Function readHeadAndTail

src/utils/sessionStoragePortable.ts:215–242

(
  filePath: string,
  fileSize: number,
  buf: Buffer,
)

 * Returns `{ head: '', tail: '' }` on any error.
 */
export async function readHeadAndTail(
  filePath: string,
  fileSize: number,
  buf: Buffer,
): Promise<{ head: string; tail: string }> {
  try {
    const fh = await fsOpen(filePath, 'r')
    try {
      const headResult = await fh.read(buf, 0, LITE_READ_BUF_SIZE, 0)
      if (headResult.bytesRead === 0) return { head: '', tail: '' }

      const head = buf.toString('utf8', 0, headResult.bytesRead)

      const tailOffset = Math.max(0, fileSize - LITE_READ_BUF_SIZE)
      let tail = head
      if (tailOffset > 0) {
        const tailResult = await fh.read(buf, 0, LITE_READ_BUF_SIZE, tailOffset)
        tail = buf.toString('utf8', 0, tailResult.bytesRead)
      }

      return { head, tail }
    } finally {
      await fh.close()
    }
  } catch {
    return { head: '', tail: '' }
  }
}

export type LiteSessionFile = {
  mtime: number