docs: function Index(keySize, block) {
    var reader = new SbonReader(block.buffer);
  
    this.level = reader.readUint8();
  
    // Number of keys in this index.
    this.keyCount = reader.readInt32();
  
    // The blocks that the keys point to. There will be one extra block in the
    // beginning of this list that points to the block to go to if the key being
    // searched for is left of the first key in this index.
    this.blockIds = new Int32Array(this.keyCount + 1);
    this.blockIds[0] = reader.readInt32();
  
    this.keys = [];
  
    // Load all key/block reference pairs.
    for (var i = 1; i <= this.keyCount; i++) {
      this.keys.push(reader.readByteString(keySize));
      this.blockIds[i] = reader.readInt32();
    }
  }