vsm

commit 1c106a53cf5cac8d322849f52aa8fa201366069d
parent 8388b8d04e1a9316dd73befe0bd5d56d541ef304
Author: Pavel Renev <an2qzavok@gmail.com>
Date:   Fri,  2 Apr 2021 22:17:20 +0000

vsm: fix IF instruction, add primitive I/O instructions

Diffstat:
M
vsm.c
 | 
40
++++++++++++++++++++++++++++------------
M
vsm.h
 | 
9
++++++++-

2 files changed, 36 insertions(+), 13 deletions(-)
diff --git a/vsm.c b/vsm.c
@@ -102,9 +102,8 @@ void i_LIT(void)
 /* Conditional Branching: */
 void i_IF(void)
 {
-	if (dsp == 0) pc = ram[pc];
-	else pc++;
-	dsp--;
+	if (*dsp == 0) pc = *(dsp - 1) - 1;
+	dsp -= 2;
 }
 
 /* Subroutine Calls: */
@@ -122,6 +121,18 @@ void i_EXIT(void)
 	rsp--;	
 }
 
+/* "Hardware" IO */
+
+void i_PUTC(void)
+{
+	write(1, dsp--, 1);
+}
+
+void i_GETC(void)
+{
+	read(0, ++dsp, 1);
+}
+
 instruction instructions[128] = {
 	[VSM_NOP] i_NOP,
 	[VSM_ADD] i_ADD,
@@ -141,6 +152,8 @@ instruction instructions[128] = {
 	[VSM_IF] i_IF,
 	[VSM_CALL] i_CALL,
 	[VSM_EXIT] i_EXIT,
+	[VSM_PUTC] i_PUTC,
+	[VSM_GETC] i_GETC,
 };
 
 /* VMS Control */
@@ -162,25 +175,28 @@ vsm_exec(CELL op)
 	pc++;
 }
 
-void
-vsm_halt(void)
-{
-}
 
 void
 vsm_run(void)
 {
+	CELL op;
 	for (;;) {
 		/* TODO: put more sanity checks here */
-		CELL op = ram[pc];
-		if (op >= NUM_OPS) {
-			fprint(2, "invalid op == %x\n", op);
-			vsm_halt();
+		if (dsp < dstack) {
+			fprint(2, "dstack underflow\n");
+			return;
+		}
+		if (rsp < rstack) {
+			fprint(2, "rstack underflow\n");
 			return;
 		}
 		if (pc >= IMAGE_SIZE) {
 			fprint(2, "pc reached end of the image\n");
-			vsm_halt();
+			return;
+		}
+		op = ram[pc];
+		if (op >= NUM_OPS) {
+			fprint(2, "invalid op == %x\n", op);
 			return;
 		}
 		vsm_exec(op);
diff --git a/vsm.h b/vsm.h
@@ -19,9 +19,12 @@ enum {
 	VSM_IF,
 /* Subroutine Calls: */
 	VSM_CALL, VSM_EXIT,
+/* "Hardware" IO: */
+	VSM_PUTC, VSM_GETC,
+/* this should be at the end of enum def: */
+	NUM_OPS,
 };
 
-#define NUM_OPS VSM_EXIT + 1
 
 CELL pc;
 CELL ir;
@@ -72,6 +75,10 @@ void i_IF(void);
 void i_CALL(void);
 void i_EXIT(void);
 
+/* "Hardware" IO */
+void i_PUTC(void);
+void i_GETC(void);
+
 /* VMS Control */
 
 void vsm_exec(CELL);