snappy-java兩種壓縮方式的區別

1.Snappy-java項目地址

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

2.Snappy-java兩種壓縮方式

使用Snappy.compress進行壓縮

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進行壓縮

    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();
        }
    } 

3.兩種壓縮方式的區別

    /**
     * 輸出如下：
     * Snappy.compress  壓縮結果：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壓縮結果：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  壓縮結果：" + bytes2hex(compressedData));
​
        byte[] compressedData2 = compressSnappy(dataString.getBytes());
        System.out.println("SnappyInputStream壓縮結果：" + bytes2hex(compressedData2));
    }
    /**
     * 將byte數組按16進制的方式輸出
     */
    public static String bytes2hex(byte[] bytes) {
        StringBuilder sb = new StringBuilder();
        String tmp = null;
        for (byte b : bytes) {
            // 將每個字節與0xFF進行與運算，然后轉化為10進制，然后借助於Integer再轉化為16進制
            tmp = Integer.toHexString(0xFF & b);
            if (tmp.length() == 1) {
                tmp = "0" + tmp;
            }
            sb.append(tmp).append(" ");
        }
        return sb.toString();
    }

區別如下：

通過Snappy.compress()進行壓縮，壓縮后的數據沒有magic header

通過SnappyInputStream進行壓縮，壓縮后的數據有固定的header