Unity使用lzma的测试记录

对资源文件的传输总会需要压缩以减小尺寸。unity支持lzma格式，其压缩效果也挺好。[下载地址: LZMA SDK ](http://www.7-zip.org/sdk.html)

    为了实现不同资源文件压缩成一个，首先需要记录每个资源文件的路径以及长度，作为头文件信息，将此头文件和对应资源文件(byte格式)一起写入memoryStream。

for (int i = 0; i < filePathCount; i++){    string assetPath = AssetDatabase.GetAssetPath(resourcesLis[i]);    string filePath = prePath + assetPath;    string zipBundlePath = assetPath.Replace("Assets/", "");    FileStream tempFileStream = File.Open(filePath, FileMode.Open);    //头文件信息设置 assets下路径 + 尺寸 + 回车分隔符    StringBuilder sb = new StringBuilder();     sb.Append(zipBundlePath).        Append(",").        Append(tempFileStream.Length).        Append("\n");    byte[] tempBuff = new byte[tempFileStream.Length];    byte[] header = Encoding.UTF8.GetBytes(sb.ToString());    //字节数组格式的文件数据    tempFileStream.Read(tempBuff, 0, (int)tempFileStream.Length);       // 写入临时内存流    memoryStream.Write(header, 0, header.Length);    memoryStream.Write(tempBuff, 0, tempBuff.Length);    tempFileStream.Close();}

之后进行lzma接口。调用需要先将组合文件的临时内存流的Position重置为0。

    SevenZip.Compression.LZMA.Encoder encoder = new SevenZip.Compression.LZMA.Encoder();    encoder.WriteCoderProperties(compressStream);    CodeProgress codeProgress = new CodeProgress();       codeProgress.totalSize = memoryStream.Length;    // 压缩有回调，可以展示进度    encoder.Code(memoryStream, compressStream, memoryStream.Length, -1, codeProgress);

解压缩就是调逆的过程。先调用lzma的接口。

        FileStream compressStream = new FileStream(destFolderPath, FileMode.Open, FileAccess.Read);        MemoryStream tempStream = new MemoryStream();        SevenZip.Compression.LZMA.Decoder decoder = new SevenZip.Compression.LZMA.Decoder();        byte[] properties = new byte[5];        compressStream.Read(properties, 0, 5);        decoder.SetDecoderProperties(properties);        long compressRealLen = compressStream.Length - compressStream.Position;        decoder.Code(compressStream, tempStream, compressRealLen, outsize, null);

解压后的文件集合，顺序读取每个文件的头文件信息， 获取解压路径以及每个文件尺寸。

    while (tempStream.Position != tempStream.Length)    {        int one = tempStream.ReadByte();        // 根据之前记录的 \n 来切割头文件数据        if (one != 10)         {            head[index++] = (byte)one;        }        else        {            index = 0;            string headStr = Encoding.UTF8.GetString(head);            head = new byte[1024];            string[] headArr = headStr.Split(',');            // assets 下路径名            string fileBundleName = headArr[0];             int lastXIndex = fileBundleName.LastIndexOf("/");            string fileName = fileBundleName.Substring(lastXIndex + 1, fileBundleName.Length - lastXIndex - 1);            string fileFolderName = fileBundleName.Substring(0, lastXIndex);            int fileSize = 0;            if(!int.TryParse(headArr[1], out fileSize))            {                EditorUtility.DisplayDialog("Error", "File size exception!!! -->> " + headArr[1], "ok");                break;            }            // 写入文件路径            string filePath = assetbundlePath + "/Decompress/" + fileFolderName;            if (!Directory.Exists(filePath))            {                Directory.CreateDirectory(filePath);            }            WriteToLocal(tempStream, fileSize, filePath + "/" + fileName);        }    }

我写时几个问题没考虑好：     1：临时memoryStream的写入后，其Position是否需要进行重置。    2：异常需要添加try catch, 否则文件写入报错会使unity目录出现一些奇怪的反应。以下是项目路径(其实一个脚本就搞定了ABTest.cs)：    https://github.com/feixus/UnityLzmaTest