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 #include <sys/types.h> 34 #include <sys/sysmacros.h> 35 36 size_t 37 zle_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n) 38 { 39 uchar_t *src = s_start; 40 uchar_t *dst = d_start; 41 uchar_t *s_end = src + s_len; 42 uchar_t *d_end = dst + d_len; 43 44 while (src < s_end && dst < d_end - 1) { 45 uchar_t *first = src; 46 uchar_t *len = dst++; 47 if (src[0] == 0) { 48 uchar_t *last = src + (256 - n); 49 while (src < MIN(last, s_end) && src[0] == 0) 50 src++; 51 *len = src - first - 1 + n; 52 } else { 53 uchar_t *last = src + n; 54 if (d_end - dst < n) 55 break; 56 while (src < MIN(last, s_end) - 1 && (src[0] | src[1])) 57 *dst++ = *src++; 58 if (src[0]) 59 *dst++ = *src++; 60 *len = src - first - 1; 61 } 62 } 63 return (src == s_end ? dst - (uchar_t *)d_start : s_len); 64 } 65 66 int 67 zle_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n) 68 { 69 uchar_t *src = s_start; 70 uchar_t *dst = d_start; 71 uchar_t *s_end = src + s_len; 72 uchar_t *d_end = dst + d_len; 73 74 while (src < s_end && dst < d_end) { 75 int len = 1 + *src++; 76 if (len <= n) { 77 while (len-- != 0) 78 *dst++ = *src++; 79 } else { 80 len -= n; 81 while (len-- != 0) 82 *dst++ = 0; 83 } 84 } 85 return (dst == d_end ? 0 : -1); 86 } 87