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>

1 files changed, 78 insertions, 0 deletions

diff --git a/libglusterfs/src/checksum.c b/libglusterfs/src/checksum.c
new file mode 100644
index 000000000..2040fe73b
--- /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;
+}