awaforge

pdfPages

AGPL-3.0-onlyRelease 2L4

Page-tree walker, ISO 32000-2 §7.7.3 — /Pages tree → ordered list of leaf references.

Module pdfPages | Source packages/front/office/pdf/src/document/pages.js | Deps pdfErrors, pdfParser | Worker-safe yes

Descends /Kids recursively from the root pointed at by the Catalog. Guard rails: maximum depth (maxDepth = 64), maximum page count (maxPages = 200000), cycle detection through a Set<'num:gen'>. Tolerant of intermediate nodes without /Type (present in some older PDFs): the fallback test is the presence of /Kids.

Resolve

const pages = runtime.resolve('pdfPages');
// Returns: { walkPageTree, readPageCount }

API

Method Signature Returns
walkPageTree (rootRef, resolveRef, opts?: { maxDepth?, maxPages? }) => Array<{num, gen}> Leaf references in document order.
readPageCount (node: PdfDict) => number | null Reads /Count off an intermediate node.

resolveRef must accept { type: 'ref', num, gen } and return the materialised dictionary — typically doc._raw.resolve.

Examples

Standard walk

const pages = runtime.resolve('pdfPages');
const refs  = pages.walkPageTree(doc.catalog.pages, doc._raw.resolve);
refs.length;             // page count
refs[0];                 // { num: 3, gen: 0 }

/Count sanity check

const root = doc._raw.resolve({ type: 'ref', ...doc.catalog.pages });
const declared = pages.readPageCount(root);
const actual   = pages.walkPageTree(doc.catalog.pages, doc._raw.resolve).length;
if (declared !== null && declared !== actual) {
    console.warn('page tree /Count mismatch', { declared, actual });
}

Limiting the depth

pages.walkPageTree(rootRef, resolve, { maxDepth: 16 });

Errors

Code Class When
pdf/pages/max-depth ParseError Tree deeper than maxDepth.
pdf/pages/cycle ParseError Reference already visited during the walk.
pdf/pages/not-dict ParseError A resolved node is not a dictionary.
pdf/pages/too-many ParseError More than maxPages leaves found.
pdf/pages/missing-kids ParseError Intermediate node without /Kids.
pdf/pages/non-ref-kid ParseError /Kids holds something other than a reference.

See also