Fix determineGltfFileType

examples/gl_viewer/gl_viewer.cpp

@@ -333,28 +333,31 @@ bool loadGltf(Viewer* viewer, std::string_view cPath) {
     std::cout << "Loading " << cPath << '\n';
 
     // Parse the glTF file and get the constructed asset
-    {
+	{
 		static constexpr auto supportedExtensions =
 			fastgltf::Extensions::KHR_mesh_quantization |
 			fastgltf::Extensions::KHR_texture_transform |
 			fastgltf::Extensions::KHR_materials_variants;
 
-        fastgltf::Parser parser(supportedExtensions);
+		fastgltf::Parser parser(supportedExtensions);
 
-        auto path = std::filesystem::path{cPath};
+		auto path = std::filesystem::path{cPath};
 
-        constexpr auto gltfOptions =
-            fastgltf::Options::DontRequireValidAssetMember |
-            fastgltf::Options::AllowDouble |
-            fastgltf::Options::LoadGLBBuffers |
-            fastgltf::Options::LoadExternalBuffers |
-            fastgltf::Options::LoadExternalImages |
+		constexpr auto gltfOptions =
+			fastgltf::Options::DontRequireValidAssetMember |
+			fastgltf::Options::AllowDouble |
+			fastgltf::Options::LoadGLBBuffers |
+			fastgltf::Options::LoadExternalBuffers |
+			fastgltf::Options::LoadExternalImages |
 			fastgltf::Options::GenerateMeshIndices;
 
-        fastgltf::GltfDataBuffer data;
-        data.loadFromFile(path);
+		fastgltf::GltfFileStream data(path);
+		if (!data.isOpen()) {
+			std::cerr << "Failed to open glTF file: " << path << '\n';
+			return false;
+		}
 
-        auto asset = parser.loadGltf(&data, path.parent_path(), gltfOptions);
+        auto asset = parser.loadGltf(data, path.parent_path(), gltfOptions);
         if (asset.error() != fastgltf::Error::None) {
             std::cerr << "Failed to load glTF: " << fastgltf::getErrorMessage(asset.error()) << '\n';
             return false;

src/fastgltf.cpp

@@ -3754,6 +3754,7 @@ std::size_t fg::GltfDataBuffer::totalSize() {
 
 fg::GltfFileStream::GltfFileStream(const std::filesystem::path &path) : fileStream(path, std::ios::binary) {
 	fileSize = std::filesystem::file_size(path);
+	reset();
 }
 
 bool fg::GltfFileStream::isOpen() const {
@@ -3840,24 +3841,30 @@ bool fg::AndroidGltfDataBuffer::loadFromAndroidAsset(const fs::path& path, std::
 
 #pragma region Parser
 fastgltf::GltfType fg::determineGltfFileType(GltfDataGetter& data) {
+	GltfType ret = GltfType::Invalid;
+
 	// We'll try and read a BinaryGltfHeader from the buffer to see if the magic is correct.
 	BinaryGltfHeader header = {};
 	data.read(&header, sizeof header);
 	if (header.magic == binaryGltfHeaderMagic) {
-		return GltfType::GLB;
+		ret = GltfType::GLB;
 	}
+	data.reset();
 
-	// First, check if any of the first four characters is a '{'.
+	// Check if any of the first four characters is a '{'.
 	std::array<std::uint8_t, 4> begin = {};
 	data.read(begin.data(), begin.size());
 	for (const auto& i : begin) {
 		if ((char)i == ' ')
 			continue;
-		if ((char)i == '{')
-			return GltfType::glTF;
+		if ((char)i == '{') {
+			ret = GltfType::glTF;
+			break;
+		}
 	}
 
-	return GltfType::Invalid;
+	data.reset();
+	return ret;
 }
 
 fg::Parser::Parser(Extensions extensionsToLoad) noexcept {