1 files changed, 29 insertions, 0 deletions

diff --git a/src/inc/stdalg.c b/src/inc/stdalg.c
new file mode 100755
index 0000000..99558a9
--- /dev/null
+++ b/src/inc/stdalg.c
@@ -0,0 +1,29 @@
+#include "stdalg.h"
+
+#ifdef STDALGO_CRC7
+  unsigned char crc7(unsigned char* bytes, unsigned char size)
+  {
+    register unsigned char val = 0; // last cycles value
+    register unsigned char cb;      // current byte.
+
+    unsigned char i;
+    for(i=0; i<=size; i++)
+    {
+      cb = bytes[i];
+
+      int q = (i==size) ? 7 : 8; // counter
+      do
+      {
+        val <<= 1;
+        if(cb & 0x80)         // check MSB of current byte
+          ++val;              // overflow, add 1
+
+        if(val & 0x80)        // check MSB of (last) seed
+          val ^= 0x9;         // polynome
+        cb     <<= 1;
+      } while(--q);
+      val &= 0x7f;            // lower 7 bits
+    }
+    return ((val<<1) + 1);
+  }
+#endif