Port I/O tested; strip unstable again, commented out

Makefile

@@ -7,7 +7,7 @@ DFLAGS=
 
 desktopcc:
 	cc -std=c89 -Os -o $(PROJNAME) $(CFILES) $(DFLAGS)
-	strip $(PROJNAME)
+#	strip $(PROJNAME)
 
 tcc:
 	tcc -std=c89 -o $(PROJNAME) $(CFILES) $(DFLAGS)

README.md

@@ -132,7 +132,7 @@ Please also note that Equi doesn't specify any graphical or sound output capabil
 
 Being a purely PC-oriented low-level runtime/programming environment, Equi has the reference implementation emulator/VM written in C (ANSI C89 standard), `equi.c`, compilable and runnable on all the systems supporting standard I/O. Note that, for portability reasons, this emulator:
 
-- doesn't fully implement `P` instruction but instead outputs its parameters to the standard error stream and puts three 0x0000 values back onto the stack,
+- only implements three ports for `P` instruction: 0 as an echo port (returns passed parameters as corresponding result values), 1 as a random port (returns two random values in the results in the range between the two parameter values) and 2 as a CRC16 calculation port for a given memory location and its length, for any other port value it outputs its parameters to the standard error stream and puts three 0x0000 values back onto the stack,
 - doesn't implement non-blocking key input (the ',' instruction is identical to blocking key input instruction `?`),
 - sandboxes the `{` and `}` operations using the file you supply in the command-line parameter. If you don't supply the file, these operations will effectively do nothing except putting 0x0000 (success status) onto the stack.
 

equi.c

@@ -17,6 +17,7 @@
 #else
 #include <stdlib.h>
 #include <stdio.h>
+#include <time.h>
 #endif
 
 /*
@@ -206,6 +207,14 @@ enum EquiInstructions {
   INS_QUIT='Q'
 };
 
+/* Equi known ports enum */
+
+enum EquiPorts {
+  PORT_ECHO = 0x0, /* echo port, used for testing: R1=P1, R2=P2 */
+  PORT_RANDOM, /* RNG port: P1 = valueFrom, P2 = valueTo => R1=rand(from, to), R2 = rand(from, to) */ 
+  PORT_CHECKSUM /* checksum port: P1 = memAddr, P2 = length => R1=CRC16(memAddr, length), R2 = 0 */
+};
+
 /* push a value onto the main stack */
 void pushMain(ushort val) {
   ram.main_stack[ram.msp++] = val;
@@ -285,12 +294,36 @@ ushort crc16(const uchar* data_p, uchar length) {
   return crc;
 }
 
-/* persistent operation handler */
+/* Persistent operation handler */
 
 ushort persistOp(maddr, dataLen, adl, adh, isWrite) {
   return 0;
 }
 
+/* Port I/O handler */
+
+void portIO(port, p2, p1) {
+  ushort r1 = 0, r2 = 0, status = 0;
+  switch(port) {
+    case PORT_ECHO:
+      r1 = p1;
+      r2 = p2;
+      break;
+    case PORT_RANDOM:
+      r1 = (ushort) (p1 + (rand()%p2));
+      r2 = (ushort) (p1 + (rand()%p2));
+      break;
+    case PORT_CHECKSUM:
+      r1 = crc16(&flatram[p1], p2);
+      break;
+    default:
+      fprintf(stderr, "[PORTIO] Unimplemented call to port 0x%X with P1=%X and P2=%X, returning status=0, R1=0, R2=0\n", port, p1, p2);
+  }
+  pushMain(r1);
+  pushMain(r2);
+  pushMain(status);
+}
+
 /* Main interpreter loop */
 
 void equi_main_loop() {
@@ -490,13 +523,10 @@ void equi_main_loop() {
       case INS_BKIN: /* blocking key input (again, no Unicode support yet, assuming a single byte incoming to the 16-bit value on the stack) */
         pushMain((ushort)cgetc());
         break;
-      case INS_PORTIO: /* ( p1 p2 port -- r1 r2 status ) - simulate port I/O according to the spec */
-        pbuf = popMain(); /* port */
-        pbuf2 = popMain(); /* p2 */
-        fprintf(stderr, "[PORTIO ] Call to port 0x%X with P1=%X and P2=%X, returning status=0, R1=0, R2=0\n", pbuf, pbuf2, popMain());
-        pushMain(0u);
-        pushMain(0u);
-        pushMain(0u);
+      case INS_PORTIO: /* ( p1 p2 port -- r1 r2 status ) - simulate/execute port I/O according to the spec */
+        if(ram.msp < 3)
+          trapout(STACK_UNDERFLOW);
+        portIO(popMain(), popMain(), popMain());
         break;
       case INS_PERSIST_READ: /* ( adh adl len maddr -- status) */
         pushMain(persistOp(popMain(), popMain(), popMain(), popMain(), 0));
@@ -534,6 +564,8 @@ int main(int argc, char* argv[]) {
   setvbuf(stdin, NULL, _IONBF, 0);
   setvbuf(stdout, NULL, _IONBF, 0);
 #endif
+  /* initialize the PRNG */
+  srand((unsigned)time(NULL));
   /* initialize the RAM in the most standard way */
   ram.gpd_start = (uchar *)&ram.gpd - (uchar *)&ram.main_stack;
   ram.cmd_start = (uchar *)&ram.cmdbuf - (uchar *)&ram.main_stack;