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StreamToStringASCII

function StreamToStringASCII(M : TStream) : string

Example​

procedure ScriptEvent(var Value: variant);
var
  Buffer: TMemoryStream;
begin
  Buffer := TMemoryStream.Create;
  try
    StringToStreamASCII('EDI-1001', Buffer);
    Value := StreamToStringASCII(Buffer);
  finally
    Buffer.Free;
  end;
end;

Usage​

StreamToStringASCII reads an entire stream from the beginning and decodes it with Velox's ASCII encoding.

Parameters

NameTypeDescription
MTStreamExisting readable, seekable caller-owned stream. The function rewinds it.

Returns

The decoded string, or an empty string for an empty stream.

Errors

Nil-object, seek, read, allocation and encoding errors propagate. No previous position is restored.

Usage notes

ASCII is suitable for deliberately restricted protocols and identifiers. Use UTF-8 when the data can contain general Unicode text.

Additional Technical Info​

StreamToStringASCII decodes a complete stream through Delphi's seven-bit ASCII encoding. Use it only when the byte contract is ASCII; it is not a generic single-byte or UTF-8 decoder.

The example round-trips a fictional ASCII identifier. It is source-reviewed and is not executed by the documentation workflow.

Implementation

The registered wrapper calls MemoryStreamToString(M, TEncoding.ASCII). The helper sets position zero, narrows size to LongInt, reads a complete allocated byte array and passes it to the installed encoding's GetString. On Windows, Delphi requests code page 20127; only if that code page is unavailable does the installed RTL fall back to OEM US code page 437.

Edge cases and quirks

  • Bytes 0-127 have the portable ASCII meaning. High bytes are outside the declared contract and follow the current OS/RTL conversion or failure path.
  • A UTF-8 or UTF-16 BOM is not detected or removed.
  • Embedded zero bytes decode to U+0000 inside the managed string; they do not terminate the read.
  • The helper ignores a short Read count, rewinds the stream and leaves it after the captured byte count.
  • Stream sizes outside signed LongInt and concurrent mutation are unsupported.

Side effects

Changes M.Position; does not change bytes, size or ownership.

Performance and concurrency

Linear time and memory in stream size. The complete byte array and result string coexist; external synchronisation is required for shared streams.

Related entries

External references

Created 2026-07-15