From c58bba1f4cc86441bcaca60f155cf5f6e319324d Mon Sep 17 00:00:00 2001 From: Matthias Date: Fri, 26 Apr 2024 11:50:38 +0200 Subject: [PATCH] Code Cleanup This adds some new directives for clippy and fixes all warnings. Also updated the dependencies to their latest versions. --- .gitignore | 1 + Cargo.toml | 4 +- src/cpu.rs | 143 +++++++++++++++++++++++++-------------------- src/instruction.rs | 16 +++-- src/lib.rs | 26 +++++++-- src/memory.rs | 40 +++++++++++-- src/registers.rs | 29 +++++---- 7 files changed, 166 insertions(+), 93 deletions(-) diff --git a/.gitignore b/.gitignore index 53c030a..b308928 100644 --- a/.gitignore +++ b/.gitignore @@ -66,3 +66,4 @@ TAGS.vi src/.DS_Store tmp.*.rs .vscode +Cargo.lock \ No newline at end of file diff --git a/Cargo.toml b/Cargo.toml index 481588c..55bb536 100644 --- a/Cargo.toml +++ b/Cargo.toml @@ -40,8 +40,8 @@ edition = "2021" name = "mos6502" [dependencies] -bitflags = "2.3.3" -log = "0.4.19" +bitflags = "2.5.0" +log = "0.4.21" [features] decimal_mode = [] diff --git a/src/cpu.rs b/src/cpu.rs index 90e8dfa..1301203 100644 --- a/src/cpu.rs +++ b/src/cpu.rs @@ -47,6 +47,10 @@ where } impl CPU { + // Allowing `needless_pass_by_value` to simplify construction. Passing by + // value avoids the borrow and improves readability when constructing the + // CPU. + #[allow(clippy::needless_pass_by_value)] pub fn new(memory: M, _variant: V) -> CPU { CPU { registers: Registers::new(), @@ -56,10 +60,23 @@ impl CPU { } pub fn reset(&mut self) { - //TODO: // should read some bytes from the stack and also get the PC from the reset vector + //TODO: should read some bytes from the stack and also get the PC from the reset vector } + /// Get the next byte from memory and decode it into an instruction and addressing mode. + /// + /// # Panics + /// + /// This function will panic if the instruction is not recognized + /// (i.e. the opcode is invalid or has not been implemented). pub fn fetch_next_and_decode(&mut self) -> Option { + // Helper function to read a 16-bit address from memory + fn read_address(mem: &mut M, addr: u16) -> [u8; 2] { + let lo = mem.get_byte(addr); + let hi = mem.get_byte(addr.wrapping_add(1)); + [lo, hi] + } + let x: u8 = self.memory.get_byte(self.registers.program_counter); match V::decode(x) { @@ -87,12 +104,6 @@ impl CPU { let memory = &mut self.memory; - fn read_address(mem: &mut M, addr: u16) -> [u8; 2] { - let lo = mem.get_byte(addr); - let hi = mem.get_byte(addr.wrapping_add(1)); - [lo, hi] - } - let am_out = match am { AddressingMode::Accumulator | AddressingMode::Implied => { // Always the same -- no input @@ -213,24 +224,25 @@ impl CPU { } } + #[allow(clippy::too_many_lines)] pub fn execute_instruction(&mut self, decoded_instr: DecodedInstr) { match decoded_instr { (Instruction::ADC, OpInput::UseImmediate(val)) => { - debug!("add with carry immediate: {}", val); + log::debug!("add with carry immediate: {}", val); self.add_with_carry(val); } (Instruction::ADC, OpInput::UseAddress(addr)) => { let val = self.memory.get_byte(addr); - debug!("add with carry. address: {:?}. value: {}", addr, val); + log::debug!("add with carry. address: {:?}. value: {}", addr, val); self.add_with_carry(val); } (Instruction::ADCnd, OpInput::UseImmediate(val)) => { - debug!("add with carry immediate: {}", val); + log::debug!("add with carry immediate: {}", val); self.add_with_no_decimal(val); } (Instruction::ADCnd, OpInput::UseAddress(addr)) => { let val = self.memory.get_byte(addr); - debug!("add with carry. address: {:?}. value: {}", addr, val); + log::debug!("add with carry. address: {:?}. value: {}", addr, val); self.add_with_no_decimal(val); } @@ -301,7 +313,7 @@ impl CPU { (Instruction::BMI, OpInput::UseRelative(rel)) => { let addr = self.registers.program_counter.wrapping_add(rel); - debug!("branch if minus relative. address: {:?}", addr); + log::debug!("branch if minus relative. address: {:?}", addr); self.branch_if_minus(addr); } @@ -317,7 +329,7 @@ impl CPU { self.push_on_stack(self.registers.status.bits()); let pcl = self.memory.get_byte(0xfffe); let pch = self.memory.get_byte(0xffff); - self.jump(((pch as u16) << 8) | pcl as u16); + self.jump((u16::from(pch) << 8) | u16::from(pcl)); self.registers.status.or(Status::PS_DISABLE_INTERRUPTS); } @@ -412,32 +424,32 @@ impl CPU { } (Instruction::LDA, OpInput::UseImmediate(val)) => { - debug!("load A immediate: {}", val); + log::debug!("load A immediate: {}", val); self.load_accumulator(val); } (Instruction::LDA, OpInput::UseAddress(addr)) => { let val = self.memory.get_byte(addr); - debug!("load A. address: {:?}. value: {}", addr, val); + log::debug!("load A. address: {:?}. value: {}", addr, val); self.load_accumulator(val); } (Instruction::LDX, OpInput::UseImmediate(val)) => { - debug!("load X immediate: {}", val); + log::debug!("load X immediate: {}", val); self.load_x_register(val); } (Instruction::LDX, OpInput::UseAddress(addr)) => { let val = self.memory.get_byte(addr); - debug!("load X. address: {:?}. value: {}", addr, val); + log::debug!("load X. address: {:?}. value: {}", addr, val); self.load_x_register(val); } (Instruction::LDY, OpInput::UseImmediate(val)) => { - debug!("load Y immediate: {}", val); + log::debug!("load Y immediate: {}", val); self.load_y_register(val); } (Instruction::LDY, OpInput::UseAddress(addr)) => { let val = self.memory.get_byte(addr); - debug!("load Y. address: {:?}. value: {}", addr, val); + log::debug!("load Y. address: {:?}. value: {}", addr, val); self.load_y_register(val); } @@ -527,32 +539,33 @@ impl CPU { self.registers.status = Status::from_bits_truncate(val); let pcl: u8 = self.pull_from_stack(); let pch: u8 = self.fetch_from_stack(); - self.registers.program_counter = ((pch as u16) << 8) | pcl as u16; + self.registers.program_counter = (u16::from(pch) << 8) | u16::from(pcl); } (Instruction::RTS, OpInput::UseImplied) => { self.pull_from_stack(); let pcl: u8 = self.pull_from_stack(); let pch: u8 = self.fetch_from_stack(); - self.registers.program_counter = (((pch as u16) << 8) | pcl as u16).wrapping_add(1); + self.registers.program_counter = + ((u16::from(pch) << 8) | u16::from(pcl)).wrapping_add(1); } (Instruction::SBC, OpInput::UseImmediate(val)) => { - debug!("subtract with carry immediate: {}", val); + log::debug!("subtract with carry immediate: {}", val); self.subtract_with_carry(val); } (Instruction::SBC, OpInput::UseAddress(addr)) => { let val = self.memory.get_byte(addr); - debug!("subtract with carry. address: {:?}. value: {}", addr, val); + log::debug!("subtract with carry. address: {:?}. value: {}", addr, val); self.subtract_with_carry(val); } (Instruction::SBCnd, OpInput::UseImmediate(val)) => { - debug!("subtract with carry immediate: {}", val); + log::debug!("subtract with carry immediate: {}", val); self.subtract_with_no_decimal(val); } (Instruction::SBCnd, OpInput::UseAddress(addr)) => { let val = self.memory.get_byte(addr); - debug!("subtract with carry. address: {:?}. value: {}", addr, val); + log::debug!("subtract with carry. address: {:?}. value: {}", addr, val); self.subtract_with_no_decimal(val); } @@ -605,10 +618,10 @@ impl CPU { } (Instruction::NOP, OpInput::UseImplied) => { - debug!("NOP instruction"); + log::debug!("NOP instruction"); } (_, _) => { - debug!( + log::debug!( "attempting to execute unimplemented or invalid \ instruction" ); @@ -628,23 +641,23 @@ impl CPU { } } - fn set_flags_from_i8(status: &mut Status, value: i8) { - let is_zero = value == 0; - let is_negative = value < 0; - - status.set_with_mask( - Status::PS_ZERO | Status::PS_NEGATIVE, - Status::new(StatusArgs { - zero: is_zero, - negative: is_negative, - ..StatusArgs::none() - }), - ); + /// Checks if a given `u8` value should be interpreted as negative when + /// considered as `i8`. + /// + /// In an 8-bit unsigned integer (`u8`), values range from 0 to 255. When + /// these values are interpreted as signed integers (`i8`), values from 128 + /// to 255 are considered negative, corresponding to the signed range -128 + /// to -1. This function checks if the provided `u8` value falls within that + /// range, effectively determining if the most significant bit is set, which + /// indicates a negative number in two's complement form. + /// ``` + const fn value_is_negative(value: u8) -> bool { + value > 127 } fn set_flags_from_u8(status: &mut Status, value: u8) { let is_zero = value == 0; - let is_negative = value > 127; + let is_negative = Self::value_is_negative(value); status.set_with_mask( Status::PS_ZERO | Status::PS_NEGATIVE, @@ -668,7 +681,7 @@ impl CPU { ..StatusArgs::none() }), ); - CPU::::set_flags_from_i8(status, *p_val as i8); + CPU::::set_flags_from_u8(status, *p_val); } fn shift_right_with_flags(p_val: &mut u8, status: &mut Status) { @@ -682,7 +695,7 @@ impl CPU { ..StatusArgs::none() }), ); - CPU::::set_flags_from_i8(status, *p_val as i8); + CPU::::set_flags_from_u8(status, *p_val); } fn rotate_left_with_flags(p_val: &mut u8, status: &mut Status) { @@ -698,7 +711,7 @@ impl CPU { ..StatusArgs::none() }), ); - CPU::::set_flags_from_i8(status, *p_val as i8); + CPU::::set_flags_from_u8(status, *p_val); } fn rotate_right_with_flags(p_val: &mut u8, status: &mut Status) { @@ -714,7 +727,7 @@ impl CPU { ..StatusArgs::none() }), ); - CPU::::set_flags_from_i8(status, *p_val as i8); + CPU::::set_flags_from_u8(status, *p_val); } fn set_u8_with_flags(mem: &mut u8, status: &mut Status, value: u8) { @@ -747,7 +760,7 @@ impl CPU { } fn add_with_carry(&mut self, value: u8) { - fn decimal_adjust(result: u8) -> u8 { + const fn decimal_adjust(result: u8) -> u8 { let bcd1: u8 = if (result & 0x0f) > 0x09 { 0x06 } else { 0x00 }; let bcd2: u8 = if (result.wrapping_add(bcd1) & 0xf0) > 0x90 { @@ -791,7 +804,7 @@ impl CPU { self.load_accumulator(result); - debug!("accumulator: {}", self.registers.accumulator); + log::debug!("accumulator: {}", self.registers.accumulator); } fn add_with_no_decimal(&mut self, value: u8) { @@ -823,7 +836,7 @@ impl CPU { self.load_accumulator(result); - debug!("accumulator: {}", self.registers.accumulator); + log::debug!("accumulator: {}", self.registers.accumulator); } fn and(&mut self, value: u8) { @@ -835,11 +848,7 @@ impl CPU { // A - M - (1 - C) // nc -- 'not carry' - let nc: u8 = if self.registers.status.contains(Status::PS_CARRY) { - 0 - } else { - 1 - }; + let nc: u8 = u8::from(!self.registers.status.contains(Status::PS_CARRY)); let a_before = self.registers.accumulator; @@ -881,11 +890,7 @@ impl CPU { // A - M - (1 - C) // nc -- 'not carry' - let nc: u8 = if self.registers.status.contains(Status::PS_CARRY) { - 0 - } else { - 1 - }; + let nc: u8 = u8::from(!self.registers.status.contains(Status::PS_CARRY)); let a_before = self.registers.accumulator; @@ -943,13 +948,12 @@ impl CPU { let value_new = val.wrapping_add(1); *val = value_new; - let is_negative = (value_new as i8) < 0; let is_zero = value_new == 0; flags.set_with_mask( Status::PS_NEGATIVE | Status::PS_ZERO, Status::new(StatusArgs { - negative: is_negative, + negative: Self::value_is_negative(value_new), zero: is_zero, ..StatusArgs::none() }), @@ -960,14 +964,14 @@ impl CPU { let value_new = val.wrapping_sub(1); *val = value_new; - let is_negative = (value_new as i8) < 0; let is_zero = value_new == 0; + let is_negative = Self::value_is_negative(value_new); flags.set_with_mask( Status::PS_NEGATIVE | Status::PS_ZERO, Status::new(StatusArgs { - negative: is_negative, zero: is_zero, + negative: is_negative, ..StatusArgs::none() }), ); @@ -1033,20 +1037,24 @@ impl CPU { // ... // The N flag contains most significant bit of the subtraction result. fn compare(&mut self, r: u8, val: u8) { + // Setting the CARRY flag: A (unsigned) >= NUM (unsigned) if r >= val { self.registers.status.insert(Status::PS_CARRY); } else { self.registers.status.remove(Status::PS_CARRY); } + // Setting the ZERO flag: A = NUM if r == val { self.registers.status.insert(Status::PS_ZERO); } else { self.registers.status.remove(Status::PS_ZERO); } - let diff: i8 = (r as i8).wrapping_sub(val as i8); - if diff < 0 { + // Set the NEGATIVE flag based on the MSB of the result of subtraction + // This checks if the 8th bit is set (0x80 in hex is 128 in decimal, which is the 8th bit in a byte) + let diff = r.wrapping_sub(val); + if Self::value_is_negative(diff) { self.registers.status.insert(Status::PS_NEGATIVE); } else { self.registers.status.remove(Status::PS_NEGATIVE); @@ -1059,7 +1067,7 @@ impl CPU { } fn compare_with_x_register(&mut self, val: u8) { - debug!("compare_with_x_register"); + log::debug!("compare_with_x_register"); let x = self.registers.index_x; self.compare(x, val); @@ -1112,6 +1120,11 @@ impl core::fmt::Debug for CPU { #[cfg(test)] mod tests { + // Casting from signed to unsigned integers is intentional in these tests + #![allow(clippy::cast_sign_loss)] + // Operations may intentionally wrap due to emulation of 8-bit unsigned + // integer arithmetic. We do this to test wrap-around conditions. + #![allow(clippy::cast_possible_wrap)] use super::*; use crate::instruction::Nmos6502; @@ -1215,6 +1228,8 @@ mod tests { assert!(!cpu.registers.status.contains(Status::PS_NEGATIVE)); assert!(!cpu.registers.status.contains(Status::PS_OVERFLOW)); + // Allow casting from i8 to u8; -127i8 wraps to 129u8, as intended for + // two's complement arithmetic. cpu.add_with_carry(-127i8 as u8); assert_eq!(cpu.registers.accumulator, 0); assert!(cpu.registers.status.contains(Status::PS_CARRY)); diff --git a/src/instruction.rs b/src/instruction.rs index f63dd5e..387b0d3 100644 --- a/src/instruction.rs +++ b/src/instruction.rs @@ -107,7 +107,7 @@ pub enum Instruction { TYA, // Transfer Y to Accumulator..... | N. ...Z. A = Y } -#[derive(Copy, Clone)] +#[derive(Copy, Clone, Debug)] pub enum OpInput { UseImplied, UseImmediate(u8), @@ -115,7 +115,7 @@ pub enum OpInput { UseAddress(u16), } -#[derive(Copy, Clone)] +#[derive(Copy, Clone, Debug)] pub enum AddressingMode { // work directly on accumulator, e. g. `lsr a`. Accumulator, @@ -161,7 +161,8 @@ pub enum AddressingMode { } impl AddressingMode { - pub fn extra_bytes(self) -> u16 { + #[must_use] + pub const fn extra_bytes(self) -> u16 { match self { AddressingMode::Accumulator => 0, AddressingMode::Implied => 0, @@ -184,6 +185,7 @@ impl AddressingMode { pub type DecodedInstr = (Instruction, OpInput); /// The NMOS 6502 variant. This one is present in the Commodore 64, early Apple IIs, etc. +#[derive(Copy, Clone, Debug)] pub struct Nmos6502; impl crate::Variant for Nmos6502 { @@ -449,8 +451,9 @@ impl crate::Variant for Nmos6502 { } } -/// The Ricoh variant which has no decimal mode. This is what to use if you want to emulate the -/// NES. +/// The Ricoh variant which has no decimal mode. This is what to use if you want +/// to emulate the NES. +#[derive(Copy, Clone, Debug)] pub struct Ricoh2a03; impl crate::Variant for Ricoh2a03 { @@ -479,10 +482,12 @@ impl crate::Variant for Ricoh2a03 { /// Emulates some very early 6502s which have no ROR instruction. This one is used in very early /// KIM-1s. +#[derive(Copy, Clone, Debug)] pub struct RevisionA; impl crate::Variant for RevisionA { fn decode(opcode: u8) -> Option<(Instruction, AddressingMode)> { + #[allow(clippy::match_same_arms)] match opcode { 0x66 => None, 0x6a => None, @@ -495,6 +500,7 @@ impl crate::Variant for RevisionA { } /// Emulates the 65C02, which has a few bugfixes, and another addressing mode +#[derive(Copy, Clone, Debug)] pub struct Cmos6502; impl crate::Variant for Cmos6502 { diff --git a/src/lib.rs b/src/lib.rs index 302a8c1..e58110c 100644 --- a/src/lib.rs +++ b/src/lib.rs @@ -25,15 +25,29 @@ // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE // POSSIBILITY OF SUCH DAMAGE. +#![warn(clippy::all, clippy::pedantic)] +#![warn( + absolute_paths_not_starting_with_crate, + rustdoc::invalid_html_tags, + missing_copy_implementations, + missing_debug_implementations, + semicolon_in_expressions_from_macros, + unreachable_pub, + unused_crate_dependencies, + unused_extern_crates, + variant_size_differences, + clippy::missing_const_for_fn +)] +#![deny(anonymous_parameters, macro_use_extern_crate, pointer_structural_match)] +#![allow(clippy::module_name_repetitions)] +// Registers and ops follow the 6502 naming convention and have similar names at +// times +#![allow(clippy::similar_names)] +#![allow(clippy::match_same_arms)] +#![allow(clippy::too_many_lines)] #![no_std] #[doc = include_str!("../README.md")] -#[macro_use] -extern crate log; - -#[macro_use] -extern crate bitflags; - pub mod cpu; pub mod instruction; pub mod memory; diff --git a/src/memory.rs b/src/memory.rs index dbe46b5..0beef1d 100644 --- a/src/memory.rs +++ b/src/memory.rs @@ -47,7 +47,7 @@ pub const IRQ_INTERRUPT_VECTOR_HI: u16 = 0xFFFF; const MEMORY_SIZE: usize = (ADDR_HI_BARE - ADDR_LO_BARE) as usize + 1usize; // FIXME: Should this use indirection for `bytes`? -#[derive(Copy, Clone)] +#[derive(Copy, Clone, Debug)] pub struct Memory { bytes: [u8; MEMORY_SIZE], } @@ -58,10 +58,37 @@ impl Default for Memory { } } +/// Trait for a bus that can read and write bytes. +/// +/// This is used to abstract the memory and I/O operations of the CPU. +/// +/// # Examples +/// +/// ``` +/// use mos6502::memory::{Bus, Memory}; +/// +/// let mut memory = Memory::new(); +/// memory.set_byte(0x0000, 0x12); +/// assert_eq!(memory.get_byte(0x0000), 0x12); +/// ``` pub trait Bus { + /// Returns the byte at the given address. fn get_byte(&mut self, address: u16) -> u8; + + /// Sets the byte at the given address to the given value. fn set_byte(&mut self, address: u16, value: u8); + /// Sets the bytes starting at the given address to the given values. + /// + /// This is a default implementation that calls `set_byte` for each byte. + /// + /// # Note + /// + /// This assumes that the length of `values` is less than or equal to + /// [`u16::MAX`] (65535). If the length of `values` is greater than `u16::MAX`, + /// this will truncate the length. This assumption is made because the + /// maximum addressable memory for the 6502 is 64KB. + #[allow(clippy::cast_possible_truncation)] fn set_bytes(&mut self, start: u16, values: &[u8]) { for i in 0..values.len() as u16 { self.set_byte(start + i, values[i as usize]); @@ -70,7 +97,8 @@ pub trait Bus { } impl Memory { - pub fn new() -> Memory { + #[must_use] + pub const fn new() -> Memory { Memory { bytes: [0; MEMORY_SIZE], } @@ -82,12 +110,14 @@ impl Bus for Memory { self.bytes[address as usize] } - // Sets the byte at the given address to the given value and returns the - // previous value at the address. + /// Sets the byte at the given address to the given value and returns the + /// previous value at the address. fn set_byte(&mut self, address: u16, value: u8) { self.bytes[address as usize] = value; } + /// Fast way to set multiple bytes in memory when the underlying memory is a + /// consecutive block of bytes. fn set_bytes(&mut self, start: u16, values: &[u8]) { let start = start as usize; @@ -103,7 +133,7 @@ mod tests { use super::*; #[test] - #[should_panic] + #[should_panic(expected = "range end index 65537 out of range for slice of length 65536")] fn test_memory_overflow_panic() { let mut memory = Memory::new(); memory.set_bytes(0xFFFE, &[1, 2, 3]); diff --git a/src/registers.rs b/src/registers.rs index 1b74fbc..827d0ae 100644 --- a/src/registers.rs +++ b/src/registers.rs @@ -25,8 +25,11 @@ // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE // POSSIBILITY OF SUCH DAMAGE. +use bitflags::bitflags; + // Useful for constructing Status instances -#[derive(Copy, Clone)] +#[derive(Copy, Clone, Debug)] +#[allow(clippy::struct_excessive_bools)] pub struct StatusArgs { pub negative: bool, pub overflow: bool, @@ -39,7 +42,8 @@ pub struct StatusArgs { } impl StatusArgs { - pub fn none() -> StatusArgs { + #[must_use] + pub const fn none() -> StatusArgs { StatusArgs { negative: false, overflow: false, @@ -71,6 +75,7 @@ bitflags! { } impl Status { + #[must_use] pub fn new( StatusArgs { negative, @@ -86,28 +91,28 @@ impl Status { let mut out = Status::empty(); if negative { - out |= Status::PS_NEGATIVE + out |= Status::PS_NEGATIVE; } if overflow { - out |= Status::PS_OVERFLOW + out |= Status::PS_OVERFLOW; } if unused { - out |= Status::PS_UNUSED + out |= Status::PS_UNUSED; } if brk { - out |= Status::PS_BRK + out |= Status::PS_BRK; } if decimal_mode { - out |= Status::PS_DECIMAL_MODE + out |= Status::PS_DECIMAL_MODE; } if disable_interrupts { - out |= Status::PS_DISABLE_INTERRUPTS + out |= Status::PS_DISABLE_INTERRUPTS; } if zero { - out |= Status::PS_ZERO + out |= Status::PS_ZERO; } if carry { - out |= Status::PS_CARRY + out |= Status::PS_CARRY; } out @@ -146,7 +151,8 @@ impl Default for Status { pub struct StackPointer(pub u8); impl StackPointer { - pub fn to_u16(self) -> u16 { + #[must_use] + pub const fn to_u16(self) -> u16 { let StackPointer(val) = self; u16::from_le_bytes([val, 0x01]) } @@ -177,6 +183,7 @@ impl Default for Registers { } impl Registers { + #[must_use] pub fn new() -> Registers { // TODO akeeton: Revisit these defaults. Registers {