io: add display unit

added rendering for modes 3,4,5
also changed how memory structuring works

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

include/memory.hh

@@ -0,0 +1,60 @@
+#pragma once
+
+#include <array>
+#include <cstddef>
+#include <cstdint>
+#include <vector>
+
+// ill use [] instead of at because i dont want if (...) throw conditions for
+// all accesses to improve performance (?)
+
+// we are also not gonna perform bound checks, as i expect the user to handle
+// those
+
+namespace matar {
+template<std::size_t N = 0>
+class Memory {
+    // we can use either a vector or an array with this
+    using Container = std::
+      conditional_t<(N != 0), std::array<uint8_t, N>, std::vector<uint8_t>>;
+
+  public:
+    Memory() = default;
+    Memory(auto x)
+      : memory(x) {}
+
+    uint8_t read_byte(std::size_t idx) const { return memory[idx]; }
+
+    void write_byte(std::size_t idx, uint8_t byte) { memory[idx] = byte; }
+
+    uint16_t read_halfword(std::size_t idx) const {
+        return memory[idx] | memory[idx + 1] << 8;
+    }
+
+    void write_halfword(std::size_t idx, uint16_t halfword) {
+        memory[idx]     = halfword & 0xFF;
+        memory[idx + 1] = halfword >> 8 & 0xFF;
+    }
+
+    uint32_t read_word(std::size_t idx) const {
+        return memory[idx] | memory[idx + 1] << 8 | memory[idx + 2] << 16 |
+               memory[idx + 3] << 24;
+    }
+
+    void write_word(std::size_t idx, uint32_t word) {
+        memory[idx]     = word & 0xFF;
+        memory[idx + 1] = word >> 8 & 0xFF;
+        memory[idx + 2] = word >> 16 & 0xFF;
+        memory[idx + 3] = word >> 24 & 0xFF;
+    }
+
+    uint8_t& operator[](std::size_t idx) { return memory.at(idx); }
+
+    Container& data() { return memory; }
+
+    std::size_t size() const { return memory.size(); }
+
+  private:
+    Container memory;
+};
+}