1 files changed, 86 insertions, 0 deletions
diff --git a/module/zfs/zle.c b/module/zfs/zle.c
new file mode 100644
index 000000000..13c5673fb
--- /dev/null
+++ b/module/zfs/zle.c
@@ -0,0 +1,86 @@
+/*
+ * 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);
+}