Function decodeSlice

msgpack/decode.ts:109–391

* Given a uint8array which contains a msgpack object, * return the value of the object as well as how many bytes * were consumed in obtaining this object

(
  uint8: Uint8Array,
  dataView: DataView,
  pointer: { consumed: number },
)

 * were consumed in obtaining this object
 */
function decodeSlice(
  uint8: Uint8Array,
  dataView: DataView,
  pointer: { consumed: number },
): ValueType {
  if (pointer.consumed >= uint8.length) {
    throw new EvalError("Messagepack decode reached end of array prematurely");
  }
  const type = dataView.getUint8(pointer.consumed);
  pointer.consumed++;

  if (type <= 0x7f) { // positive fixint - really small positive number
    return type;
  }

  if ((type & FIXMAP_MASK) === FIXMAP_BITS) { // fixmap - small map
    const size = type & ~FIXMAP_MASK;
    return decodeMap(uint8, dataView, size, pointer);
  }

  if ((type & FIXARRAY_MASK) === FIXARRAY_BITS) { // fixarray - small array
    const size = type & ~FIXARRAY_MASK;
    return decodeArray(uint8, dataView, size, pointer);
  }

  if ((type & FIXSTR_MASK) === FIXSTR_BITS) { // fixstr - small string
    const size = type & ~FIXSTR_MASK;
    return decodeString(uint8, size, pointer);
  }

  if (type >= 0xe0) { // negative fixint - really small negative number
    return type - 256;
  }

  switch (type) {
    case 0xc0: // nil
      return null;
    case 0xc1: // (never used)
      throw new Error(
        "Messagepack decode encountered a type that is never used",
      );
    case 0xc2: // false
      return false;
    case 0xc3: // true
      return true;
    case 0xc4: { // bin 8 - small Uint8Array
      if (pointer.consumed >= uint8.length) {
        throw new EvalError(
          "Messagepack decode reached end of array prematurely",
        );
      }
      const length = dataView.getUint8(pointer.consumed);
      pointer.consumed++;
      const u8 = uint8.subarray(pointer.consumed, pointer.consumed + length);
      if (u8.length !== length) {
        throw new EvalError(
          "Messagepack decode reached end of array prematurely",
        );