Micro VM sandbox + CLI

WormBox.cpp

typedef unsigned char byte;

byte memory[byte(-1)+1]; // global 8-bit memory pool

struct { char name[32]; void(*fn)(byte&); }

const instructions[byte(-1)+1] =
{ 
	{ "NOP", [](byte&) {} },

	{ "INC <%i>", [](byte& b) {
		byte addr1 = b + memory[b++];
		memory[addr1]++; } 
	},

	{ "JMP <%i>", [](byte& b) { b += memory[b]; } },

	{ "SET [%i] at <%i>", [](byte& b) {
		byte val = memory[b++];
		memory[memory[b++]] = val;
	} },

	{ "CPY from <%i> to <%i>", [](byte& b) {
		byte addr1 = memory[b++] + b;
		byte addr2 = memory[b++] + b;
		memory[addr2] = memory[addr1];
	} },

};

void step(byte& counter)
{
	if (auto fn = instructions[memory[counter]].fn)
		fn(++counter);
}


enum : byte {NOP, INC, JMP, SET, CPY};

const byte worm1[] = { INC, 2, INC, 2, JMP };
const byte worm2[] = { CPY, 1, 5, INC, -2, JMP, -6 };

byte counters[] = { 0 };


#include <Windows.h>
#include <stdio.h>

void print()
{
	SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE), {});

	for (int i = 0; i != 16; i++) printf("%5X", i); putchar('\n');
	for (int j = 0; j != 16; j++)
	{
		printf("%X", j);
		for (int i = 0; i != 16; i++)
		{
			byte id = i + 16 * j;
			byte m = memory[id];
			printf("  %c%2hhX", (id == *counters) ? '>' : ' ', m);
		}
		putchar('\n');
	}

	for (auto& counter : counters)
	{
		printf("#%i @%02X: ", &counter - counters, counter);
		if (auto name = instructions[memory[counter]].name) if (*name)
		{
			char arg1 = memory[byte(counter + 1)];
			char arg2 = memory[byte(counter + 2)];
			printf(name, arg1, arg2, 0, 0, 0);
		}
		else puts("INVALID INSTRUCTION");
		puts("                       \r");
	}
}

template<byte N>
byte write(const byte(&worm)[N], byte offset)
{
	for (auto w : worm) memory[offset++] = w;
	return offset;
}

#define pressed(X) (GetAsyncKeyState(X) & 1)

void main()
{
	write(worm2, counters[0]);
	puts("hold SPACE to step");
	const CONSOLE_CURSOR_INFO cursor = {0, FALSE};
	SetConsoleCursorInfo(GetStdHandle(STD_OUTPUT_HANDLE), &cursor);

	print();

	while (!pressed(VK_ESCAPE)) for (auto& counter : counters)
	{
		if (pressed(VK_SPACE)) step(counter);
		else if (pressed(VK_PRIOR)) memory[counter]++;
		else if (pressed(VK_NEXT)) memory[counter]--;
		else if (pressed(VK_LEFT)) counter--;
		else if (pressed(VK_RIGHT)) counter++;
		else if (pressed(VK_UP)) counter-=16;
		else if (pressed(VK_DOWN)) counter+=16;
		else
		{
			Sleep(20);
			continue;
		}
		print();
	}
}