Function fromList

lib/internal/streams/readable.js:1630–1728

(n, state)

// This function is designed to be inlinable, so please take care when making
// changes to the function body.
function fromList(n, state) {
  // nothing buffered.
  if (state.length === 0)
    return null;

  let idx = state.bufferIndex;
  let ret;

  const buf = state.buffer;
  const len = buf.length;

  if ((state[kState] & kObjectMode) !== 0) {
    ret = buf[idx];
    buf[idx++] = null;
  } else if (!n || n >= state.length) {
    // Read it all, truncate the list.
    if ((state[kState] & kDecoder) !== 0) {
      ret = '';
      while (idx < len) {
        ret += buf[idx];
        buf[idx++] = null;
      }
    } else if (len - idx === 0) {
      ret = new FastBuffer();
    } else if (len - idx === 1) {
      ret = buf[idx];
      buf[idx++] = null;
    } else {
      ret = Buffer.allocUnsafe(state.length);

      let i = 0;
      while (idx < len) {
        TypedArrayPrototypeSet(ret, buf[idx], i);
        i += buf[idx].length;
        buf[idx++] = null;
      }
    }
  } else if (n < buf[idx].length) {
    // `slice` is the same for buffers and strings.
    ret = buf[idx].slice(0, n);
    buf[idx] = buf[idx].slice(n);
  } else if (n === buf[idx].length) {
    // First chunk is a perfect match.
    ret = buf[idx];
    buf[idx++] = null;
  } else if ((state[kState] & kDecoder) !== 0) {
    ret = '';
    while (idx < len) {
      const str = buf[idx];
      if (n > str.length) {
        ret += str;
        n -= str.length;
        buf[idx++] = null;
      } else {
        if (n === str.length) {
          ret += str;
          buf[idx++] = null;
        } else {