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authorVikas Gorur <vikas@gluster.com>2009-09-17 05:56:24 +0000
committerAnand V. Avati <avati@dev.gluster.com>2009-09-22 06:13:32 -0700
commit239d2cbdb0a4c32df9f21de8385e2c466b934178 (patch)
tree75f85e25d6aa79e9503b85ad637cd184d6f1801b /libglusterfs/src/checksum.c
parent0def744b2e66e81ac37532b26716e83d3b8bc9dd (diff)
libglusterfs: Add checksum functions.
gf_rsync_weak_checksum: Calculates a simple 32-bit checksum. gf_rsync_strong_checksum: Calculates the MD5 checksum. The strong checksum function makes use of Christophe Devine's MD5 implementation (adapted from the rsync source code, version 3.0.6. <http://www.samba.org/ftp/rsync/>). Signed-off-by: Anand V. Avati <avati@dev.gluster.com>
Diffstat (limited to 'libglusterfs/src/checksum.c')
-rw-r--r--libglusterfs/src/checksum.c78
1 files changed, 78 insertions, 0 deletions
diff --git a/libglusterfs/src/checksum.c b/libglusterfs/src/checksum.c
new file mode 100644
index 00000000000..2040fe73b79
--- /dev/null
+++ b/libglusterfs/src/checksum.c
@@ -0,0 +1,78 @@
+/*
+ Copyright (c) 2009 Z RESEARCH, Inc. <http://www.zresearch.com>
+ This file is part of GlusterFS.
+
+ GlusterFS is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published
+ by the Free Software Foundation; either version 3 of the License,
+ or (at your option) any later version.
+
+ GlusterFS is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see
+ <http://www.gnu.org/licenses/>.
+*/
+
+#include <inttypes.h>
+
+#include "glusterfs.h"
+#include "md5.h"
+#include "checksum.h"
+
+
+/*
+ * The "weak" checksum required for the rsync algorithm,
+ * adapted from the rsync source code. The following comment
+ * appears there:
+ *
+ * "a simple 32 bit checksum that can be upadted from either end
+ * (inspired by Mark Adler's Adler-32 checksum)"
+ */
+
+uint32_t
+gf_rsync_weak_checksum (char *buf1, int32_t len)
+{
+ int32_t i;
+ uint32_t s1, s2;
+
+ signed char *buf = (signed char *) buf1;
+ uint32_t csum;
+
+ s1 = s2 = 0;
+ for (i = 0; i < (len-4); i+=4) {
+ s2 += 4*(s1 + buf[i]) + 3*buf[i+1] + 2*buf[i+2] + buf[i+3];
+
+ s1 += buf[i+0] + buf[i+1] + buf[i+2] + buf[i+3];
+ }
+
+ for (; i < len; i++) {
+ s1 += buf[i];
+ s2 += s1;
+ }
+
+ csum = (s1 & 0xffff) + (s2 << 16);
+
+ return csum;
+}
+
+
+/*
+ * The "strong" checksum required for the rsync algorithm,
+ * adapted from the rsync source code.
+ */
+
+void
+gf_rsync_strong_checksum (char *buf, int32_t len, uint8_t *sum)
+{
+ md_context m;
+
+ md5_begin (&m);
+ md5_update (&m, (unsigned char *) buf, len);
+ md5_result (&m, (unsigned char *) sum);
+
+ return;
+}