fe-protocol2.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

				case 'P':		/* synchronous (normal) portal */
					if (pqGets(&conn->workBuffer, conn))
						return;
					/* We pretty much ignore this message type... */
					break;
				case 'T':		/* row descriptions (start of query results) */
					if (conn->result == NULL)
					{
						/* First 'T' in a query sequence */
						if (getRowDescriptions(conn))
							return;
					}
					else
					{
						/*
						 * A new 'T' message is treated as the start of
						 * another PGresult.  (It is not clear that this is
						 * really possible with the current backend.) We stop
						 * parsing until the application accepts the current
						 * result.
						 */
						conn->asyncStatus = PGASYNC_READY;
						return;
					}
					break;
				case 'D':		/* ASCII data tuple */
					if (conn->result != NULL)
					{
						/* Read another tuple of a normal query response */
						if (getAnotherTuple(conn, FALSE))
							return;
					}
					else
					{
						pqInternalNotice(&conn->noticeHooks,
										 "server sent data (\"D\" message) without prior row description (\"T\" message)");
						/* Discard the unexpected message; good idea?? */
						conn->inStart = conn->inEnd;
						return;
					}
					break;
				case 'B':		/* Binary data tuple */
					if (conn->result != NULL)
					{
						/* Read another tuple of a normal query response */
						if (getAnotherTuple(conn, TRUE))
							return;
					}
					else
					{
						pqInternalNotice(&conn->noticeHooks,
										 "server sent binary data (\"B\" message) without prior row description (\"T\" message)");
						/* Discard the unexpected message; good idea?? */
						conn->inStart = conn->inEnd;
						return;
					}
					break;
				case 'G':		/* Start Copy In */
					conn->asyncStatus = PGASYNC_COPY_IN;
					break;
				case 'H':		/* Start Copy Out */
					conn->asyncStatus = PGASYNC_COPY_OUT;
					break;
				default:
					printfPQExpBuffer(&conn->errorMessage,
									  libpq_gettext(
													"unexpected response from server; first received character was \"%c\"\n"),
									  id);
					/* build an error result holding the error message */
					pqSaveErrorResult(conn);
					/* Discard the unexpected message; good idea?? */
					conn->inStart = conn->inEnd;
					conn->asyncStatus = PGASYNC_READY;
					return;
			}					/* switch on protocol character */
		}
		/* Successfully consumed this message */
		conn->inStart = conn->inCursor;
	}
}

/*
 * parseInput subroutine to read a 'T' (row descriptions) message.
 * We build a PGresult structure containing the attribute data.
 * Returns: 0 if completed message, EOF if not enough data yet.
 *
 * Note that if we run out of data, we have to release the partially
 * constructed PGresult, and rebuild it again next time.  Fortunately,
 * that shouldn't happen often, since 'T' messages usually fit in a packet.
 */
static int
getRowDescriptions(PGconn *conn)
{
	PGresult   *result = NULL;
	int			nfields;
	int			i;

	result = PQmakeEmptyPGresult(conn, PGRES_TUPLES_OK);
	if (!result)
		goto failure;

	/* parseInput already read the 'T' label. */
	/* the next two bytes are the number of fields	*/
	if (pqGetInt(&(result->numAttributes), 2, conn))
		goto failure;
	nfields = result->numAttributes;

	/* allocate space for the attribute descriptors */
	if (nfields > 0)
	{
		result->attDescs = (PGresAttDesc *)
			pqResultAlloc(result, nfields * sizeof(PGresAttDesc), TRUE);
		if (!result->attDescs)
			goto failure;
		MemSet(result->attDescs, 0, nfields * sizeof(PGresAttDesc));
	}

	/* get type info */
	for (i = 0; i < nfields; i++)
	{
		int			typid;
		int			typlen;
		int			atttypmod;

		if (pqGets(&conn->workBuffer, conn) ||
			pqGetInt(&typid, 4, conn) ||
			pqGetInt(&typlen, 2, conn) ||
			pqGetInt(&atttypmod, 4, conn))
			goto failure;

		/*
		 * Since pqGetInt treats 2-byte integers as unsigned, we need to
		 * coerce the result to signed form.
		 */
		typlen = (int) ((int16) typlen);

		result->attDescs[i].name = pqResultStrdup(result,
												  conn->workBuffer.data);
		if (!result->attDescs[i].name)
			goto failure;
		result->attDescs[i].tableid = 0;
		result->attDescs[i].columnid = 0;
		result->attDescs[i].format = 0;
		result->attDescs[i].typid = typid;
		result->attDescs[i].typlen = typlen;
		result->attDescs[i].atttypmod = atttypmod;
	}

	/* Success! */
	conn->result = result;
	return 0;

failure:
	if (result)
		PQclear(result);
	return EOF;
}

/*
 * parseInput subroutine to read a 'B' or 'D' (row data) message.
 * We add another tuple to the existing PGresult structure.
 * Returns: 0 if completed message, EOF if error or not enough data yet.
 *
 * Note that if we run out of data, we have to suspend and reprocess
 * the message after more data is received.  We keep a partially constructed
 * tuple in conn->curTuple, and avoid reallocating already-allocated storage.
 */
static int
getAnotherTuple(PGconn *conn, bool binary)
{
	PGresult   *result = conn->result;
	int			nfields = result->numAttributes;
	PGresAttValue *tup;

	/* the backend sends us a bitmap of which attributes are null */
	char		std_bitmap[64]; /* used unless it doesn't fit */
	char	   *bitmap = std_bitmap;
	int			i;
	size_t		nbytes;			/* the number of bytes in bitmap  */
	char		bmap;			/* One byte of the bitmap */
	int			bitmap_index;	/* Its index */
	int			bitcnt;			/* number of bits examined in current byte */
	int			vlen;			/* length of the current field value */

	result->binary = binary;

	/* Allocate tuple space if first time for this data message */
	if (conn->curTuple == NULL)
	{
		conn->curTuple = (PGresAttValue *)
			pqResultAlloc(result, nfields * sizeof(PGresAttValue), TRUE);
		if (conn->curTuple == NULL)
			goto outOfMemory;
		MemSet(conn->curTuple, 0, nfields * sizeof(PGresAttValue));

		/*
		 * If it's binary, fix the column format indicators.  We assume the
		 * backend will consistently send either B or D, not a mix.
		 */
		if (binary)
		{
			for (i = 0; i < nfields; i++)
				result->attDescs[i].format = 1;
		}
	}
	tup = conn->curTuple;

	/* Get the null-value bitmap */
	nbytes = (nfields + BITS_PER_BYTE - 1) / BITS_PER_BYTE;
	/* malloc() only for unusually large field counts... */
	if (nbytes > sizeof(std_bitmap))
	{
		bitmap = (char *) malloc(nbytes);
		if (!bitmap)
			goto outOfMemory;
	}

	if (pqGetnchar(bitmap, nbytes, conn))
		goto EOFexit;

	/* Scan the fields */
	bitmap_index = 0;
	bmap = bitmap[bitmap_index];
	bitcnt = 0;

	for (i = 0; i < nfields; i++)
	{
		if (!(bmap & 0200))
		{
			/* if the field value is absent, make it a null string */
			tup[i].value = result->null_field;
			tup[i].len = NULL_LEN;
		}
		else
		{
			/* get the value length (the first four bytes are for length) */
			if (pqGetInt(&vlen, 4, conn))
				goto EOFexit;
			if (!binary)
				vlen = vlen - 4;
			if (vlen < 0)
				vlen = 0;
			if (tup[i].value == NULL)
			{
				tup[i].value = (char *) pqResultAlloc(result, vlen + 1, binary);
				if (tup[i].value == NULL)
					goto outOfMemory;
			}
			tup[i].len = vlen;
			/* read in the value */
			if (vlen > 0)
				if (pqGetnchar((char *) (tup[i].value), vlen, conn))
					goto EOFexit;
			/* we have to terminate this ourselves */
			tup[i].value[vlen] = '\0';
		}
		/* advance the bitmap stuff */
		bitcnt++;
		if (bitcnt == BITS_PER_BYTE)
		{
			bitmap_index++;
			bmap = bitmap[bitmap_index];
			bitcnt = 0;
		}
		else
			bmap <<= 1;
	}

	/* Success!  Store the completed tuple in the result */
	if (!pqAddTuple(result, tup))
		goto outOfMemory;
	/* and reset for a new message */
	conn->curTuple = NULL;

	if (bitmap != std_bitmap)
		free(bitmap);
	return 0;

outOfMemory:
	/* Replace partially constructed result with an error result */

	/*
	 * we do NOT use pqSaveErrorResult() here, because of the likelihood that
	 * there's not enough memory to concatenate messages...
	 */
	pqClearAsyncResult(conn);
	printfPQExpBuffer(&conn->errorMessage,
					  libpq_gettext("out of memory for query result\n"));

	/*
	 * XXX: if PQmakeEmptyPGresult() fails, there's probably not much we can
	 * do to recover...
	 */
	conn->result = PQmakeEmptyPGresult(conn, PGRES_FATAL_ERROR);
	conn->asyncStatus = PGASYNC_READY;
	/* Discard the failed message --- good idea? */
	conn->inStart = conn->inEnd;

EOFexit:
	if (bitmap != NULL && bitmap != std_bitmap)
		free(bitmap);
	return EOF;
}


/*
 * Attempt to read an Error or Notice response message.
 * This is possible in several places, so we break it out as a subroutine.
 * Entry: 'E' or 'N' message type has already been consumed.
 * Exit: returns 0 if successfully consumed message.
 *		 returns EOF if not enough data.
 */
static int
pqGetErrorNotice2(PGconn *conn, bool isError)
{
	PGresult   *res = NULL;
	PQExpBufferData workBuf;
	char	   *startp;
	char	   *splitp;

	/*
	 * Since the message might be pretty long, we create a temporary
	 * PQExpBuffer rather than using conn->workBuffer.	workBuffer is intended
	 * for stuff that is expected to be short.
	 */
	initPQExpBuffer(&workBuf);
	if (pqGets(&workBuf, conn))
		goto failure;

	/*
	 * Make a PGresult to hold the message.  We temporarily lie about the
	 * result status, so that PQmakeEmptyPGresult doesn't uselessly copy
	 * conn->errorMessage.
	 */
	res = PQmakeEmptyPGresult(conn, PGRES_EMPTY_QUERY);
	if (!res)
		goto failure;
	res->resultStatus = isError ? PGRES_FATAL_ERROR : PGRES_NONFATAL_ERROR;
	res->errMsg = pqResultStrdup(res, workBuf.data);
	if (!res->errMsg)
		goto failure;

	/*
	 * Break the message into fields.  We can't do very much here, but we can
	 * split the severity code off, and remove trailing newlines. Also, we use
	 * the heuristic that the primary message extends only to the first
	 * newline --- anything after that is detail message.  (In some cases it'd
	 * be better classed as hint, but we can hardly be expected to guess that
	 * here.)
	 */
	while (workBuf.len > 0 && workBuf.data[workBuf.len - 1] == '\n')
		workBuf.data[--workBuf.len] = '\0';
	splitp = strstr(workBuf.data, ":  ");
	if (splitp)
	{
		/* what comes before the colon is severity */
		*splitp = '\0';
		pqSaveMessageField(res, PG_DIAG_SEVERITY, workBuf.data);
		startp = splitp + 3;
	}
	else
	{
		/* can't find a colon?  oh well... */
		startp = workBuf.data;
	}
	splitp = strchr(startp, '\n');
	if (splitp)
	{
		/* what comes before the newline is primary message */
		*splitp++ = '\0';
		pqSaveMessageField(res, PG_DIAG_MESSAGE_PRIMARY, startp);
		/* the rest is detail; strip any leading whitespace */
		while (*splitp && isspace((unsigned char) *splitp))
			splitp++;
		pqSaveMessageField(res, PG_DIAG_MESSAGE_DETAIL, splitp);
	}
	else
	{
		/* single-line message, so all primary */
		pqSaveMessageField(res, PG_DIAG_MESSAGE_PRIMARY, startp);
	}

	/*
	 * Either save error as current async result, or just emit the notice.
	 * Also, if it's an error and we were in a transaction block, assume the
	 * server has now gone to error-in-transaction state.
	 */
	if (isError)
	{
		pqClearAsyncResult(conn);
		conn->result = res;
		resetPQExpBuffer(&conn->errorMessage);
		appendPQExpBufferStr(&conn->errorMessage, res->errMsg);
		if (conn->xactStatus == PQTRANS_INTRANS)
			conn->xactStatus = PQTRANS_INERROR;
	}
	else
	{
		if (res->noticeHooks.noticeRec != NULL)
			(*res->noticeHooks.noticeRec) (res->noticeHooks.noticeRecArg, res);
		PQclear(res);
	}

	termPQExpBuffer(&workBuf);
	return 0;

failure:
	if (res)
		PQclear(res);
	termPQExpBuffer(&workBuf);
	return EOF;
}

/*
 * checkXactStatus - attempt to track transaction-block status of server
 *
 * This is called each time we receive a command-complete message.	By
 * watching for messages from BEGIN/COMMIT/ROLLBACK commands, we can do
 * a passable job of tracking the server's xact status.  BUT: this does
 * not work at all on 7.3 servers with AUTOCOMMIT OFF.	(Man, was that
 * feature ever a mistake.)  Caveat user.
 *
 * The tags known here are all those used as far back as 7.0; is it worth
 * adding those from even-older servers?
 */
static void
checkXactStatus(PGconn *conn, const char *cmdTag)
{
	if (strcmp(cmdTag, "BEGIN") == 0)
		conn->xactStatus = PQTRANS_INTRANS;
	else if (strcmp(cmdTag, "COMMIT") == 0)
		conn->xactStatus = PQTRANS_IDLE;
	else if (strcmp(cmdTag, "ROLLBACK") == 0)
		conn->xactStatus = PQTRANS_IDLE;
	else if (strcmp(cmdTag, "START TRANSACTION") == 0)	/* 7.3 only */
		conn->xactStatus = PQTRANS_INTRANS;

	/*
	 * Normally we get into INERROR state by detecting an Error message.
	 * However, if we see one of these tags then we know for sure the server
	 * is in abort state ...
	 */
	else if (strcmp(cmdTag, "*ABORT STATE*") == 0)		/* pre-7.3 only */
		conn->xactStatus = PQTRANS_INERROR;
}

/*
 * Attempt to read a Notify response message.
 * This is possible in several places, so we break it out as a subroutine.
 * Entry: 'A' message type and length have already been consumed.
 * Exit: returns 0 if successfully consumed Notify message.
 *		 returns EOF if not enough data.
 */
static int
getNotify(PGconn *conn)
{
	int			be_pid;
	int			nmlen;
	PGnotify   *newNotify;

	if (pqGetInt(&be_pid, 4, conn))
		return EOF;
	if (pqGets(&conn->workBuffer, conn))
		return EOF;

	/*
	 * Store the relation name right after the PQnotify structure so it can
	 * all be freed at once.  We don't use NAMEDATALEN because we don't want
	 * to tie this interface to a specific server name length.
	 */
	nmlen = strlen(conn->workBuffer.data);
	newNotify = (PGnotify *) malloc(sizeof(PGnotify) + nmlen + 1);
	if (newNotify)
	{
		newNotify->relname = (char *) newNotify + sizeof(PGnotify);
		strcpy(newNotify->relname, conn->workBuffer.data);
		/* fake up an empty-string extra field */
		newNotify->extra = newNotify->relname + nmlen;
		newNotify->be_pid = be_pid;
		newNotify->next = NULL;
		if (conn->notifyTail)
			conn->notifyTail->next = newNotify;