Scalable and Random-Access PDF Loading

HotPDF keeps large loaded files responsive by delaying stream copies and compressed-object parsing until the data is required

File-backed stream windows

Unencrypted documents opened with LoadFromFile retain immutable stream bodies as source-file ranges

Reads seek to the required range and release the source handle immediately, so the original file remains replaceable on Windows

The first write materialises the stream in memory when it is at or below LoadedStreamMemoryThreshold, or in an owned temporary file when it is larger

Lazy object streams

Each decoded /Type /ObjStm container is indexed by authoritative xref object number without parsing every member during open

Catalog, page-tree, and later link resolution materialise individual members once and reuse their parsed objects

A full rewrite automatically materialises every remaining member, whilst an unchanged file-backed save can preserve the original bytes directly

Custom random access

Derive from THPDFRandomAccessSource and implement GetSize plus ReadAt to load from HTTP ranges, databases, archives, or virtual storage

LoadFromRandomAccessSource adapts the source to HotPDF's seekable parser and can optionally own the source for the document lifetime

Diagnostics

GetLoadedStreamCacheInfo reports source-backed, memory-materialised, and disk-materialised stream counts
GetLoadedObjectStreamCacheInfo reports indexed and materialised members, cache hits and misses, and retained decoded bytes