avm1 转化成 avm2

/*
 * ForcibleLoader
 *
 * Licensed under the MIT License
 *
 * Copyright (c) 2007-2009 BeInteractive! (www.be-interactive.org) and
 *                         Spark project  (www.libspark.org)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 */
package
{
  import flash.display.Loader;
  import flash.net.URLRequest;
  import flash.net.URLStream;
  import flash.events.IOErrorEvent;
  import flash.events.SecurityErrorEvent;
  import flash.events.Event;
  import flash.utils.ByteArray;
  import flash.utils.Endian;
  import flash.errors.EOFError;
 
  /**
   * Loads a SWF file as version 9 format forcibly even if version is under 9.
   *
   * Usage:
   * <pre>
   * var loader:Loader = Loader(addChild(new Loader()));
   * var fLoader:ForcibleLoader = new ForcibleLoader(loader);
   * fLoader.load(new URLRequest('swf7.swf'));
   * </pre>
   *
   * @author yossy:beinteractive
   * @see http://www.be-interactive.org/?itemid=250
   * @see http://fladdict.net/blog/2007/05/avm2avm1swf.html
   */
  public class ForcibleLoader
  {
    public function ForcibleLoader(loader:Loader)
    {
      this.loader = loader;
     
      _stream = new URLStream();
      _stream.addEventListener(Event.COMPLETE, completeHandler);
      _stream.addEventListener(IOErrorEvent.IO_ERROR, ioErrorHandler);
      _stream.addEventListener(SecurityErrorEvent.SECURITY_ERROR, securityErrorHandler);
    }
   
    private var _loader:Loader;
    private var _stream:URLStream;
   
    public function get loader():Loader
    {
      return _loader;
    }
   
    public function set loader(value:Loader):void
    {
      _loader = value;
    }
   
    public function load(request:URLRequest):void
    {
      _stream.load(request);
    }
   
    private function completeHandler(event:Event):void
    {
      var inputBytes:ByteArray = new ByteArray();
      _stream.readBytes(inputBytes);
      _stream.close();
      inputBytes.endian = Endian.LITTLE_ENDIAN;
     
      if (isCompressed(inputBytes)) {
        uncompress(inputBytes);
      }
     
      var version:uint = uint(inputBytes[3]);
     
      if (version < 9) {
        updateVersion(inputBytes, 9);
      }
      if (version > 7) {
        flagSWF9Bit(inputBytes);
      }
      else {
        insertFileAttributesTag(inputBytes);
      }
     
      loader.loadBytes(inputBytes);
    }
   
    private function isCompressed(bytes:ByteArray):Boolean
    {
      return bytes[0] == 0x43;
    }
   
    private function uncompress(bytes:ByteArray):void
    {
      var cBytes:ByteArray = new ByteArray();
      cBytes.writeBytes(bytes, 8);
      bytes.length = 8;
      bytes.position = 8;
      cBytes.uncompress();
      bytes.writeBytes(cBytes);
      bytes[0] = 0x46;
      cBytes.length = 0;
    }
   
    private function getBodyPosition(bytes:ByteArray):uint
    {
      var result:uint = 0;
     
      result += 3; // FWS/CWS
      result += 1; // version(byte)
      result += 4; // length(32bit-uint)
     
      var rectNBits:uint = bytes[result] >>> 3;
      result += (5 + rectNBits * 4) / 8; // stage(rect)
     
      result += 2;
     
      result += 1; // frameRate(byte)
      result += 2; // totalFrames(16bit-uint)
     
      return result;
    }
   
    private function findFileAttributesPosition(offset:uint, bytes:ByteArray):uint
    {
      bytes.position = offset;
     
      try {
        for (;;) {
          var byte:uint = bytes.readShort();
          var tag:uint = byte >>> 6;
          if (tag == 69) {
            return bytes.position - 2;
          }
          var length:uint = byte & 0x3f;
          if (length == 0x3f) {
            length = bytes.readInt();
          }
          bytes.position += length;
        }
      }
      catch (e:EOFError) {
      }
     
      return NaN;
    }
   
    private function flagSWF9Bit(bytes:ByteArray):void
    {
      var pos:uint = findFileAttributesPosition(getBodyPosition(bytes), bytes);
      if (!isNaN(pos)) {
        bytes[pos + 2] |= 0x08;
      }
    }
   
    private function insertFileAttributesTag(bytes:ByteArray):void
    {
      var pos:uint = getBodyPosition(bytes);
      var afterBytes:ByteArray = new ByteArray();
      afterBytes.writeBytes(bytes, pos);
      bytes.length = pos;
      bytes.position = pos;
      bytes.writeByte(0x44);
      bytes.writeByte(0x11);
      bytes.writeByte(0x08);
      bytes.writeByte(0x00);
      bytes.writeByte(0x00);
      bytes.writeByte(0x00);
      bytes.writeBytes(afterBytes);
      afterBytes.length = 0;
    }
   
    private function updateVersion(bytes:ByteArray, version:uint):void
    {
      bytes[3] = version;
    }
   
    private function ioErrorHandler(event:IOErrorEvent):void
    {
      loader.contentLoaderInfo.dispatchEvent(event.clone());
    }
   
    private function securityErrorHandler(event:SecurityErrorEvent):void
    {
      loader.contentLoaderInfo.dispatchEvent(event.clone());
    }
  }
}