vm 0.1.0

A general purpose virtual machine
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82

use crate::error::Error;
use crate::instructions::{Execute, Operand};
use crate::processor::Processor;
use crate::register::{Flag, Width};
use crate::{
    assign_memory_value, assign_memory_value_by_width, assign_register_value, get_memory_value,
    get_memory_value_by_width, get_register_value,
};

#[derive(Debug, Default)]
/// Add two operands and store the result in the destination.
pub struct Sub {
    value: Operand,
    source: Operand,
    destination: Operand,
}

impl Sub {
    #[must_use]
    /// Constructs a new [`Sub`].
    pub fn new(value: Operand, source: Operand, destination: Operand) -> Self {
        Sub {
            value,
            source,
            destination,
        }
    }
}

impl Execute for Sub {
    fn execute(&self, processor: &mut Processor) -> Result<(), Error> {
        let source = match self.source {
            Operand::Value(value) => value,
            Operand::Register(ref register) => get_register_value!(processor, register),
            Operand::Memory(ref memory) => get_memory_value_by_width!(processor, memory),
            Operand::MemoryRegister(ref memory_register) => {
                let address = get_register_value!(processor, memory_register);

                get_memory_value!(processor, memory_register, address as usize)
            }

            _ => return Err(Error::InvalidOperand),
        };

        let value = match self.value {
            Operand::Value(value) => value,
            Operand::Register(ref register) => get_register_value!(processor, register),
            Operand::Memory(ref memory) => get_memory_value_by_width!(processor, memory),
            Operand::MemoryRegister(ref memory_register) => {
                let address = get_register_value!(processor, memory_register);

                get_memory_value!(processor, memory_register, address as usize)
            }

            _ => return Err(Error::InvalidOperand),
        };

        let result = source.overflowing_sub(value);

        if let (_, true) = result {
            processor.set_flag(Flag::Overflow, true);
        }

        match self.destination {
            Operand::Register(ref register) => {
                assign_register_value!(processor, register, result.0)
            }
            Operand::Memory(ref memory) => {
                assign_memory_value_by_width!(processor, memory, result.0)
            }
            Operand::MemoryRegister(ref memory_register) => {
                let memory = get_register_value!(processor, memory_register);

                assign_memory_value!(processor, memory_register, memory as usize, result.0)
            }

            _ => return Err(Error::InvalidOperand),
        }

        Ok(())
    }
}