add direct char casting

src/vm.c

@@ -20,23 +20,10 @@ int core_dump(Data *memory, uint32_t memory_size) {
   return EXIT_SUCCESS;
 }
 
-uint8_t get_char(uint32_t word, int index) {
+/**
-  return (word >> (8 * index)) & 0xFF;
+ * String copy in data memory.
-}
+ */
-
+void mem_strcpy(Data *memory, const char *str, uint32_t length,
-uint32_t set_char(uint32_t word, int index, uint8_t ch) {
-  return (word & ~(0xFF << (8 * index))) | (ch << (8 * index));
-}
-
-void set_memory_char(Data *memory, uint8_t ch, uint32_t buffer_addr,
-                     uint32_t length) {
-  uint32_t word = memory[buffer_addr + (length / 4)].u;
-  word = set_char(word, length % 4, ch);
-  memory[buffer_addr + (length / 4)].u = word;
-}
-
-/* Pack string into union-based memory */
-void pack_string(Data *memory, const char *str, uint32_t length,
                  uint32_t dest_addr) {
   memory[dest_addr].u = length;
   uint32_t buffer_addr = dest_addr + 1;
@@ -46,7 +33,7 @@ void pack_string(Data *memory, const char *str, uint32_t length,
     if (ch == '\0') {
       break;
     }
-    set_memory_char(memory, ch, buffer_addr, i);
+    memory[buffer_addr + (i / 4)].c[i % 4] = ch;
     i++;
   }
 }
@@ -69,6 +56,8 @@ void run_vm(Data *memory, uint32_t memory_size) {
     }
 
     switch (opcode) {
+    case OP_HALT:
+      return;
     case OP_ADD:
       memory[dest_addr].u = memory[src1_addr].u + memory[src2_addr].u;
       break;
@@ -112,8 +101,6 @@ void run_vm(Data *memory, uint32_t memory_size) {
       memory[dest_addr].f = (float)memory[src1_addr].u;
       break;
     }
-    case OP_HALT:
-      return;
     case OP_MOV:
       memory[dest_addr] = memory[src1_addr];
       break;
@@ -133,28 +120,14 @@ void run_vm(Data *memory, uint32_t memory_size) {
       int32_t a = (int32_t)memory[src1_addr].u;
       char buffer[32];
       sprintf(buffer, "%d", a);
-      pack_string(memory, buffer, strlen(buffer), dest_addr);
+      mem_strcpy(memory, buffer, strlen(buffer), dest_addr);
       break;
     }
     case OP_F32_TO_STRING: {
       float a = memory[src1_addr].f;
       char buffer[32];
       sprintf(buffer, "%f", a);
-      pack_string(memory, buffer, strlen(buffer), dest_addr);
+      mem_strcpy(memory, buffer, strlen(buffer), dest_addr);
-      break;
-    }
-    case OP_PRINT_STRING: {
-      uint32_t string_addr = src1_addr;
-      uint32_t length = memory[src1_addr - 1].u;
-      uint32_t i;
-      for (i = 0; i < length; i++) {
-        uint32_t word = memory[string_addr + (i / 4)].u;
-        uint8_t ch = get_char(word, i % 4);
-        if (ch == '\0')
-          break;
-        putchar(ch);
-      }
-      putchar('\n');
       break;
     }
     case OP_READ_STRING: {
@@ -163,34 +136,47 @@ void run_vm(Data *memory, uint32_t memory_size) {
       while (1) {
         int ch = getchar();
         if (ch == '\n' || ch == EOF) {
-          set_memory_char(memory, '\0', buffer_addr, length);
+          memory[buffer_addr + (length / 4)].c[length % 4] = '\0';
           break;
         }
-        set_memory_char(memory, ch, buffer_addr, length);
+        memory[buffer_addr + (length / 4)].c[length % 4] = ch;
         length++;
       }
       memory[dest_addr].u = length;
       break;
     }
+    case OP_PRINT_STRING: {
+      uint32_t string_addr = src1_addr;
+      uint32_t length = memory[src1_addr - 1].u;
+      uint32_t i;
+      for (i = 0; i < length; i++) {
+        uint8_t ch = memory[string_addr + (i / 4)].c[i % 4];
+        if (ch == '\0')
+          break;
+        putchar(ch);
+      }
+      putchar('\n');
+      break;
+    }
     case OP_CMP_STRING: {
       uint32_t addr1 = src1_addr;
       uint32_t addr2 = src2_addr;
       uint32_t length1 = memory[src1_addr - 1].u;
       uint32_t length2 = memory[src2_addr - 1].u;
-      int equal = 1;
+      uint32_t equal = 1;
 
       if (length1 != length2) {
         equal = 0;
       } else {
         uint32_t i = 0;
         while (i < length1) {
-          uint32_t word1 = memory[addr1 + i].u;
+          uint32_t char1 = memory[addr1 + i].u;
-          uint32_t word2 = memory[addr2 + i].u;
+          uint32_t char2 = memory[addr2 + i].u;
-          if (word1 != word2) {
+          if (char1 != char2) {
             equal = 0;
             break;
           }
-          if ((word1 & 0xFF) == '\0' && (word2 & 0xFF) == '\0')
+          if ((char1 & 0xFF) == '\0' && (char2 & 0xFF) == '\0')
             break;
         }
       }

src/vm.h

@@ -6,6 +6,7 @@
 typedef union {
   float f;
   uint32_t u;
+  char c[4];
 } Data;
 
 typedef enum {