readForward method

Future<SessionChunk> readForward(int fromOffset, { int? maxRecords, int? maxBytes, })

Reads records from the line boundary fromOffset to EOF. With maxRecords/maxBytes (the jump and page-down paths) at most that much is kept, scanned block-wise — the below-range of a deep-paged window is never read whole; without caps (the live-tail ingest path — an external CLI appended while the app held the window) everything is returned, so a burst of external appends is never silently dropped. The chunk's SessionChunk.limitOffset is the end of the last kept record, so a capped read resumes exactly after it.

Implementation

Future<SessionChunk> readForward(
  int fromOffset, {
  int? maxRecords,
  int? maxBytes,
}) async {
  final info = await stat();
  if (info == null) {
    throw SessionException(
      'Session not found: $path',
      code: SessionErrorCode.notFound,
    );
  }
  if (fromOffset >= info.size) {
    return SessionChunk(
      entries: const [],
      fileSize: info.size,
      fileMtimeMs: info.mtimeMs,
      hasOlder: false,
      limitOffset: info.size,
    );
  }
  if (maxRecords != null || maxBytes != null) {
    return _scanForwardCapped(
      fromOffset,
      size: info.size,
      mtimeMs: info.mtimeMs,
      // Literals, not `1 << 40`/`1 << 60`: dart2js shifts are 32-bit —
      // 0 on web would read nothing (issue #1074).
      maxRecords: maxRecords ?? 0x10000000000,
      maxBytes: maxBytes ?? 0x1000000000000000,
    );
  }
  final bytes = await _readRange(fromOffset, info.size);
  final lines = _splitLines(bytes, fromOffset);
  final entries = await _parseAllLines(lines);
  return SessionChunk(
    entries: entries,
    fileSize: info.size,
    fileMtimeMs: info.mtimeMs,
    hasOlder: false,
    limitOffset: info.size,
  );
}