fe-misc.c

来自「PostgreSQL7.4.6 for Linux」· C语言 代码 · 共 1,131 行 · 第 1/2 页

	 * If the buffer is fairly full, enlarge it. We need to be able to
	 * enlarge the buffer in case a single message exceeds the initial
	 * buffer size.  We enlarge before filling the buffer entirely so as
	 * to avoid asking the kernel for a partial packet. The magic constant
	 * here should be large enough for a TCP packet or Unix pipe
	 * bufferload.	8K is the usual pipe buffer size, so...
	 */
	if (conn->inBufSize - conn->inEnd < 8192)
	{
		if (pqCheckInBufferSpace(conn->inEnd + 8192, conn))
		{
			/*
			 * We don't insist that the enlarge worked, but we need some
			 * room
			 */
			if (conn->inBufSize - conn->inEnd < 100)
				return -1;		/* errorMessage already set */
		}
	}

	/* OK, try to read some data */
retry3:
	nread = pqsecure_read(conn, conn->inBuffer + conn->inEnd,
						  conn->inBufSize - conn->inEnd);
	if (nread < 0)
	{
		if (SOCK_ERRNO == EINTR)
			goto retry3;
		/* Some systems return EAGAIN/EWOULDBLOCK for no data */
#ifdef EAGAIN
		if (SOCK_ERRNO == EAGAIN)
			return someread;
#endif
#if defined(EWOULDBLOCK) && (!defined(EAGAIN) || (EWOULDBLOCK != EAGAIN))
		if (SOCK_ERRNO == EWOULDBLOCK)
			return someread;
#endif
		/* We might get ECONNRESET here if using TCP and backend died */
#ifdef ECONNRESET
		if (SOCK_ERRNO == ECONNRESET)
			goto definitelyFailed;
#endif
		printfPQExpBuffer(&conn->errorMessage,
			   libpq_gettext("could not receive data from server: %s\n"),
						SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
		return -1;
	}
	if (nread > 0)
	{
		conn->inEnd += nread;

		/*
		 * Hack to deal with the fact that some kernels will only give us
		 * back 1 packet per recv() call, even if we asked for more and
		 * there is more available.  If it looks like we are reading a
		 * long message, loop back to recv() again immediately, until we
		 * run out of data or buffer space.  Without this, the
		 * block-and-restart behavior of libpq's higher levels leads to
		 * O(N^2) performance on long messages.
		 *
		 * Since we left-justified the data above, conn->inEnd gives the
		 * amount of data already read in the current message.	We
		 * consider the message "long" once we have acquired 32k ...
		 */
		if (conn->inEnd > 32768 &&
			(conn->inBufSize - conn->inEnd) >= 8192)
		{
			someread = 1;
			goto retry3;
		}
		return 1;
	}

	if (someread)
		return 1;				/* got a zero read after successful tries */

	/*
	 * A return value of 0 could mean just that no data is now available,
	 * or it could mean EOF --- that is, the server has closed the
	 * connection. Since we have the socket in nonblock mode, the only way
	 * to tell the difference is to see if select() is saying that the
	 * file is ready. Grumble.	Fortunately, we don't expect this path to
	 * be taken much, since in normal practice we should not be trying to
	 * read data unless the file selected for reading already.
	 *
	 * In SSL mode it's even worse: SSL_read() could say WANT_READ and then
	 * data could arrive before we make the pqReadReady() test.  So we
	 * must play dumb and assume there is more data, relying on the SSL
	 * layer to detect true EOF.
	 */

#ifdef USE_SSL
	if (conn->ssl)
		return 0;
#endif

	switch (pqReadReady(conn))
	{
		case 0:
			/* definitely no data available */
			return 0;
		case 1:
			/* ready for read */
			break;
		default:
			goto definitelyFailed;
	}

	/*
	 * Still not sure that it's EOF, because some data could have just
	 * arrived.
	 */
retry4:
	nread = pqsecure_read(conn, conn->inBuffer + conn->inEnd,
						  conn->inBufSize - conn->inEnd);
	if (nread < 0)
	{
		if (SOCK_ERRNO == EINTR)
			goto retry4;
		/* Some systems return EAGAIN/EWOULDBLOCK for no data */
#ifdef EAGAIN
		if (SOCK_ERRNO == EAGAIN)
			return 0;
#endif
#if defined(EWOULDBLOCK) && (!defined(EAGAIN) || (EWOULDBLOCK != EAGAIN))
		if (SOCK_ERRNO == EWOULDBLOCK)
			return 0;
#endif
		/* We might get ECONNRESET here if using TCP and backend died */
#ifdef ECONNRESET
		if (SOCK_ERRNO == ECONNRESET)
			goto definitelyFailed;
#endif
		printfPQExpBuffer(&conn->errorMessage,
			   libpq_gettext("could not receive data from server: %s\n"),
						SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
		return -1;
	}
	if (nread > 0)
	{
		conn->inEnd += nread;
		return 1;
	}

	/*
	 * OK, we are getting a zero read even though select() says ready.
	 * This means the connection has been closed.  Cope.
	 */
definitelyFailed:
	printfPQExpBuffer(&conn->errorMessage,
					  libpq_gettext(
							"server closed the connection unexpectedly\n"
			   "\tThis probably means the server terminated abnormally\n"
						 "\tbefore or while processing the request.\n"));
	conn->status = CONNECTION_BAD;		/* No more connection to backend */
	pqsecure_close(conn);
	closesocket(conn->sock);
	conn->sock = -1;

	return -1;
}

/*
 * pqSendSome: send data waiting in the output buffer.
 *
 * len is how much to try to send (typically equal to outCount, but may
 * be less).
 *
 * Return 0 on success, -1 on failure and 1 when not all data could be sent
 * because the socket would block and the connection is non-blocking.
 */
static int
pqSendSome(PGconn *conn, int len)
{
	char	   *ptr = conn->outBuffer;
	int			remaining = conn->outCount;
	int			result = 0;

	if (conn->sock < 0)
	{
		printfPQExpBuffer(&conn->errorMessage,
						  libpq_gettext("connection not open\n"));
		return -1;
	}

	/* while there's still data to send */
	while (len > 0)
	{
		int			sent;
		char		sebuf[256];

		sent = pqsecure_write(conn, ptr, len);

		if (sent < 0)
		{
			/*
			 * Anything except EAGAIN/EWOULDBLOCK/EINTR is trouble. If
			 * it's EPIPE or ECONNRESET, assume we've lost the backend
			 * connection permanently.
			 */
			switch (SOCK_ERRNO)
			{
#ifdef EAGAIN
				case EAGAIN:
					break;
#endif
#if defined(EWOULDBLOCK) && (!defined(EAGAIN) || (EWOULDBLOCK != EAGAIN))
				case EWOULDBLOCK:
					break;
#endif
				case EINTR:
					continue;

				case EPIPE:
#ifdef ECONNRESET
				case ECONNRESET:
#endif
					printfPQExpBuffer(&conn->errorMessage,
									  libpq_gettext(
							"server closed the connection unexpectedly\n"
													"\tThis probably means the server terminated abnormally\n"
						 "\tbefore or while processing the request.\n"));

					/*
					 * We used to close the socket here, but that's a bad
					 * idea since there might be unread data waiting
					 * (typically, a NOTICE message from the backend
					 * telling us it's committing hara-kiri...).  Leave
					 * the socket open until pqReadData finds no more data
					 * can be read.  But abandon attempt to send data.
					 */
					conn->outCount = 0;
					return -1;

				default:
					printfPQExpBuffer(&conn->errorMessage,
					libpq_gettext("could not send data to server: %s\n"),
						SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
					/* We don't assume it's a fatal error... */
					conn->outCount = 0;
					return -1;
			}
		}
		else
		{
			ptr += sent;
			len -= sent;
			remaining -= sent;
		}

		if (len > 0)
		{
			/*
			 * We didn't send it all, wait till we can send more.
			 *
			 * If the connection is in non-blocking mode we don't wait, but
			 * return 1 to indicate that data is still pending.
			 */
			if (pqIsnonblocking(conn))
			{
				result = 1;
				break;
			}

			/*
			 * There are scenarios in which we can't send data because the
			 * communications channel is full, but we cannot expect the server
			 * to clear the channel eventually because it's blocked trying to
			 * send data to us.  (This can happen when we are sending a large
			 * amount of COPY data, and the server has generated lots of
			 * NOTICE responses.)  To avoid a deadlock situation, we must be
			 * prepared to accept and buffer incoming data before we try
			 * again.  Furthermore, it is possible that such incoming data
			 * might not arrive until after we've gone to sleep.  Therefore,
			 * we wait for either read ready or write ready.
			 */
			if (pqReadData(conn) < 0)
			{
				result = -1;	/* error message already set up */
				break;
			}
			if (pqWait(TRUE, TRUE, conn))
			{
				result = -1;
				break;
			}
		}
	}

	/* shift the remaining contents of the buffer */
	if (remaining > 0)
		memmove(conn->outBuffer, ptr, remaining);
	conn->outCount = remaining;

	return result;
}


/*
 * pqFlush: send any data waiting in the output buffer
 *
 * Return 0 on success, -1 on failure and 1 when not all data could be sent
 * because the socket would block and the connection is non-blocking.
 */
int
pqFlush(PGconn *conn)
{
	if (conn->Pfdebug)
		fflush(conn->Pfdebug);

	if (conn->outCount > 0)
		return pqSendSome(conn, conn->outCount);

	return 0;
}


/*
 * pqWait: wait until we can read or write the connection socket
 *
 * JAB: If SSL enabled and used and forRead, buffered bytes short-circuit the
 * call to select().
 *
 * We also stop waiting and return if the kernel flags an exception condition
 * on the socket.  The actual error condition will be detected and reported
 * when the caller tries to read or write the socket.
 */
int
pqWait(int forRead, int forWrite, PGconn *conn)
{
	return pqWaitTimed(forRead, forWrite, conn, (time_t) -1);
}

/*
 * pqWaitTimed: wait, but not past finish_time.
 *
 * If finish_time is exceeded then we return failure (EOF).  This is like
 * the response for a kernel exception because we don't want the caller
 * to try to read/write in that case.
 *
 * finish_time = ((time_t) -1) disables the wait limit.
 */
int
pqWaitTimed(int forRead, int forWrite, PGconn *conn, time_t finish_time)
{
	int			result;

	result = pqSocketCheck(conn, forRead, forWrite, finish_time);

	if (result < 0)
		return EOF;				/* errorMessage is already set */

	if (result == 0)
	{
		printfPQExpBuffer(&conn->errorMessage,
						  libpq_gettext("timeout expired\n"));
		return EOF;
	}

	return 0;
}

/*
 * pqReadReady: is select() saying the file is ready to read?
 * Returns -1 on failure, 0 if not ready, 1 if ready.
 */
int
pqReadReady(PGconn *conn)
{
	return pqSocketCheck(conn, 1, 0, (time_t) 0);
}

/*
 * pqWriteReady: is select() saying the file is ready to write?
 * Returns -1 on failure, 0 if not ready, 1 if ready.
 */
int
pqWriteReady(PGconn *conn)
{
	return pqSocketCheck(conn, 0, 1, (time_t) 0);
}

/*
 * Checks a socket, using poll or select, for data to be read, written,
 * or both.  Returns >0 if one or more conditions are met, 0 if it timed
 * out, -1 if an error occurred.
 *
 * If SSL is in use, the SSL buffer is checked prior to checking the socket
 * for read data directly.
 */
static int
pqSocketCheck(PGconn *conn, int forRead, int forWrite, time_t end_time)
{
	int			result;

	if (!conn)
		return -1;
	if (conn->sock < 0)
	{
		printfPQExpBuffer(&conn->errorMessage,
						  libpq_gettext("socket not open\n"));
		return -1;
	}

#ifdef USE_SSL
	/* Check for SSL library buffering read bytes */
	if (forRead && conn->ssl && SSL_pending(conn->ssl) > 0)
	{
		/* short-circuit the select */
		return 1;
	}
#endif

	/* We will retry as long as we get EINTR */
	do
		result = pqSocketPoll(conn->sock, forRead, forWrite, end_time);
	while (result < 0 && SOCK_ERRNO == EINTR);

	if (result < 0)
	{
		char		sebuf[256];

		printfPQExpBuffer(&conn->errorMessage,
						  libpq_gettext("select() failed: %s\n"),
						SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
	}

	return result;
}


/*
 * Check a file descriptor for read and/or write data, possibly waiting.
 * If neither forRead nor forWrite are set, immediately return a timeout
 * condition (without waiting).  Return >0 if condition is met, 0
 * if a timeout occurred, -1 if an error or interrupt occurred.
 *
 * Timeout is infinite if end_time is -1.  Timeout is immediate (no blocking)
 * if end_time is 0 (or indeed, any time before now).
 */
static int
pqSocketPoll(int sock, int forRead, int forWrite, time_t end_time)
{
	/* We use poll(2) if available, otherwise select(2) */
#ifdef HAVE_POLL
	struct pollfd input_fd;
	int			timeout_ms;

	if (!forRead && !forWrite)
		return 0;

	input_fd.fd = sock;
	input_fd.events = POLLERR;
	input_fd.revents = 0;

	if (forRead)
		input_fd.events |= POLLIN;
	if (forWrite)
		input_fd.events |= POLLOUT;

	/* Compute appropriate timeout interval */
	if (end_time == ((time_t) -1))
		timeout_ms = -1;
	else
	{
		time_t		now = time(NULL);

		if (end_time > now)
			timeout_ms = (end_time - now) * 1000;
		else
			timeout_ms = 0;
	}

	return poll(&input_fd, 1, timeout_ms);

#else							/* !HAVE_POLL */

	fd_set		input_mask;
	fd_set		output_mask;
	fd_set		except_mask;
	struct timeval timeout;
	struct timeval *ptr_timeout;

	if (!forRead && !forWrite)
		return 0;

	FD_ZERO(&input_mask);
	FD_ZERO(&output_mask);
	FD_ZERO(&except_mask);
	if (forRead)
		FD_SET(sock, &input_mask);
	if (forWrite)
		FD_SET(sock, &output_mask);
	FD_SET(sock, &except_mask);

	/* Compute appropriate timeout interval */
	if (end_time == ((time_t) -1))
		ptr_timeout = NULL;
	else
	{
		time_t		now = time(NULL);

		if (end_time > now)
			timeout.tv_sec = end_time - now;
		else
			timeout.tv_sec = 0;
		timeout.tv_usec = 0;
		ptr_timeout = &timeout;
	}

	return select(sock + 1, &input_mask, &output_mask,
				  &except_mask, ptr_timeout);
#endif   /* HAVE_POLL */
}


/*
 * A couple of "miscellaneous" multibyte related functions. They used
 * to be in fe-print.c but that file is doomed.
 */

/*
 * returns the byte length of the word beginning s, using the
 * specified encoding.
 */
int
PQmblen(const unsigned char *s, int encoding)
{
	return (pg_encoding_mblen(encoding, s));
}

/*
 * Get encoding id from environment variable PGCLIENTENCODING.
 */
int
PQenv2encoding(void)
{
	char	   *str;
	int			encoding = PG_SQL_ASCII;

	str = getenv("PGCLIENTENCODING");
	if (str && *str != '\0')
		encoding = pg_char_to_encoding(str);
	return (encoding);
}


#ifdef ENABLE_NLS

char *
libpq_gettext(const char *msgid)
{
	static int	already_bound = 0;

	if (!already_bound)
	{
		already_bound = 1;
		bindtextdomain("libpq", LOCALEDIR);
	}

	return dgettext("libpq", msgid);
}

#endif   /* ENABLE_NLS */