glTF2: Avoid lookups for generating IDs (#6120)

* glTF2: Reduce lookups for generating IDs
- closes https://github.com/assimp/assimp/issues/5661

code/AssetLib/FBX/FBXCompileConfig.h

@@ -49,7 +49,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <set>
 
 //
-#if _MSC_VER > 1500 || (defined __GNUC___)
+#if _MSC_VER > 1500 || (defined __GNUC__)
 #   define ASSIMP_FBX_USE_UNORDERED_MULTIMAP
 #   else
 #   define fbx_unordered_map map

code/AssetLib/Step/STEPFile.h

@@ -58,7 +58,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #    pragma warning(disable : 4127 4456 4245 4512 )
 #endif // _MSC_VER
 
-#if _MSC_VER > 1500 || (defined __GNUC___)
+#if _MSC_VER > 1500 || (defined __GNUC__)
 #    define ASSIMP_STEP_USE_UNORDERED_MULTIMAP
 #else
 #    define step_unordered_map map

code/AssetLib/Step/StepExporter.cpp

@@ -63,7 +63,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <memory>
 
 //
-#if _MSC_VER > 1500 || (defined __GNUC___)
+#if _MSC_VER > 1500 || (defined __GNUC__)
 #   define ASSIMP_STEP_USE_UNORDERED_MULTIMAP
 #   else
 #   define step_unordered_map map

code/AssetLib/glTF/glTFAsset.h

@@ -83,7 +83,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #endif
 
 
-#if _MSC_VER > 1500 || (defined __GNUC___)
+#if _MSC_VER > 1500 || (defined __GNUC__)
 #       define ASSIMP_GLTF_USE_UNORDERED_MULTIMAP
 #   else
 #       define gltf_unordered_map map

code/AssetLib/glTF2/glTF2Asset.h

@@ -64,7 +64,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include <algorithm>
 #include <list>
-#include <map>
+#include <unordered_map>
 #include <set>
 #include <stdexcept>
 #include <string>
@@ -95,7 +95,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #   define ai_assert
 #endif
 
-#if _MSC_VER > 1500 || (defined __GNUC___)
+#if _MSC_VER > 1500 || (defined __GNUC__)
 #   define ASSIMP_GLTF_USE_UNORDERED_MULTIMAP
 #else
 #   define gltf_unordered_map map
@@ -1266,9 +1266,8 @@ private:
     size_t mSceneLength;
     size_t mBodyOffset;
     size_t mBodyLength;
-    IdMap mUsedIds;
-    std::map<std::string, int, std::less<>> mUsedNamesMap;
     Ref<Buffer> mBodyBuffer;
+    std::unordered_map<std::string, int> lastUsedID;
 };
 
 inline std::string getContextForErrorMessages(const std::string &id, const std::string &name) {

code/AssetLib/glTF2/glTF2Asset.inl

@@ -438,7 +438,6 @@ unsigned int LazyDict<T>::Remove(const char *id) {
 
     const unsigned int index = objIt->second;
 
-    mAsset.mUsedIds[id] = false;
     mObjsById.erase(id);
     mObjsByOIndex.erase(index);
     delete mObjs[index];
@@ -472,7 +471,6 @@ unsigned int LazyDict<T>::Remove(const char *id) {
 
 template <class T>
 Ref<T> LazyDict<T>::Retrieve(unsigned int i) {
-
     typename Dict::iterator it = mObjsByOIndex.find(i);
     if (it != mObjsByOIndex.end()) { // already created?
         return Ref<T>(mObjs, it->second);
@@ -540,16 +538,11 @@ Ref<T> LazyDict<T>::Add(T *obj) {
     mObjs.push_back(obj);
     mObjsByOIndex[obj->oIndex] = idx;
     mObjsById[obj->id] = idx;
-    mAsset.mUsedIds[obj->id] = true;
     return Ref<T>(mObjs, idx);
 }
 
 template <class T>
 Ref<T> LazyDict<T>::Create(const char *id) {
-    Asset::IdMap::iterator it = mAsset.mUsedIds.find(id);
-    if (it != mAsset.mUsedIds.end()) {
-        throw DeadlyImportError("GLTF: two objects with the same ID exist");
-    }
     T *inst = new T();
     unsigned int idx = unsigned(mObjs.size());
     inst->id = id;
@@ -565,11 +558,12 @@ inline Buffer::Buffer() :
         byteLength(0),
         type(Type_arraybuffer),
         EncodedRegion_Current(nullptr),
-        mIsSpecial(false) {}
+        mIsSpecial(false) {
+    // empty
+}
 
 inline Buffer::~Buffer() {
-    for (SEncodedRegion *reg : EncodedRegion_List)
-        delete reg;
+    for (SEncodedRegion *reg : EncodedRegion_List) delete reg;
 }
 
 inline const char *Buffer::TranslateId(Asset & /*r*/, const char *id) {
@@ -693,7 +687,6 @@ inline void Buffer::EncodedRegion_SetCurrent(const std::string &pID) {
 }
 
 inline bool Buffer::ReplaceData(const size_t pBufferData_Offset, const size_t pBufferData_Count, const uint8_t *pReplace_Data, const size_t pReplace_Count) {
-
     if ((pBufferData_Count == 0) || (pReplace_Count == 0) || (pReplace_Data == nullptr)) {
         return false;
     }
@@ -809,8 +802,7 @@ inline uint8_t *BufferView::GetPointerAndTailSize(size_t accOffset, size_t& outT
         }
     }
 
-    if (offset >= buffer->byteLength)
-    {
+    if (offset >= buffer->byteLength) {
         outTailSize = 0;
         return nullptr;
     }
@@ -2206,29 +2198,27 @@ inline IOStream *Asset::OpenFile(const std::string &path, const char *mode, bool
 
 inline std::string Asset::FindUniqueID(const std::string &str, const char *suffix) {
     std::string id = str;
-
-    if (!id.empty()) {
-        if (mUsedIds.find(id) == mUsedIds.end()){
-            mUsedNamesMap[id] = 0;
+    int n = 1;
+    if(!id.empty()) {
+        n = lastUsedID[id];
+        if(!n) {
+            lastUsedID[id] = n+1;
             return id;
         }
-
         id += "_";
     }
 
-    id += suffix;
-
-    Asset::IdMap::iterator it = mUsedIds.find(id);
-    if (it == mUsedIds.end()) {
-        mUsedNamesMap[id] = 0;
-        return id;
+    if(suffix) {
+        id += suffix;
+        n = lastUsedID[id];
+        if(!n) {
+            lastUsedID[id] = n+1;
+            return id;
+        }
     }
 
-    auto key = id;
-    id += "_" + std::to_string(mUsedNamesMap[key]);
-    mUsedNamesMap[key] = mUsedNamesMap[key] + 1;
-
-    return id;
+    lastUsedID[id] = n+1;
+    return id + "_" + std::to_string(n-1);
 }
 
 #if _MSC_VER

code/AssetLib/glTFCommon/glTFCommon.h

@@ -69,7 +69,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #   define ai_assert
 #endif
 
-#if _MSC_VER > 1500 || (defined __GNUC___)
+#if _MSC_VER > 1500 || (defined __GNUC__)
 #   define ASSIMP_GLTF_USE_UNORDERED_MULTIMAP
 #else
 #   define gltf_unordered_map map