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Move the ObjectLoader from src/core/obj.js and into its own file

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The size of the `src/core/obj.js` file has increased slowly over the years, and it also contains a fair amount of *distinct* functionality.
In order to improve readability and make it easier to navigate through the code, this patch moves the `ObjectLoader` into its own file.
This commit is contained in:
Jonas Jenwald 2021-04-13 18:25:34 +02:00
parent ebeb3f7999
commit 604cd6d600
4 changed files with 162 additions and 140 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
src/core/annotation.js
View File

@ -34,7 +34,7 @@ import {
Util,
warn,
} from "../shared/util.js";
import { Catalog, FileSpec, ObjectLoader } from "./obj.js";
import { Catalog, FileSpec } from "./obj.js";
import { collectActions, getInheritableProperty } from "./core_utils.js";
import {
createDefaultAppearance,
@ -50,6 +50,7 @@ import {
RefSet,
} from "./primitives.js";
import { ColorSpace } from "./colorspace.js";
import { ObjectLoader } from "./object_loader.js";
import { OperatorList } from "./operator_list.js";
import { StringStream } from "./stream.js";
import { writeDict } from "./writer.js";

3
src/core/document.js
View File

@ -34,7 +34,7 @@ import {
Util,
warn,
} from "../shared/util.js";
import { Catalog, ObjectLoader, XRef } from "./obj.js";
import { Catalog, XRef } from "./obj.js";
import {
clearPrimitiveCaches,
Dict,
@ -56,6 +56,7 @@ import { NullStream, Stream, StreamsSequenceStream } from "./stream.js";
import { AnnotationFactory } from "./annotation.js";
import { calculateMD5 } from "./crypto.js";
import { Linearization } from "./parser.js";
import { ObjectLoader } from "./object_loader.js";
import { OperatorList } from "./operator_list.js";
import { PartialEvaluator } from "./evaluator.js";
import { StructTreePage } from "./struct_tree.js";

139
src/core/obj.js
View File

@ -2512,141 +2512,4 @@ var FileSpec = (function FileSpecClosure() {
return FileSpec;
})();
/**
* A helper for loading missing data in `Dict` graphs. It traverses the graph
* depth first and queues up any objects that have missing data. Once it has
* has traversed as many objects that are available it attempts to bundle the
* missing data requests and then resume from the nodes that weren't ready.
*
* NOTE: It provides protection from circular references by keeping track of
* loaded references. However, you must be careful not to load any graphs
* that have references to the catalog or other pages since that will cause the
* entire PDF document object graph to be traversed.
*/
const ObjectLoader = (function () {
function mayHaveChildren(value) {
return (
value instanceof Ref ||
value instanceof Dict ||
Array.isArray(value) ||
isStream(value)
);
}
function addChildren(node, nodesToVisit) {
if (node instanceof Dict) {
node = node.getRawValues();
} else if (isStream(node)) {
node = node.dict.getRawValues();
} else if (!Array.isArray(node)) {
return;
}
for (const rawValue of node) {
if (mayHaveChildren(rawValue)) {
nodesToVisit.push(rawValue);
}
}
}
// eslint-disable-next-line no-shadow
function ObjectLoader(dict, keys, xref) {
this.dict = dict;
this.keys = keys;
this.xref = xref;
this.refSet = null;
}
ObjectLoader.prototype = {
async load() {
// Don't walk the graph if all the data is already loaded; note that only
// `ChunkedStream` instances have a `allChunksLoaded` method.
if (
!this.xref.stream.allChunksLoaded ||
this.xref.stream.allChunksLoaded()
) {
return undefined;
}
const { keys, dict } = this;
this.refSet = new RefSet();
// Setup the initial nodes to visit.
const nodesToVisit = [];
for (let i = 0, ii = keys.length; i < ii; i++) {
const rawValue = dict.getRaw(keys[i]);
// Skip nodes that are guaranteed to be empty.
if (rawValue !== undefined) {
nodesToVisit.push(rawValue);
}
}
return this._walk(nodesToVisit);
},
async _walk(nodesToVisit) {
const nodesToRevisit = [];
const pendingRequests = [];
// DFS walk of the object graph.
while (nodesToVisit.length) {
let currentNode = nodesToVisit.pop();
// Only references or chunked streams can cause missing data exceptions.
if (currentNode instanceof Ref) {
// Skip nodes that have already been visited.
if (this.refSet.has(currentNode)) {
continue;
}
try {
this.refSet.put(currentNode);
currentNode = this.xref.fetch(currentNode);
} catch (ex) {
if (!(ex instanceof MissingDataException)) {
warn(`ObjectLoader._walk - requesting all data: "${ex}".`);
this.refSet = null;
const { manager } = this.xref.stream;
return manager.requestAllChunks();
}
nodesToRevisit.push(currentNode);
pendingRequests.push({ begin: ex.begin, end: ex.end });
}
}
if (currentNode && currentNode.getBaseStreams) {
const baseStreams = currentNode.getBaseStreams();
let foundMissingData = false;
for (let i = 0, ii = baseStreams.length; i < ii; i++) {
const stream = baseStreams[i];
if (stream.allChunksLoaded && !stream.allChunksLoaded()) {
foundMissingData = true;
pendingRequests.push({ begin: stream.start, end: stream.end });
}
}
if (foundMissingData) {
nodesToRevisit.push(currentNode);
}
}
addChildren(currentNode, nodesToVisit);
}
if (pendingRequests.length) {
await this.xref.stream.manager.requestRanges(pendingRequests);
for (let i = 0, ii = nodesToRevisit.length; i < ii; i++) {
const node = nodesToRevisit[i];
// Remove any reference nodes from the current `RefSet` so they
// aren't skipped when we revist them.
if (node instanceof Ref) {
this.refSet.remove(node);
}
}
return this._walk(nodesToRevisit);
}
// Everything is loaded.
this.refSet = null;
return undefined;
},
};
return ObjectLoader;
})();
export { Catalog, FileSpec, NumberTree, ObjectLoader, XRef };
export { Catalog, FileSpec, NumberTree, XRef };

157
src/core/object_loader.js Normal file
View File

@ -0,0 +1,157 @@
/* 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 { Dict, isStream, Ref, RefSet } from "./primitives.js";
import { MissingDataException } from "./core_utils.js";
import { warn } from "../shared/util.js";
/**
* A helper for loading missing data in `Dict` graphs. It traverses the graph
* depth first and queues up any objects that have missing data. Once it has
* has traversed as many objects that are available it attempts to bundle the
* missing data requests and then resume from the nodes that weren't ready.
*
* NOTE: It provides protection from circular references by keeping track of
* loaded references. However, you must be careful not to load any graphs
* that have references to the catalog or other pages since that will cause the
* entire PDF document object graph to be traversed.
*/
const ObjectLoader = (function () {
function mayHaveChildren(value) {
return (
value instanceof Ref ||
value instanceof Dict ||
Array.isArray(value) ||
isStream(value)
);
}
function addChildren(node, nodesToVisit) {
if (node instanceof Dict) {
node = node.getRawValues();
} else if (isStream(node)) {
node = node.dict.getRawValues();
} else if (!Array.isArray(node)) {
return;
}
for (const rawValue of node) {
if (mayHaveChildren(rawValue)) {
nodesToVisit.push(rawValue);
}
}
}
// eslint-disable-next-line no-shadow
function ObjectLoader(dict, keys, xref) {
this.dict = dict;
this.keys = keys;
this.xref = xref;
this.refSet = null;
}
ObjectLoader.prototype = {
async load() {
// Don't walk the graph if all the data is already loaded; note that only
// `ChunkedStream` instances have a `allChunksLoaded` method.
if (
!this.xref.stream.allChunksLoaded ||
this.xref.stream.allChunksLoaded()
) {
return undefined;
}
const { keys, dict } = this;
this.refSet = new RefSet();
// Setup the initial nodes to visit.
const nodesToVisit = [];
for (let i = 0, ii = keys.length; i < ii; i++) {
const rawValue = dict.getRaw(keys[i]);
// Skip nodes that are guaranteed to be empty.
if (rawValue !== undefined) {
nodesToVisit.push(rawValue);
}
}
return this._walk(nodesToVisit);
},
async _walk(nodesToVisit) {
const nodesToRevisit = [];
const pendingRequests = [];
// DFS walk of the object graph.
while (nodesToVisit.length) {
let currentNode = nodesToVisit.pop();
// Only references or chunked streams can cause missing data exceptions.
if (currentNode instanceof Ref) {
// Skip nodes that have already been visited.
if (this.refSet.has(currentNode)) {
continue;
}
try {
this.refSet.put(currentNode);
currentNode = this.xref.fetch(currentNode);
} catch (ex) {
if (!(ex instanceof MissingDataException)) {
warn(`ObjectLoader._walk - requesting all data: "${ex}".`);
this.refSet = null;
const { manager } = this.xref.stream;
return manager.requestAllChunks();
}
nodesToRevisit.push(currentNode);
pendingRequests.push({ begin: ex.begin, end: ex.end });
}
}
if (currentNode && currentNode.getBaseStreams) {
const baseStreams = currentNode.getBaseStreams();
let foundMissingData = false;
for (let i = 0, ii = baseStreams.length; i < ii; i++) {
const stream = baseStreams[i];
if (stream.allChunksLoaded && !stream.allChunksLoaded()) {
foundMissingData = true;
pendingRequests.push({ begin: stream.start, end: stream.end });
}
}
if (foundMissingData) {
nodesToRevisit.push(currentNode);
}
}
addChildren(currentNode, nodesToVisit);
}
if (pendingRequests.length) {
await this.xref.stream.manager.requestRanges(pendingRequests);
for (let i = 0, ii = nodesToRevisit.length; i < ii; i++) {
const node = nodesToRevisit[i];
// Remove any reference nodes from the current `RefSet` so they
// aren't skipped when we revist them.
if (node instanceof Ref) {
this.refSet.remove(node);
}
}
return this._walk(nodesToRevisit);
}
// Everything is loaded.
this.refSet = null;
return undefined;
},
};
return ObjectLoader;
})();
export { ObjectLoader };