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284 lines
11 KiB
Rust
284 lines
11 KiB
Rust
// Copyright (C) 2014 The 6502-rs Developers
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions
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// are met:
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// 1. Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// 2. Redistributions in binary form must reproduce the above copyright
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// notice, this list of conditions and the following disclaimer in the
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// documentation and/or other materials provided with the distribution.
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// 3. Neither the names of the copyright holders nor the names of any
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// contributors may be used to endorse or promote products derived from this
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// software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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// POSSIBILITY OF SUCH DAMAGE.
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use log;
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use std;
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use address::{AddressDiff};
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use instruction;
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use instruction::{DecodedInstr};
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use memory::Memory;
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use registers::{ Registers, Status, StatusArgs };
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use registers::{ ps_negative, ps_overflow, ps_zero, ps_carry };
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pub struct Machine {
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pub registers: Registers,
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pub memory: Memory
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}
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impl Machine {
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pub fn new() -> Machine {
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Machine{
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registers: Registers::new(),
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memory: Memory::new()
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}
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}
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pub fn reset(&mut self) {
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*self = Machine::new();
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}
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pub fn fetch_next_and_decode(&mut self) -> Option<DecodedInstr> {
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let x: u8 = self.memory.get_byte(self.registers.program_counter);
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match instruction::OPCODES[x as uint] {
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Some((instr, am)) => {
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let extra_bytes = am.extra_bytes();
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let num_bytes = AddressDiff(1) + extra_bytes;
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let data_start = self.registers.program_counter
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+ AddressDiff(1);
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let slice = self.memory.get_slice(data_start, extra_bytes);
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let am_out = am.process(self, slice);
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// Increment program counter
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self.registers.program_counter =
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self.registers.program_counter + num_bytes;
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Some((instr, am_out))
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}
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_ => None
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}
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}
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pub fn execute_instruction(&mut self, decoded_instr: DecodedInstr) {
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match decoded_instr {
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(instruction::ADC, instruction::UseImmediate(val)) => {
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log!(log::DEBUG, "add with carry immediate: {}", val);
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self.add_with_carry(val as i8);
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},
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(instruction::ADC, instruction::UseAddress(addr)) => {
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let val = self.memory.get_byte(addr) as i8;
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log!(log::DEBUG, "add with carry. address: {}. value: {}",
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addr, val);
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self.add_with_carry(val);
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},
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(instruction::LDA, instruction::UseImmediate(val)) => {
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log!(log::DEBUG, "load A immediate: {}", val);
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self.load_accumulator(val as i8);
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},
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(instruction::LDA, instruction::UseAddress(addr)) => {
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let val = self.memory.get_byte(addr);
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log!(log::DEBUG, "load A. address: {}. value: {}", addr, val);
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self.load_accumulator(val as i8);
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},
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(instruction::LDX, instruction::UseImmediate(val)) => {
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log!(log::DEBUG, "load X immediate: {}", val);
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self.load_x_register(val as i8);
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},
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(instruction::LDX, instruction::UseAddress(addr)) => {
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let val = self.memory.get_byte(addr);
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log!(log::DEBUG, "load X. address: {}. value: {}", addr, val);
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self.load_x_register(val as i8);
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},
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(instruction::LDY, instruction::UseImmediate(val)) => {
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log!(log::DEBUG, "load Y immediate: {}", val);
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self.load_y_register(val as i8);
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},
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(instruction::LDY, instruction::UseAddress(addr)) => {
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let val = self.memory.get_byte(addr);
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log!(log::DEBUG, "load Y. address: {}. value: {}", addr, val);
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self.load_y_register(val as i8);
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},
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(instruction::NOP, _) => {
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log!(log::DEBUG, "nop instr");
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},
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(_, _) => {
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log!(log::DEBUG, "attempting to execute unimplemented \
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instruction");
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},
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};
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}
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pub fn run(&mut self) {
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loop {
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if let Some(decoded_instr) = self.fetch_next_and_decode() {
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self.execute_instruction(decoded_instr);
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} else {
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break
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}
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}
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}
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fn load_register_with_flags(register: &mut i8,
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status: &mut Status,
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value: i8) {
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*register = value;
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let is_zero = value == 0;
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let is_negative = value < 0;
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status.set_with_mask(
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ps_zero | ps_negative,
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Status::new(StatusArgs { zero: is_zero,
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negative: is_negative,
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..StatusArgs::none() } ));
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}
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pub fn load_x_register(&mut self, value: i8) {
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Machine::load_register_with_flags(&mut self.registers.index_x,
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&mut self.registers.status,
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value);
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}
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pub fn load_y_register(&mut self, value: i8) {
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Machine::load_register_with_flags(&mut self.registers.index_y,
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&mut self.registers.status,
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value);
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}
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pub fn load_accumulator(&mut self, value: i8) {
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Machine::load_register_with_flags(&mut self.registers.accumulator,
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&mut self.registers.status,
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value);
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}
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// TODO akeeton: Implement binary-coded decimal.
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pub fn add_with_carry(&mut self, value: i8) {
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let a_before: i8 = self.registers.accumulator;
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let c_before: i8 = self.registers.status.get_carry();
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let a_after: i8 = a_before + c_before + value;
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debug_assert_eq!(a_after as u8, a_before as u8 + c_before as u8
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+ value as u8);
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let did_carry = (a_after as u8) < (a_before as u8);
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let did_overflow =
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(a_before < 0 && value < 0 && a_after >= 0)
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|| (a_before > 0 && value > 0 && a_after <= 0);
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let mask = ps_carry | ps_overflow;
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self.registers.status.set_with_mask(mask,
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Status::new(StatusArgs { carry: did_carry,
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overflow: did_overflow,
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..StatusArgs::none() } ));
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self.load_accumulator(a_after);
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log!(log::DEBUG, "accumulator: {}", self.registers.accumulator);
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}
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}
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impl std::fmt::Show for Machine {
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fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
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write!(f, "Machine Dump:\n\nAccumulator: {}",
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self.registers.accumulator)
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}
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}
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#[test]
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fn add_with_carry_test() {
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let mut machine = Machine::new();
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machine.add_with_carry(1);
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assert_eq!(machine.registers.accumulator, 1);
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assert_eq!(machine.registers.status.contains(ps_carry), false);
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assert_eq!(machine.registers.status.contains(ps_zero), false);
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assert_eq!(machine.registers.status.contains(ps_negative), false);
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assert_eq!(machine.registers.status.contains(ps_overflow), false);
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machine.add_with_carry(-1);
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assert_eq!(machine.registers.accumulator, 0);
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assert_eq!(machine.registers.status.contains(ps_carry), true);
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assert_eq!(machine.registers.status.contains(ps_zero), true);
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assert_eq!(machine.registers.status.contains(ps_negative), false);
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assert_eq!(machine.registers.status.contains(ps_overflow), false);
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machine.add_with_carry(1);
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assert_eq!(machine.registers.accumulator, 2);
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assert_eq!(machine.registers.status.contains(ps_carry), false);
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assert_eq!(machine.registers.status.contains(ps_zero), false);
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assert_eq!(machine.registers.status.contains(ps_negative), false);
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assert_eq!(machine.registers.status.contains(ps_overflow), false);
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let mut machine = Machine::new();
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machine.add_with_carry(127);
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assert_eq!(machine.registers.accumulator, 127);
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assert_eq!(machine.registers.status.contains(ps_carry), false);
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assert_eq!(machine.registers.status.contains(ps_zero), false);
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assert_eq!(machine.registers.status.contains(ps_negative), false);
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assert_eq!(machine.registers.status.contains(ps_overflow), false);
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machine.add_with_carry(-127);
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assert_eq!(machine.registers.accumulator, 0);
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assert_eq!(machine.registers.status.contains(ps_carry), true);
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assert_eq!(machine.registers.status.contains(ps_zero), true);
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assert_eq!(machine.registers.status.contains(ps_negative), false);
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assert_eq!(machine.registers.status.contains(ps_overflow), false);
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machine.registers.status.remove(ps_carry);
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machine.add_with_carry(-128);
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assert_eq!(machine.registers.accumulator, -128);
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assert_eq!(machine.registers.status.contains(ps_carry), false);
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assert_eq!(machine.registers.status.contains(ps_zero), false);
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assert_eq!(machine.registers.status.contains(ps_negative), true);
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assert_eq!(machine.registers.status.contains(ps_overflow), false);
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machine.add_with_carry(127);
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assert_eq!(machine.registers.accumulator, -1);
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assert_eq!(machine.registers.status.contains(ps_carry), false);
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assert_eq!(machine.registers.status.contains(ps_zero), false);
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assert_eq!(machine.registers.status.contains(ps_negative), true);
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assert_eq!(machine.registers.status.contains(ps_overflow), false);
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let mut machine = Machine::new();
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machine.add_with_carry(127);
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assert_eq!(machine.registers.accumulator, 127);
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assert_eq!(machine.registers.status.contains(ps_carry), false);
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assert_eq!(machine.registers.status.contains(ps_zero), false);
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assert_eq!(machine.registers.status.contains(ps_negative), false);
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assert_eq!(machine.registers.status.contains(ps_overflow), false);
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machine.add_with_carry(1);
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assert_eq!(machine.registers.accumulator, -128);
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assert_eq!(machine.registers.status.contains(ps_carry), false);
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assert_eq!(machine.registers.status.contains(ps_zero), false);
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assert_eq!(machine.registers.status.contains(ps_negative), true);
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assert_eq!(machine.registers.status.contains(ps_overflow), true);
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}
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