refactor to step intead of loop

src/main.c

@@ -1,13 +1,24 @@
-#include "vm.h"
 #include "debug.h"
+#include "vm.h"
 
 /* #define MEMORY_SIZE 65536 /\* 64KB memory (adjustable) *\/ */
 #define MEMORY_SIZE 1024
 
+void run_vm(Data *memory, uint32_t memory_size) {
+  uint32_t pc = 1; /* Program counter */
+  while (pc) {
+    pc = step_vm(memory, memory_size, pc);
+  }
+}
+
 int main() {
   Data memory[MEMORY_SIZE] = {0}; /* Memory array */
 
-  int i = 0;
+  int i = 1;
+  memory[0].c[0] = 'z';
+  memory[0].c[1] = '0';
+  memory[0].c[2] = '0';
+  memory[0].c[3] = '0';
   memory[i++].u = OP_ADD_REAL;
   memory[i++].u = 102;
   memory[i++].u = 103;
@@ -19,27 +30,27 @@ int main() {
   memory[i++].u = OP_JGT_INT;
   memory[i++].u = 100;
   memory[i++].u = 99;
-  memory[i++].u = 0;
+  memory[i++].u = 1;
   memory[i++].u = OP_REAL_TO_INT;
   memory[i++].u = 103;
-  memory[i++].u = 0;
+  memory[i++].u = 1;
   memory[i++].u = 103;
   memory[i++].u = OP_INT_TO_STRING;
   memory[i++].u = 103;
-  memory[i++].u = 0;
+  memory[i++].u = 1;
   memory[i++].u = 104;
   memory[i++].u = OP_PRINT_STRING;
   memory[i++].u = 105;
-  memory[i++].u = 0;
+  memory[i++].u = 1;
-  memory[i++].u = 0;
+  memory[i++].u = 1;
   memory[i++].u = OP_READ_STRING;
-  memory[i++].u = 0;
+  memory[i++].u = 1;
-  memory[i++].u = 0;
+  memory[i++].u = 1;
   memory[i++].u = 109;
   memory[i++].u = OP_PRINT_STRING;
   memory[i++].u = 110;
-  memory[i++].u = 0;
+  memory[i++].u = 1;
-  memory[i++].u = 0;
+  memory[i++].u = 1;
   memory[i++].u = OP_HALT;
   memory[i++].u = 0;
   memory[i++].u = 0;

src/vm.c

@@ -9,22 +9,16 @@ void mem_strcpy(Data *memory, const char *str, uint32_t length,
                 uint32_t dest_addr) {
   memory[dest_addr].u = length;
   uint32_t buffer_addr = dest_addr + 1;
-  uint32_t i = 0;
+  uint32_t i;
-  while (i < length) {
+  for (i = 0; i < length; i++) {
-    char ch = str[i];
+    memory[buffer_addr + (i / 4)].c[i % 4] = str[i];
-    if (ch == '\0') {
-      break;
-    }
-    memory[buffer_addr + (i / 4)].c[i % 4] = ch;
-    i++;
   }
 }
 
-void run_vm(Data *memory, uint32_t memory_size) {
+/**
-  uint32_t pc = 0; /* Program counter */
+ * Step to the next opcode in the vm.
-
+ */
-  while (pc < memory_size - 4) {
+uint32_t step_vm(Data *memory, uint32_t memory_size, uint32_t pc) {
-
   Opcode opcode = memory[pc].u;
   uint32_t src1_addr = memory[pc + 1].u;
   uint32_t src2_addr = memory[pc + 2].u;
@@ -34,68 +28,76 @@ void run_vm(Data *memory, uint32_t memory_size) {
   if (src1_addr >= memory_size || src2_addr >= memory_size ||
       dest_addr >= memory_size) {
     printf("Invalid memory address!\n");
-      exit(1);
+    return 0;
   }
 
   switch (opcode) {
   case OP_HALT:
-      return;
+    return 0;
   case OP_ADD:
     memory[dest_addr].u = memory[src1_addr].u + memory[src2_addr].u;
-      break;
+    return pc;
 
   case OP_SUB:
     memory[dest_addr].u = memory[src1_addr].u - memory[src2_addr].u;
-      break;
+    return pc;
 
   case OP_MUL:
     memory[dest_addr].u = memory[src1_addr].u * memory[src2_addr].u;
-      break;
+    return pc;
 
   case OP_DIV:
     memory[dest_addr].u = memory[src1_addr].u / memory[src2_addr].u;
-      break;
+    return pc;
 
   case OP_ADD_REAL:
     memory[dest_addr].f = memory[src1_addr].f + memory[src2_addr].f;
-      break;
+    return pc;
 
   case OP_SUB_REAL:
     memory[dest_addr].f = memory[src1_addr].f - memory[src2_addr].f;
-      break;
+    return pc;
 
   case OP_MUL_REAL:
     memory[dest_addr].f = memory[src1_addr].f * memory[src2_addr].f;
-      break;
+    return pc;
 
   case OP_DIV_REAL:
     if (memory[src2_addr].f == 0.0f) {
       printf("Division by zero error at address %d\n", pc - 4);
-        exit(1);
+      return 0;
     }
     memory[dest_addr].f = memory[src1_addr].f / memory[src2_addr].f;
-      break;
+    return pc;
   case OP_REAL_TO_INT: {
     memory[dest_addr].u = (uint32_t)memory[src1_addr].f;
-      break;
+    return pc;
   }
   case OP_INT_TO_REAL: {
     memory[dest_addr].f = (float)memory[src1_addr].u;
-      break;
+    return pc;
   }
   case OP_MOV:
     memory[dest_addr] = memory[src1_addr];
-      break;
+    return pc;
   case OP_JMP:
     pc = src1_addr; /* Jump to address */
-      break;
+    return pc;
+  case OP_JEQ_INT: {
+    uint32_t value = memory[src1_addr].u;
+    uint32_t value2 = memory[src2_addr].u;
+    uint32_t jump_target = dest_addr;
+
+    pc = (value == value2) ? jump_target : pc;
+    return pc;
+  }
   case OP_JGT_INT: {
     uint32_t value = memory[src1_addr].u;
     uint32_t value2 = memory[src2_addr].u;
     uint32_t jump_target = dest_addr;
 
     pc = (value > value2) ? jump_target : pc;
-      break;
+    return pc;
   }
   case OP_JLT_INT: {
     uint32_t value = memory[src1_addr].u;
@@ -103,47 +105,7 @@ void run_vm(Data *memory, uint32_t memory_size) {
     uint32_t jump_target = dest_addr;
 
     pc = (value < value2) ? jump_target : pc;
-      break;
+    return pc;
-    }
-    case OP_JEQ_REAL: {
-      float value = memory[src1_addr].f;
-      float value2 = memory[src2_addr].f;
-      uint32_t jump_target = dest_addr;
-
-      pc = (value == value2) ? jump_target : pc;
-      break;
-    }
-    case OP_JGT_REAL: {
-      float value = memory[src1_addr].f;
-      float value2 = memory[src2_addr].f;
-      uint32_t jump_target = dest_addr;
-
-      pc = (value > value2) ? jump_target : pc;
-      break;
-    }
-    case OP_JLT_REAL: {
-      float value = memory[src1_addr].f;
-      float value2 = memory[src2_addr].f;
-      uint32_t jump_target = dest_addr;
-
-      pc = (value < value2) ? jump_target : pc;
-      break;
-    }
-    case OP_JEQ_INT: {
-      uint32_t value = memory[src1_addr].u;
-      uint32_t value2 = memory[src2_addr].u;
-      uint32_t jump_target = dest_addr;
-
-      pc = (value == value2) ? jump_target : pc;
-      break;
-    }
-    case OP_JGE_INT: {
-      uint32_t value = memory[src1_addr].u;
-      uint32_t value2 = memory[src2_addr].u;
-      uint32_t jump_target = dest_addr;
-
-      pc = (value >= value2) ? jump_target : pc;
-      break;
   }
   case OP_JLE_INT: {
     uint32_t value = memory[src1_addr].u;
@@ -151,7 +113,39 @@ void run_vm(Data *memory, uint32_t memory_size) {
     uint32_t jump_target = dest_addr;
 
     pc = (value <= value2) ? jump_target : pc;
-      break;
+    return pc;
+  }
+  case OP_JGE_INT: {
+    uint32_t value = memory[src1_addr].u;
+    uint32_t value2 = memory[src2_addr].u;
+    uint32_t jump_target = dest_addr;
+
+    pc = (value >= value2) ? jump_target : pc;
+    return pc;
+  }
+  case OP_JEQ_REAL: {
+    float value = memory[src1_addr].f;
+    float value2 = memory[src2_addr].f;
+    uint32_t jump_target = dest_addr;
+
+    pc = (value == value2) ? jump_target : pc;
+    return pc;
+  }
+  case OP_JGT_REAL: {
+    float value = memory[src1_addr].f;
+    float value2 = memory[src2_addr].f;
+    uint32_t jump_target = dest_addr;
+
+    pc = (value > value2) ? jump_target : pc;
+    return pc;
+  }
+  case OP_JLT_REAL: {
+    float value = memory[src1_addr].f;
+    float value2 = memory[src2_addr].f;
+    uint32_t jump_target = dest_addr;
+
+    pc = (value < value2) ? jump_target : pc;
+    return pc;
   }
   case OP_JGE_REAL: {
     float value = memory[src1_addr].f;
@@ -159,7 +153,7 @@ void run_vm(Data *memory, uint32_t memory_size) {
     uint32_t jump_target = dest_addr;
 
     pc = (value >= value2) ? jump_target : pc;
-      break;
+    return pc;
   }
   case OP_JLE_REAL: {
     float value = memory[src1_addr].f;
@@ -167,21 +161,21 @@ void run_vm(Data *memory, uint32_t memory_size) {
     uint32_t jump_target = dest_addr;
 
     pc = (value <= value2) ? jump_target : pc;
-      break;
+    return pc;
   }
   case OP_INT_TO_STRING: {
     int32_t a = (int32_t)memory[src1_addr].u;
     char buffer[32];
     sprintf(buffer, "%d", a);
     mem_strcpy(memory, buffer, strlen(buffer), dest_addr);
-      break;
+    return pc;
   }
   case OP_REAL_TO_STRING: {
     float a = memory[src1_addr].f;
     char buffer[32];
     sprintf(buffer, "%f", a);
     mem_strcpy(memory, buffer, strlen(buffer), dest_addr);
-      break;
+    return pc;
   }
   case OP_READ_STRING: {
     uint32_t buffer_addr = dest_addr + 1;
@@ -196,7 +190,7 @@ void run_vm(Data *memory, uint32_t memory_size) {
       length++;
     }
     memory[dest_addr].u = length;
-      break;
+    return pc;
   }
   case OP_PRINT_STRING: {
     uint32_t string_addr = src1_addr;
@@ -209,7 +203,7 @@ void run_vm(Data *memory, uint32_t memory_size) {
       putchar(ch);
     }
     putchar('\n');
-      break;
+    return pc;
   }
   case OP_CMP_STRING: {
     uint32_t addr1 = src1_addr;
@@ -230,15 +224,12 @@ void run_vm(Data *memory, uint32_t memory_size) {
 	  break;
         }
         if ((char1 & 0xFF) == '\0' && (char2 & 0xFF) == '\0')
-            break;
+          return pc;
       }
     }
     memory[dest_addr].u = equal;
-      break;
+    return pc;
-    }
-    default:
-      printf("Unknown opcode: %d\n", opcode);
-      return;
   }
   }
+  return 0;
 }

src/vm.h

@@ -40,6 +40,6 @@ typedef enum {
   OP_CMP_STRING,     /* dest = src1 */
 } Opcode;
 
-void run_vm(Data *memory, uint32_t memory_size);
+uint32_t step_vm(Data *memory, uint32_t memory_size, uint32_t pc);
 
 #endif