Fixes for gmsh parser for periodic meshes

src/third_party/GMSH2Parser.cpp

@@ -158,14 +158,16 @@ bool GMSH2Parser::parsePeriodic() {
     getNextToken();
     [[maybe_unused]] const std::size_t entityIdentifyId = expectNonNegativeInt();
 
-    // fixed to 16; the main difference to MSH4.1
-    const std::size_t affineSize = 16;
-    for (std::size_t i = 0; i < affineSize; ++i) {
+    getNextToken();
+    if (curTok == GMSHToken::string) {
+      // Gmsh msh2 may write: "Affine a11 a12 ... a44" (16 values)
+      constexpr std::size_t affineSize = 16;
+      for (std::size_t i = 0; i < affineSize; ++i) {
+        getNextToken();
+        [[maybe_unused]] const double affineValue = expectNumber();
+      }
       getNextToken();
-      [[maybe_unused]] const double affineValue = expectNumber();
     }
-
-    getNextToken();
     const std::size_t identifySize = expectNonNegativeInt();
 
     for (std::size_t i = 0; i < identifySize; ++i) {

src/third_party/GMSHLexer.cpp

@@ -112,6 +112,15 @@ GMSHToken GMSHLexer::getToken() {
     advance();
     return GMSHToken::string;
   }
+  if (isalpha(lastChar)) {
+    do {
+      advance();
+    } while (isalpha(lastChar));
+    return GMSHToken::string;
+  }
+  // Always consume at least one character for unknown tokens to avoid
+  // getting stuck in an infinite tokenization loop.
+  advance();
   return GMSHToken::unknown_token;
 }