.gitignore

@@ -6,9 +6,6 @@
 **/*.log
 **/*.bin
 
-# Build on Windows
+# Build on WIndows
 /.build_config
-/lib/SDL2
+/lib/SDL2
-
-# Any Custom Scripts for Debugging purposes
-*.sh

README.md

@@ -1 +0,0 @@
-Built using Zig v0.10.0-dev.548+4ca9a8d19

src/bus/Ewram.zig

@@ -7,11 +7,8 @@ buf: []u8,
 alloc: Allocator,
 
 pub fn init(alloc: Allocator) !Self {
-    const buf = try alloc.alloc(u8, 0x8000);
-    std.mem.set(u8, buf, 0);
-
     return Self{
-        .buf = buf,
+        .buf = try alloc.alloc(u8, 0x8000),
         .alloc = alloc,
     };
 }

src/bus/Iwram.zig

@@ -7,11 +7,8 @@ buf: []u8,
 alloc: Allocator,
 
 pub fn init(alloc: Allocator) !Self {
-    const buf = try alloc.alloc(u8, 0x40000);
-    std.mem.set(u8, buf, 0);
-
     return Self{
-        .buf = buf,
+        .buf = try alloc.alloc(u8, 0x40000),
         .alloc = alloc,
     };
 }

src/bus/io.zig

@@ -30,6 +30,7 @@ pub const Io = struct {
             0x0400_0000 => @as(u32, self.dispcnt.raw),
             0x0400_0004 => @as(u32, self.dispstat.raw),
             0x0400_0006 => @as(u32, self.vcount.raw),
+            0x0400_0130 => @as(u32, self.keyinput.raw),
             0x0400_0200 => @as(u32, self.ie.raw),
             0x0400_0208 => @boolToInt(self.ime),
             else => std.debug.panic("[I/O:32] tried to read from {X:}", .{addr}),

src/cpu/thumb/data_transfer.zig

@@ -28,28 +28,26 @@ pub fn format78(comptime op: u2, comptime T: bool) InstrFn {
             const address = cpu.r[rb] + cpu.r[ro];
 
             if (T) {
-                // Format 8
                 switch (op) {
                     0b00 => {
                         // STRH
                         bus.write16(address & 0xFFFF_FFFE, @truncate(u16, cpu.r[rd]));
                     },
                     0b01 => {
-                        // LDSB
-                        cpu.r[rd] = u32SignExtend(8, @as(u32, bus.read8(address)));
-                    },
-                    0b10 => {
                         // LDRH
                         const value = bus.read16(address & 0xFFFF_FFFE);
                         cpu.r[rd] = std.math.rotr(u32, @as(u32, value), 8 * (address & 1));
                     },
+                    0b10 => {
+                        // LDSB
+                        cpu.r[rd] = u32SignExtend(8, @as(u32, bus.read8(address)));
+                    },
                     0b11 => {
                         // LDSH
                         cpu.r[rd] = u32SignExtend(16, @as(u32, bus.read16(address & 0xFFFF_FFFE)));
                     },
                 }
             } else {
-                // Format 7
                 switch (op) {
                     0b00 => {
                         // STR

src/main.zig

@@ -15,7 +15,7 @@ const File = std.fs.File;
 const window_scale = 3;
 const gba_width = @import("ppu.zig").width;
 const gba_height = @import("ppu.zig").height;
-const framebuf_pitch = @import("ppu.zig").framebuf_pitch;
+const buf_pitch = @import("ppu.zig").buf_pitch;
 
 pub const enable_logging: bool = false;
 const is_binary: bool = false;
@@ -164,8 +164,8 @@ pub fn main() anyerror!void {
         }
 
         // FIXME: Is it OK just to copy the Emulator's Frame Buffer to SDL?
-        const buf_ptr = bus.ppu.framebuf.ptr;
+        const buf_ptr = bus.ppu.frame_buf.ptr;
-        _ = SDL.SDL_UpdateTexture(texture, null, buf_ptr, framebuf_pitch);
+        _ = SDL.SDL_UpdateTexture(texture, null, buf_ptr, buf_pitch);
         _ = SDL.SDL_RenderCopy(renderer, texture, null, null);
         SDL.SDL_RenderPresent(renderer);
 

src/ppu.zig

@@ -7,7 +7,8 @@ const Scheduler = @import("scheduler.zig").Scheduler;
 const Allocator = std.mem.Allocator;
 pub const width = 240;
 pub const height = 160;
-pub const framebuf_pitch = width * @sizeOf(u16);
+pub const buf_pitch = width * @sizeOf(u16);
+const buf_len = buf_pitch * height;
 
 pub const Ppu = struct {
     const Self = @This();
@@ -15,27 +16,24 @@ pub const Ppu = struct {
     vram: Vram,
     palette: Palette,
     sched: *Scheduler,
-    framebuf: []u8,
+    frame_buf: []u8,
     alloc: Allocator,
 
     pub fn init(alloc: Allocator, sched: *Scheduler) !Self {
         // Queue first Hblank
         sched.push(.Draw, sched.tick + (240 * 4));
 
-        const framebuf = try alloc.alloc(u8, framebuf_pitch * height);
-        std.mem.set(u8, framebuf, 0);
-
         return Self{
             .vram = try Vram.init(alloc),
             .palette = try Palette.init(alloc),
             .sched = sched,
-            .framebuf = framebuf,
+            .frame_buf = try alloc.alloc(u8, buf_len),
             .alloc = alloc,
         };
     }
 
     pub fn deinit(self: Self) void {
-        self.alloc.free(self.framebuf);
+        self.alloc.free(self.frame_buf);
         self.vram.deinit();
         self.palette.deinit();
     }
@@ -46,10 +44,10 @@ pub const Ppu = struct {
 
         switch (bg_mode) {
             0x3 => {
-                const start = framebuf_pitch * @as(usize, scanline);
+                const start = buf_pitch * @as(usize, scanline);
-                const end = start + framebuf_pitch;
+                const end = start + buf_pitch;
 
-                std.mem.copy(u8, self.framebuf[start..end], self.vram.buf[start..end]);
+                std.mem.copy(u8, self.frame_buf[start..end], self.vram.buf[start..end]);
             },
             0x4 => {
                 const select = io.dispcnt.frame_select.read();
@@ -64,8 +62,8 @@ pub const Ppu = struct {
                     const id = byte * 2;
                     const j = i * @sizeOf(u16);
 
-                    self.framebuf[buf_start + j + 1] = self.palette.buf[id + 1];
+                    self.frame_buf[buf_start + j + 1] = self.palette.buf[id + 1];
-                    self.framebuf[buf_start + j] = self.palette.buf[id];
+                    self.frame_buf[buf_start + j] = self.palette.buf[id];
                 }
             },
             else => {}, // std.debug.panic("[PPU] TODO: Implement BG Mode {}", .{bg_mode}),
@@ -80,11 +78,8 @@ const Palette = struct {
     alloc: Allocator,
 
     fn init(alloc: Allocator) !Self {
-        const buf = try alloc.alloc(u8, 0x400);
-        std.mem.set(u8, buf, 0);
-
         return Self{
-            .buf = buf,
+            .buf = try alloc.alloc(u8, 0x400),
             .alloc = alloc,
         };
     }
@@ -123,8 +118,13 @@ const Vram = struct {
     alloc: Allocator,
 
     fn init(alloc: Allocator) !Self {
+        // In Modes 3 and 4, parts of the VRAM are copied to the
+        // frame buffer, therefore we want to zero-initialize Vram
+        //
+        // some programs like Armwrestler assume that VRAM is zeroed-out.
+        const black = std.mem.zeroes([0x18000]u8);
         const buf = try alloc.alloc(u8, 0x18000);
-        std.mem.set(u8, buf, 0);
+        std.mem.copy(u8, buf, &black);
 
         return Self{
             .buf = buf,

src/util.zig

@@ -1,10 +1,6 @@
 const std = @import("std");
 
-pub fn u32SignExtend(comptime bits: usize, value: u32) u32 {
+pub fn signExtend(comptime T: type, comptime bits: usize, value: anytype) T {
-    return @bitCast(u32, signExtend(i32, bits, @bitCast(i32, value)));
-}
-
-fn signExtend(comptime T: type, comptime bits: usize, value: anytype) T {
     const ValT = comptime @TypeOf(value);
     comptime std.debug.assert(isInteger(ValT));
     comptime std.debug.assert(isSigned(ValT));
@@ -20,6 +16,10 @@ fn signExtend(comptime T: type, comptime bits: usize, value: anytype) T {
     return ((value & ((1 << bits) - 1)) << bit_diff) >> bit_diff;
 }
 
+pub fn u32SignExtend(comptime bits: usize, value: u32) u32 {
+    return @bitCast(u32, signExtend(i32, bits, @bitCast(i32, value)));
+}
+
 fn isInteger(comptime T: type) bool {
     return @typeInfo(T) == .Int;
 }