feat(bus): implement IWRAM and EWRAM

src/bus/Iwram.zig

@@ -0,0 +1,44 @@
+const std = @import("std");
+
+const Allocator = std.mem.Allocator;
+const Self = @This();
+
+buf: []u8,
+alloc: Allocator,
+
+pub fn init(alloc: Allocator) !Self {
+    return Self{
+        .buf = try alloc.alloc(u8, 0x40000),
+        .alloc = alloc,
+    };
+}
+
+pub fn deinit(self: Self) void {
+    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 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 set8(self: *Self, idx: usize, byte: u8) void {
+    self.buf[idx] = byte;
+}