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-rw-r--r--uts/common/fs/zfs/lzjb.c123
1 files changed, 123 insertions, 0 deletions
diff --git a/uts/common/fs/zfs/lzjb.c b/uts/common/fs/zfs/lzjb.c
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+++ b/uts/common/fs/zfs/lzjb.c
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+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ */
+
+/*
+ * We keep our own copy of this algorithm for 3 main reasons:
+ * 1. If we didn't, anyone modifying common/os/compress.c would
+ * directly break our on disk format
+ * 2. Our version of lzjb does not have a number of checks that the
+ * common/os version needs and uses
+ * 3. We initialize the lempel to ensure deterministic results,
+ * so that identical blocks can always be deduplicated.
+ * In particular, we are adding the "feature" that compress() can
+ * take a destination buffer size and returns the compressed length, or the
+ * source length if compression would overflow the destination buffer.
+ */
+
+#include <sys/types.h>
+
+#define MATCH_BITS 6
+#define MATCH_MIN 3
+#define MATCH_MAX ((1 << MATCH_BITS) + (MATCH_MIN - 1))
+#define OFFSET_MASK ((1 << (16 - MATCH_BITS)) - 1)
+#define LEMPEL_SIZE 1024
+
+/*ARGSUSED*/
+size_t
+lzjb_compress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
+{
+ uchar_t *src = s_start;
+ uchar_t *dst = d_start;
+ uchar_t *cpy, *copymap;
+ int copymask = 1 << (NBBY - 1);
+ int mlen, offset, hash;
+ uint16_t *hp;
+ uint16_t lempel[LEMPEL_SIZE] = { 0 };
+
+ while (src < (uchar_t *)s_start + s_len) {
+ if ((copymask <<= 1) == (1 << NBBY)) {
+ if (dst >= (uchar_t *)d_start + d_len - 1 - 2 * NBBY)
+ return (s_len);
+ copymask = 1;
+ copymap = dst;
+ *dst++ = 0;
+ }
+ if (src > (uchar_t *)s_start + s_len - MATCH_MAX) {
+ *dst++ = *src++;
+ continue;
+ }
+ hash = (src[0] << 16) + (src[1] << 8) + src[2];
+ hash += hash >> 9;
+ hash += hash >> 5;
+ hp = &lempel[hash & (LEMPEL_SIZE - 1)];
+ offset = (intptr_t)(src - *hp) & OFFSET_MASK;
+ *hp = (uint16_t)(uintptr_t)src;
+ cpy = src - offset;
+ if (cpy >= (uchar_t *)s_start && cpy != src &&
+ src[0] == cpy[0] && src[1] == cpy[1] && src[2] == cpy[2]) {
+ *copymap |= copymask;
+ for (mlen = MATCH_MIN; mlen < MATCH_MAX; mlen++)
+ if (src[mlen] != cpy[mlen])
+ break;
+ *dst++ = ((mlen - MATCH_MIN) << (NBBY - MATCH_BITS)) |
+ (offset >> NBBY);
+ *dst++ = (uchar_t)offset;
+ src += mlen;
+ } else {
+ *dst++ = *src++;
+ }
+ }
+ return (dst - (uchar_t *)d_start);
+}
+
+/*ARGSUSED*/
+int
+lzjb_decompress(void *s_start, void *d_start, size_t s_len, size_t d_len, int n)
+{
+ uchar_t *src = s_start;
+ uchar_t *dst = d_start;
+ uchar_t *d_end = (uchar_t *)d_start + d_len;
+ uchar_t *cpy, copymap;
+ int copymask = 1 << (NBBY - 1);
+
+ while (dst < d_end) {
+ if ((copymask <<= 1) == (1 << NBBY)) {
+ copymask = 1;
+ copymap = *src++;
+ }
+ if (copymap & copymask) {
+ int mlen = (src[0] >> (NBBY - MATCH_BITS)) + MATCH_MIN;
+ int offset = ((src[0] << NBBY) | src[1]) & OFFSET_MASK;
+ src += 2;
+ if ((cpy = dst - offset) < (uchar_t *)d_start)
+ return (-1);
+ while (--mlen >= 0 && dst < d_end)
+ *dst++ = *cpy++;
+ } else {
+ *dst++ = *src++;
+ }
+ }
+ return (0);
+}