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fix(ppu): fix integer overflow error in bg fetcher

This commit is contained in:
Rekai Nyangadzayi Musuka 2021-06-03 00:41:21 -05:00
parent 66c2b51e10
commit 138aba52c1
1 changed files with 12 additions and 12 deletions
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24
src/ppu.rs
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@ -337,7 +337,7 @@ impl Ppu {
}
ToLowByteSleep => self.fetch.back.next(TileLowByte),
TileLowByte => {
let addr = self.fetch.bg_byte_low_addr(&self.control, &self.pos);
let addr = self.fetch.bg_byte_addr(&self.control, &self.pos);
let low = self.read_byte(addr);
self.fetch.back.tile.with_low_byte(low);
@ -346,7 +346,7 @@ impl Ppu {
}
ToHighByteSleep => self.fetch.back.next(TileHighByte),
TileHighByte => {
let addr = self.fetch.bg_byte_low_addr(&self.control, &self.pos);
let addr = self.fetch.bg_byte_addr(&self.control, &self.pos);
let high = self.read_byte(addr + 1);
self.fetch.back.tile.with_high_byte(high);
@ -655,21 +655,21 @@ impl PixelFetcher {
// Both Offsets are used to offset the tile map address we found above
// Offsets are ANDed wih 0x3FF so that we stay in bounds of tile map memory
// TODO: Is this necessary / important in other fetcher modes?
let scx_offset = if is_window { 0u16 } else { scroll_x as u16 / 8 } & 0x1F;
let scx_offset = if is_window { 0 } else { scroll_x / 8 };
let y_offset = if is_window {
self.back.window_line.count() as u16 / 8
} else {
((line_y as u16 + scroll_y as u16) & 0xFF) / 8
} * 32;
};
let x_offset = x_pos as u16 + scx_offset;
let x_offset = (scx_offset + x_pos) & 0x1F;
let offset = (32 * y_offset) + (x_offset as u16);
tile_map_addr + ((x_offset + y_offset) & 0x3FF)
tile_map_addr + (offset & 0x3FF)
}
fn bg_byte_low_addr(&mut self, control: &LCDControl, pos: &ScreenPosition) -> u16 {
fn bg_byte_addr(&mut self, control: &LCDControl, pos: &ScreenPosition) -> u16 {
let line_y = pos.line_y;
let scroll_y = pos.scroll_y;
let is_window = self.back.is_window_tile();
@ -677,17 +677,17 @@ impl PixelFetcher {
let id = self.back.tile.id.expect("Tile Number unexpectedly missing");
let tile_data_addr = match control.tile_data_addr() {
TileDataAddress::X8800 => 0x9000u16.wrapping_add((id as i8).wrapping_mul(16) as u16),
TileDataAddress::X8000 => 0x8000 + (id as u16).wrapping_mul(16),
TileDataAddress::X8800 => 0x9000u16.wrapping_add((id as u16) * 16),
TileDataAddress::X8000 => 0x8000 + (id as u16 * 16),
};
let offset = if is_window {
self.back.window_line.count() % 8
} else {
(line_y + scroll_y) % 8
} * 2;
};
tile_data_addr + offset as u16
tile_data_addr + (2 * offset as u16)
}
fn send_to_fifo(&self, fifo: &mut FifoRenderer, palette: &BackgroundPalette) {