// "source" should contain the pathname to your mesh file 
Ogre::String source;

/* 
   An alternate (better) way of doing the following would be to 
   use the FileStreamDataStream class, which avoids having to use
   the more esoteric "stat" struct and stdio APIs. For more, see
   http://stderr.org/doc/ogre-doc/api/classOgre_1_1FileStreamDataStream.html

   This prevents having to create and fill a MemoryDataStream instance, as 
   the FileStreamDataStream can be used directly in the "stream" c'tor below.
*/
FILE* pFile = fopen( source.c_str(), "rb" );
if (!pFile)
    OGRE_EXCEPT(Exception::ERR_FILE_NOT_FOUND,"File " + source + " not found.", "OgreMeshLoaded");

struct stat tagStat;
stat( source.c_str(), &tagStat );
MemoryDataStream* memstream = new MemoryDataStream(source, tagStat.st_size, true);
fread( (void*)memstream->getPtr(), tagStat.st_size, 1, pFile );
fclose( pFile );

// give the resource a name -- it can be the full pathname if you like, since it's 
// just going to be the key in an STL associative tree container
MeshPtr pMesh = MeshManager::getSingleton().createManual("LocalMesh",ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME);

// this part does the actual load into the live Mesh object created above
MeshSerializer meshSerializer;
DataStreamPtr stream(memstream);
meshSerializer.importMesh(stream, pMesh.getPointer());

// and finally, now that we have a named Mesh resource, we can use it
// in our createEntity() call...
Entity* pF35_1 = m_pSceneMgr->createEntity("LocalMesh_Ent", "LocalMesh");