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Assume that a top level /Pages list contains /Page dicts directly if it is the right length, and there are enough pages to be worth the optimisation

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This commit is contained in:
Richard Smith (smir) 2024-08-20 09:46:49 +01:00
parent 0cec644372
commit 83e68b3b27
1 changed files with 32 additions and 6 deletions
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38
src/core/catalog.js
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@ -121,6 +121,8 @@ function fetchRemoteDest(action) {
return null;
}
const MIN_PAGES_TO_ASSUME_ALL_TOP_LEVEL = 20;
class Catalog {
constructor(pdfManager, xref) {
this.pdfManager = pdfManager;
@ -1186,6 +1188,14 @@ class Catalog {
pageIndexCache = this.pageIndexCache;
let currentPageIndex = 0;
const getIsPage = async obj => {
let type = obj.getRaw("Type");
if (type instanceof Ref) {
type = await xref.fetchAsync(type);
}
return isName(type, "Page") || !obj.has("Kids");
};
while (nodesToVisit.length) {
const currentNode = nodesToVisit.pop();
@ -1202,13 +1212,13 @@ class Catalog {
}
visitedNodes.put(currentNode);
const obj = await xref.fetchAsync(currentNode);
const obj =
(await this.pageDictCache.get(currentNode)) ||
xref.fetchAsync(currentNode);
if (obj instanceof Dict) {
let type = obj.getRaw("Type");
if (type instanceof Ref) {
type = await xref.fetchAsync(type);
}
if (isName(type, "Page") || !obj.has("Kids")) {
const isPage = await getIsPage(obj);
if (isPage) {
// 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.
@ -1283,6 +1293,22 @@ class Catalog {
// 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.
// EXCEPT if it looks like this is likely an "everything in the top level
// /Pages" PDF and there's enough pages to be worth not reading everything
// See if the n'th item is a page
if (
currentNode === this.toplevelPagesDict &&
count >= MIN_PAGES_TO_ASSUME_ALL_TOP_LEVEL &&
count === kids.length
) {
const maybePage = await xref.fetchAsync(kids[currentPageIndex]);
const isPage = await getIsPage(maybePage);
if (isPage) {
return [maybePage, kids[currentPageIndex]];
}
}
for (let last = kids.length - 1; last >= 0; last--) {
nodesToVisit.push(kids[last]);
}