Question

我正在使用jpountz LZ4来尝试压缩文件，我想使用Java文件输入和输出流读入和输出文件。我试图在网上找到一个解决方案，但没有什么，我发现了一个关于如何正确实现LZ4的先前stackoverflow问题，我已经采取了这个并尝试修改它以使用流，但我不确定这是否是纠正或者它是否正常工作。

在文本文件上运行压缩时，它会输出一个缺少某些字符或用符号替换的文件

ðHello world Heðo world Hello ðrld Hello worlðHello worl

但是当使用图像文件运行它时会抛出一个越界错误。我也无法使解压缩工作，因为它会输出错误解码输入缓冲区的偏移量3。

这是我的代码任何帮助将不胜感激

public void LZ4Compress(InputStream in, OutputStream out){
    int noBytesRead = 0;        //number of bytes read from input
    int noBytesProcessed = 0;   //number of bytes processed
    try {
        while ((noBytesRead = in.read(inputBuffer)) >= 0) {
            noBytesProcessed = inputBuffer.length;
            decompressedLength = inputBuffer.length;
            outputBuffer = compress(inputBuffer, decompressedLength);
            out.write(outputBuffer, 0, noBytesRead);
        }
        out.flush();
        in.close();
        out.close();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

public void LZ4decompress(InputStream in, OutputStream out){
    int noBytesRead = 0;        //number of bytes read from input
    try {
        while((noBytesRead = in.read(inputBuffer)) >= 0){
            noBytesProcessed = inputBuffer.length;
            outputBuffer = decompress(inputBuffer);
            out.write(outputBuffer, 0, noBytesRead);

        }
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

public static byte[] compress(byte[] src, int srcLen) {
    decompressedLength = srcLen;
    int maxCompressedLength = compressor.maxCompressedLength(decompressedLength);
    byte[] compressed = new byte[maxCompressedLength];
    int compressLen = compressor.compress(src, 0, decompressedLength, compressed, 0, maxCompressedLength);
    byte[] finalCompressedArray = Arrays.copyOf(compressed, compressLen);
    return finalCompressedArray;
}

private static LZ4SafeDecompressor decompressor = factory.safeDecompressor();

public static byte[] decompress(byte[] finalCompressedArray) {
    byte[] restored = new byte[finalCompressedArray.length];
    restored = decompressor.decompress(finalCompressedArray, finalCompressedArray.length);
    return restored;
}

Answer 1

所以我通过使用LZ4block输入/输出流解决了我的问题

public static void LZ4compress(String filename, String lz4file){
    byte[] buf = new byte[2048];
    try {
        String outFilename = lz4file;
        LZ4BlockOutputStream out = new LZ4BlockOutputStream(new FileOutputStream(outFilename), 32*1024*1024);
        FileInputStream in = new FileInputStream(filename);
        int len;
        while((len = in.read(buf)) > 0){
            out.write(buf, 0, len);
        }
        in.close();
        out.close();
    } catch (IOException e) {

    }
}

public static void LZ4Uncompress(String lz4file, String filename){
    byte[] buf = new byte[2048];
    try {
        String outFilename = filename;
        LZ4BlockInputStream in = new LZ4BlockInputStream(new FileInputStream(lz4file));
        FileOutputStream out = new FileOutputStream(outFilename);
        int len;
        while((len = in.read(buf)) > 0){
            out.write(buf, 0, len);
        }
        in.close();
        out.close();
    } catch (IOException e) {

    }
}

Answer 2

只看代码，我会说你错了：

 outputBuffer = compress(inputBuffer, decompressedLength);
 out.write(outputBuffer, 0, noBytesRead);

你已经在压缩中修剪了outputBuffer。尝试：

out.write(outputBuffer);

使用输入/输出流进行Java LZ4压缩

2 个答案: