Allow for the state to be const initialized

mos6502/src/generate_decoder.rb

@@ -303,7 +303,7 @@ def generate_opcode_attributes
         }
 
         impl OpcodeAttributes {
-            fn empty() -> OpcodeAttributes {
+            const fn empty() -> OpcodeAttributes {
                 OpcodeAttributes {
                     attr: 0
                 }

mos6502/src/virtual_mos6502.rs

@@ -115,14 +115,14 @@ pub struct State {
 }
 
 impl State {
-    pub fn new() -> State {
+    pub const fn new() -> State {
         State {
             pc: 0,
             a: 0,
             x: 0,
             y: 0,
             sp: 0xFD,
-            status: (StatusFlag::Unused | StatusFlag::IRQDisable).bits(),
+            status: StatusFlag::Unused.bits() | StatusFlag::IRQDisable.bits(),
             irq_line_state: false,
             nmi_latch_state: false,
             nmi_pending: false,

mos6502/src/virtual_mos6502_decoder.rs

@@ -716,7 +716,7 @@ macro_rules! decoding_logic {
         }
         
         impl OpcodeAttributes {
-            fn empty() -> OpcodeAttributes {
+            const fn empty() -> OpcodeAttributes {
                 OpcodeAttributes {
                     attr: 0
                 }

nes/src/dma.rs

@@ -41,7 +41,7 @@ pub struct State {
 }
 
 impl State {
-    pub fn new() -> State {
+    pub const fn new() -> State {
         State {
             dmc_dma_requested: false,
             dmc_dma_source_address: 0,

nes/src/filter.rs

@@ -14,7 +14,7 @@ pub struct Filter {
 }
 
 impl Filter {
-    pub fn new() -> Filter {
+    pub const fn new() -> Filter {
         Filter {
             delay_00: 0.0,
             delay_01: 0.0,

nes/src/generate_ppu.rb

@@ -255,7 +255,8 @@ end
 
 def generate_scanlines( constant_name, chunks_per_scanline )
 
-    output "static #{constant_name}: &'static [Scanline] = &["
+    output "static #{constant_name}: &'static [Scanline] = #{constant_name}_CONST;"
+    output "const #{constant_name}_CONST: &'static [Scanline] = &["
 
     index = 0
     chunks_per_scanline.each do |scanline|
@@ -278,7 +279,8 @@ end
 
 def generate_chunks( constant_name, chunks_per_scanline )
 
-    output "static #{constant_name}: &'static [Chunk] = &["
+    output "static #{constant_name}: &'static [Chunk] = #{constant_name}_CONST;"
+    output "const #{constant_name}_CONST: &'static [Chunk] = &["
 
     index = 0
     chunks_per_scanline.flat_map { |scanline| scanline[:chunks] }.each do |chunk|

nes/src/rp2c02.rs

@@ -1,7 +1,6 @@
 use core::mem;
 use core::default::Default;
 use core::slice;
-use alloc::vec::Vec;
 
 use emumisc::{WrappingExtra, BitExtra, HiLoAccess, PeekPoke, At, is_b5_set, is_b6_set, is_b7_set, reverse_bits};
 
@@ -18,7 +17,7 @@ pub trait Context: Sized {
 
 pub trait Interface: Sized + Context {
     #[inline]
-    fn framebuffer( &self ) -> &Framebuffer {
+    fn framebuffer( &mut self ) -> &Framebuffer {
         Private::framebuffer( self )
     }
 
@@ -95,7 +94,7 @@ pub struct State {
     palette_ram: [u8; 32],
     sprite_list_ram: [u8; 256],
     secondary_sprite_list_ram: [u8; 32],
-    framebuffer: Framebuffer,
+    framebuffer: Option< Framebuffer >,
     odd_frame_flag: bool,
     vblank_flag_was_cleared: bool,
 
@@ -151,12 +150,17 @@ pub struct State {
 }
 
 impl State {
-    pub fn new() -> State {
+    pub const fn new() -> State {
+        let last_scanline = match SCANLINES_CONST.last() {
+            Some(value) => value,
+            None => unreachable!()
+        };
+
         State {
             palette_ram: [0; 32],
             sprite_list_ram: [0; 64 * 4],
             secondary_sprite_list_ram: [0;  8 * 4],
-            framebuffer: Framebuffer::new(),
+            framebuffer: None,
             odd_frame_flag: false,
             vblank_flag_was_cleared: false,
 
@@ -173,7 +177,7 @@ impl State {
             bg_palette_index_lo_shift_register: 0,
             bg_palette_index_hi_shift_register: 0,
 
-            sprites: [Sprite::default(); 8],
+            sprites: [Sprite::new(); 8],
 
             sprite_list_address: 0,
             ppudata_read_buffer: 0,
@@ -192,11 +196,11 @@ impl State {
             background_palette_index_latch: 0,
             tile_lo_latch: 0,
             tile_hi_latch: 0,
-            scanline_index: SCANLINES.len() as u8 - 1, // Point at the prerender scanline.
+            scanline_index: SCANLINES_CONST.len() as u8 - 1, // Point at the prerender scanline.
             scanline_counter: 0,
-            chunk_index: SCANLINES.last().unwrap().first_chunk_index,
+            chunk_index: last_scanline.first_chunk_index,
             chunk_counter: 0,
-            action_index: CHUNKS[ SCANLINES.last().unwrap().first_chunk_index as usize ].first_action_index,
+            action_index: CHUNKS_CONST[ last_scanline.first_chunk_index as usize ].first_action_index,
             auxiliary_sprite_list_address: 0,
             secondary_sprite_list_address: 0,
             sprite_list_data_latch: 0,
@@ -210,9 +214,12 @@ impl State {
         }
     }
 
+    fn initialize_framebuffer_if_needed( &mut self ) {
+    }
+
     #[inline]
-    pub fn framebuffer( &self ) -> &Framebuffer {
-        &self.framebuffer
+    pub fn framebuffer( &mut self ) -> &mut Framebuffer {
+        self.framebuffer.get_or_insert_with( Framebuffer::default )
     }
 }
 
@@ -220,7 +227,7 @@ impl State {
 struct PpuCtrl(u8);
 
 impl PpuCtrl {
-    fn new() -> PpuCtrl {
+    const fn new() -> PpuCtrl {
         PpuCtrl(0)
     }
 
@@ -273,7 +280,7 @@ impl PpuCtrl {
 struct PpuMask(u8);
 
 impl PpuMask {
-    fn new() -> PpuMask {
+    const fn new() -> PpuMask {
         PpuMask(0)
     }
 
@@ -296,7 +303,7 @@ impl PpuMask {
 struct PpuStatus(u8);
 
 impl PpuStatus {
-    fn new() -> PpuStatus {
+    const fn new() -> PpuStatus {
         PpuStatus(0)
     }
 
@@ -455,18 +462,11 @@ impl PpuStatus {
     Each scanline takes 341 PPU cycles, with each cycle producing one pixel.
 */
 
+#[derive(PartialEq, Eq)]
 pub struct Framebuffer {
-    buffer: Vec< u16 >
+    buffer: alloc::boxed::Box<[u16; 256 * 240]>
 }
 
-impl PartialEq for Framebuffer {
-    fn eq( &self, other: &Framebuffer ) -> bool {
-        &self.buffer[..] == &other.buffer[..]
-    }
-}
-
-impl Eq for Framebuffer {}
-
 impl Framebuffer {
     fn new() -> Framebuffer {
         Framebuffer::default()
@@ -534,11 +534,8 @@ impl< 'a > Iterator for FramebufferIterator< 'a > {
 
 impl Default for Framebuffer {
     fn default() -> Self {
-        let mut buffer = Vec::new();
-        buffer.resize( 256 * 240, 0 );
-
         Framebuffer {
-            buffer
+            buffer: alloc::boxed::Box::new([0; 256 * 240])
         }
     }
 }
@@ -649,6 +646,16 @@ struct Sprite {
 }
 
 impl Sprite {
+    #[inline]
+    const fn new() -> Self {
+        Sprite {
+            pattern_lo_shift_register: 0,
+            pattern_hi_shift_register: 0,
+            attributes_latch: 0,
+            dots_until_is_displayed: 0
+        }
+    }
+
     #[inline]
     fn display_sprite_behind_background( &self ) -> bool {
         is_b5_set( self.attributes_latch )
@@ -662,12 +669,7 @@ impl Sprite {
 
 impl Default for Sprite {
     fn default() -> Self {
-        Sprite {
-            pattern_lo_shift_register: 0,
-            pattern_hi_shift_register: 0,
-            attributes_latch: 0,
-            dots_until_is_displayed: 0
-        }
+        Self::new()
     }
 }
 
@@ -883,12 +885,12 @@ trait Private: Sized + Context {
         (self.sprite_tile_hi_address() >> 8) as u8
     }
 
-    fn framebuffer( &self ) -> &Framebuffer {
-        &self.state().framebuffer
+    fn framebuffer( &mut self ) -> &Framebuffer {
+        self.state_mut().framebuffer()
     }
 
     fn swap_framebuffer( &mut self, mut other: Framebuffer ) -> Framebuffer {
-        mem::swap( &mut self.state_mut().framebuffer, &mut other );
+        mem::swap( self.state_mut().framebuffer(), &mut other );
         other
     }
 
@@ -1077,7 +1079,13 @@ trait Private: Sized + Context {
         // let color_in_system_palette_index = self.state_mut().palette_ram.peek( (palette_index as usize * 4) + color_in_palette_index as usize );
         let nth = self.state().n_pixel;
         let pixel = ((self.state().ppumask.color_emphasize_bits() as u16) << 6) | (color_in_system_palette_index as u16);
-        self.state_mut().framebuffer.buffer.poke( nth, pixel );
+        {
+            let framebuffer = match self.state_mut().framebuffer {
+                Some( ref mut framebuffer ) => framebuffer,
+                None => unsafe { core::hint::unreachable_unchecked() }
+            };
+            framebuffer.buffer.poke( nth, pixel );
+        }
         self.state_mut().n_pixel += 1;
     }
 
@@ -1093,6 +1101,8 @@ trait Private: Sized + Context {
     }
 
     fn execute( &mut self ) {
+        self.state_mut().framebuffer(); // Make sure the framebuffer is initialized.
+
         self.execute_next_action();
         self.on_cycle();
 

nes/src/rp2c02_scheduler.rs

@@ -16,7 +16,8 @@ macro_rules! ppu_scheduling_logic {
             last_action_index: u16
         }
 
-        static SCANLINES: &'static [Scanline] = &[
+        static SCANLINES: &'static [Scanline] = SCANLINES_CONST;
+        const SCANLINES_CONST: &'static [Scanline] = &[
             Scanline {
                 times: 1,
                 first_chunk_index: 0,
@@ -59,7 +60,8 @@ macro_rules! ppu_scheduling_logic {
             },
         ];
 
-        static CHUNKS: &'static [Chunk] = &[
+        static CHUNKS: &'static [Chunk] = CHUNKS_CONST;
+        const CHUNKS_CONST: &'static [Chunk] = &[
             Chunk {
                 times: 1,
                 first_action_index: 0,

nes/src/virtual_apu.rs

@@ -160,11 +160,11 @@ pub struct State {
 }
 
 impl State {
-    pub fn new() -> State {
+    pub const fn new() -> State {
         State {
-            cycles_to_next_step: SEQUENCER_STEPS_MODE_0[ 2 ].0,
+            cycles_to_next_step: SEQUENCER_STEPS_MODE_0_CONST[ 2 ].0,
             sequencer_reconfigured: None,
-            sequencer_table: SEQUENCER_STEPS_MODE_0,
+            sequencer_table: SEQUENCER_STEPS_MODE_0_CONST,
             sequencer_current_step: 2,
             sequencer_mode: SequencerMode::Mode0,
             inhibit_interrupts: false,
@@ -250,7 +250,7 @@ impl Sequence {
     fn clk_volume_generator( &self ) -> bool { self.6 }
 }
 
-static SEQUENCER_STEPS_MODE_0: &'static [Sequence] = &[
+const SEQUENCER_STEPS_MODE_0_CONST: &'static [Sequence] = &[
     Sequence(    1, 1, false, false, false, false, false ),
     Sequence(    1, 2, false, false, false, false, false ),
     Sequence(    1, 3, false, false, false, false, false ),
@@ -262,6 +262,8 @@ static SEQUENCER_STEPS_MODE_0: &'static [Sequence] = &[
     Sequence(    1, 3,  true, false, false, false, false )
 ];
 
+static SEQUENCER_STEPS_MODE_0: &'static [Sequence] = SEQUENCER_STEPS_MODE_0_CONST;
+
 static SEQUENCER_STEPS_MODE_1: &'static [Sequence] = &[
     Sequence(     1, 1, false, false, false, false, false ),
     Sequence(     3, 2, false,  true,  true,  true,  true ),
@@ -313,7 +315,7 @@ struct Channel {
 }
 
 impl Channel {
-    fn new() -> Channel {
+    const fn new() -> Channel {
         Channel {
             length_counter: 0,
             length_counter_disabled: false,
@@ -365,7 +367,7 @@ struct VolumeGenerator {
 }
 
 impl VolumeGenerator {
-    fn new() -> VolumeGenerator {
+    const fn new() -> VolumeGenerator {
         VolumeGenerator {
             is_manually_controlled: false,
             should_loop: false,
@@ -445,7 +447,7 @@ struct ChannelSquare {
 }
 
 impl ChannelSquare {
-    fn new( is_second_channel: bool ) -> ChannelSquare {
+    const fn new( is_second_channel: bool ) -> ChannelSquare {
         ChannelSquare {
             base: Channel::new(),
             duty: SquareChannelDuty::Duty125,
@@ -592,7 +594,7 @@ struct ChannelTriangle {
 }
 
 impl ChannelTriangle {
-    fn new() -> ChannelTriangle {
+    const fn new() -> ChannelTriangle {
         ChannelTriangle {
             base: Channel::new(),
             period: 0,
@@ -699,7 +701,7 @@ struct ChannelNoise {
 }
 
 impl ChannelNoise {
-    fn new() -> ChannelNoise {
+    const fn new() -> ChannelNoise {
         ChannelNoise {
             base: Channel::new(),
             volume_generator: VolumeGenerator::new(),
@@ -786,7 +788,7 @@ struct ChannelDeltaModulation {
 // The DMC channel plays back DPCM samples stored in memory as 1-bit deltas.
 // A bit of 1 will increment the output; a bit of 0 will decrement the output.
 impl ChannelDeltaModulation {
-    fn new() -> ChannelDeltaModulation {
+    const fn new() -> ChannelDeltaModulation {
         ChannelDeltaModulation {
             enabled: false,
 

nes/src/virtual_nes.rs

@@ -50,7 +50,7 @@ pub trait Interface: Sized + Context {
         Private::execute_cycle( self )
     }
 
-    fn framebuffer( &self ) -> &rp2c02::Framebuffer {
+    fn framebuffer( &mut self ) -> &rp2c02::Framebuffer {
         Private::framebuffer( self )
     }
 
@@ -87,12 +87,13 @@ impl< T: Context > Interface for T {}
 impl< T: Context > Private for T {}
 
 pub struct State {
+    mapper_null: MapperNull,
     ram: [u8; 2048],
     cpu_state: mos6502::State,
     ppu_state: rp2c02::State,
     apu_state: virtual_apu::State,
     dma_state: dma::State,
-    mapper: Box< dyn Mapper >,
+    mapper: Option< Box< dyn Mapper > >,
     error: Option< Box< dyn Error > >,
     ready: bool,
     cpu_cycle: u32,
@@ -107,14 +108,15 @@ pub struct State {
 }
 
 impl State {
-    pub fn new() -> State {
+    pub const fn new() -> State {
         State {
+            mapper_null: MapperNull,
             ram: [0; 2048],
             cpu_state: mos6502::State::new(),
             ppu_state: rp2c02::State::new(),
             apu_state: virtual_apu::State::new(),
             dma_state: dma::State::new(),
-            mapper: Box::new( MapperNull ),
+            mapper: None,
             error: None,
             ready: false,
             cpu_cycle: 0,
@@ -130,9 +132,19 @@ impl State {
     }
 
     #[inline]
-    pub fn framebuffer( &self ) -> &rp2c02::Framebuffer {
+    pub fn framebuffer( &mut self ) -> &rp2c02::Framebuffer {
         self.ppu_state.framebuffer()
     }
+
+    #[inline]
+    fn mapper( &self ) -> &dyn Mapper {
+        self.mapper.as_ref().map( |mapper| &**mapper ).unwrap_or( &self.mapper_null )
+    }
+
+    #[inline]
+    fn mapper_mut( &mut self ) -> &mut dyn Mapper {
+        self.mapper.as_mut().map( |mapper| &mut **mapper ).unwrap_or( &mut self.mapper_null )
+    }
 }
 
 #[derive(Debug, Eq, PartialEq, Copy, Clone)]
@@ -221,12 +233,12 @@ impl< C: Context > rp2c02::Context for Orphan< C > {
 
     #[inline]
     fn peek_video_memory( &self, address: u16 ) -> u8 {
-        self.as_ref().state().mapper.peek_video_memory( address )
+        self.as_ref().state().mapper().peek_video_memory( address )
     }
 
     #[inline]
     fn poke_video_memory( &mut self, address: u16, value: u8 ) {
-        self.as_mut().state_mut().mapper.poke_video_memory( address, value );
+        self.as_mut().state_mut().mapper_mut().poke_video_memory( address, value );
     }
 }
 
@@ -320,7 +332,7 @@ trait Private: Sized + Context {
 
         let mapper = create_mapper( rom )?;
 
-        self.state_mut().mapper = mapper;
+        self.state_mut().mapper = Some( mapper );
         self.state_mut().ready = true;
         self.hard_reset();
 
@@ -328,7 +340,7 @@ trait Private: Sized + Context {
     }
 
     fn hard_reset( &mut self ) {
-        let mut mapper: Box< dyn Mapper + 'static > = Box::new( MapperNull );
+        let mut mapper: Option< Box< dyn Mapper + 'static > > = None;
         mem::swap( &mut mapper, &mut self.state_mut().mapper );
         let ready = self.state().ready;
 
@@ -405,8 +417,8 @@ trait Private: Sized + Context {
         Ok( self.state().full_frame_counter != last_counter_value )
     }
 
-    fn framebuffer( &self ) -> &rp2c02::Framebuffer {
-        rp2c02::Interface::framebuffer( self.newtype() )
+    fn framebuffer( &mut self ) -> &rp2c02::Framebuffer {
+        rp2c02::Interface::framebuffer( self.newtype_mut() )
     }
 
     fn swap_framebuffer( &mut self, other: rp2c02::Framebuffer ) -> rp2c02::Framebuffer {
@@ -461,11 +473,11 @@ trait Private: Sized + Context {
                     _ => unsafe { fast_unreachable!() }
                 }
             }, {
-                self.state().mapper.peek_expansion_rom( address )
+                self.state().mapper().peek_expansion_rom( address )
             }, {
-                self.state().mapper.peek_sram( address )
+                self.state().mapper().peek_sram( address )
             }, {
-                self.state().mapper.peek_rom( address )
+                self.state().mapper().peek_rom( address )
             }
         )
     }
@@ -533,11 +545,11 @@ trait Private: Sized + Context {
                     }
                 }
             }, {
-                self.state().mapper.poke_expansion_rom( address, value );
+                self.state().mapper().poke_expansion_rom( address, value );
             }, {
-                self.state_mut().mapper.poke_sram( address, value );
+                self.state_mut().mapper_mut().poke_sram( address, value );
             }, {
-                self.state_mut().mapper.poke_rom( address, value );
+                self.state_mut().mapper_mut().poke_rom( address, value );
             }
         )
     }