Split vm/runtime.c into two files

struct.c is used for the general construction, inspection and deletion
of the virtual machine structure (vm_t).  runtime defines the
execution routines, error enum, lookup tables, etc.

vm/struct.h

@@ -0,0 +1,69 @@
+/* Copyright (C) 2024 Aryadev Chavali
+
+ * You may distribute and modify this code under the terms of the
+ * GPLv2 license.  You should have received a copy of the GPLv2
+ * license with this file.  If not, please write to:
+ * aryadev@aryadevchavali.com.
+
+ * Created: 2024-04-25
+ * Author: Aryadev Chavali
+ * Description: Virtual machine data structures and some helpers
+ */
+
+#ifndef STRUCT_H
+#define STRUCT_H
+
+#include <lib/darr.h>
+#include <lib/heap.h>
+#include <lib/inst.h>
+
+typedef darr_t registers_t;
+#define VM_NTH_REGISTER(REGISTERS, N)     (((word *)((REGISTERS).data))[N])
+#define VM_REGISTERS_AVAILABLE(REGISTERS) (((REGISTERS).available) / WORD_SIZE)
+
+struct Stack
+{
+  byte *data;
+  size_t ptr, max;
+};
+
+struct Program
+{
+  prog_t *data;
+  word ptr;
+};
+
+struct CallStack
+{
+  word *address_pointers;
+  size_t ptr, max;
+};
+
+typedef struct
+{
+  registers_t registers;
+  struct Stack stack;
+  heap_t heap;
+
+  struct CallStack call_stack;
+  struct Program program;
+} vm_t;
+
+// Start and stop
+void vm_load_stack(vm_t *, byte *, size_t);
+void vm_load_registers(vm_t *, registers_t);
+void vm_load_heap(vm_t *, heap_t);
+void vm_load_program(vm_t *, prog_t *);
+void vm_load_call_stack(vm_t *, word *, size_t);
+void vm_stop(vm_t *);
+
+// Printing the VM
+#define VM_PRINT_PROGRAM_EXCERPT 5
+void vm_print_registers(vm_t *, FILE *);
+void vm_print_stack(vm_t *, FILE *);
+void vm_print_program(vm_t *, FILE *);
+void vm_print_heap(vm_t *, FILE *);
+void vm_print_call_stack(vm_t *, FILE *);
+void vm_print_all(vm_t *, FILE *);
+
+#endif