snappy-java两种压缩方式的区别

1.Snappy-java项目地址

https://github.com/xerial/snappy-java

2.Snappy-java两种压缩方式

使用Snappy.compress进行压缩

String dataString = "The quick brown fox jumps over the lazy dog";
byte[] compressed = Snappy.compress(dataString.getBytes("UTF-8"));
byte[] uncompressed = Snappy.uncompress(compressed);
String result = new String(uncompressed, "UTF-8");
System.out.println(result);

使用SnappyInputStream进行压缩

    public static byte[] compressSnappy(byte[] data) throws IOException {
        ByteArrayInputStream is = new ByteArrayInputStream(data);
        ByteArrayOutputStream os = new ByteArrayOutputStream();
        SnappyOutputStream sos = new SnappyOutputStream(os);
        int count;
        byte temp[] = new byte[BUFFER];
        try {
            while ((count = is.read(temp)) != -1) {
                sos.write(temp, 0, count);
            }
            sos.flush();
            byte[] output = os.toByteArray();
            return output;
        } finally {
            sos.close();
            is.close();
        }
    } 

3.两种压缩方式的区别

    /**
     * 输出如下：
     * Snappy.compress  压缩结果：2b a8 54 68 65 20 71 75 69 63 6b 20 62 72 6f 77 6e 20 66 6f 78 20 6a 75 6d 70 73 20 6f 76 65 72 20 74 68 65 20 6c 61 7a 79 20 64 6f 67
     * SnappyInputStream压缩结果：82 53 4e 41 50 50 59 00 00 00 00 01 00 00 00 01 00 00 00 2d 2b a8 54 68 65 20 71 75 69 63 6b 20 62 72 6f 77 6e 20 66 6f 78 20 6a 75 6d 70 73 20 6f 76 65 72 20 74 68 65 20 6c 61 7a 79 20 64 6f 67
     *                         |---------------------magic header(16bytes)-----|size(4bytes)|----compressed data-----
     */
    @Test
    public void testSnappyCompress() throws Exception {
        String dataString = "The quick brown fox jumps over the lazy dog";
​
        byte[] compressedData = Snappy.compress(dataString.getBytes());
        System.out.println("Snappy.compress  压缩结果：" + bytes2hex(compressedData));
​
        byte[] compressedData2 = compressSnappy(dataString.getBytes());
        System.out.println("SnappyInputStream压缩结果：" + bytes2hex(compressedData2));
    }
    /**
     * 将byte数组按16进制的方式输出
     */
    public static String bytes2hex(byte[] bytes) {
        StringBuilder sb = new StringBuilder();
        String tmp = null;
        for (byte b : bytes) {
            // 将每个字节与0xFF进行与运算，然后转化为10进制，然后借助于Integer再转化为16进制
            tmp = Integer.toHexString(0xFF & b);
            if (tmp.length() == 1) {
                tmp = "0" + tmp;
            }
            sb.append(tmp).append(" ");
        }
        return sb.toString();
    }

区别如下：

通过Snappy.compress()进行压缩，压缩后的数据没有magic header

通过SnappyInputStream进行压缩，压缩后的数据有固定的header