Function tailFile

src/utils/fsOperations.ts:682–714

(
  path: string,
  maxBytes: number,
)

 * Returns the whole file if it's smaller than maxBytes.
 */
export async function tailFile(
  path: string,
  maxBytes: number,
): Promise<ReadFileRangeResult> {
  await using fh = await open(path, 'r')
  const size = (await fh.stat()).size
  if (size === 0) {
    return { content: '', bytesRead: 0, bytesTotal: 0 }
  }
  const offset = Math.max(0, size - maxBytes)
  const bytesToRead = size - offset
  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,
  }
}

/**
 * Async generator that yields lines from a file in reverse order.