Function readFileRange

source code/utils/fsOperations.ts:646–678

(
  path: string,
  offset: number,
  maxBytes: number,
)

 * larger parent. Returns null if the file is smaller than the offset.
 */
export async function readFileRange(
  path: string,
  offset: number,
  maxBytes: number,
): Promise<ReadFileRangeResult | null> {
  await using fh = await open(path, 'r')
  const size = (await fh.stat()).size
  if (size <= offset) {
    return null
  }
  const bytesToRead = Math.min(size - offset, maxBytes)
  const buffer = Buffer.allocUnsafe(bytesToRead)

  let totalRead = 0
  while (totalRead < bytesToRead) {
    const { bytesRead } = await fh.read(
      buffer,
      totalRead,
      bytesToRead - totalRead,
      offset + totalRead,
    )
    if (bytesRead === 0) {
      break
    }
    totalRead += bytesRead
  }

  return {
    content: buffer.toString('utf8', 0, totalRead),
    bytesRead: totalRead,
    bytesTotal: size,
  }
}

/**
 * Read the last `maxBytes` of a file.