Import ax25-apps 0.0.1 from tarballax25-apps-0.0.1

1 files changed, 38 insertions, 0 deletions

diff --git a/call/crc.c b/call/crc.c
new file mode 100644
index 0000000..637b0f5
--- /dev/null
+++ b/call/crc.c
@@ -0,0 +1,38 @@
+
+/* tnt: Hostmode Terminal for TNC
+   Copyright (C) 1993 by Mark Wahl
+   For license details see documentation
+   Procedures for autobin-checksum (crc.c)
+   created: Mark Wahl DL4YBG 94/01/17
+   updated: Mark Wahl DL4YBG 94/01/17
+*/
+
+static int crcbit[8] = {
+  0x9188,0x48c4,0x2462,0x1231,0x8108,0x4084,0x2042,0x1021
+                       };
+                       
+static int bittab[8] = { 128,64,32,16,8,4,2,1 };
+
+static int crctab[256];
+
+void init_crc(void)
+{
+  int i,j;
+  
+  for (i = 0; i < 256; i++) {
+    crctab[i] = 0;
+    for (j = 0; j < 8; j++) {
+      if ((bittab[j] & i) != 0) {
+        crctab[i] = crctab[i] ^ crcbit[j];
+      }
+    }
+  }
+}
+
+/* calculate checksum for autobin-protocol */
+unsigned int calc_crc(unsigned char* buf, int n, unsigned crc)
+{
+  while (--n >= 0)
+    crc = (crctab[(crc >> 8)] ^ ((crc << 8) | *buf++)) & 0xffff;
+  return crc;
+}