[Ace-users] [ace-users] nonblock io

[Douglas C. Schmidt]

Hi,

Thanks for using the PRF.

>ACE VERSION: 5.5.10
>HOST MACHINE and OPERATING SYSTEM:    winxp
>COMPILER NAME AND VERSION (AND PATCHLEVEL): g++
>THE $ACE_ROOT/ace/config.h FILE : #include "ace/config-win32.h"
>THE $ACE_ROOT/include/makeinclude/platform_macros.GNU
>FILE :platform_macros.GNU
>DESCRIPTION: The recv fuction like ACE_wrappers\apps\Gateway\Peer
>\Peer.cpp recv function.When i didn't get the whole event or i've got
>an entire event everytime, do i need sleep a short time?

No, using sleep() is definitely not the right thing to do!

Doug

>............
>if (this->msg_frag_ == 0) {
>		// No existing fragment... loog out delete last new mem
>		ACE_NEW_RETURN (this->msg_frag_,
>				ACE_Message_Block (MAX_PACKET_LEN),
>				-1);
>	}
>
>	MRI_NET_HEADER *mnh = (MRI_NET_HEADER *) this->msg_frag_->rd_ptr();
>	ssize_t header_received = 0;
>
>	const size_t HEADER_SIZE = sizeof(MRI_NET_HEADER);
>	ssize_t header_bytes_left_to_read =HEADER_SIZE - this->msg_frag_-
>>length();
>
>	if (header_bytes_left_to_read > 0) {
>		header_received = ::g_host_stream_sock().recv(this->msg_frag_-
>>wr_ptr(), header_bytes_left_to_read);
>
>		if (header_received == -1 /* error */
>		|| header_received == 0 /* EOF */) {
>			ACE_ERROR ((LM_ERROR,
>							ACE_TEXT ("%p\n"),
>							ACE_TEXT ("Recv error during header read")));
>			ACE_DEBUG ((LM_DEBUG,
>							ACE_TEXT ("attempted to read %d bytes\n"),
>							header_bytes_left_to_read));
>			this->msg_frag_ = this->msg_frag_->release();
>			return header_received;
>		}
>
>		// Bump the write pointer by the amount read.
>		this->msg_frag_->wr_ptr(header_received);
>
>		// At this point we may or may not have the ENTIRE header.
>		if (this->msg_frag_->length() < HEADER_SIZE) {
>			ACE_DEBUG ((LM_DEBUG,
>							ACE_TEXT ("Partial header received: only %d bytes\n"),
>							this->msg_frag_->length ()));
>			// Notify the caller that we didn't get an entire mnh.
>			errno = EWOULDBLOCK;
>			return -1;
>		}
>
>	}
>
>	//Here We get a whole message header already.
>	//Now we need to get the event payload.
>	ssize_t data_bytes_left_to_read = ssize_t (mnh->wLen - msg_frag_-
>>length());
>
>	while (data_bytes_left_to_read >=0) {
>		ssize_t data_received = !data_bytes_left_to_read ? 0
>				: ::g_host_stream_sock().recv(this->msg_frag_->wr_ptr(),
>						data_bytes_left_to_read);
>
>		// Try to receive the remainder of the message.
>		switch (data_received) {
>		case -1:
>			if (errno == EWOULDBLOCK) {
>				// This might happen if only the header came through.
>				return -1;
>			} else
>				/* FALLTHROUGH */;
>
>		case 0: // Premature EOF.
>			if (data_bytes_left_to_read) {
>				this->msg_frag_ = this->msg_frag_->release();
>				return 0;
>			}
>			/* FALLTHROUGH */
>			;
>
>		default:
>			// Set the write pointer at 1 past the end of the event.
>			this->msg_frag_->wr_ptr(data_received);
>
>			ACE_Time_Value interval = ACE_Time_Value (0, 1000);
>			if (data_received != data_bytes_left_to_read) {
>				ACE_OS::sleep(interval);
>				ssize_t tmp = data_bytes_left_to_read;
>				data_bytes_left_to_read = tmp - data_received;
>				break;
>			} else {
>				ACE_OS::sleep(interval);
>				// Set the read pointer to the beginning of the event.
>				this->msg_frag_->rd_ptr(this->msg_frag_->base());
>
>				mb = this->msg_frag_;
>
>				// Reset the pointer to indicate we've got an entire event.
>				this->msg_frag_ = 0;
>			}
>
>			return 1;
>		}//switch
>	}//while
>...........
>


-- 
Dr. Douglas C. Schmidt                       Professor and Associate Chair
Electrical Engineering and Computer Science  TEL: (615) 343-8197
Vanderbilt University                        WEB: www.dre.vanderbilt.edu/~schmidt
Nashville, TN 37203                          NET: d.schmidt at vanderbilt.edu