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chore: mirror VRAM

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This commit is contained in:
Rekai Nyangadzayi Musuka
2022-04-08 00:55:04 -03:00
parent 9b9de11e0c
commit 5310c12669
2 changed files with 21 additions and 12 deletions
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23
src/ppu.zig
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@@ -479,16 +479,20 @@ const Vram = struct {
self.alloc.free(self.buf);
}
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],
pub fn read(self: *const Self, comptime T: type, address: usize) T {
const addr = Self.mirror(address);
return switch (T) {
u32 => (@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 => (@as(T, self.buf[addr + 1]) << 8) | @as(T, self.buf[addr]),
u8 => self.buf[addr],
else => @compileError("VRAM: Unsupported read width"),
}
};
}
pub fn write(self: *Self, comptime T: type, addr: usize, value: T) void {
pub fn write(self: *Self, comptime T: type, address: usize, value: T) void {
const addr = Self.mirror(address);
switch (T) {
u32 => {
self.buf[addr + 3] = @truncate(u8, value >> 24);
@@ -503,6 +507,11 @@ const Vram = struct {
else => @compileError("VRAM: Unsupported write width"),
}
}
fn mirror(address: usize) usize {
const addr = address & 0x1FFFF; // repeated in steps of 128KiB
return if (addr >= 0x18000) addr & 0x7FFF else addr; // 64K + 32K + 32K (abcc)
}
};
const Oam = struct {