do{;}while 妙用

do
{
    ZeroMemory ( szProtoBuffer, sizeof ( szProtoBuffer ) );

    pMsgHdr = ( PNFS_MSG_HEADER ) szProtoBuffer ;

    ZeroMemory ( pMsgHdr , sizeof ( NFS_MSG_HEADER ) ) ;

    pMsgHdr->dwSignature = RNFS_MAGIC ;
    pMsgHdr->wProtocolVersion = RNFS_PROTOVERSION ;
    pMsgHdr->btPacketType = RNFS_DGRAM_REQUEST ;
    pMsgHdr->dwPacketLength = 0 ;
    pMsgHdr->wFunctionNum = RNFS_OPEN_SESSION ;
    pMsgHdr->dwAckNumber = dwAckNumber ;

    dwSize = MSG_HDR_LEN + pMsgHdr->dwPacketLength ;

    dwStatus = GU_SendAll (
                   SessionSocket ,
                   szProtoBuffer ,
                   dwSize ) ;

    if ( 0 != dwStatus )
    {
        break ;
    }

    dwSize = MSG_HDR_LEN ;

    dwStatus = GU_RecvAll (
                   SessionSocket ,
                   szProtoBuffer,
                   dwSize ) ;

    if ( 0 != dwStatus )
    {
        break ;
    }

    if ( pMsgHdr->dwAckNumber != dwAckNumber )
    {
        dwStatus = ERROR_BAD_FORMAT ;
        break ;
    }

    if ( pMsgHdr->dwRetStatus != 0 )
    {
        dwStatus = pMsgHdr->dwRetStatus ;
        break ;
    }

    dwSize = pMsgHdr->dwPacketLength ;

    dwStatus = GU_RecvAll (
                   SessionSocket ,
                   szProtoBuffer ,
                   dwSize ) ;

    if ( 0 == dwStatus )
    {
        PNFS_SESSION pSession = ( PNFS_SESSION ) szProtoBuffer ;
        * pdwSessionId = pSession->dwSessionId ;
    }
}
while ( FALSE ) ;

  开始觉得不是多此一举吗？仔细分析了以后，才发现很妙，因为在不同的条件判断中就可以按需break;从而达到最终执行到最后一个返回语句。而以前的实现都是以goto来实现的。