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| author | Jeffrey Armstrong <jeffrey.armstrong@approximatrix.com> | 2015-10-09 10:34:49 -0400 |
|---|---|---|
| committer | Jeffrey Armstrong <jeffrey.armstrong@approximatrix.com> | 2015-10-09 10:34:49 -0400 |
| commit | 8b756e368a33a02d7783053b84bc1e5b50419ff0 (patch) | |
| tree | 658a81b96d4522fe3b7e0b33661dc265dbc968e8 /client/f16.c | |
| download | rback-master.tar.gz rback-master.zip | |
Diffstat (limited to 'client/f16.c')
| -rw-r--r-- | client/f16.c | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/client/f16.c b/client/f16.c new file mode 100644 index 0000000..2fd05f9 --- /dev/null +++ b/client/f16.c @@ -0,0 +1,73 @@ +/* Recursive Walking Backup
+ * Copyright © 2015 Jeffrey Armstrong <jeff@rainbow-100.com>
+ * http://jeff.rainbow-100.com/
+ *
+ * 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 3 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, see <http://www.gnu.org/licenses/>.
+ */
+
+/* f16.c - Implementation of a Fletcher 16-bit checksum. The file also
+ * contains a simple test program that can be enabled by defining
+ * TEST_FLETCHER at compile time.
+ */
+
+#include <stdio.h>
+
+/* Computes the Fletcher 16-bit checksum and returns the value in the
+ * b1 and b2 arguments.
+ */
+void fletcher16(unsigned char *data,
+ int n,
+ unsigned char *b1,
+ unsigned char *b2)
+{
+int c1, c2;
+int i;
+int toint;
+
+ c1 = 0; c2 = 0;
+ for(i=0;i<n;i++) {
+ toint = (int)data[i];
+ c1 = (c1 + toint) % 255;
+ c2 = (c2 + c1) % 255;
+ }
+
+ i = (255 - (c1 + c2) % 255);
+ *b1 = (int)i;
+ *b2 = (char)(255 - (c1 + i) % 255);
+}
+
+#ifdef TEST_FLETCHER
+
+#define TEST_STR "The IBM PC/XT is inferior"
+int main(int argc, char *argv[])
+{
+char b1, b2;
+FILE *fp;
+char buf[64];
+int i;
+
+ if(argc > 2) {
+ fletcher16(TEST_STR, strlen(TEST_STR), &b1, &b2);
+ printf("Results for '%s': %d, %d\n", TEST_STR, (int)b1, (int)b2);
+ } else {
+ fp = fopen(argv[1], "rb");
+ fread(buf, sizeof(char), 64, fp);
+ fletcher16(buf, 64, &b1, &b2);
+ printf("Results for 1st 64 bytes: %d, %d\n", (int)b1, (int)b2);
+ fclose(fp);
+ }
+ return (int)b1;
+}
+
+#endif
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