1 files changed, 50 insertions, 0 deletions
diff --git a/src/firecode.c b/src/firecode.c
new file mode 100644
index 0000000..47ee976
--- /dev/null
+++ b/src/firecode.c
@@ -0,0 +1,50 @@
+/*
+    Copyright (C) 2014 Matthias P. Braendli (http://www.opendigitalradio.org)
+
+    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/>.
+
+    firecode.c
+         Implement a FireCode CRC calculator
+
+    Authors:
+         Matthias P. Braendli <matthias@mpb.li>
+*/
+
+#include "firecode.h"
+
+uint16_t firecode_crc(uint8_t* buf, size_t size)
+{
+    int crc;
+    int gen_poly;
+
+    crc = 0x0000;
+    gen_poly = 0x782F;	// 0111 1000 0010 1111 (16, 14, 13, 12, 11, 5, 3, 2, 1, 0)
+
+    for (size_t len = 0; len < size; len++) {
+        for (int i = 0x80; i != 0; i >>= 1) {
+            if ((crc & 0x8000) != 0) {
+                crc = (crc << 1) ^ gen_poly;
+            }
+            else {
+                crc = crc << 1;
+            }
+            if ((buf[len] & i) != 0) {
+                crc ^= gen_poly;
+            }
+        }
+    }
+
+    return crc & 0xFFFF;
+}
+