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LoadFromStream

procedure LoadFromStream(Stream: TStream);

Example​

procedure LoadXmlBytes(Xml: TNativeXML; Source: TStream);
begin
  if (Xml = nil) or (Source = nil) then Exit;

  Source.Position := 0;
  Xml.LoadFromStream(Source);
end;

Usage​

LoadFromStream clears the document and parses a borrowed stream, with special absolute rewind and whole-stream buffering for detected binary XML.

Additional Technical Info​

LoadFromStream destructively replaces the document from a borrowed stream. It never frees Stream, but it advances and, on one path, rewinds its shared cursor.

The method first clears the symbol table and owned root-node list. It then constructs a NativeXML parser using cParserChunkSize = $100 (256 bytes); the source comment claiming 64K chunks is stale. Normal XML parsing begins from the supplied current Position and proceeds to its terminal parser position.

After successful normal parsing, the document remembers detected external encoding, code page and BOM. This state drives later SaveToStream calls. The stream is not restored. A final progress call evaluates Stream.Size, so a custom stream that cannot report Size can fail even after the parser has consumed it.

Binary XML branch​

The parser also auto-detects NativeXML binary XML. On that branch it assigns Stream.Position := 0, ignoring the caller's initial offset, copies the complete stream into a new memory stream and invokes the binary loader. Binary input therefore requires seeking/Size support and can allocate memory proportional to the entire source.

Failure and security state​

The operation is not transactional. Parser construction, malformed data, unsupported encodings, stream operations or memory exhaustion can leave no tree or a partially parsed tree; prior node references are already invalid. The previous external-encoding settings are only replaced after successful normal parsing, so failed parsing can combine a partial new tree with older output settings.

The reviewed parser does not resolve an external DTD through files or the network, but it accepts DTD/entity structures and exposes no input-size, nesting-depth or node-count limit. Bound untrusted input before calling, and avoid concurrent stream or document access.

The example is source-reviewed only; no stream was parsed.

External references

Created 2026-07-15