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vm.c

#include "vm.h"

#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <assert.h>

#define VM_REG_MASK (1<<31)
#define VM_CODE_MASK (1<<30)
#define VM_DATA_MASK ((1<<16)-1)

struct _vm_state {
	int regi[8];
	double regf[8];
	unsigned int code_len;
	int *code;
	unsigned int data_len;
	int *data;
	unsigned int iptr;
	unsigned int sptr;
	vm_interrupt_handler interrupt_table[VM_INTERRUPT_TABLE_SIZE];
};

vm_state vm_create_state(int *code, unsigned int code_len, unsigned int data_len) {
	vm_state s = malloc(sizeof(struct _vm_state));
	memset(s, 0, sizeof(struct _vm_state));
	s->code = code; // TODO: Create a copy?
	s->code_len = code_len;
	s->data_len = data_len;
	s->data = malloc(sizeof(int) * data_len);
	return s;
}

void *vm_decode_rm(vm_state s, unsigned int rm, bool write) {
	unsigned int data_val = rm & VM_DATA_MASK;
	if (rm & VM_REG_MASK) {
		assert(data_val < 16);
		return &s->regi[data_val];
	}
	if (rm & VM_CODE_MASK && !write) {
		assert(data_val < s->code_len);
		return &s->code[data_val];
	}
	assert(data_val < s->data_len);
	return s->data + data_val;
}

int vm_get_int(vm_state s, unsigned int ptr) {
	int *ret = vm_decode_rm(s, ptr, false);
	return *ret;
}

void vm_set_int(vm_state s, unsigned int ptr, int val) {
	int *ret = vm_decode_rm(s, ptr, true);
	*ret = val;
}