Implement initial Unity-style asset library cache

engine/src/Core/IO/IResourceLoader.cpp

@@ -1,28 +1,57 @@
 #include <XCEngine/Core/IO/IResourceLoader.h>
+#include <XCEngine/Core/Asset/ResourceManager.h>
+#include <filesystem>
 #include <fstream>
 
 namespace XCEngine {
 namespace Resources {
 
-Containers::Array<Core::uint8> IResourceLoader::ReadFileData(const Containers::String& path) {
+namespace {
+
+Containers::Array<Core::uint8> TryReadFileData(
+    const std::filesystem::path& filePath,
+    bool& opened) {
     Containers::Array<Core::uint8> data;
-    
-    std::ifstream file(path.CStr(), std::ios::binary | std::ios::ate);
+
+    std::ifstream file(filePath, std::ios::binary | std::ios::ate);
     if (!file.is_open()) {
+        opened = false;
         return data;
     }
-    
-    std::streamsize size = file.tellg();
+
+    opened = true;
+    const std::streamsize size = file.tellg();
+    if (size <= 0) {
+        return data;
+    }
+
     file.seekg(0, std::ios::beg);
-    
     data.Resize(static_cast<size_t>(size));
     if (!file.read(reinterpret_cast<char*>(data.Data()), size)) {
         data.Clear();
     }
-    
+
     return data;
 }
 
+} // namespace
+
+Containers::Array<Core::uint8> IResourceLoader::ReadFileData(const Containers::String& path) {
+    bool opened = false;
+    const std::filesystem::path inputPath(path.CStr());
+    Containers::Array<Core::uint8> data = TryReadFileData(inputPath, opened);
+    if (opened || path.Empty() || inputPath.is_absolute()) {
+        return data;
+    }
+
+    const Containers::String& resourceRoot = ResourceManager::Get().GetResourceRoot();
+    if (resourceRoot.Empty()) {
+        return data;
+    }
+
+    return TryReadFileData(std::filesystem::path(resourceRoot.CStr()) / inputPath, opened);
+}
+
 Containers::String IResourceLoader::GetExtension(const Containers::String& path) {
     Containers::String ext;
     size_t dotPos = Containers::String::npos;