Examples of com.sleepycat.je.utilint.Adler32

com.sleepycat.je.utilint.Adler32
Adler32 checksum implementation. This class is used rather than the native java.util.zip.Adler32 class because we have seen a JIT problem when calling the Adler32 class using the Server JVM on Linux and Solaris. Specifically, we suspect this may be Bug Parade number 4965907. See SR [#9376]. We also believe that this bug is fixed in Java 5 and therefore only use this class conditionally if we find that we're in a 1.4 JVM. [#13354]. The Adler32 checksum is discussed in RFC1950. The sample implementation from this RFC is shown below:
```
 #define BASE 65521  largest prime smaller than 65536 unsigned long update_adler32(unsigned long adler, unsigned char *buf, int len) { unsigned long s1 = adler & 0xffff; unsigned long s2 = (adler >> 16) & 0xffff; int n; for (n = 0; n < len; n++) { s1 = (s1 + buf[n]) % BASE; s2 = (s2 + s1)     % BASE; } return (s2 << 16) + s1; } unsigned long adler32(unsigned char *buf, int len) { return update_adler32(1L, buf, len); } 
```
The NMAX optimization is so that we don't have to do modulo calculations on every iteration. NMAX is the max number of additions to make before you have to perform the modulo calculation.

     * of the bytes representing the concatenation of the key/value pair.
     * 
     * @return the checksum
     */
    public static int getXi(byte[] keyValue) {
        Adler32 adler32 = new Adler32();
        adler32.update(keyValue, 0, keyValue.length);
        return (int) adler32.getValue();
    }

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        /* DatabaseEntry represents the key and data of each record. */
        DatabaseEntry key = new DatabaseEntry();
        DatabaseEntry data = new DatabaseEntry();
        /* Adler32 to compute the rolling checksum of key/data pair. */
        Adler32 adler32 = new Adler32();
        int i = 0;
        int a = 0, b = 0;
        md.reset();
        Block block = new Block(blockId);


        /* Please pay attention to the check order in while loop. */
        while ((i < numKeys) &&
               (cursor.getNext(key, data, LockMode.DEFAULT) ==
                OperationStatus.SUCCESS)) {
            /* Indicates having a new block. */
            if (i == 0) {
                block.setBeginKey(key.getData());
                block.setBeginData(data.getData());
            }


            /* Calculate rollingChksum on "key|data" bytes. */
            adler32.reset();
            adler32.update(key.getData(), 0, key.getData().length);
            adler32.update(data.getData(), 0, data.getData().length);
            final int xi = (int) adler32.getValue();
            a += xi;
            b += a;
            /* Update MessageDigest with "key|data" bytes. */
            md.update(key.getData());
            md.update(data.getData());

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     * algorithm to logically use 32 bit bytes.
     */
    private void setChecksum() {


        /* Adler32 to compute the rolling checksum of key/data pair. */
        Adler32 adler32 = new Adler32();


        int a = 0, b = 0;
        for (int i = 0; i < size(); i++) {
            byte[] element = window.get(i);
            adler32.reset();
            adler32.update(element, 0, element.length);
            final int xi = (int) adler32.getValue(); /* It's really 32 bits */
            a += xi;
            b += (xi * (size() - i));
        }
        chksum = (a & LDiffUtil.MASK_32BIT) | ((long) b << 32);
    }

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    private static final boolean DEBUG = false;


    private Checksum cksum;


    ChecksumValidator() {
        cksum = new Adler32();
    }

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    private ByteBuffer addPrevOffsetAndChecksum(ByteBuffer destBuffer,
                                                long lastOffset,
                                                int entrySize) {


        Checksum checksum = new Adler32();
            
        /* Add the prev pointer */
        destBuffer.position(HEADER_PREV_OFFSET);
        LogUtils.writeUnsignedInt(destBuffer, lastOffset);


        /* Now calculate the checksum and write it into the buffer. */
        checksum.update(destBuffer.array(), CHECKSUM_BYTES,
                        (entrySize - CHECKSUM_BYTES));
        destBuffer.position(0);
        LogUtils.putUnsignedInt(destBuffer, checksum.getValue());


        /* Leave this buffer ready for copying into another buffer. */
        destBuffer.position(0);


        return destBuffer;

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Related Classes of com.sleepycat.je.utilint.Adler32

com.sleepycat.je.log.ChecksumValidator

com.sleepycat.je.log.LogManager

com.sleepycat.je.rep.util.ldiff.LDiffUtil

com.sleepycat.je.rep.util.ldiff.Window

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