[GPU] Surface cache vol 1

include/renderer_gl/surface_cache.hpp

@@ -0,0 +1,62 @@
+#pragma once
+#include <functional>
+#include <optional>
+#include "surfaces.hpp"
+
+// Surface cache class that can fit "capacity" instances of the "SurfaceType" class of surfaces
+// SurfaceType *must* have all of the following
+// - An "allocate" function that allocates GL resources for the surfaces
+// - A "free" function that frees up all resources the surface is taking up
+// - A "matches" function that, when provided with a SurfaceType object reference
+// Will tell us if the 2 surfaces match (Only as far as location in VRAM, format, dimensions, etc)
+// Are concerned. We could overload the == operator, but that implies full equality
+// Including equality of the allocated OpenGL resources, which we don't want
+// - A "valid" member that tells us whether the function is still valid or not
+template <typename SurfaceType, size_t capacity>
+class SurfaceCache {
+    // Vanilla std::optional can't hold actual references
+    using OptionalRef = std::optional<std::reference_wrapper<SurfaceType>>;
+    static_assert(std::is_same<SurfaceType, ColourBuffer>() || std::is_same<SurfaceType, DepthBuffer>(),
+        "Invalid surface type");
+
+    size_t size;
+    std::array<SurfaceType, capacity> buffer;
+
+public:
+    void reset() {
+        size = 0;
+        for (auto& e : buffer) { // Free the VRAM of all surfaces
+            e.free();
+        }
+    }
+
+    OptionalRef find(SurfaceType& other) {
+        for (auto& e : buffer) {
+            if (e.matches(other) && e.valid)
+                return e;
+        }
+
+        return std::nullopt;
+    }
+
+    // Adds a surface object to the cache and returns it
+    SurfaceType add(SurfaceType& surface) {
+        if (size >= capacity) {
+            Helpers::panic("Surface cache full! Add emptying!");
+        }
+        size++;
+
+        // Find an invalid entry in the cache and overwrite it with the new surface
+        for (auto& e : buffer) {
+            if (!e.valid) {
+                e = surface;
+                e.allocate();
+                Sleep(2000);
+                return e;
+            }
+        }
+
+        // This should be unreachable but helps to panic anyways
+        Helpers::panic("Couldn't add surface to cache\n");
+    }
+};