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 (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. 24 */ 25 26/* 27 * We keep our own copy of this algorithm for 3 main reasons: 28 * 1. If we didn't, anyone modifying common/os/compress.c would 29 * directly break our on disk format 30 * 2. Our version of lzjb does not have a number of checks that the 31 * common/os version needs and uses 32 * 3. We initialize the lempel to ensure deterministic results, 33 * so that identical blocks can always be deduplicated. 34 * In particular, we are adding the "feature" that compress() can 35 * take a destination buffer size and returns the compressed length, or the 36 * source length if compression would overflow the destination buffer. 37 */ 38 39#include <sys/zfs_context.h> 40#include <sys/types.h> 41#include <sys/param.h> 42 43#define MATCH_BITS 6 44#define MATCH_MIN 3 45#define MATCH_MAX ((1 << MATCH_BITS) + (MATCH_MIN - 1)) 46#define OFFSET_MASK ((1 << (16 - MATCH_BITS)) - 1) 47#define LEMPEL_SIZE 1024 48 49/*ARGSUSED*/ 50size_t 51lzjb_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n) 52{ 53 uchar_t *src = s_start; 54 uchar_t *dst = d_start; 55 uchar_t *cpy; 56 uchar_t *copymap = NULL; 57 int copymask = 1 << (NBBY - 1); 58 int mlen, offset, hash; 59 uint16_t *hp; 60 uint16_t lempel[LEMPEL_SIZE] = { 0 }; 61 62 while (src < (uchar_t *)s_start + s_len) { 63 if ((copymask <<= 1) == (1 << NBBY)) { 64 if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY) 65 return (s_len); 66 copymask = 1; 67 copymap = dst; 68 *dst++ = 0; 69 } 70 if (src > (uchar_t *)s_start + s_len - MATCH_MAX) { 71 *dst++ = *src++; 72 continue; 73 } 74 hash = (src[0] << 16) + (src[1] << 8) + src[2]; 75 hash += hash >> 9; 76 hash += hash >> 5; 77 hp = &lempel[hash & (LEMPEL_SIZE - 1)]; 78 offset = (intptr_t)(src - *hp) & OFFSET_MASK; 79 *hp = (uint16_t)(uintptr_t)src; 80 cpy = src - offset; 81 if (cpy >= (uchar_t *)s_start && cpy != src && 82 src[0] == cpy[0] && src[1] == cpy[1] && src[2] == cpy[2]) { 83 *copymap |= copymask; 84 for (mlen = MATCH_MIN; mlen < MATCH_MAX; mlen++) 85 if (src[mlen] != cpy[mlen]) 86 break; 87 *dst++ = ((mlen - MATCH_MIN) << (NBBY - MATCH_BITS)) | 88 (offset >> NBBY); 89 *dst++ = (uchar_t)offset; 90 src += mlen; 91 } else { 92 *dst++ = *src++; 93 } 94 } 95 return (dst - (uchar_t *)d_start); 96} 97 98/*ARGSUSED*/ 99int 100lzjb_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n) 101{ 102 uchar_t *src = s_start; 103 uchar_t *dst = d_start; 104 uchar_t *d_end = (uchar_t *)d_start + d_len; 105 uchar_t *cpy; 106 uchar_t copymap = 0; 107 int copymask = 1 << (NBBY - 1); 108 109 while (dst < d_end) { 110 if ((copymask <<= 1) == (1 << NBBY)) { 111 copymask = 1; 112 copymap = *src++; 113 } 114 if (copymap & copymask) { 115 int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN; 116 int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK; 117 src += 2; 118 if ((cpy = dst - offset) < (uchar_t *)d_start) 119 return (-1); 120 if (mlen > (d_end - dst)) 121 mlen = d_end - dst; 122 while (--mlen >= 0) 123 *dst++ = *cpy++; 124 } else { 125 *dst++ = *src++; 126 } 127 } 128 return (0); 129} 130