vm.odin

package vm

import "core:fmt"

InstructionSet :: enum u8 {
	NOOP    = 0x00,
	LITERAL = 0x01,
	SUM     = 0x02,
	PRINT   = 0x03,
}

Stack :: struct($T: typeid, $N: uint = 128) {
	data:     [N]T,
	size:     uint,
}

stack_push :: proc(stack: ^Stack($T, $N), value: int) {
	assert(stack.size < N)
	stack.data[stack.size] = value
	stack.size += 1
}

stack_pop :: proc(stack: ^Stack($T, $N)) -> int {
	assert(stack.size > 0)
	stack.size -= 1
	ret := stack.data[stack.size]
	return ret
}

VM :: struct {
	code:  []u8,
	stack: Stack(int),
}

vm_interpret :: proc(vm: ^VM) {
	for i := 0; i < len(vm.code); i += 1 {
		bytecode := vm.code[i]
		switch InstructionSet(bytecode) {
		case InstructionSet.NOOP:
			continue
		case InstructionSet.LITERAL:
			val := vm.code[i + 1]
			stack_push(&vm.stack, int(val))
			i += 1
		case InstructionSet.SUM:
			val_1 := stack_pop(&vm.stack)
			val_2 := stack_pop(&vm.stack)
			stack_push(&vm.stack, val_1 + val_2)
		case InstructionSet.PRINT:
			fmt.println(stack_pop(&vm.stack))
		}
	}
}

main :: proc() {
	code := []u8 {
		u8(InstructionSet.LITERAL),
		10,
		u8(InstructionSet.LITERAL),
		10,
		u8(InstructionSet.SUM),
		u8(InstructionSet.PRINT),
	}

	stack: Stack(int)

	vm := VM {
		code  = code,
		stack = stack,
	}

	vm_interpret(&vm)
}