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-rw-r--r--uts/common/fs/zfs/zle.c86
1 files changed, 86 insertions, 0 deletions
diff --git a/uts/common/fs/zfs/zle.c b/uts/common/fs/zfs/zle.c
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+++ b/uts/common/fs/zfs/zle.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 2009 Sun Microsystems, Inc. All rights reserved.
+ * Use is subject to license terms.
+ */
+
+/*
+ * Zero-length encoding. This is a fast and simple algorithm to eliminate
+ * runs of zeroes. Each chunk of compressed data begins with a length byte, b.
+ * If b < n (where n is the compression parameter) then the next b + 1 bytes
+ * are literal values. If b >= n then the next (256 - b + 1) bytes are zero.
+ */
+#include <sys/types.h>
+#include <sys/sysmacros.h>
+
+size_t
+zle_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 *s_end = src + s_len;
+ uchar_t *d_end = dst + d_len;
+
+ while (src < s_end && dst < d_end - 1) {
+ uchar_t *first = src;
+ uchar_t *len = dst++;
+ if (src[0] == 0) {
+ uchar_t *last = src + (256 - n);
+ while (src < MIN(last, s_end) && src[0] == 0)
+ src++;
+ *len = src - first - 1 + n;
+ } else {
+ uchar_t *last = src + n;
+ if (d_end - dst < n)
+ break;
+ while (src < MIN(last, s_end) - 1 && (src[0] | src[1]))
+ *dst++ = *src++;
+ if (src[0])
+ *dst++ = *src++;
+ *len = src - first - 1;
+ }
+ }
+ return (src == s_end ? dst - (uchar_t *)d_start : s_len);
+}
+
+int
+zle_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 *s_end = src + s_len;
+ uchar_t *d_end = dst + d_len;
+
+ while (src < s_end && dst < d_end) {
+ int len = 1 + *src++;
+ if (len <= n) {
+ while (len-- != 0)
+ *dst++ = *src++;
+ } else {
+ len -= n;
+ while (len-- != 0)
+ *dst++ = 0;
+ }
+ }
+ return (dst == d_end ? 0 : -1);
+}