
|
|
|
|
if (startXRefParsedCache.has(startXRef)) {
|
|
warn("readXRef - skipping XRef table since it was already parsed.");
|
|
this.startXRefQueue.shift();
|
|
continue;
|
|
}
|
|
startXRefParsedCache.add(startXRef);
|
|
|
|
stream.pos = startXRef + stream.start;
|
|
|
|
const parser = new Parser({
|
|
lexer: new Lexer(stream),
|
|
xref: this,
|
|
allowStreams: true,
|
|
});
|
|
let obj = parser.getObj();
|
|
let dict;
|
|
|
|
// Get dictionary
|
|
if (isCmd(obj, "xref")) {
|
|
// Parse end-of-file XRef
|
|
dict = this.processXRefTable(parser);
|
|
if (!this.topDict) {
|
|
this.topDict = dict;
|
|
}
|
|
|
|
// Recursively get other XRefs 'XRefStm', if any
|
|
obj = dict.get("XRefStm");
|
|
if (Number.isInteger(obj)) {
|
|
const pos = obj;
|
|
// ignore previously loaded xref streams
|
|
// (possible infinite recursion)
|
|
if (!(pos in this.xrefstms)) {
|
|
this.xrefstms[pos] = 1;
|
|
this.startXRefQueue.push(pos);
|
|
}
|
|
}
|
|
} else if (Number.isInteger(obj)) {
|
|
// Parse in-stream XRef
|
|
if (
|
|
!Number.isInteger(parser.getObj()) ||
|
|
!isCmd(parser.getObj(), "obj") ||
|
|
!((obj = parser.getObj()) instanceof BaseStream)
|
|
) {
|
|
throw new FormatError("Invalid XRef stream");
|
|
}
|
|
dict = this.processXRefStream(obj);
|
|
if (!this.topDict) {
|
|
this.topDict = dict;
|
|
}
|
|
if (!dict) {
|
|
throw new FormatError("Failed to read XRef stream");
|
|
}
|
|
} else {
|
|
throw new FormatError("Invalid XRef stream header");
|
|
}
|
|
|
|
// Recursively get previous dictionary, if any
|
|
obj = dict.get("Prev");
|
|
if (Number.isInteger(obj)) {
|
|
this.startXRefQueue.push(obj);
|
|
} else if (obj instanceof Ref) {
|
|
// The spec says Prev must not be a reference, i.e. "/Prev NNN"
|
|
// This is a fallback for non-compliant PDFs, i.e. "/Prev NNN 0 R"
|
|
this.startXRefQueue.push(obj.num);
|
|
}
|
|
|
|
this.startXRefQueue.shift();
|
|
}
|
|
|
|
return this.topDict;
|
|
} catch (e) {
|
|
if (e instanceof MissingDataException) {
|
|
throw e;
|
|
}
|
|
info("(while reading XRef): " + e);
|
|
|
|
this.startXRefQueue.shift();
|
|
}
|
|
|
|
if (recoveryMode) {
|
|
return undefined;
|
|
}
|
|
throw new XRefParseException();
|
|
}
|
|
|
|
getEntry(i) {
|
|
const xrefEntry = this.entries[i];
|
|
if (xrefEntry && !xrefEntry.free && xrefEntry.offset) {
|
|
return xrefEntry;
|
|
}
|
|
return null;
|
|
}
|
|
|
|
fetchIfRef(obj, suppressEncryption = false) {
|
|
if (obj instanceof Ref) {
|
|
return this.fetch(obj, suppressEncryption);
|
|
}
|
|
return obj;
|
|
}
|
|
|
|
fetch(ref, suppressEncryption = false) {
|
|
if (!(ref instanceof Ref)) {
|
|
throw new Error("ref object is not a reference");
|
|
}
|
|
const num = ref.num;
|
|
|
|
// The XRef cache is populated with objects which are obtained through
|
|
// `Parser.getObj`, and indirectly via `Lexer.getObj`. Neither of these
|
|
// methods should ever return `undefined` (note the `assert` calls below).
|
|
const cacheEntry = this._cacheMap.get(num);
|
|
if (cacheEntry !== undefined) {
|
|
// In documents with Object Streams, it's possible that cached `Dict`s
|
|
// have not been assigned an `objId` yet (see e.g. issue3115r.pdf).
|
|
if (cacheEntry instanceof Dict && !cacheEntry.objId) {
|
|
cacheEntry.objId = ref.toString();
|
|
}
|
|
return cacheEntry;
|
|
}
|
|
let xrefEntry = this.getEntry(num);
|
|
|
|
if (xrefEntry === null) {
|
|
// The referenced entry can be free.
|
|
this._cacheMap.set(num, xrefEntry);
|
|
return xrefEntry;
|
|
}
|
|
// Prevent circular references, in corrupt PDF documents, from hanging the
|
|
// worker-thread. This relies, implicitly, on the parsing being synchronous.
|
|
if (this._pendingRefs.has(ref)) {
|
|
this._pendingRefs.remove(ref);
|
|
|
|
warn(`Ignoring circular reference: ${ref}.`);
|
|
return CIRCULAR_REF;
|
|
}
|
|
this._pendingRefs.put(ref);
|
|
|
|
try {
|
|
if (xrefEntry.uncompressed) {
|
|
xrefEntry = this.fetchUncompressed(ref, xrefEntry, suppressEncryption);
|
|
} else {
|
|
xrefEntry = this.fetchCompressed(ref, xrefEntry, suppressEncryption);
|
|
}
|
|
this._pendingRefs.remove(ref);
|
|
} catch (ex) {
|
|
this._pendingRefs.remove(ref);
|
|
throw ex;
|
|
}
|
|
if (xrefEntry instanceof Dict) {
|
|
xrefEntry.objId = ref.toString();
|
|
} else if (xrefEntry instanceof BaseStream) {
|
|
xrefEntry.dict.objId = ref.toString();
|
|
}
|
|
return xrefEntry;
|
|
}
|
|
|
|
fetchUncompressed(ref, xrefEntry, suppressEncryption = false) {
|
|
const gen = ref.gen;
|
|
let num = ref.num;
|
|
if (xrefEntry.gen !== gen) {
|
|
throw new XRefEntryException(`Inconsistent generation in XRef: ${ref}`);
|
|
}
|
|
const stream = this.stream.makeSubStream(
|
|
xrefEntry.offset + this.stream.start
|
|
);
|
|
const parser = new Parser({
|
|
lexer: new Lexer(stream),
|
|
xref: this,
|
|
allowStreams: true,
|
|
});
|
|
const obj1 = parser.getObj();
|
|
const obj2 = parser.getObj();
|
|
const obj3 = parser.getObj();
|
|
|
|
if (obj1 !== num || obj2 !== gen || !(obj3 instanceof Cmd)) {
|
|
throw new XRefEntryException(`Bad (uncompressed) XRef entry: ${ref}`);
|
|
}
|
|
if (obj3.cmd !== "obj") {
|
|
// some bad PDFs use "obj1234" and really mean 1234
|
|
if (obj3.cmd.startsWith("obj")) {
|
|
num = parseInt(obj3.cmd.substring(3), 10);
|
|
if (!Number.isNaN(num)) {
|
|
return num;
|
|
}
|
|
}
|
|
throw new XRefEntryException(`Bad (uncompressed) XRef entry: ${ref}`);
|
|
}
|
|
if (this.encrypt && !suppressEncryption) {
|
|
xrefEntry = parser.getObj(this.encrypt.createCipherTransform(num, gen));
|
|
} else {
|
|
xrefEntry = parser.getObj();
|
|
}
|
|
if (!(xrefEntry instanceof BaseStream)) {
|
|
if (
|
|
typeof PDFJSDev === "undefined" ||
|
|
PDFJSDev.test("!PRODUCTION || TESTING")
|
|
) {
|
|
assert(
|
|
xrefEntry !== undefined,
|
|
'fetchUncompressed: The "xrefEntry" cannot be undefined.'
|
|
);
|
|
}
|
|
this._cacheMap.set(num, xrefEntry);
|
|
}
|
|
return xrefEntry;
|
|
}
|
|
|
|
fetchCompressed(ref, xrefEntry, suppressEncryption = false) {
|
|
const tableOffset = xrefEntry.offset;
|
|
const stream = this.fetch(Ref.get(tableOffset, 0));
|
|
if (!(stream instanceof BaseStream)) {
|
|
throw new FormatError("bad ObjStm stream");
|
|
}
|
|
const first = stream.dict.get("First");
|
|
const n = stream.dict.get("N");
|
|
if (!Number.isInteger(first) || !Number.isInteger(n)) {
|
|
throw new FormatError("invalid first and n parameters for ObjStm stream");
|
|
}
|
|
let parser = new Parser({
|
|
lexer: new Lexer(stream),
|
|
xref: this,
|
|
allowStreams: true,
|
|
});
|
|
const nums = new Array(n);
|
|
const offsets = new Array(n);
|
|
// read the object numbers to populate cache
|
|
for (let i = 0; i < n; ++i) {
|
|
const num = parser.getObj();
|
|
if (!Number.isInteger(num)) {
|
|
throw new FormatError(
|
|
`invalid object number in the ObjStm stream: ${num}`
|
|
);
|
|
}
|
|
const offset = parser.getObj();
|
|
if (!Number.isInteger(offset)) {
|
|
throw new FormatError(
|
|
`invalid object offset in the ObjStm stream: ${offset}`
|
|
);
|
|
}
|
|
nums[i] = num;
|
|
offsets[i] = offset;
|
|
}
|
|
|
|
const start = (stream.start || 0) + first;
|
|
const entries = new Array(n);
|
|
// read stream objects for cache
|
|
for (let i = 0; i < n; ++i) {
|
|
const length = i < n - 1 ? offsets[i + 1] - offsets[i] : undefined;
|
|
if (length < 0) {
|
|
throw new FormatError("Invalid offset in the ObjStm stream.");
|
|
}
|
|
parser = new Parser({
|
|
lexer: new Lexer(
|
|
stream.makeSubStream(start + offsets[i], length, stream.dict)
|
|
),
|
|
xref: this,
|
|
allowStreams: true,
|
|
});
|
|
|
|
const obj = parser.getObj();
|
|
entries[i] = obj;
|
|
if (obj instanceof BaseStream) {
|
|
continue;
|
|
}
|
|
const num = nums[i],
|
|
entry = this.entries[num];
|
|
if (entry && entry.offset === tableOffset && entry.gen === i) {
|
|
if (
|
|
typeof PDFJSDev === "undefined" ||
|
|
PDFJSDev.test("!PRODUCTION || TESTING")
|
|
) {
|
|
assert(
|
|
obj !== undefined,
|
|
'fetchCompressed: The "obj" cannot be undefined.'
|
|
);
|
|
}
|
|
this._cacheMap.set(num, obj);
|
|
}
|
|
}
|
|
xrefEntry = entries[xrefEntry.gen];
|
|
if (xrefEntry === undefined) {
|
|
throw new XRefEntryException(`Bad (compressed) XRef entry: ${ref}`);
|
|
}
|
|
return xrefEntry;
|
|
}
|
|
|
|
async fetchIfRefAsync(obj, suppressEncryption) {
|
|
if (obj instanceof Ref) {
|
|
return this.fetchAsync(obj, suppressEncryption);
|
|
}
|
|
return obj;
|
|
}
|
|
|
|
async fetchAsync(ref, suppressEncryption) {
|
|
try {
|
|
return this.fetch(ref, suppressEncryption);
|
|
} catch (ex) {
|
|
if (!(ex instanceof MissingDataException)) {
|
|
throw ex;
|
|
}
|
|
await this.pdfManager.requestRange(ex.begin, ex.end);
|
|
return this.fetchAsync(ref, suppressEncryption);
|
|
}
|
|
}
|
|
|
|
getCatalogObj() {
|
|
return this.root;
|
|
}
|
|
}
|
|
|
|
export { XRef };
|