如何在 As3 中使用 ByteArray 方法解压 LZMA 压缩文件？

Question

这是我用来压缩/解压缩文件的代码：

package {
import flash.display.Sprite;
import flash.events.Event;
import flash.net.FileFilter;
import flash.net.FileReference;
import flash.utils.ByteArray;

public class Compressor extends Sprite
{
    private var ref:FileReference;

    public function Compressor()
    {
        ref = new FileReference();
        ref.addEventListener(Event.SELECT, load);
        ref.browse([new FileFilter("SWF Files", "*.swf")]);
    }

    private function load(e:Event):void
    {
        ref.addEventListener(Event.COMPLETE, processSWF);
        ref.load();
    }

    private function processSWF(e:Event):void
    {
        var swf:ByteArray;
        switch(ref.data.readMultiByte(3, "us-ascii"))
        {
            case "CWS":
                swf = decompress(ref.data);
                break;
            case "FWS":
                swf = compress(ref.data);
                break;
            default:
                throw Error("Not SWF...");
                break;
        }

        new FileReference().save(swf);
    }

    private function compress(data:ByteArray):ByteArray
    {
        var header:ByteArray = new ByteArray();
        var decompressed:ByteArray = new ByteArray();
        var compressed:ByteArray = new ByteArray();

        header.writeBytes(data, 3, 5); //read the header, excluding the signature
        decompressed.writeBytes(data, 8); //read the rest

        decompressed.compress();

        compressed.writeMultiByte("CWS", "us-ascii"); //mark as compressed
        compressed.writeBytes(header);
        compressed.writeBytes(decompressed);

        return compressed;
    }

    private function decompress(data:ByteArray):ByteArray
    {
        var header:ByteArray = new ByteArray();
        var compressed:ByteArray = new ByteArray();
        var decompressed:ByteArray = new ByteArray();

        header.writeBytes(data, 3, 5); //read the uncompressed header, excluding the signature
        compressed.writeBytes(data, 8); //read the rest, compressed

        compressed.uncompress();

        decompressed.writeMultiByte("FWS", "us-ascii"); //mark as uncompressed
        decompressed.writeBytes(header); //write the header back
        decompressed.writeBytes(compressed); //write the now uncompressed content

        return decompressed;
    }

}
}

我的问题：这种方法不能解压 LZMA 压缩文件 :(

谁能告诉我如何重构上面的代码来实现 LZMA 解压缩以及上面的压缩代码是否足够好用于 LZMA 压缩？如果不是，请举个例子。

编辑：经过长时间的搜索，我得到了this 但我不太明白其中的示例代码:(有人帮忙吗？

Answer 1

找到了一种解决方法，Flash 只有DEFLATE 和ZLIB 压缩算法，所以我不得不等待LZMA 更新，这可能会发生也可能不会发生，或者创建我自己的实用程序，所以我得到了Python，经过几次脖子-花了几个小时试图弄清楚如何使用它，我终于能够得到我想要的。

参考地点：

1. The python code to decompress LZMA-format swf files
2. The pylzma source file

Answer 2

我只是想补充一下您编辑中提供的the link，以防有人偶然发现它并像我一样对格式感到困惑，它也有一些奇怪的东西，两次写入几个字节，所以这是我对其进行了大量修改的版本（文件部分需要 AIR）。例如。我放弃了按位运算符，转而使用 ByteArray 读/写函数。

注意：至少现在AS3的ByteArray.decompress()支持LZMA解​​压，所以我在用那个，但它不直接支持SWF LZMA格式，只有LZMA，所以还有点修修补补请注意，此代码可能会有所改进。

import flash.filesystem.File;
import flash.filesystem.FileStream;
import flash.filesystem.FileMode;
import flash.utils.ByteArray; 

function decompressLZMA(idata:ByteArray){
    idata.endian = "littleEndian"
    var signature:ByteArray = new ByteArray;
    //I 0-3 = signature + version
    idata.readBytes(signature, 0, 3)
    var version:uint = idata.readUnsignedByte()
    switch (signature[0]){
        case 90: // Z = lzma compressed

        var odata:ByteArray = new ByteArray;
        odata.endian = "littleEndian"

        var i:uint;

        //O 0-3 = signature + version
        signature[0] = 70 // F = uncompressed
        odata.writeBytes(signature)
        odata.writeByte(version)

        //I 4-7 = swf file length
        idata.position = 4
        var scriptlen:uint = idata.readUnsignedInt()
        //8 = swf header size
        scriptlen -= 8

        //O 4-7 swf file length
        odata.writeUnsignedInt(scriptlen + 8) // Re-add swf header removed earlier

        var tdata:ByteArray = new ByteArray;
        tdata.endian = "littleEndian"
        //I 12    = lzma properties
        //I 13-16 = lzma dictionary size
        idata.position = 12
        //T 0   = lzma properties
        //T 1-4 = lzma dictionary size
        tdata.writeByte(idata.readByte())
        tdata.writeUnsignedInt(idata.readUnsignedInt())

        // lzma uncompressed length is stored as LE UI64:
        //T 5-8 = uncompressed length
        tdata.writeUnsignedInt(scriptlen)
        //T 9-12 = uncompressed length continued
        tdata.writeUnsignedInt(0)

        //16 = LZMA header size
        idata.position = 17
        //12 = SWF LZMA header size
        idata.readBytes(tdata, 13, idata.length-idata.position)

        tdata.uncompress(CompressionAlgorithm.LZMA)
        odata.writeBytes(tdata)
        return odata;

        break
    }
    return idata;
}

var file:File;
var stream:FileStream;
var idata:ByteArray;
var odata:ByteArray;
var path:String

path = File.applicationDirectory.resolvePath('LZMA.swf').nativePath;
file = new File(path);
stream = new FileStream();
stream.open(file, FileMode.READ); 
idata = new ByteArray
stream.readBytes(idata)
stream.close()

odata = decompressLZMA(idata)

path = File.applicationDirectory.resolvePath('LZMA_decompressed.swf').nativePath;
file = new File(path);
stream = new FileStream(); 
stream.open(file, FileMode.WRITE);
stream.writeBytes(odata)
stream.close()