Function readFileInRange

source code/utils/readFileInRange.ts:75–124

(
  filePath: string,
  offset = 0,
  maxLines?: number,
  maxBytes?: number,
  signal?: AbortSignal,
  options?: { truncateOnByteLimit?: boolean },
)

// ---------------------------------------------------------------------------

export async function readFileInRange(
  filePath: string,
  offset = 0,
  maxLines?: number,
  maxBytes?: number,
  signal?: AbortSignal,
  options?: { truncateOnByteLimit?: boolean },
): Promise<ReadFileRangeResult> {
  signal?.throwIfAborted()
  const truncateOnByteLimit = options?.truncateOnByteLimit ?? false

  // stat to decide the code path and guard against OOM.
  // For regular files under 10 MB: readFile + in-memory split (fast).
  // Everything else (large files, FIFOs, devices): streaming.
  const stats = await fsStat(filePath)

  if (stats.isDirectory()) {
    throw new Error(
      `EISDIR: illegal operation on a directory, read '${filePath}'`,
    )
  }

  if (stats.isFile() && stats.size < FAST_PATH_MAX_SIZE) {
    if (
      !truncateOnByteLimit &&
      maxBytes !== undefined &&
      stats.size > maxBytes
    ) {
      throw new FileTooLargeError(stats.size, maxBytes)
    }

    const text = await readFile(filePath, { encoding: 'utf8', signal })
    return readFileInRangeFast(
      text,
      stats.mtimeMs,
      offset,
      maxLines,
      truncateOnByteLimit ? maxBytes : undefined,
    )
  }

  return readFileInRangeStreaming(
    filePath,
    offset,
    maxLines,
    maxBytes,
    truncateOnByteLimit,
    signal,
  )
}

// ---------------------------------------------------------------------------
// Fast path — readFile + in-memory split