From: ian <ian>
Date: Wed, 5 Jan 2005 00:38:07 +0000 (+0000)
Subject: generate nmra checksums
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ijackson/git?a=commitdiff_plain;h=774102c2f858e1de3bad1a366f1eab587acbb230;p=trains.git

generate nmra checksums
---

diff --git a/hostside/hostside.h b/hostside/hostside.h
index 279bae8..8e5dfe6 100644
--- a/hostside/hostside.h
+++ b/hostside/hostside.h
@@ -8,10 +8,11 @@ typedef unsigned char Byte;
 #define COMMAND_ENCODED_MAX 16
 #define NMRA_PACKET_MAX ((COMMAND_ENCODED_MAX*7 - 14) / 8)
 
-void nmra_transmit(const Byte *nmra_packet, int length);
+void xmit_nmra_raw(const Byte *with_csum, int length);
+void xmit_nmra(const Byte *without_csum, int length);
+void xmit_command(const Byte *command, int length);
 
 void sysfatal(const char *m);
 void serial_open(const char *device);
-void command_transmit(const Byte *command, int length);
 
 #endif /*HOSTSIDE_H*/
diff --git a/hostside/main.c b/hostside/main.c
index 186bc1c..dab5244 100644
--- a/hostside/main.c
+++ b/hostside/main.c
@@ -19,7 +19,8 @@ int main(int argc, const char **argv) {
   char hbuf[3], *ep;
   Byte buf[NMRA_PACKET_MAX + COMMAND_ENCODED_MAX];
   
-  assert(argc==3 || (argc==4 && !strcmp(argv[3],"command")));
+  assert(argc==4);
+  assert(argv[3]);
   serial_open(argv[1]);
 
   l= strlen(argv[2]);
@@ -35,10 +36,12 @@ int main(int argc, const char **argv) {
     assert(ep==&hbuf[2]);
   }
 
-  if (argc==4)
-    command_transmit(buf,l);
-  else
-    nmra_transmit(buf,l);
+  switch (argv[3][0]) {
+  case 'c': xmit_command(buf,l);  break;
+  case 'r': xmit_nmra_raw(buf,l); break;
+  case 'n': xmit_nmra(buf,l);     break;
+  default: abort();
+  }
 
   return 0;
 }
diff --git a/hostside/nmra.c b/hostside/nmra.c
index 7c48f46..e6697da 100644
--- a/hostside/nmra.c
+++ b/hostside/nmra.c
@@ -4,7 +4,7 @@
 
 #include "hostside.h"
 
-void nmra_transmit(const Byte *nmra_packet, int length) {
+void xmit_nmra_raw(const Byte *nmra_packet, int length) {
   Byte encoded[COMMAND_ENCODED_MAX], *encp;
   unsigned working, newbits;
   int working_qty;
@@ -43,5 +43,22 @@ void nmra_transmit(const Byte *nmra_packet, int length) {
   assert(encp > encoded);
   encp[-1] |= 0x80; /* `end of command' bit */
 
-  command_transmit(encoded, encp - encoded);
+  xmit_command(encoded, encp - encoded);
+}
+
+void xmit_nmra(const Byte *without_csum, int length) {
+  Byte with_csum[NMRA_PACKET_MAX];
+  const Byte *in;
+  Byte *out;
+  int left;
+  unsigned running;
+
+  assert(length >=0 && length < sizeof(with_csum));
+  for (left=length, running=0, in=without_csum, out=with_csum;
+       left>0;
+       in++, out++, left--)
+    running ^= (*out = *in);
+
+  *out= running;
+  xmit_nmra_raw(with_csum, length+1);
 }
diff --git a/hostside/serialio.c b/hostside/serialio.c
index 5502a21..b4bd7fb 100644
--- a/hostside/serialio.c
+++ b/hostside/serialio.c
@@ -22,7 +22,7 @@ void serial_open(const char *device) {
   if (serial_fd<0) sysfatal(device);
 }
 
-void command_transmit(const Byte *command, int length) {
+void xmit_command(const Byte *command, int length) {
   int r;
   assert(length <= COMMAND_ENCODED_MAX);