net.whitbeck.rdbparser.Lzf Maven / Gradle / Ivy
/**
* Copyright (c) 2015-2018 John Whitbeck. All rights reserved.
*
* The use and distribution terms for this software are covered by the
* Apache License 2.0 (https://www.apache.org/licenses/LICENSE-2.0.txt)
* which can be found in the file al-v20.txt at the root of this distribution.
* By using this software in any fashion, you are agreeing to be bound by
* the terms of this license.
*
*
You must not remove this notice, or any other, from this software.
*/
package net.whitbeck.rdbparser;
// adapted from https://github.com/ganghuawang/java-redis-rdb
final class Lzf {
// The maximum number of literals in a chunk (32).
private static int MAX_LITERAL = 32;
static void expand(byte[] src, byte[] dest) {
int srcPos = 0;
int destPos = 0;
do {
int ctrl = src[srcPos++] & 0xff;
if (ctrl < MAX_LITERAL) {
// literal run of length = ctrl + 1,
ctrl++;
// copy to output and move forward this many bytes
System.arraycopy(src, srcPos, dest, destPos, ctrl);
destPos += ctrl;
srcPos += ctrl;
} else {
/* back reference
the highest 3 bits are the match length */
int len = ctrl >> 5;
// if the length is maxed, add the next byte to the length
if (len == 7) {
len += src[srcPos++] & 0xff;
}
/* minimum back-reference is 3 bytes,
so 2 was subtracted before storing size */
len += 2;
/* ctrl is now the offset for a back-reference...
the logical AND operation removes the length bits */
ctrl = -((ctrl & 0x1f) << 8) - 1;
// the next byte augments/increases the offset
ctrl -= src[srcPos++] & 0xff;
/* copy the back-reference bytes from the given
location in output to current position */
ctrl += destPos;
for (int i = 0; i < len; i++) {
dest[destPos++] = dest[ctrl++];
}
}
} while (destPos < dest.length);
}
}