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TMemoryStream

TMemoryStream = class(TCustomMemoryStream)

Example​

procedure BufferSource(Source: TStream);
var
  Buffer: TMemoryStream;
begin
  Buffer := TMemoryStream.Create;
  try
    Buffer.CopyFrom(Source, 0, 65536);
    Buffer.Position := 0;
    // Pass Buffer to the next operation while it is still alive.
  finally
    Buffer.Free;
  end;
end;

Usage​

TMemoryStream provides a script-owned resizable in-memory byte stream with cursor-based I/O, full replacement and explicit lifetime rules.

Additional Technical Info​

TMemoryStream stores bytes in a resizable heap buffer. Its hidden TCustomMemoryStream ancestor supplies inherited save operations, while the visible TStream surface supplies cursor, size, copy and raw byte I/O.

The no-argument constructor is inherited and callable as TMemoryStream.Create. A constructed stream is script-owned; release it with Free in finally. It owns its memory but does not own stream objects passed to LoadFromStream or CopyFrom.

State model​

  • Size is the number of logical bytes.
  • Position is the next read/write byte offset.
  • capacity is internal allocated storage and can exceed Size.
  • writes at/after the end grow the stream as needed.
  • Clear releases the allocation and resets Size/Position.

The visible Position and Size properties are registered as 32-bit LongInt even though the native stream uses Int64. Keep script-managed buffers below LongInt limits and check size before allocation. Memory exhaustion, range errors and host process pressure are real failure modes; do not buffer unbounded partner payloads without an external limit.

Raw Read/Write methods expose a PascalScript String as byte storage. They do not perform text encoding and do not allocate the String. Prefer higher-level conversion functions for text and CopyFrom for stream-to-stream movement.

Methods mutate the object in place and are not transactional or thread-safe. On an exception, Size, Position and some bytes can already have changed. Do not share one instance between concurrent flow work.

The example is source-reviewed only; no memory stream was created or copied.

External references

Created 2026-07-15