Java 使用LZ4解压缩字节[]

我使用LZ4压缩和解压字符串

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");
    }
}

这是一个例外

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

这里的问题是，只有当我传递实际的字符串字节[]长度，即

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);
    }

它需要实际的字符串字节[]大小。

---

有人能帮我解决这个问题吗？还原的字节[]长度太小了，你不应该使用压缩的data.length，而应该使用data[].length*3或大于3。

我这样解决：

public static byte[] decompress( byte[] finalCompressedArray,String ... extInfo) {
    int len = finalCompressedArray.length * 3;
    int i = 5;
    while (i > 0) {
        try {
            return decompress(finalCompressedArray, len);
        } catch (Exception e) {
            len = len * 2;
            i--;
            if (LOGGER.isInfoEnabled()) {
                LOGGER.info("decompress Error: extInfo ={} ", extInfo, e);
            }

        }

    }

    throw new ItemException(1, "decompress error");
}

/**
 * 解压一个数组
 *
 * @param finalCompressedArray 压缩后的数据
 * @param length               原始数据长度, 精确的长度,不能大,也不能小。
 * @return
 */
private static byte[] decompress(byte[] finalCompressedArray, int length) {
    byte[] desc = new byte[length ];
    int decompressLen = decompressor.decompress(finalCompressedArray, desc);

    byte[] result = new byte[decompressLen];
    System.arraycopy(desc,0,result,0,decompressLen);
    return result;
}

---

我只是在Android上遇到了同样的错误，并根据以下问题解决了它：

简言之，确保两个操作（压缩+解压缩）使用相同的工厂，并使用Arrays.copyOf（），如下所示：

  byte[] compress(final byte[] data) {
     LZ4Factory lz4Factory = LZ4Factory.safeInstance();
     LZ4Compressor fastCompressor = lz4Factory.fastCompressor();
     int maxCompressedLength = fastCompressor.maxCompressedLength(data.length);
     byte[] comp = new byte[maxCompressedLength];
     int compressedLength = fastCompressor.compress(data, 0, data.length, comp, 0, maxCompressedLength);
     return Arrays.copyOf(comp, compressedLength);
}

  byte[] decompress(final byte[] compressed) {
     LZ4Factory lz4Factory = LZ4Factory.safeInstance();
     LZ4SafeDecompressor decompressor = lz4Factory.safeDecompressor();
     byte[] decomp = new byte[compressed.length * 4];//you might need to allocate more
     decomp = decompressor.decompress(Arrays.copyOf(compressed, compressed.length), decomp.length);
     return decomp;

---

希望这会有所帮助。

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，因此也应该指出编码

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

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);
}

---

应该指出的是，

String

不适用于二进制数据，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。转换为二进制数据通常需要对二进制数据进行编码。这会耗费内存、速度和可能的数据损坏。）

这是一个答案，您能否提供更多信息以帮助他人@你有没有找到解决问题的方法？是的，我已经解决了@pppavan您能为我的问题提供建议吗？或者请给我一些数组解压缩的示例。