+#ifdef ENABLE_TRACING
+extern volatile int cp_line[];
+extern volatile char *cp_file[];
+extern volatile int cp_index;
+extern void cp_trace(void);
+
+ #define cp { cp_line[cp_index] = __LINE__; cp_file[cp_index] = __FILE__; cp_index++; cp_index %= 16; }
+ #define ecp { fprintf(stderr, "Explicit checkpoint in %s line %d\n", __FILE__, __LINE__); }
+#else
+ #define cp
+ #define ecp
+ #define cp_trace()
+#endif
+
+extern void hex2bin(char *src, char *dst, int length);
+extern void bin2hex(char *src, char *dst, int length);