zle.c

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    1 /*
    2  * CDDL HEADER START
    3  *
    4  * The contents of this file are subject to the terms of the
    5  * Common Development and Distribution License (the "License").
    6  * You may not use this file except in compliance with the License.
    7  *
    8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
    9  * or http://www.opensolaris.org/os/licensing.
   10  * See the License for the specific language governing permissions
   11  * and limitations under the License.
   12  *
   13  * When distributing Covered Code, include this CDDL HEADER in each
   14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
   15  * If applicable, add the following below this CDDL HEADER, with the
   16  * fields enclosed by brackets "[]" replaced with your own identifying
   17  * information: Portions Copyright [yyyy] [name of copyright owner]
   18  *
   19  * CDDL HEADER END
   20  */
   21 
   22 /*
   23  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
   24  * Use is subject to license terms.
   25  */
   26 
   27 /*
   28  * Zero-length encoding.  This is a fast and simple algorithm to eliminate
   29  * runs of zeroes.  Each chunk of compressed data begins with a length byte, b.
   30  * If b < n (where n is the compression parameter) then the next b + 1 bytes
   31  * are literal values.  If b >= n then the next (256 - b + 1) bytes are zero.
   32  */
   33 
   34 static int
   35 zle_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
   36 {
   37         unsigned char *src = s_start;
   38         unsigned char *dst = d_start;
   39         unsigned char *s_end = src + s_len;
   40         unsigned char *d_end = dst + d_len;
   41 
   42         while (src < s_end && dst < d_end) {
   43                 int len = 1 + *src++;
   44                 if (len <= n) {
   45                         while (len-- != 0)
   46                                 *dst++ = *src++;
   47                 } else {
   48                         len -= n;
   49                         while (len-- != 0)
   50                                 *dst++ = 0;
   51                 }
   52         }
   53         return (dst == d_end ? 0 : -1);
   54 }

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FreeBSD/Linux Kernel Cross Reference sys/cddl/boot/zfs/zle.c

FreeBSD/Linux Kernel Cross Reference
sys/cddl/boot/zfs/zle.c