1 files changed, 78 insertions, 0 deletions
diff --git a/checksum.c b/checksum.c
new file mode 100644
index 00000000..cdd554fd
--- /dev/null
+++ b/checksum.c
@@ -0,0 +1,78 @@
+/* 
+   Copyright (C) Andrew Tridgell 1996
+   Copyright (C) Paul Mackerras 1996
+   
+   This program 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 2 of the License, or
+   (at your option) any later version.
+   
+   This program 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, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include "rsync.h"
+
+
+/*
+  a simple 32 bit checksum that can be upadted from either end
+  (inspired by Mark Adler's Adler-32 checksum)
+  */
+uint32 get_checksum1(char *buf,int len)
+{
+    int i;
+    uint32 s1, s2;
+
+    s1 = s2 = 0;
+    for (i = 0; i < len; i++) {
+	s1 += buf[i];
+	s2 += s1;
+    }
+    return (s1 & 0xffff) + (s2 << 16);
+}
+
+
+void get_checksum2(char *buf,int len,char *sum)
+{
+  char buf2[64];
+  int i;
+  MDstruct MD;
+
+  MDbegin(&MD);
+  for(i = 0; i + 64 <= len; i += 64) {
+    bcopy(buf+i,buf2,64);
+    MDupdate(&MD, buf2, 512);
+  }
+  bcopy(buf+i,buf2,len-i);
+  MDupdate(&MD, buf2, (len-i)*8);
+  SIVAL(sum,0,MD.buffer[0]);
+  SIVAL(sum,4,MD.buffer[1]);
+  SIVAL(sum,8,MD.buffer[2]);
+  SIVAL(sum,12,MD.buffer[3]);
+}
+
+void file_checksum(char *fname,char *sum,off_t size)
+{
+  char *buf;
+  int fd;
+  bzero(sum,SUM_LENGTH);
+
+  fd = open(fname,O_RDONLY);
+  if (fd == -1) return;
+
+  buf = map_file(fd,size);
+  if (!buf) {
+    close(fd);
+    return;
+  }
+
+  get_checksum2(buf,size,sum);
+  close(fd);
+  unmap_file(buf,size);
+}