Add: C interface

README.md

@@ -40,6 +40,8 @@ the CMake script. The library is tested on GCC 9, GCC 10, Clang 12, and MSVC 14
 using CI. The project uses a simple CMake 3.11, and can be simply used by adding fastgltf as a
 subdirectory. Also, fastgltf is available from [vcpkg](https://github.com/microsoft/vcpkg).
 
+### C++ API
+
 ```cpp
 #include <fastgltf_parser.hpp>
 #include <fastgltf_types.hpp>
@@ -84,6 +86,41 @@ All the nodes, meshes, buffers, textures, ... can now be accessed through the `f
 type. References in between objects are done with a single `size_t`, which is used to index into
 the various vectors in the asset.
 
+### C89 API
+
+```c
+#include <fastgltf_c.h>
+
+void load(const char* path, const char* directory) {
+    // Creates a parser object
+    fastgltf_parser* parser = fastgltf_create_parser(0);
+    
+    fastgltf_json_data* data = fastgltf_create_json_data_from_file(path);
+    
+    // For GLB files, use fastgltf_load_binary_gltf
+    fastgltf_gltf* gltf = fastgltf_load_gltf(parser, data, directory, OptionsDontRequireValidAssetMember);
+    if (fastgltf_get_parser_error(parser) != ErrorNone) {
+        // error
+    }
+    
+    // Tell fastgltf to parse the whole glTF structure. Optionally, you can parse individual
+    // aspects of glTF files by calling the various parse methods.
+    fastgltf_parse_all(gltf);
+
+    // You can now destroy the parser and JSON data. It is advised, however, to reuse parsers.
+    fastgltf_destroy_json_data(data);
+    fastgltf_destroy_parser(parser);
+    
+    // You can now query the parsed asset and destroy the glTF object. 
+    fastgltf_asset* asset = fastgltf_get_parsed_asset(gltf);
+    fastgltf_destroy_gltf(gltf);
+    
+    // Use the parsed asset here.
+    
+    fastgltf_destroy_asset(asset);
+}
+```
+
 ## Performance
 
 [spreadsheet-link]: https://docs.google.com/spreadsheets/d/1ocdHGoty-rF0N46ZlAlswzcPHVRsqG_tncy8paD3iMY/edit?usp=sharing

cmake/compiler_flags.cmake

@@ -9,7 +9,13 @@ macro(compiler_flags)
     # cpuid, meaning no architecture flags or other compile flags need to be passed.
     # See https://github.com/simdjson/simdjson/blob/master/doc/implementation-selection.md.
     if (MSVC)
-        target_compile_options(${PARAM_TARGET} PRIVATE /EHsc $<$<CONFIG:RELEASE>:/O2 /Ob2 /Ot>)
+        target_compile_options(${PARAM_TARGET} PRIVATE /EHsc $<$<CONFIG:RELEASE>:/O2>)
+        if (MSVC_VERSION GREATER_EQUAL 1920)
+            # With VS 16 (2019) /Ob3 was added to more aggressively inline functions.
+            target_compile_options(${PARAM_TARGET} PRIVATE $<$<CONFIG:RELEASE>:/Ob3>)
+        else()
+            target_compile_options(${PARAM_TARGET} PRIVATE $<$<CONFIG:RELEASE>:/Ob2>)
+        endif()
     elseif(CMAKE_CXX_COMPILER_ID STREQUAL "Clang" OR CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
         target_compile_options(${PARAM_TARGET} PRIVATE $<$<CONFIG:RELEASE>:-O3>)
     endif()

src/fastgltf_c.cpp

@@ -0,0 +1,65 @@
+#include <fastgltf_c.h>
+
+#include <fastgltf_parser.hpp>
+#include <fastgltf_types.hpp>
+
+fastgltf_parser* fastgltf_create_parser(fastgltf_extensions extensions) {
+    return reinterpret_cast<fastgltf_parser*>(
+        new fastgltf::Parser(static_cast<fastgltf::Extensions>(extensions)));
+}
+
+void fastgltf_destroy_parser(fastgltf_parser* parser) {
+    delete reinterpret_cast<fastgltf::Parser*>(parser);
+}
+
+fastgltf_gltf_data_buffer* fastgltf_create_gltf_data_buffer(unsigned char* bytes, size_t size) {
+    auto data = new (std::nothrow) fastgltf::GltfDataBuffer();
+    data->copyBytes(bytes, size);
+    return reinterpret_cast<fastgltf_gltf_data_buffer*>(data);
+}
+
+fastgltf_gltf_data_buffer* fastgltf_create_gltf_data_buffer_from_file(const char* file) {
+    auto data = new (std::nothrow) fastgltf::GltfDataBuffer();
+    data->loadFromFile(std::string_view { file });
+    return reinterpret_cast<fastgltf_gltf_data_buffer*>(data);
+}
+
+void fastgltf_destroy_json_data(fastgltf_gltf_data_buffer* data) {
+    delete reinterpret_cast<fastgltf::GltfDataBuffer*>(data);
+}
+
+fastgltf_error fastgltf_get_parser_error(fastgltf_parser* parser) {
+    return static_cast<fastgltf_error>(
+        reinterpret_cast<fastgltf::Parser*>(parser)->getError());
+}
+
+fastgltf_gltf* fastgltf_load_gltf(fastgltf_parser* parser, fastgltf_gltf_data_buffer* json, const char* directory, fastgltf_options options) {
+    auto gltf = reinterpret_cast<fastgltf::Parser*>(parser)->loadGLTF(
+        reinterpret_cast<fastgltf::GltfDataBuffer*>(json), std::string_view { directory }, static_cast<fastgltf::Options>(options));
+    return reinterpret_cast<fastgltf_gltf*>(gltf.release());
+}
+
+fastgltf_gltf* fastgltf_load_binary_gltf(fastgltf_parser* parser, fastgltf_gltf_data_buffer* data, const char* directory, fastgltf_options options) {
+    auto gltf = reinterpret_cast<fastgltf::Parser*>(parser)->loadBinaryGLTF(
+        reinterpret_cast<fastgltf::GltfDataBuffer*>(data), std::string_view { directory }, static_cast<fastgltf::Options>(options));
+    return reinterpret_cast<fastgltf_gltf*>(gltf.release());
+}
+
+void fastgltf_destroy_gltf(fastgltf_gltf* gltf) {
+    delete reinterpret_cast<fastgltf::glTF*>(gltf);
+}
+
+fastgltf_error fastgltf_parse(fastgltf_gltf* gltf, fastgltf_category categories) {
+    return static_cast<fastgltf_error>(reinterpret_cast<fastgltf::glTF*>(gltf)->parse(static_cast<fastgltf::Category>(categories)));
+}
+
+fastgltf_asset* fastgltf_get_parsed_asset(fastgltf_gltf* gltf) {
+    // Obtain the unique_ptr from the glTF and release it. Otherwise, it gets destroyed with the
+    // destructor of fastgltf::glTF.
+    auto asset = reinterpret_cast<fastgltf::glTF*>(gltf)->getParsedAsset();
+    return reinterpret_cast<fastgltf_asset*>(asset.release());
+}
+
+void fastgltf_destroy_asset(fastgltf_asset* asset) {
+    delete reinterpret_cast<fastgltf::Asset*>(asset);
+}

src/fastgltf_c.h

@@ -0,0 +1,85 @@
+enum fastgltf_extensions {
+    KHR_texture_transform = 1 << 1,
+    KHR_texture_basisu = 1 << 2,
+    MSFT_texture_dds = 1 << 3,
+    KHR_mesh_quantization = 1 << 4,
+    EXT_meshopt_compression = 1 << 5,
+};
+
+enum fastgltf_options {
+    OptionsAllowDouble = 1 << 0,
+    OptionsDontRequireValidAssetMember = 1 << 1,
+    OptionsDontUseSIMD = 1 << 2,
+    OptionsLoadGLBBuffers = 1 << 3,
+    OptionsLoadExternalBuffers = 1 << 4,
+    OptionsDecomposeNodeMatrices = 1 << 5,
+};
+
+enum fastgltf_error {
+    ErrorNone = 0,
+    ErrorInvalidPath = 1,
+    ErrorMissingExtensions = 2,
+    ErrorUnsupportedExtensions = 3,
+    ErrorInvalidJson = 4,
+    ErrorInvalidGltf = 5,
+    ErrorInvalidOrMissingAssetField = 6,
+    ErrorInvalidGLB = 6,
+    ErrorMissingField = 7,
+    ErrorMissingExternalBuffer = 8,
+    ErrorUnsupportedVersion = 9,
+};
+
+enum fastgltf_category {
+    CategoryNone = 0,
+
+    CategoryBuffers = 1 << 0,
+    CategoryBufferViews = 1 << 1 | CategoryBuffers,
+    CategoryAccessors = 1 << 2 | CategoryBufferViews,
+    CategoryImages = 1 << 3 | CategoryBufferViews,
+    CategorySamplers = 1 << 4,
+    CategoryTextures = 1 << 5 | CategoryImages | CategorySamplers,
+    CategoryAnimations = 1 << 6 | CategoryAccessors,
+    CategoryCameras = 1 << 7,
+    CategoryMaterials = 1 << 8 | CategoryTextures,
+    CategoryMeshes = 1 << 9 | CategoryAccessors | CategoryMaterials,
+    CategorySkins = 1 << 10 | CategoryAccessors | (1 << 11),
+    CategoryNodes = 1 << 11 | CategoryCameras | CategoryMeshes | CategorySkins,
+    CategoryScenes = 1 << 12 | CategoryNodes,
+    CategoryAsset = 1 << 13,
+
+    CategoryAll = CategoryAsset | CategoryScenes | CategoryAnimations,
+};
+
+#define FASTGLTF_EXPORT
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct fastgltf_parser_s fastgltf_parser;
+typedef struct fastgltf_gltf_data_buffer_s fastgltf_gltf_data_buffer;
+typedef struct fastgltf_gltf_s fastgltf_gltf;
+typedef struct fastgltf_asset_s fastgltf_asset;
+
+FASTGLTF_EXPORT fastgltf_parser* fastgltf_create_parser(fastgltf_extensions extensions);
+FASTGLTF_EXPORT void fastgltf_destroy_parser(fastgltf_parser* parser);
+
+FASTGLTF_EXPORT fastgltf_gltf_data_buffer_s* fastgltf_create_gltf_data_buffer(unsigned char* bytes, size_t size);
+FASTGLTF_EXPORT fastgltf_gltf_data_buffer_s* fastgltf_create_gltf_data_buffer_from_file(const char* filePath);
+FASTGLTF_EXPORT void fastgltf_destroy_json_data(fastgltf_gltf_data_buffer* data);
+
+FASTGLTF_EXPORT fastgltf_error fastgltf_get_parser_error(fastgltf_parser* parser);
+FASTGLTF_EXPORT fastgltf_gltf* fastgltf_load_gltf(fastgltf_parser* parser, fastgltf_gltf_data_buffer* json, const char* directory, fastgltf_options options);
+FASTGLTF_EXPORT fastgltf_gltf* fastgltf_load_binary_gltf(fastgltf_parser* parser, fastgltf_gltf_data_buffer* data, const char* directory, fastgltf_options options);
+FASTGLTF_EXPORT void fastgltf_destroy_gltf(fastgltf_gltf* gltf);
+
+FASTGLTF_EXPORT fastgltf_error fastgltf_parse(fastgltf_gltf* gltf, fastgltf_category categories);
+
+FASTGLTF_EXPORT fastgltf_asset* fastgltf_get_parsed_asset(fastgltf_gltf* gltf);
+FASTGLTF_EXPORT void fastgltf_destroy_asset(fastgltf_asset* asset);
+
+#ifdef __cplusplus
+}
+#endif
+
+#undef FASTGLTF_EXPORT

src/fastgltf_types.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <array>
+#include <cassert>
 #include <cstdint>
 #include <filesystem>
 #include <optional>