Function pqParseInput3

src/interfaces/libpq/fe-protocol3.c:78–626

* parseInput: if appropriate, parse input data from backend * until input is exhausted or a stopping state is reached. * Note that this function will NOT attempt to read more data from the backend. */

 * Note that this function will NOT attempt to read more data from the backend.
 */
void
pqParseInput3(PGconn *conn)
{
	char		id;
	int			msgLength;
	int			avail;
#ifndef FRONTEND
	int			i;
	int64		numRejected  = 0;
	int64		numCompleted = 0;
#endif


	/*
	 * Loop to parse successive complete messages available in the buffer.
	 */
	for (;;)
	{
		/*
		 * Try to read a message.  First get the type code and length. Return
		 * if not enough data.
		 */
		conn->inCursor = conn->inStart;
		if (pqGetc(&id, conn))
			return;
		if (pqGetInt(&msgLength, 4, conn))
			return;

		/*
		 * Try to validate message type/length here.  A length less than 4 is
		 * definitely broken.  Large lengths should only be believed for a few
		 * message types.
		 */
		if (msgLength < 4)
		{
			handleSyncLoss(conn, id, msgLength);
			return;
		}
		if (msgLength > 30000 && !VALID_LONG_MESSAGE_TYPE(id))
		{
			handleSyncLoss(conn, id, msgLength);
			return;
		}

		/*
		 * Can't process if message body isn't all here yet.
		 */
		msgLength -= 4;
		avail = conn->inEnd - conn->inCursor;
		if (avail < msgLength)
		{
			/*
			 * Before returning, enlarge the input buffer if needed to hold
			 * the whole message.  This is better than leaving it to
			 * pqReadData because we can avoid multiple cycles of realloc()
			 * when the message is large; also, we can implement a reasonable
			 * recovery strategy if we are unable to make the buffer big
			 * enough.