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Merge pull request #14400 from Snuffleupagus/getPageDict-async
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[api-minor] Convert `Catalog.getPageDict` to an asynchronous method
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@timvandermeij
timvandermeij authored Dec 28, 2021
2 parents 01b25b2 + b513c64 commit e42d54e
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Showing 3 changed files with 100 additions and 118 deletions.
208 changes: 97 additions & 111 deletions src/core/catalog.js
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Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,6 @@ import {
XRefEntryException,
} from "./core_utils.js";
import {
createPromiseCapability,
createValidAbsoluteUrl,
DocumentActionEventType,
FormatError,
Expand Down Expand Up @@ -1091,8 +1090,7 @@ class Catalog {
});
}

getPageDict(pageIndex) {
const capability = createPromiseCapability();
async getPageDict(pageIndex) {
const nodesToVisit = [this.toplevelPagesDict];
const visitedNodes = new RefSet();

Expand All @@ -1104,130 +1102,105 @@ class Catalog {
pageKidsCountCache = this.pageKidsCountCache;
let currentPageIndex = 0;

function next() {
while (nodesToVisit.length) {
const currentNode = nodesToVisit.pop();
while (nodesToVisit.length) {
const currentNode = nodesToVisit.pop();

if (currentNode instanceof Ref) {
const count = pageKidsCountCache.get(currentNode);
// Skip nodes where the page can't be.
if (count >= 0 && currentPageIndex + count <= pageIndex) {
currentPageIndex += count;
continue;
}
// Prevent circular references in the /Pages tree.
if (visitedNodes.has(currentNode)) {
capability.reject(
new FormatError("Pages tree contains circular reference.")
);
return;
}
visitedNodes.put(currentNode);

xref.fetchAsync(currentNode).then(function (obj) {
if (isDict(obj, "Page") || (isDict(obj) && !obj.has("Kids"))) {
// Cache the Page reference, since it can *greatly* improve
// performance by reducing redundant lookups in long documents
// where all nodes are found at *one* level of the tree.
if (currentNode && !pageKidsCountCache.has(currentNode)) {
pageKidsCountCache.put(currentNode, 1);
}

if (pageIndex === currentPageIndex) {
capability.resolve([obj, currentNode]);
} else {
currentPageIndex++;
next();
}
return;
}
nodesToVisit.push(obj);
next();
}, capability.reject);
return;
}

// Must be a child page dictionary.
if (!(currentNode instanceof Dict)) {
capability.reject(
new FormatError(
"Page dictionary kid reference points to wrong type of object."
)
);
return;
}

let count;
try {
count = currentNode.get("Count");
} catch (ex) {
if (ex instanceof MissingDataException) {
throw ex;
}
if (currentNode instanceof Ref) {
const count = pageKidsCountCache.get(currentNode);
// Skip nodes where the page can't be.
if (count >= 0 && currentPageIndex + count <= pageIndex) {
currentPageIndex += count;
continue;
}
if (Number.isInteger(count) && count >= 0) {
// Cache the Kids count, since it can reduce redundant lookups in
// documents where all nodes are found at *one* level of the tree.
const objId = currentNode.objId;
if (objId && !pageKidsCountCache.has(objId)) {
pageKidsCountCache.put(objId, count);
}
// Skip nodes where the page can't be.
if (currentPageIndex + count <= pageIndex) {
currentPageIndex += count;
continue;
}
// Prevent circular references in the /Pages tree.
if (visitedNodes.has(currentNode)) {
throw new FormatError("Pages tree contains circular reference.");
}
visitedNodes.put(currentNode);

let kids;
try {
kids = currentNode.get("Kids");
} catch (ex) {
if (ex instanceof MissingDataException) {
throw ex;
const obj = await xref.fetchAsync(currentNode);
if (obj instanceof Dict) {
let type = obj.getRaw("Type");
if (type instanceof Ref) {
type = await xref.fetchAsync(type);
}
}
if (!Array.isArray(kids)) {
// Prevent errors in corrupt PDF documents that violate the
// specification by *inlining* Page dicts directly in the Kids
// array, rather than using indirect objects (fixes issue9540.pdf).
let type;
try {
type = currentNode.get("Type");
} catch (ex) {
if (ex instanceof MissingDataException) {
throw ex;
if (isName(type, "Page") || !obj.has("Kids")) {
// Cache the Page reference, since it can *greatly* improve
// performance by reducing redundant lookups in long documents
// where all nodes are found at *one* level of the tree.
if (currentNode && !pageKidsCountCache.has(currentNode)) {
pageKidsCountCache.put(currentNode, 1);
}
}
if (
isName(type, "Page") ||
(!currentNode.has("Type") && currentNode.has("Contents"))
) {

if (currentPageIndex === pageIndex) {
capability.resolve([currentNode, null]);
return;
return [obj, currentNode];
}
currentPageIndex++;
continue;
}
}
nodesToVisit.push(obj);
continue;
}

capability.reject(
new FormatError("Page dictionary kids object is not an array.")
);
return;
// Must be a child page dictionary.
if (!(currentNode instanceof Dict)) {
throw new FormatError(
"Page dictionary kid reference points to wrong type of object."
);
}
const { objId } = currentNode;

let count = currentNode.getRaw("Count");
if (count instanceof Ref) {
count = await xref.fetchAsync(count);
}
if (Number.isInteger(count) && count >= 0) {
// Cache the Kids count, since it can reduce redundant lookups in
// documents where all nodes are found at *one* level of the tree.
if (objId && !pageKidsCountCache.has(objId)) {
pageKidsCountCache.put(objId, count);
}

// Always check all `Kids` nodes, to avoid getting stuck in an empty
// node further down in the tree (see issue5644.pdf, issue8088.pdf),
// and to ensure that we actually find the correct `Page` dict.
for (let last = kids.length - 1; last >= 0; last--) {
nodesToVisit.push(kids[last]);
// Skip nodes where the page can't be.
if (currentPageIndex + count <= pageIndex) {
currentPageIndex += count;
continue;
}
}

let kids = currentNode.getRaw("Kids");
if (kids instanceof Ref) {
kids = await xref.fetchAsync(kids);
}
if (!Array.isArray(kids)) {
// Prevent errors in corrupt PDF documents that violate the
// specification by *inlining* Page dicts directly in the Kids
// array, rather than using indirect objects (fixes issue9540.pdf).
let type = currentNode.getRaw("Type");
if (type instanceof Ref) {
type = await xref.fetchAsync(type);
}
if (isName(type, "Page") || !currentNode.has("Kids")) {
if (currentPageIndex === pageIndex) {
return [currentNode, null];
}
currentPageIndex++;
continue;
}

throw new FormatError("Page dictionary kids object is not an array.");
}

// Always check all `Kids` nodes, to avoid getting stuck in an empty
// node further down in the tree (see issue5644.pdf, issue8088.pdf),
// and to ensure that we actually find the correct `Page` dict.
for (let last = kids.length - 1; last >= 0; last--) {
nodesToVisit.push(kids[last]);
}
capability.reject(new Error(`Page index ${pageIndex} not found.`));
}
next();
return capability.promise;

throw new Error(`Page index ${pageIndex} not found.`);
}

/**
Expand Down Expand Up @@ -1319,7 +1292,20 @@ class Catalog {
break;
}

if (isDict(obj, "Page") || !obj.has("Kids")) {
let type;
try {
type = obj.get("Type");
} catch (ex) {
if (ex instanceof MissingDataException) {
throw ex;
}
if (ex instanceof XRefEntryException && !recoveryMode) {
throw ex;
}
addPageError(ex);
break;
}
if (isName(type, "Page") || !obj.has("Kids")) {
addPageDict(obj, kidObj instanceof Ref ? kidObj : null);
} else {
queue.push({ currentNode: obj, posInKids: 0 });
Expand Down
8 changes: 2 additions & 6 deletions test/unit/api_spec.js
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Original file line number Diff line number Diff line change
Expand Up @@ -622,9 +622,7 @@ describe("api", function () {
expect(false).toEqual(true);
} catch (reason) {
expect(reason instanceof UnknownErrorException).toEqual(true);
expect(reason.message).toEqual(
"Page dictionary kids object is not an array."
);
expect(reason.message).toEqual("Illegal character: 41");
}
try {
await pdfDocument2.getPage(1);
Expand All @@ -633,9 +631,7 @@ describe("api", function () {
expect(false).toEqual(true);
} catch (reason) {
expect(reason instanceof UnknownErrorException).toEqual(true);
expect(reason.message).toEqual(
"Page dictionary kids object is not an array."
);
expect(reason.message).toEqual("End of file inside array.");
}

await Promise.all([loadingTask1.destroy(), loadingTask2.destroy()]);
Expand Down
2 changes: 1 addition & 1 deletion web/base_viewer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -76,7 +76,7 @@ const ENABLE_PERMISSIONS_CLASS = "enablePermissions";
const PagesCountLimit = {
FORCE_SCROLL_MODE_PAGE: 15000,
FORCE_LAZY_PAGE_INIT: 7500,
PAUSE_EAGER_PAGE_INIT: 500,
PAUSE_EAGER_PAGE_INIT: 250,
};

/**
Expand Down

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