I understand that the C driver has broad compatibility as a specific goal, but easy platform-specific optimizations can be very useful.

Functions like mongo_insert() currently include a call to mongo_message_create() which then calls bson_malloc(). This supports the requirement to transmit the existing bson data prefixed by the collection name in a single send() call on the socket.

Linux and Windows both support the required network semantics without the additional bson_malloc() by using vector-oriented send() equivalents.

Here is a simplified example :

int mongo_insert_bson( mongo * pMongo, const char * pCollection, bson * pBSON )
{
#if defined( linux ) || defined( _WIN32 )
mongo_header header ;

int nBSON = *( ( int32_t * ) pBSON->data ) ;
int nCollection = 1 + strlen( pCollection ) ;

header.len = sizeof( header ) + sizeof( ZERO ) + nCollection + nBSON ;
header.op = MONGO_OP_INSERT ;
header.id = rand() ;
header.responseTo = 0 ;

#if defined( _WIN32 )
{
WSABUF pSend[ 3 ] ;
int nSent ;

pSend[ 0 ].len = sizeof( header ) ;
pSend[ 0 ].buf = ( char * ) &( header ) ;

if( 0 != WSASend( pMongo->sock, pSend, 1, &( nSent ), 0, 0, 0 ) )

{ pMongo->err = MONGO_IO_ERROR ; return MONGO_ERROR ; }

pSend[ 0 ].len = sizeof( ZERO ) ;
pSend[ 0 ].buf = ( char * ) &( ZERO ) ;

pSend[ 1 ].len = nCollection ;
pSend[ 1 ].buf = ( char * ) pCollection ;

pSend[ 2 ].len = nBSON ;
pSend[ 2 ].buf = ( char * ) pBSON->data ;

if( 0 != WSASend( pMongo->sock, pSend, 3, &( nSent ), 0, 0, 0 ) )
{ pMongo->err = MONGO_IO_ERROR ; return MONGO_ERROR ; }

return MONGO_OK ;
}
#endif // defined( _WIN32 )

#if defined( linux )
{
struct iovec pSend[ 3 ] ;

ssize_t nSent ;

pSend[ 0 ].iov_len = sizeof( header ) ;
pSend[ 0 ].iov_base = &( header ) ;

if( 1 == ( nSent = writev( pMongo>sock, pSend, 1 ) ) )

{ pMongo->err = MONGO_IO_ERROR ; return MONGO_ERROR ; }

pSend[ 0 ].iov_len = sizeof( ZERO ) ;
pSend[ 0 ].iov_base = &( ZERO ) ;

pSend[ 1 ].iov_len = nCollection ;
pSend[ 1 ].iov_base = pCollection ;

pSend[ 2 ].iov_len = nBSON ;
pSend[ 2 ].iov_base = pBSON->data ;

if( 1 == ( nSent = writev( pMongo>sock, pSend, 3 ) ) )
{ pMongo->err = MONGO_IO_ERROR ; return MONGO_ERROR ; }

return MONGO_OK ;
}
#endif // defined( _WIN32 )

#else
return mongo_insert( pMongo, pCollection, pBSON ) ;

#endif // defined( linux ) || defined( _WIN32 )

} // mongo_insert()

Incorporating this kind of optimization generically in the mongo C driver probably requires a fair amount of well-considered refactoring, so I am not just sending in a hasty patch. I am, however, more than happy to collaborate on this effort.