nerve-sdk-js/lib/utils/bufferreader.js

nerve nerve-js nerve-sdk nerve-js-sdk

let BigInteger = require("bigi");

var BufferReader = function (buffer, cursor) {
  this.buf = buffer;
  this.cursor = cursor;
};

BufferReader.prototype.getCursor = function () {
  return this.cursor;
};

BufferReader.prototype.getBuffer = function () {
  return this.buf;
};

BufferReader.prototype.slice = function (length) {
  var result = this.buf.slice(this.cursor, this.cursor + length);
  this.cursor += length;
  return result;
};

BufferReader.prototype.readUInt64LE = function () {
  var bytes = this.slice(8);
  return bytes[0] & 0xff | (bytes[1] & 0xff) << 8 | (bytes[2] & 0xff) << 16 | (bytes[3] & 0xff) << 24 | (bytes[4] & 0xff) << 32 | (bytes[5] & 0xff) << 40 | (bytes[6] & 0xff) << 48 | (bytes[7] & 0xff) << 56;
};

BufferReader.prototype.readUInt32LE = function () {
  var result = this.buf.readUInt32LE(this.cursor);
  this.cursor += 4;
  return result;
};

BufferReader.prototype.readUInt16LE = function () {
  var result = this.buf.readUInt16LE(this.cursor);
  this.cursor += 2;
  return result;
};

BufferReader.prototype.readUInt8 = function () {
  var result = this.buf.readUInt8(this.cursor);
  this.cursor += 1;
  return result;
};

BufferReader.prototype.readBytesByLength = function () {
  var length = this.readVarInt();
  var result = this.slice(length);
  return result;
};

BufferReader.prototype.isFinished = function () {
  return this.buf.length == this.cursor;
};

BufferReader.prototype.readBoolean = function () {
  var result = this.buf.readUInt8(this.cursor);
  this.cursor += 1;
  return result != 0;
};

BufferReader.prototype.readBigInteger = function () {
  var bytes = this.slice(32);
  var value = new BigInteger(bytes.reverse());
  return value.toString();
};

BufferReader.prototype.readVarInt = function () {
  var first = 0xFF & this.buf.readInt8(this.cursor);
  var result = first;

  if (first < 253) {
    this.cursor += 1;
  } else if (first == 253) {
    result = this.buf.readInt16LE(this.cursor + 1);
    this.cursor += 3;
  } else if (first == 254) {
    result = this.buf.readUInt32LE(this.cursor + 1);
    this.cursor += 5;
  } else {
    result = this.buf.readUInt64LE(this.cursor + 1);
    this.cursor += 9;
  }

  return result;
};

module.exports = BufferReader;