LoadFromMappedFile
Document management, Performance, File input
Description
Loads and selects a local PDF through a bounded read-only mapped view, allowing large deferred object and stream reads to reuse operating-system file pages without retaining the complete source in memory
Syntax
Delphi
Function TPDFlib.LoadFromMappedFile(Const FileName, Password: WideString;
WindowSize: Int64= 0; Options: Integer= 0): Integer;Parameters
| FileName | The path of the local PDF |
|---|---|
| Password | The password used to open the PDF, or an empty string for an unencrypted document |
| WindowSize | The requested mapped-view size in bytes; zero selects 64 MiB, values below the operating-system allocation granularity are raised to that granularity and values above 1 GiB are capped |
| Options | Zero permits a read-only file-stream fallback, while PDF_MAPPED_FILE_REQUIRE_MAPPING fails unless a mapped view is active |
Return values
| 0 | The arguments were invalid, the file could not be opened, required mapping was unavailable or the PDF could not be loaded; inspect LastErrorCode |
|---|---|
| 1 | The document was loaded and selected |
Remarks
Windows builds retain one read-only view and remap it on demand at allocation-granularity boundaries; other platforms and mapping failures use the same absolute-read contract over a normal read-only file stream unless mapping is required
The default 64 MiB view bounds address-space use independently of source size and is suitable for sparse access to large local files; a smaller view can reduce resident address space at the cost of more remaps
Absolute object-slice reads copy directly from the current view into parser-owned storage without changing the positional stream cursor; this is not a persistent zero-copy pointer API because remapping invalidates view addresses
The source remains open until the loaded document is removed, and saving or deferred extraction can continue reading it
OnPassword is assigned, every rejected password retry receives a fresh mapped stream and parser state. Use
GetMappedFileInfo to confirm whether mapping is active and inspect current view and read statistics