Function readFileHandle

lib/internal/fs/promises.js:1214–1307

(filehandle, options)

}

async function readFileHandle(filehandle, options) {
  const signal = options?.signal;
  const encoding = options?.encoding;
  const decoder = encoding && new StringDecoder(encoding);

  checkAborted(signal);

  const statFields = await PromisePrototypeThen(
    binding.fstat(filehandle.fd, false, kUsePromises),
    undefined,
    handleErrorFromBinding,
  );

  checkAborted(signal);

  let size = 0;
  let length = 0;
  if ((statFields[1/* mode */] & S_IFMT) === S_IFREG) {
    size = statFields[8/* size */];
    length = encoding ? MathMin(size, kReadFileBufferLength) : size;
  }
  if (length === 0) {
    length = kReadFileUnknownBufferLength;
  }

  if (size > kIoMaxLength)
    throw new ERR_FS_FILE_TOO_LARGE(size);

  if (options.buffer !== undefined) {
    return readFileHandleWithUserBuffer(filehandle, options, size);
  }

  let totalRead = 0;
  const noSize = size === 0;
  let buffer = Buffer.allocUnsafeSlow(length);
  let result = '';
  let offset = 0;
  let buffers;
  const chunkedRead = length > kReadFileBufferLength;

  while (true) {
    checkAborted(signal);

    if (chunkedRead) {
      length = MathMin(size - totalRead, kReadFileBufferLength);
    }

    const bytesRead = (await PromisePrototypeThen(
      binding.read(filehandle.fd, buffer, offset, length, -1, kUsePromises),
      undefined,
      handleErrorFromBinding,
    )) ?? 0;
    totalRead += bytesRead;

    if (bytesRead === 0 ||
        totalRead === size ||
        (bytesRead !== buffer.length && !chunkedRead && !noSize)) {
      const singleRead = bytesRead === totalRead;