From ae8ba5d80beec27c9d2024cbd441820afee59d84 Mon Sep 17 00:00:00 2001
From: g1n <g1n@ttm.sh>
Date: Tue, 10 May 2022 17:28:29 +0300
Subject: [PATCH] common and ocpu: Implemented stack, added PUSH and POP
 instructions

---
 src/include/yemu/ocpu.h  |  2 ++
 src/include/yemu/stack.h | 10 ++++++++++
 src/ocpu/ocpu.c          | 16 ++++++++++++++++
 src/stack.c              | 37 +++++++++++++++++++++++++++++++++++++
 4 files changed, 65 insertions(+)
 create mode 100644 src/include/yemu/stack.h
 create mode 100644 src/stack.c

diff --git a/src/include/yemu/ocpu.h b/src/include/yemu/ocpu.h
index 89daeef..d2d47ff 100644
--- a/src/include/yemu/ocpu.h
+++ b/src/include/yemu/ocpu.h
@@ -61,6 +61,8 @@
 #define INS_NAND_REG 0xC5
 #define INS_CMP_IM 0x26
 #define INS_CMP_REG 0xC6
+#define INS_PUSH_IM 0x30
+#define INS_POP 0x31
 #define INS_OCPU_NOP 0x90
 #define INS_OCPU_SEC 0x61
 #define INS_OCPU_CLC 0x62
diff --git a/src/include/yemu/stack.h b/src/include/yemu/stack.h
new file mode 100644
index 0000000..afeb1b0
--- /dev/null
+++ b/src/include/yemu/stack.h
@@ -0,0 +1,10 @@
+#ifndef YEMU_STACK_H
+#define YEMU_STACK_H
+
+typedef int stack_t;
+
+int get_last_item_from_stack();
+int pop();
+void push(int value);
+
+#endif
diff --git a/src/ocpu/ocpu.c b/src/ocpu/ocpu.c
index c4a4fb5..c677d0d 100644
--- a/src/ocpu/ocpu.c
+++ b/src/ocpu/ocpu.c
@@ -1,8 +1,13 @@
 #include <yemu/ocpu.h>
+#include <yemu/stack.h>
 #include <stdbool.h>
+#include <stdlib.h>
 
 struct OCPU ocpu;
 struct OCPU_MEMORY ocpu_mem;
+int stack_size = 64000;
+stack_t *stack;
+byte *sp;
 
 void ocpu_memory_init () {
   for (int i = 0; i < MAX_MEMORY; i++){
@@ -448,6 +453,13 @@ void ocpu_execute() {
         ocpu.CF = 0;
       }
       break;
+    case INS_PUSH_IM:
+      push(ocpu_fetch_byte());
+      printf("STACK: push 0x%x to stack address 0x%x\n", get_last_item_from_stack(), ocpu.SP);
+      break;
+    case INS_POP:
+      printf("STACK: pop 0x%x from stack address 0x%x\n", pop(), ocpu.SP);
+      break;
     case INS_OCPU_NOP:
       break;
     case INS_OCPU_SEC:
@@ -469,6 +481,9 @@ void initOCPU(FILE *infile) {
   ocpu_reset();
   int ch;
   int pos = 0;
+  stack = malloc(stack_size*sizeof(byte));
+  ocpu.SP = 0;
+  sp = &ocpu.SP;
   while (1) { // FIXME
     ch = fgetc(infile);
     if (ch == EOF)
@@ -479,5 +494,6 @@ void initOCPU(FILE *infile) {
       
   ocpu_execute();
   ocpu_dump_ocpu(ocpu);
+  free(stack);
   return;
 }
diff --git a/src/stack.c b/src/stack.c
new file mode 100644
index 0000000..fbbb669
--- /dev/null
+++ b/src/stack.c
@@ -0,0 +1,37 @@
+#include <yemu/stack.h>
+#include <yemu/common.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+extern stack_t *stack;
+extern unsigned int stack_size;
+extern byte *sp;
+
+int get_last_item_from_stack() {
+  if ((int)(*sp) <= 0) {
+    printf("Stack Underflow\n");
+    return -1;
+  }
+  return stack[(*sp)];
+}
+
+void push(int value) {
+  if (*sp >= stack_size-1) {
+    printf("Stack Overflow\n");
+  } else {
+    (*sp)++;
+    stack[*sp] = value;
+  }
+}
+
+int pop() {
+  int value = -1;
+  if ((int)(*sp) <= 0) {
+    printf("Stack Underflow\n");
+  } else {
+    value = stack[*sp];
+    (*sp)--;
+  }
+  return value;
+}