java – 使用LZ4解压缩byte []

我正在使用LZ4来压缩和解压缩字符串.我尝试了以下方法

public class CompressionDemo {

    public static byte[] compressLZ4(LZ4Factory factory, String data) throws IOException {
        final int decompressedLength = data.getBytes().length;
        LZ4Compressor compressor = factory.fastCompressor();
        int maxCompressedLength = compressor.maxCompressedLength(decompressedLength);
        byte[] compressed = new byte[maxCompressedLength];
        compressor.compress(data.getBytes(), 0, decompressedLength, compressed, 0, maxCompressedLength);
        return compressed;

    }

    public static String deCompressLZ4(LZ4Factory factory, byte[] data) throws IOException {
        LZ4FastDecompressor decompressor = factory.fastDecompressor();
        byte[] restored = new byte[data.length];
        decompressor.decompress(data,0,restored, 0,data.length);
        return new String(restored);
    }

    public static void main(String[] args) throws IOException, DataFormatException {
        String string = "kjshfhshfashfhsakjfhksjafhkjsafhkjashfkjhfjkfhhjdshfhhjdfhdsjkfhdshfdskjfhksjdfhskjdhfkjsdhfk";
        LZ4Factory factory = LZ4Factory.fastestInstance();
        byte[] arr = compressLZ4(factory, string);
        System.out.println(arr.length);
        System.out.println(deCompressLZ4(factory, arr) + "decom");
    }
}

它给予了以下的激励

线程“main”中的异常net.jpountz.lz4.LZ4Exception：解码输入缓冲区的偏移量92时出错

这里的问题是只有当我传递实际的String byte []长度时,解压缩才有效

public static String deCompressLZ4(LZ4Factory factory, byte[] data) throws IOException {
        LZ4FastDecompressor decompressor = factory.fastDecompressor();
        byte[] restored = new byte[data.length];
        decompressor.decompress(data,0,restored, 0,"kjshfhshfashfhsakjfhksjafhkjsafhkjashfkjhfjkfhhjdshfhhjdfhdsjkfhdshfdskjfhksjdfhskjdhfkjsdhfk".getBytes().length);
        return new String(restored);
    }

它期望实际的字符串byte []大小.
有人可以帮我弄这个吗

解决方法:

由于压缩和解压缩可能发生在不同的机器上,或者机器默认字符编码不是Unicode格式之一,因此也应该指示编码.

对于其余部分,它使用实际的压缩和解压缩长度,并且更好地以普通格式存储未压缩数据的大小,因此可以在解压缩之前提取它.

public static byte[] compressLZ4(LZ4Factory factory, String data) throws IOException {
    byte[] decompressed = data.getBytes(StandardCharsets.UTF_8).length;
    LZ4Compressor compressor = factory.fastCompressor();
    int maxCompressedLength = compressor.maxCompressedLength(decompressed.length);
    byte[] compressed = new byte[4 + maxCompressedLength];
    int compressedSize = compressor.compress(decompressed, 0, decompressed.length,
                                             compressed, 4, maxCompressedLength);
    ByteBuffer.wrap(compressed).putInt(decompressed.length);
    return Arrays.copyOf(compressed, 0, 4 + compressedSize);
}

public static String deCompressLZ4(LZ4Factory factory, byte[] data) throws IOException {
    LZ4FastDecompressor decompressor = factory.fastDecompressor();
    int decrompressedLength = ByteBuffer.wrap(data).getInt();
    byte[] restored = new byte[decrompressedLength];
    decompressor.decompress(data, 4, restored, 0, decrompressedLength);
    return new String(restored, StandardCharsets.UTF_8);
}

应该告诉我,String不适合二进制数据,压缩/解压缩仅用于文本处理. (字符串包含UTF-16双字节字符形式的Unicode文本.转换为二进制数据总是涉及二进制数据编码的转换.这会降低内存,速度和可能的数据损坏.)

标签：java,lz4
来源： https://codeday.me/bug/20190628/1311483.html