THPDFRandomAccessSource.ReadAtCancellable Method

Reads bytes at Offset, observing a cancellation token both before and after the underlying read

Declaration

function ReadAtCancellable(Offset: Int64; var Buffer; Count: Longint;
  CancellationToken: THPDFCancellationToken): Longint; virtual;

HPDFDoc

Name	Purpose
`Offset`	Zero-based byte offset from which to read
`Buffer`	Untyped buffer into which the bytes go
`Count`	Greatest number of bytes to read
`CancellationToken`	Token polled for cancellation, or nil so as to read without cancellation checks

Number of bytes read, exactly as ReadAt reports it

The base implementation raises the cancellation exception before and after ReadAt whenever the token is signalled
Override in slow sources such as network or archive-backed inputs so as to poll the token between transport chunks
Deterministic replay wraps this method so that recorded runs reproduce the same cancellation decisions