fma-snes65816/dist/ChecksumCalculator.js

SNES 65816 assembler backend for FMA

'use strict';

Object.defineProperty(exports, "__esModule", {
  value: true
});

var _classCallCheck2 = require('babel-runtime/helpers/classCallCheck');

var _classCallCheck3 = _interopRequireDefault(_classCallCheck2);

var _createClass2 = require('babel-runtime/helpers/createClass');

var _createClass3 = _interopRequireDefault(_createClass2);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

var ChecksumCalculator = function () {
  function ChecksumCalculator() {
    (0, _classCallCheck3.default)(this, ChecksumCalculator);
  }

  (0, _createClass3.default)(ChecksumCalculator, [{
    key: 'calculate',
    value: function calculate(buffer, headerLocation) {
      var checksum = this.calculateChecksum(buffer);

      buffer[headerLocation + 0x2E] = checksum & 0xFF;
      buffer[headerLocation + 0x2F] = checksum >> 8 & 0xFF;
      checksum ^= 0xFFFF;
      buffer[headerLocation + 0x2C] = checksum & 0xFF;
      buffer[headerLocation + 0x2D] = checksum >> 8 & 0xFF;
    }
  }, {
    key: 'calculateChecksumMirror',
    value: function calculateChecksumMirror(buffer, start, size, mask) {
      while (!(size & mask)) {
        if (mask === 0) {
          throw new Error('Fatal error');
        }
        mask >>= 1;
      }

      var part1 = this.calculateChecksumDefault(buffer, start, mask);
      var part2 = 0;

      var nextLength = size - mask;
      if (nextLength) {
        part2 = this.calculateChecksumDefault(buffer, start + mask, nextLength, mask >> 1);

        while (nextLength < mask) {
          nextLength += nextLength;
          part2 += part2;
        }
      }

      return part1 + part2 & 0xFFFF;
    }
  }, {
    key: 'calculateChecksumDefault',
    value: function calculateChecksumDefault(buffer, start, size) {
      var sum = 0;
      for (var i = 0; i < size; i++) {
        sum = sum + buffer[start++] & 0xFFFF;
      }
      return sum;
    }
  }, {
    key: 'calculateChecksum',
    value: function calculateChecksum(buffer) {
      if (buffer.length & 0x7FFF) {
        throw new Error('TODO');
      } else {
        return this.calculateChecksumMirror(buffer, 0, buffer.length, 0x800000);
      }
    }
  }]);
  return ChecksumCalculator;
}();

exports.default = ChecksumCalculator;
//# sourceMappingURL=ChecksumCalculator.js.map