chore: change directory structure

src/core/bus/Bios.zig

@@ -0,0 +1,58 @@
+const std = @import("std");
+
+const Allocator = std.mem.Allocator;
+const log = std.log.scoped(.Bios);
+
+/// Size of the BIOS in bytes
+pub const size = 0x4000;
+const Self = @This();
+
+buf: ?[]u8,
+alloc: Allocator,
+
+addr_latch: u32,
+
+pub fn init(alloc: Allocator, maybe_path: ?[]const u8) !Self {
+    var buf: ?[]u8 = null;
+    if (maybe_path) |path| {
+        const file = try std.fs.cwd().openFile(path, .{});
+        defer file.close();
+        buf = try file.readToEndAlloc(alloc, try file.getEndPos());
+    }
+
+    return Self{
+        .buf = buf,
+        .alloc = alloc,
+        .addr_latch = 0,
+    };
+}
+
+pub fn deinit(self: Self) void {
+    if (self.buf) |buf| self.alloc.free(buf);
+}
+
+pub fn checkedRead(self: *Self, comptime T: type, r15: u32, addr: u32) T {
+    if (r15 < Self.size) {
+        self.addr_latch = addr;
+        return self.read(T, addr);
+    }
+
+    log.debug("Rejected read since r15=0x{X:0>8}", .{r15});
+    return @truncate(T, self.read(T, self.addr_latch + 8));
+}
+
+fn read(self: *const Self, comptime T: type, addr: u32) T {
+    if (self.buf) |buf| {
+        return switch (T) {
+            u32, u16, u8 => std.mem.readIntSliceLittle(T, buf[addr..][0..@sizeOf(T)]),
+            else => @compileError("BIOS: Unsupported read width"),
+        };
+    }
+
+    std.debug.panic("[BIOS] ZBA tried to read {} from 0x{X:0>8} but not BIOS was present", .{ T, addr });
+}
+
+pub fn write(_: *Self, comptime T: type, addr: u32, value: T) void {
+    @setCold(true);
+    log.debug("Tried to write {} 0x{X:} to 0x{X:0>8} ", .{ T, value, addr });
+}