Unify extension check for importers.

This enables proper checking for all kinds of extensions (including the
ones with multiple dots) for all importers and internal usage.

code/Common/BaseImporter.cpp

@@ -229,27 +229,30 @@ void BaseImporter::GetExtensionList(std::set<std::string> &extensions) {
         const char *ext0,
         const char *ext1,
         const char *ext2) {
-    std::string::size_type pos = pFile.find_last_of('.');
-
-    // no file extension - can't read
-    if (pos == std::string::npos) {
-        return false;
-    }
-
-    const char *ext_real = &pFile[pos + 1];
-    if (!ASSIMP_stricmp(ext_real, ext0)) {
-        return true;
-    }
-
-    // check for other, optional, file extensions
-    if (ext1 && !ASSIMP_stricmp(ext_real, ext1)) {
-        return true;
+    std::set<std::string> extensions;
+    for (const char* ext : {ext0, ext1, ext2}) {
+        if (ext == nullptr) continue;
+        extensions.emplace(ext);
     }
+    return HasExtension(pFile, extensions);
+}
 
-    if (ext2 && !ASSIMP_stricmp(ext_real, ext2)) {
-        return true;
+// ------------------------------------------------------------------------------------------------
+// Check for file extension
+/*static*/ bool BaseImporter::HasExtension(const std::string &pFile, const std::set<std::string> &extensions) {
+    // CAUTION: Do not just search for the extension!
+    // GetExtension() returns the part after the *last* dot, but some extensions
+    // have dots inside them, e.g. ogre.mesh.xml. Compare the entire end of the
+    // string.
+    for (std::set<std::string>::const_iterator it = extensions.cbegin(); it != extensions.cend(); ++it) {
+        // Yay for C++<20 not having std::string::ends_with()
+        const std::string extension = "." + *it;
+        if (extension.length() > pFile.length()) continue;
+        // Possible optimization: Fetch the lowercase filename!
+        if (0 == ASSIMP_stricmp(pFile.c_str() + pFile.length() - extension.length(), extension.c_str())) {
+            return true;
+        }
     }
-
     return false;
 }
 

code/Common/Importer.cpp

@@ -637,24 +637,10 @@ const aiScene* Importer::ReadFile( const char* _pFile, unsigned int pFlags) {
             std::set<std::string> extensions;
             pimpl->mImporter[a]->GetExtensionList(extensions);
 
-            // CAUTION: Do not just search for the extension!
-            // GetExtension() returns the part after the *last* dot, but some extensions have dots
-            // inside them, e.g. ogre.mesh.xml. Compare the entire end of the string.
-            for (std::set<std::string>::const_iterator it = extensions.cbegin(); it != extensions.cend(); ++it) {
-
-                // Yay for C++<20 not having std::string::ends_with()
-                std::string extension = "." + *it;
-                if (extension.length() <= pFile.length()) {
-                    // Possible optimization: Fetch the lowercase filename!
-                    if (0 == ASSIMP_stricmp(pFile.c_str() + pFile.length() - extension.length(), extension.c_str())) {
-                        ImporterAndIndex candidate = { pimpl->mImporter[a], a };
-                        possibleImporters.push_back(candidate);
-                        break;
-                    }
-                }
-
+            if (BaseImporter::HasExtension(pFile, extensions)) {
+                ImporterAndIndex candidate = { pimpl->mImporter[a], a };
+                possibleImporters.push_back(candidate);
             }
-
         }
 
         // If just one importer supports this extension, pick it and close the case.

include/assimp/BaseImporter.h

@@ -275,6 +275,16 @@ public: // static utilities
             const char *ext1 = nullptr,
             const char *ext2 = nullptr);
 
+    // -------------------------------------------------------------------
+    /** @brief Check whether a file has one of the passed file extensions
+     *  @param pFile Input file
+     *  @param extensions Extensions to check for. Lowercase characters only, no dot!
+     *  @note Case-insensitive
+     */
+    static bool HasExtension(
+            const std::string &pFile,
+            const std::set<std::string> &extensions);
+
     // -------------------------------------------------------------------
     /** @brief Extract file extension from a string
      *  @param pFile Input file