From effb6315e973701af0d0e726170d05066b5b6c4e Mon Sep 17 00:00:00 2001
From: Rekai Musuka <rekai@musuka.dev>
Date: Fri, 21 Oct 2022 05:12:31 -0300
Subject: [PATCH] chore: write generic read/write for VRAM

---
 src/Bus.zig | 10 +++++-----
 src/ppu.zig | 43 +++++++++++++++++++++++--------------------
 2 files changed, 28 insertions(+), 25 deletions(-)

diff --git a/src/Bus.zig b/src/Bus.zig
index a1eec70..91162ea 100644
--- a/src/Bus.zig
+++ b/src/Bus.zig
@@ -61,7 +61,7 @@ pub fn read32(self: *const Self, addr: u32) u32 {
 
         // Internal Display Memory
         0x0500_0000...0x05FF_FFFF => self.ppu.palette.get32(addr & 0x3FF),
-        0x0600_0000...0x0601_7FFF => self.ppu.vram.get32(addr - 0x0600_0000),
+        0x0600_0000...0x0601_7FFF => self.ppu.vram.read(u32, addr - 0x0600_0000),
         0x0700_0000...0x07FF_FFFF => self.ppu.oam.get32(addr & 0x3FF),
 
         // External Memory (Game Pak)
@@ -84,7 +84,7 @@ pub fn write32(self: *Self, addr: u32, word: u32) void {
 
         // Internal Display Memory
         0x0500_0000...0x05FF_FFFF => self.ppu.palette.set32(addr & 0x3FF, word),
-        0x0600_0000...0x0601_7FFF => self.ppu.vram.set32(addr - 0x0600_0000, word),
+        0x0600_0000...0x0601_7FFF => self.ppu.vram.write(u32, addr - 0x0600_0000, word),
         0x0700_0000...0x07FF_FFFF => self.ppu.oam.set32(addr & 0x3FF, word),
 
         else => undWrite("Tried to write 0x{X:0>8} to 0x{X:0>8}", .{ word, addr }),
@@ -101,7 +101,7 @@ pub fn read16(self: *const Self, addr: u32) u16 {
 
         // Internal Display Memory
         0x0500_0000...0x05FF_FFFF => self.ppu.palette.get16(addr & 0x3FF),
-        0x0600_0000...0x0601_7FFF => self.ppu.vram.get16(addr - 0x0600_0000),
+        0x0600_0000...0x0601_7FFF => self.ppu.vram.read(u16, addr - 0x0600_0000),
         0x0700_0000...0x07FF_FFFF => self.ppu.oam.get16(addr & 0x3FF),
 
         // External Memory (Game Pak)
@@ -123,7 +123,7 @@ pub fn write16(self: *Self, addr: u32, halfword: u16) void {
 
         // Internal Display Memory
         0x0500_0000...0x05FF_FFFF => self.ppu.palette.set16(addr & 0x3FF, halfword),
-        0x0600_0000...0x0601_7FFF => self.ppu.vram.set16(addr - 0x0600_0000, halfword),
+        0x0600_0000...0x0601_7FFF => self.ppu.vram.write(u16, addr - 0x0600_0000, halfword),
         0x0700_0000...0x07FF_FFFF => self.ppu.oam.set16(addr & 0x3FF, halfword),
         0x0800_00C4, 0x0800_00C6, 0x0800_00C8 => log.warn("Tried to write 0x{X:0>4} to GPIO", .{halfword}),
 
@@ -141,7 +141,7 @@ pub fn read8(self: *const Self, addr: u32) u8 {
 
         // Internal Display Memory
         0x0500_0000...0x05FF_FFFF => self.ppu.palette.get8(addr & 0x3FF),
-        0x0600_0000...0x0601_7FFF => self.ppu.vram.get8(addr - 0x0600_0000),
+        0x0600_0000...0x0601_7FFF => self.ppu.vram.read(u8, addr - 0x0600_0000),
         0x0700_0000...0x07FF_FFFF => self.ppu.oam.get8(addr & 0x3FF),
 
         // External Memory (Game Pak)
diff --git a/src/ppu.zig b/src/ppu.zig
index d8766da..5fb37d3 100644
--- a/src/ppu.zig
+++ b/src/ppu.zig
@@ -241,7 +241,7 @@ pub const Ppu = struct {
 
             // Grab the Screen Entry from VRAM
             const entry_addr = screen_base + tilemapOffset(size, x, y);
-            const entry = @bitCast(ScreenEntry, self.vram.get16(entry_addr));
+            const entry = @bitCast(ScreenEntry, self.vram.read(u16, entry_addr));
 
             // Calculate the Address of the Tile in the designated Charblock
             // We also take this opportunity to flip tiles if necessary
@@ -309,7 +309,7 @@ pub const Ppu = struct {
 
                 var i: usize = 0;
                 while (i < width) : (i += 1) {
-                    const bgr555 = self.vram.get16(vram_base + i * @sizeOf(u16));
+                    const bgr555 = self.vram.read(u16, vram_base + i * @sizeOf(u16));
                     std.mem.copy(u8, self.framebuf[fb_base + i * @sizeOf(u32) ..][0..4], &intToBytes(u32, toRgba8888(bgr555)));
                 }
             },
@@ -479,26 +479,29 @@ const Vram = struct {
         self.alloc.free(self.buf);
     }
 
-    pub fn get32(self: *const Self, idx: usize) u32 {
-        return (@as(u32, self.get16(idx + 2)) << 16) | @as(u32, self.get16(idx));
+    pub fn read(self: *const Self, comptime T: type, addr: usize) T {
+        switch (T) {
+            u32 => return (@as(T, self.buf[addr + 3]) << 24) | (@as(T, self.buf[addr + 2]) << 16) | (@as(T, self.buf[addr + 1]) << 8) | (@as(T, self.buf[addr])),
+            u16 => return (@as(T, self.buf[addr + 1]) << 8) | @as(T, self.buf[addr]),
+            u8 => return self.buf[addr],
+            else => @compileError("VRAM: Unsupported read width"),
+        }
     }
 
-    pub fn set32(self: *Self, idx: usize, word: u32) void {
-        self.set16(idx + 2, @truncate(u16, word >> 16));
-        self.set16(idx, @truncate(u16, word));
-    }
-
-    pub fn get16(self: *const Self, idx: usize) u16 {
-        return (@as(u16, self.buf[idx + 1]) << 8) | @as(u16, self.buf[idx]);
-    }
-
-    pub fn set16(self: *Self, idx: usize, halfword: u16) void {
-        self.buf[idx + 1] = @truncate(u8, halfword >> 8);
-        self.buf[idx] = @truncate(u8, halfword);
-    }
-
-    pub fn get8(self: *const Self, idx: usize) u8 {
-        return self.buf[idx];
+    pub fn write(self: *Self, comptime T: type, addr: usize, value: T) void {
+        switch (T) {
+            u32 => {
+                self.buf[addr + 3] = @truncate(u8, value >> 24);
+                self.buf[addr + 2] = @truncate(u8, value >> 16);
+                self.buf[addr + 1] = @truncate(u8, value >> 8);
+                self.buf[addr + 0] = @truncate(u8, value >> 0);
+            },
+            u16 => {
+                self.buf[addr + 1] = @truncate(u8, value >> 8);
+                self.buf[addr + 0] = @truncate(u8, value >> 0);
+            },
+            else => @compileError("VRAM: Unsupported write width"),
+        }
     }
 };