Implement an isBytecodeArchive method to determine if an archive contains

bytecode file members or not.
Patch Contributed By Adam Treat

llvm-svn: 20338

include/llvm/Bytecode/Archive.h

@@ -414,6 +414,15 @@ class Archive {
       std::set<std::string>& symbols,     ///< Symbols to be sought
       std::set<ModuleProvider*>& modules  ///< The modules matching \p symbols
     );
+    
+    /// This method determines whether the archive is a properly formed llvm 
+    /// bytecode archive.  It first makes sure the symbol table has been loaded 
+    /// and has a non-zero size.  If it does, then it is an archive.  If not, 
+    /// then it tries to load all the bytecode modules of the archive.  Finally, 
+    /// it returns whether it was successfull.
+    /// @returns true if the archive is a proper llvm bytecode archive
+    /// @brief Determine whether the archive is a proper llvm bytecode archive.
+    bool isBytecodeArchive();
 
   /// @}
   /// @name Mutators

lib/Bytecode/Archive/ArchiveReader.cpp

@@ -503,3 +503,32 @@ Archive::findModulesDefiningSymbols(std::set<std::string>& symbols,
     }
   }
 }
+
+bool
+Archive::isBytecodeArchive()
+{
+  //Make sure the symTab has been loaded...
+  //in most cases this should have been done
+  //when the archive was constructed, but still, 
+  //this is just in case.
+  if ( !symTab.size() )
+    loadSymbolTable();
+
+  //Now that we know it's been loaded, return true
+  //if it has a size  
+  if ( symTab.size() ) return true;
+
+  //We still can't be sure it isn't a bytecode archive
+  loadArchive();
+
+  std::vector<Module *> Modules;
+  std::string ErrorMessage;
+
+  //If getAllModules gives an error then this isn't a proper
+  //bytecode archive
+  if ( getAllModules( Modules, &ErrorMessage ) ) return false;
+
+  //Finally, if we find any bytecode modules then this is a proper
+  //bytecode archive
+  return Modules.size();
+}