add nes cartridge subsystem and 41 ines mapper variants

src/system/nes/mapper/mapper119.zig

@@ -0,0 +1,113 @@
+const types = @import("types.zig");
+const Mirroring = types.Mirroring;
+const Mmc3 = @import("mmc3.zig");
+
+const Mapper119 = @This();
+
+mmc3: Mmc3,
+
+pub fn init(
+    prg_size: usize,
+    chr_size: usize,
+) Mapper119 {
+    return .{
+        .mmc3 = Mmc3.init(prg_size, chr_size),
+    };
+}
+
+pub fn cpuMapRead(
+    self: *const Mapper119,
+    address: u16,
+) ?usize {
+    return self.mmc3.cpuMapRead(address);
+}
+
+pub fn cpuWrite(
+    self: *Mapper119,
+    address: u16,
+    value: u8,
+) void {
+    self.mmc3.cpuWrite(address, value);
+}
+
+pub fn ppuMapRead(
+    self: *Mapper119,
+    address: u16,
+) ?usize {
+    if (address >= 0x2000) return null;
+
+    const bank_val = self.getChrBankValue(address);
+    const offset = (address % 0x0400);
+
+    if ((bank_val & 0x40) != 0) {
+        // Bit 6 is set -> Route to CHR RAM
+        const ram_bank = @as(usize, bank_val & 7);
+        return 0x80000000 | (ram_bank * 0x0400 + offset);
+    } else {
+        // Route to CHR ROM
+        return self.mmc3.ppuMapRead(address);
+    }
+}
+
+pub fn ppuMapWrite(
+    self: *const Mapper119,
+    address: u16,
+) ?usize {
+    if (address >= 0x2000) return null;
+
+    const bank_val = self.getChrBankValue(address);
+    const offset = (address % 0x0400);
+
+    if ((bank_val & 0x40) != 0) {
+        // Bit 6 is set -> Route write to CHR RAM
+        const ram_bank = @as(usize, bank_val & 7);
+        return 0x80000000 | (ram_bank * 0x0400 + offset);
+    } else {
+        return self.mmc3.ppuMapWrite(address);
+    }
+}
+
+fn getChrBankValue(self: *const Mapper119, address: u16) u8 {
+    const chr_mode = (self.mmc3.bank_select & 0x80) != 0;
+    const addr_k = address / 0x0400;
+
+    if (!chr_mode) {
+        return switch (addr_k) {
+            0, 1 => (self.mmc3.bank_registers[0] & 0xfe) + @as(u8, @intCast(addr_k & 1)),
+            2, 3 => (self.mmc3.bank_registers[1] & 0xfe) + @as(u8, @intCast(addr_k & 1)),
+            4 => self.mmc3.bank_registers[2],
+            5 => self.mmc3.bank_registers[3],
+            6 => self.mmc3.bank_registers[4],
+            7 => self.mmc3.bank_registers[5],
+            else => unreachable,
+        };
+    } else {
+        return switch (addr_k) {
+            0 => self.mmc3.bank_registers[2],
+            1 => self.mmc3.bank_registers[3],
+            2 => self.mmc3.bank_registers[4],
+            3 => self.mmc3.bank_registers[5],
+            4, 5 => (self.mmc3.bank_registers[0] & 0xfe) + @as(u8, @intCast(addr_k & 1)),
+            6, 7 => (self.mmc3.bank_registers[1] & 0xfe) + @as(u8, @intCast(addr_k & 1)),
+            else => unreachable,
+        };
+    }
+}
+
+pub fn mirroring(
+    self: *const Mapper119,
+) Mirroring {
+    return self.mmc3.mirroring();
+}
+
+pub fn irqAsserted(
+    self: *const Mapper119,
+) bool {
+    return self.mmc3.irqAsserted();
+}
+
+pub fn handleScanline(
+    self: *Mapper119,
+) void {
+    self.mmc3.handleScanline();
+}