postgresql/src/interfaces/libpq/fe-exec.c

/*-------------------------------------------------------------------------
 *
 * fe-exec.c
 *	  functions related to sending a query down to the backend
 *
 * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-exec.c,v 1.136 2003/05/26 20:05:20 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres_fe.h"

#include <errno.h>
#include <ctype.h>
#include <fcntl.h>

#include "libpq-fe.h"
#include "libpq-int.h"

#include "mb/pg_wchar.h"

#ifdef WIN32
#include "win32.h"
#else
#include <unistd.h>
#endif

/* keep this in same order as ExecStatusType in libpq-fe.h */
char	   *const pgresStatus[] = {
	"PGRES_EMPTY_QUERY",
	"PGRES_COMMAND_OK",
	"PGRES_TUPLES_OK",
	"PGRES_COPY_OUT",
	"PGRES_COPY_IN",
	"PGRES_BAD_RESPONSE",
	"PGRES_NONFATAL_ERROR",
	"PGRES_FATAL_ERROR"
};


/* Note: DONOTICE macro will work if applied to either PGconn or PGresult */
#define DONOTICE(conn,message) \
	((*(conn)->noticeHook) ((conn)->noticeArg, (message)))


static void pqCatenateResultError(PGresult *res, const char *msg);
static void saveErrorResult(PGconn *conn);
static PGresult *prepareAsyncResult(PGconn *conn);
static int	addTuple(PGresult *res, PGresAttValue * tup);
static void parseInput(PGconn *conn);
static void handleSendFailure(PGconn *conn);
static void handleSyncLoss(PGconn *conn, char id, int msgLength);
static int	getRowDescriptions(PGconn *conn);
static int	getAnotherTuple(PGconn *conn, int msgLength);
static int	getParameterStatus(PGconn *conn);
static int	getNotify(PGconn *conn);


/* ----------------
 * Space management for PGresult.
 *
 * Formerly, libpq did a separate malloc() for each field of each tuple
 * returned by a query.  This was remarkably expensive --- malloc/free
 * consumed a sizable part of the application's runtime.  And there is
 * no real need to keep track of the fields separately, since they will
 * all be freed together when the PGresult is released.  So now, we grab
 * large blocks of storage from malloc and allocate space for query data
 * within these blocks, using a trivially simple allocator.  This reduces
 * the number of malloc/free calls dramatically, and it also avoids
 * fragmentation of the malloc storage arena.
 * The PGresult structure itself is still malloc'd separately.  We could
 * combine it with the first allocation block, but that would waste space
 * for the common case that no extra storage is actually needed (that is,
 * the SQL command did not return tuples).
 *
 * We also malloc the top-level array of tuple pointers separately, because
 * we need to be able to enlarge it via realloc, and our trivial space
 * allocator doesn't handle that effectively.  (Too bad the FE/BE protocol
 * doesn't tell us up front how many tuples will be returned.)
 * All other subsidiary storage for a PGresult is kept in PGresult_data blocks
 * of size PGRESULT_DATA_BLOCKSIZE.  The overhead at the start of each block
 * is just a link to the next one, if any.	Free-space management info is
 * kept in the owning PGresult.
 * A query returning a small amount of data will thus require three malloc
 * calls: one for the PGresult, one for the tuples pointer array, and one
 * PGresult_data block.
 *
 * Only the most recently allocated PGresult_data block is a candidate to
 * have more stuff added to it --- any extra space left over in older blocks
 * is wasted.  We could be smarter and search the whole chain, but the point
 * here is to be simple and fast.  Typical applications do not keep a PGresult
 * around very long anyway, so some wasted space within one is not a problem.
 *
 * Tuning constants for the space allocator are:
 * PGRESULT_DATA_BLOCKSIZE: size of a standard allocation block, in bytes
 * PGRESULT_ALIGN_BOUNDARY: assumed alignment requirement for binary data
 * PGRESULT_SEP_ALLOC_THRESHOLD: objects bigger than this are given separate
 *	 blocks, instead of being crammed into a regular allocation block.
 * Requirements for correct function are:
 * PGRESULT_ALIGN_BOUNDARY must be a multiple of the alignment requirements
 *		of all machine data types.	(Currently this is set from configure
 *		tests, so it should be OK automatically.)
 * PGRESULT_SEP_ALLOC_THRESHOLD + PGRESULT_BLOCK_OVERHEAD <=
 *			PGRESULT_DATA_BLOCKSIZE
 *		pqResultAlloc assumes an object smaller than the threshold will fit
 *		in a new block.
 * The amount of space wasted at the end of a block could be as much as
 * PGRESULT_SEP_ALLOC_THRESHOLD, so it doesn't pay to make that too large.
 * ----------------
 */

#ifdef MAX
#undef MAX
#endif
#define MAX(a,b)  ((a) > (b) ? (a) : (b))

#define PGRESULT_DATA_BLOCKSIZE		2048
#define PGRESULT_ALIGN_BOUNDARY		MAXIMUM_ALIGNOF		/* from configure */
#define PGRESULT_BLOCK_OVERHEAD		MAX(sizeof(PGresult_data), PGRESULT_ALIGN_BOUNDARY)
#define PGRESULT_SEP_ALLOC_THRESHOLD	(PGRESULT_DATA_BLOCKSIZE / 2)


/*
 * PQmakeEmptyPGresult
 *	 returns a newly allocated, initialized PGresult with given status.
 *	 If conn is not NULL and status indicates an error, the conn's
 *	 errorMessage is copied.
 *
 * Note this is exported --- you wouldn't think an application would need
 * to build its own PGresults, but this has proven useful in both libpgtcl
 * and the Perl5 interface, so maybe it's not so unreasonable.
 */

PGresult *
PQmakeEmptyPGresult(PGconn *conn, ExecStatusType status)
{
	PGresult   *result;

	result = (PGresult *) malloc(sizeof(PGresult));

	result->xconn = conn;		/* might be NULL */
	result->ntups = 0;
	result->numAttributes = 0;
	result->attDescs = NULL;
	result->tuples = NULL;
	result->tupArrSize = 0;
	result->resultStatus = status;
	result->cmdStatus[0] = '\0';
	result->binary = 0;
	result->errMsg = NULL;
	result->errSeverity = NULL;
	result->errCode = NULL;
	result->errPrimary = NULL;
	result->errDetail = NULL;
	result->errHint = NULL;
	result->errPosition = NULL;
	result->errContext = NULL;
	result->errFilename = NULL;
	result->errLineno = NULL;
	result->errFuncname = NULL;
	result->null_field[0] = '\0';
	result->curBlock = NULL;
	result->curOffset = 0;
	result->spaceLeft = 0;

	if (conn)
	{
		/* copy connection data we might need for operations on PGresult */
		result->noticeHook = conn->noticeHook;
		result->noticeArg = conn->noticeArg;
		result->client_encoding = conn->client_encoding;

		/* consider copying conn's errorMessage */
		switch (status)
		{
			case PGRES_EMPTY_QUERY:
			case PGRES_COMMAND_OK:
			case PGRES_TUPLES_OK:
			case PGRES_COPY_OUT:
			case PGRES_COPY_IN:
				/* non-error cases */
				break;
			default:
				pqSetResultError(result, conn->errorMessage.data);
				break;
		}
	}
	else
	{
		/* defaults... */
		result->noticeHook = NULL;
		result->noticeArg = NULL;
		result->client_encoding = 0;	/* should be SQL_ASCII */
	}

	return result;
}

/*
 * pqResultAlloc -
 *		Allocate subsidiary storage for a PGresult.
 *
 * nBytes is the amount of space needed for the object.
 * If isBinary is true, we assume that we need to align the object on
 * a machine allocation boundary.
 * If isBinary is false, we assume the object is a char string and can
 * be allocated on any byte boundary.
 */
void *
pqResultAlloc(PGresult *res, size_t nBytes, bool isBinary)
{
	char	   *space;
	PGresult_data *block;

	if (!res)
		return NULL;

	if (nBytes <= 0)
		return res->null_field;

	/*
	 * If alignment is needed, round up the current position to an
	 * alignment boundary.
	 */
	if (isBinary)
	{
		int			offset = res->curOffset % PGRESULT_ALIGN_BOUNDARY;

		if (offset)
		{
			res->curOffset += PGRESULT_ALIGN_BOUNDARY - offset;
			res->spaceLeft -= PGRESULT_ALIGN_BOUNDARY - offset;
		}
	}

	/* If there's enough space in the current block, no problem. */
	if (nBytes <= (size_t) res->spaceLeft)
	{
		space = res->curBlock->space + res->curOffset;
		res->curOffset += nBytes;
		res->spaceLeft -= nBytes;
		return space;
	}

	/*
	 * If the requested object is very large, give it its own block; this
	 * avoids wasting what might be most of the current block to start a
	 * new block.  (We'd have to special-case requests bigger than the
	 * block size anyway.)	The object is always given binary alignment in
	 * this case.
	 */
	if (nBytes >= PGRESULT_SEP_ALLOC_THRESHOLD)
	{
		block = (PGresult_data *) malloc(nBytes + PGRESULT_BLOCK_OVERHEAD);
		if (!block)
			return NULL;
		space = block->space + PGRESULT_BLOCK_OVERHEAD;
		if (res->curBlock)
		{
			/*
			 * Tuck special block below the active block, so that we don't
			 * have to waste the free space in the active block.
			 */
			block->next = res->curBlock->next;
			res->curBlock->next = block;
		}
		else
		{
			/* Must set up the new block as the first active block. */
			block->next = NULL;
			res->curBlock = block;
			res->spaceLeft = 0; /* be sure it's marked full */
		}
		return space;
	}

	/* Otherwise, start a new block. */
	block = (PGresult_data *) malloc(PGRESULT_DATA_BLOCKSIZE);
	if (!block)
		return NULL;
	block->next = res->curBlock;
	res->curBlock = block;
	if (isBinary)
	{
		/* object needs full alignment */
		res->curOffset = PGRESULT_BLOCK_OVERHEAD;
		res->spaceLeft = PGRESULT_DATA_BLOCKSIZE - PGRESULT_BLOCK_OVERHEAD;
	}
	else
	{
		/* we can cram it right after the overhead pointer */
		res->curOffset = sizeof(PGresult_data);
		res->spaceLeft = PGRESULT_DATA_BLOCKSIZE - sizeof(PGresult_data);
	}

	space = block->space + res->curOffset;
	res->curOffset += nBytes;
	res->spaceLeft -= nBytes;
	return space;
}

/*
 * pqResultStrdup -
 *		Like strdup, but the space is subsidiary PGresult space.
 */
char *
pqResultStrdup(PGresult *res, const char *str)
{
	char	   *space = (char *) pqResultAlloc(res, strlen(str) + 1, FALSE);

	if (space)
		strcpy(space, str);
	return space;
}

/*
 * pqSetResultError -
 *		assign a new error message to a PGresult
 */
void
pqSetResultError(PGresult *res, const char *msg)
{
	if (!res)
		return;
	if (msg && *msg)
		res->errMsg = pqResultStrdup(res, msg);
	else
		res->errMsg = NULL;
}

/*
 * pqCatenateResultError -
 *		concatenate a new error message to the one already in a PGresult
 */
static void
pqCatenateResultError(PGresult *res, const char *msg)
{
	PQExpBufferData errorBuf;

	if (!res || !msg)
		return;
	initPQExpBuffer(&errorBuf);
	if (res->errMsg)
		appendPQExpBufferStr(&errorBuf, res->errMsg);
	appendPQExpBufferStr(&errorBuf, msg);
	pqSetResultError(res, errorBuf.data);
	termPQExpBuffer(&errorBuf);
}

/*
 * PQclear -
 *	  free's the memory associated with a PGresult
 */
void
PQclear(PGresult *res)
{
	PGresult_data *block;

	if (!res)
		return;

	/* Free all the subsidiary blocks */
	while ((block = res->curBlock) != NULL)
	{
		res->curBlock = block->next;
		free(block);
	}

	/* Free the top-level tuple pointer array */
	if (res->tuples)
		free(res->tuples);

	/* Free the PGresult structure itself */
	free(res);
}

/*
 * Handy subroutine to deallocate any partially constructed async result.
 */

void
pqClearAsyncResult(PGconn *conn)
{
	if (conn->result)
		PQclear(conn->result);
	conn->result = NULL;
	conn->curTuple = NULL;
}

/*
 * This subroutine deletes any existing async result, sets conn->result
 * to a PGresult with status PGRES_FATAL_ERROR, and stores the current
 * contents of conn->errorMessage into that result.  It differs from a
 * plain call on PQmakeEmptyPGresult() in that if there is already an
 * async result with status PGRES_FATAL_ERROR, the current error message
 * is APPENDED to the old error message instead of replacing it.  This
 * behavior lets us report multiple error conditions properly, if necessary.
 * (An example where this is needed is when the backend sends an 'E' message
 * and immediately closes the connection --- we want to report both the
 * backend error and the connection closure error.)
 */
static void
saveErrorResult(PGconn *conn)
{
	/*
	 * If no old async result, just let PQmakeEmptyPGresult make one.
	 * Likewise if old result is not an error message.
	 */
	if (conn->result == NULL ||
		conn->result->resultStatus != PGRES_FATAL_ERROR ||
		conn->result->errMsg == NULL)
	{
		pqClearAsyncResult(conn);
		conn->result = PQmakeEmptyPGresult(conn, PGRES_FATAL_ERROR);
	}
	else
	{
		/* Else, concatenate error message to existing async result. */
		pqCatenateResultError(conn->result, conn->errorMessage.data);
	}
}

/*
 * This subroutine prepares an async result object for return to the caller.
 * If there is not already an async result object, build an error object
 * using whatever is in conn->errorMessage.  In any case, clear the async
 * result storage and make sure PQerrorMessage will agree with the result's
 * error string.
 */
static PGresult *
prepareAsyncResult(PGconn *conn)
{
	PGresult   *res;

	/*
	 * conn->result is the PGresult to return.	If it is NULL (which
	 * probably shouldn't happen) we assume there is an appropriate error
	 * message in conn->errorMessage.
	 */
	res = conn->result;
	conn->result = NULL;		/* handing over ownership to caller */
	conn->curTuple = NULL;		/* just in case */
	if (!res)
		res = PQmakeEmptyPGresult(conn, PGRES_FATAL_ERROR);
	else
	{
		/*
		 * Make sure PQerrorMessage agrees with result; it could be
		 * different if we have concatenated messages.
		 */
		resetPQExpBuffer(&conn->errorMessage);
		appendPQExpBufferStr(&conn->errorMessage,
							 PQresultErrorMessage(res));
	}
	return res;
}

/*
 * addTuple
 *	  add a row pointer to the PGresult structure, growing it if necessary
 *	  Returns TRUE if OK, FALSE if not enough memory to add the row
 */
static int
addTuple(PGresult *res, PGresAttValue * tup)
{
	if (res->ntups >= res->tupArrSize)
	{
		/*
		 * Try to grow the array.
		 *
		 * We can use realloc because shallow copying of the structure is
		 * okay.  Note that the first time through, res->tuples is NULL.
		 * While ANSI says that realloc() should act like malloc() in that
		 * case, some old C libraries (like SunOS 4.1.x) coredump instead.
		 * On failure realloc is supposed to return NULL without damaging
		 * the existing allocation. Note that the positions beyond
		 * res->ntups are garbage, not necessarily NULL.
		 */
		int			newSize = (res->tupArrSize > 0) ? res->tupArrSize * 2 : 128;
		PGresAttValue **newTuples;

		if (res->tuples == NULL)
			newTuples = (PGresAttValue **)
				malloc(newSize * sizeof(PGresAttValue *));
		else
			newTuples = (PGresAttValue **)
				realloc(res->tuples, newSize * sizeof(PGresAttValue *));
		if (!newTuples)
			return FALSE;		/* malloc or realloc failed */
		res->tupArrSize = newSize;
		res->tuples = newTuples;
	}
	res->tuples[res->ntups] = tup;
	res->ntups++;
	return TRUE;
}


/*
 * PQsendQuery
 *	 Submit a query, but don't wait for it to finish
 *
 * Returns: 1 if successfully submitted
 *			0 if error (conn->errorMessage is set)
 */
int
PQsendQuery(PGconn *conn, const char *query)
{
	if (!conn)
		return 0;

	/* clear the error string */
	resetPQExpBuffer(&conn->errorMessage);

	if (!query)
	{
		printfPQExpBuffer(&conn->errorMessage,
					libpq_gettext("command string is a null pointer\n"));
		return 0;
	}

	/* Don't try to send if we know there's no live connection. */
	if (conn->status != CONNECTION_OK)
	{
		printfPQExpBuffer(&conn->errorMessage,
						  libpq_gettext("no connection to the server\n"));
		return 0;
	}
	/* Can't send while already busy, either. */
	if (conn->asyncStatus != PGASYNC_IDLE)
	{
		printfPQExpBuffer(&conn->errorMessage,
			  libpq_gettext("another command is already in progress\n"));
		return 0;
	}

	/* initialize async result-accumulation state */
	conn->result = NULL;
	conn->curTuple = NULL;

	/* construct the outgoing Query message */
	if (pqPutMsgStart('Q', conn) < 0 ||
		pqPuts(query, conn) < 0 ||
		pqPutMsgEnd(conn) < 0)
	{
		handleSendFailure(conn);
		return 0;
	}

	/*
	 * Give the data a push.  In nonblock mode, don't complain if we're
	 * unable to send it all; PQconsumeInput() will do any additional flushing
	 * needed.
	 */
	if (pqFlush(conn) < 0)
	{
		handleSendFailure(conn);
		return 0;
	}

	/* OK, it's launched! */
	conn->asyncStatus = PGASYNC_BUSY;
	return 1;
}

/*
 * handleSendFailure: try to clean up after failure to send command.
 *
 * Primarily, what we want to accomplish here is to process an async
 * NOTICE message that the backend might have sent just before it died.
 *
 * NOTE: this routine should only be called in PGASYNC_IDLE state.
 */
static void
handleSendFailure(PGconn *conn)
{
	/*
	 * Accept any available input data, ignoring errors.  Note that if
	 * pqReadData decides the backend has closed the channel, it will
	 * close our side of the socket --- that's just what we want here.
	 */
	while (pqReadData(conn) > 0)
		 /* loop until no more data readable */ ;

	/*
	 * Parse any available input messages.	Since we are in PGASYNC_IDLE
	 * state, only NOTICE and NOTIFY messages will be eaten.
	 */
	parseInput(conn);
}

/*
 * Consume any available input from the backend
 * 0 return: some kind of trouble
 * 1 return: no problem
 */
int
PQconsumeInput(PGconn *conn)
{
	if (!conn)
		return 0;

	/*
	 * for non-blocking connections try to flush the send-queue,
	 * otherwise we may never get a response for something that may
	 * not have already been sent because it's in our write buffer!
	 */
	if (pqIsnonblocking(conn))
	{
		if (pqFlush(conn) < 0)
			return 0;
	}

	/*
	 * Load more data, if available. We do this no matter what state we
	 * are in, since we are probably getting called because the
	 * application wants to get rid of a read-select condition. Note that
	 * we will NOT block waiting for more input.
	 */
	if (pqReadData(conn) < 0)
		return 0;

	/* Parsing of the data waits till later. */
	return 1;
}


/*
 * 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.
 */

static void
parseInput(PGconn *conn)
{
	char		id;
	int			msgLength;
	int			avail;
	char		noticeWorkspace[128];

	/*
	 * 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 &&
			!(id == 'T' || id == 'D' || id == 'd'))
		{
			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.
			 */
			if (pqCheckInBufferSpace(conn->inCursor + msgLength, conn))
			{
				/*
				 * XXX add some better recovery code... plan is to skip
				 * over the message using its length, then report an error.
				 * For the moment, just treat this like loss of sync (which
				 * indeed it might be!)
				 */
				handleSyncLoss(conn, id, msgLength);
			}
			return;
		}

		/*
		 * NOTIFY and NOTICE messages can happen in any state; always process
		 * them right away.
		 *
		 * Most other messages should only be processed while in BUSY state.
		 * (In particular, in READY state we hold off further parsing
		 * until the application collects the current PGresult.)
		 *
		 * However, if the state is IDLE then we got trouble; we need to deal
		 * with the unexpected message somehow.
		 *
		 * ParameterStatus ('S') messages are a special case: in IDLE state
		 * we must process 'em (this case could happen if a new value was
		 * adopted from config file due to SIGHUP), but otherwise we hold
		 * off until BUSY state.
		 */
		if (id == 'A')
		{
			if (getNotify(conn))
				return;
		}
		else if (id == 'N')
		{
			if (pqGetErrorNotice(conn, false))
				return;
		}
		else if (conn->asyncStatus != PGASYNC_BUSY)
		{
			/* If not IDLE state, just wait ... */
			if (conn->asyncStatus != PGASYNC_IDLE)
				return;

			/*
			 * Unexpected message in IDLE state; need to recover somehow.
			 * ERROR messages are displayed using the notice processor;
			 * ParameterStatus is handled normally;
			 * anything else is just dropped on the floor after displaying
			 * a suitable warning notice.  (An ERROR is very possibly the
			 * backend telling us why it is about to close the connection,
			 * so we don't want to just discard it...)
			 */
			if (id == 'E')
			{
				if (pqGetErrorNotice(conn, false /* treat as notice */))
					return;
			}
			else if (id == 'S')
			{
				if (getParameterStatus(conn))
					return;
			}
			else
			{
				snprintf(noticeWorkspace, sizeof(noticeWorkspace),
						 libpq_gettext("message type 0x%02x arrived from server while idle\n"),
						 id);
				DONOTICE(conn, noticeWorkspace);
				/* Discard the unexpected message */
				conn->inCursor += msgLength;
			}
		}
		else
		{
			/*
			 * In BUSY state, we can process everything.
			 */
			switch (id)
			{
				case 'C':		/* command complete */
					if (pqGets(&conn->workBuffer, conn))
						return;
					if (conn->result == NULL)
						conn->result = PQmakeEmptyPGresult(conn,
													   PGRES_COMMAND_OK);
					strncpy(conn->result->cmdStatus, conn->workBuffer.data,
							CMDSTATUS_LEN);
					conn->asyncStatus = PGASYNC_READY;
					break;
				case 'E':		/* error return */
					if (pqGetErrorNotice(conn, true))
						return;
					conn->asyncStatus = PGASYNC_READY;
					break;
				case 'Z':		/* backend is ready for new query */
					if (pqGetc(&conn->xact_status, conn))
						return;
					conn->asyncStatus = PGASYNC_IDLE;
					break;
				case 'I':		/* empty query */
					if (conn->result == NULL)
						conn->result = PQmakeEmptyPGresult(conn,
													  PGRES_EMPTY_QUERY);
					conn->asyncStatus = PGASYNC_READY;
					break;
				case 'S':		/* parameter status */
					if (getParameterStatus(conn))
						return;
					break;
				case 'K':		/* secret key data from the backend */

					/*
					 * This is expected only during backend startup, but
					 * it's just as easy to handle it as part of the main
					 * loop.  Save the data and continue processing.
					 */
					if (pqGetInt(&(conn->be_pid), 4, conn))
						return;
					if (pqGetInt(&(conn->be_key), 4, conn))
						return;
					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':		/* Data Row */
					if (conn->result != NULL &&
						conn->result->resultStatus == PGRES_TUPLES_OK)
					{
						/* Read another tuple of a normal query response */
						if (getAnotherTuple(conn, msgLength))
							return;
					}
					else if (conn->result != NULL &&
							 conn->result->resultStatus == PGRES_FATAL_ERROR)
					{
						/*
						 * We've already choked for some reason.  Just discard
						 * tuples till we get to the end of the query.
						 */
						conn->inCursor += msgLength;
					}
					else
					{
						/* Set up to report error at end of query */
						printfPQExpBuffer(&conn->errorMessage,
								 libpq_gettext("server sent data (\"D\" message) without prior row description (\"T\" message)\n"));
						saveErrorResult(conn);
						/* Discard the unexpected message */
						conn->inCursor += msgLength;
					}
					break;
				case 'G':		/* Start Copy In */
					if (pqGetc(&conn->copy_is_binary, conn))
						return;
					/* XXX we currently ignore the rest of the message */
					conn->inCursor = conn->inStart + 5 + msgLength;
					conn->asyncStatus = PGASYNC_COPY_IN;
					break;
				case 'H':		/* Start Copy Out */
					if (pqGetc(&conn->copy_is_binary, conn))
						return;
					/* XXX we currently ignore the rest of the message */
					conn->inCursor = conn->inStart + 5 + msgLength;
					conn->asyncStatus = PGASYNC_COPY_OUT;
					conn->copy_already_done = 0;
					break;
				case 'd':		/* Copy Data */
					/*
					 * If we see Copy Data, just silently drop it.  This
					 * would only occur if application exits COPY OUT mode
					 * too early.
					 */
					conn->inCursor += msgLength;
					break;
				case 'c':		/* Copy Done */
					/*
					 * If we see Copy Done, just silently drop it.  This
					 * is the normal case during PQendcopy.  We will keep
					 * swallowing data, expecting to see command-complete
					 * for the COPY command.
					 */
					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 */
					saveErrorResult(conn);
					/* not sure if we will see more, so go to ready state */
					conn->asyncStatus = PGASYNC_READY;
					/* Discard the unexpected message */
					conn->inCursor += msgLength;
					break;
			}					/* switch on protocol character */
		}
		/* Successfully consumed this message */
		if (conn->inCursor == conn->inStart + 5 + msgLength)
		{
			/* Normal case: parsing agrees with specified length */
			conn->inStart = conn->inCursor;
		}
		else
		{
			/* Trouble --- report it */
			printfPQExpBuffer(&conn->errorMessage,
							  libpq_gettext("Message contents do not agree with length in message type \"%c\"\n"),
							  id);
			/* build an error result holding the error message */
			saveErrorResult(conn);
			conn->asyncStatus = PGASYNC_READY;
			/* trust the specified message length as what to skip */
			conn->inStart += 5 + msgLength;
		}
	}
}

/*
 * handleSyncLoss: clean up after loss of message-boundary sync
 *
 * There isn't really a lot we can do here except abandon the connection.
 */
static void
handleSyncLoss(PGconn *conn, char id, int msgLength)
{
	printfPQExpBuffer(&conn->errorMessage,
					  libpq_gettext(
						  "lost synchronization with server: got message type \"%c\", length %d\n"),
					  id, msgLength);
	conn->status = CONNECTION_BAD;		/* No more connection to backend */
	pqsecure_close(conn);
	closesocket(conn->sock);
	conn->sock = -1;
	conn->asyncStatus = PGASYNC_READY; /* drop out of GetResult wait loop */
}

/*
 * 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;
	int			nfields;
	int			i;

	result = PQmakeEmptyPGresult(conn, PGRES_TUPLES_OK);

	/* parseInput already read the 'T' label and message length. */
	/* the next two bytes are the number of fields	*/
	if (pqGetInt(&(result->numAttributes), 2, conn))
	{
		PQclear(result);
		return EOF;
	}
	nfields = result->numAttributes;

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

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

		if (pqGets(&conn->workBuffer, conn) ||
			pqGetInt(&tableid, 4, conn) ||
			pqGetInt(&columnid, 2, conn) ||
			pqGetInt(&typid, 4, conn) ||
			pqGetInt(&typlen, 2, conn) ||
			pqGetInt(&atttypmod, 4, conn) ||
			pqGetInt(&format, 2, conn))
		{
			PQclear(result);
			return EOF;
		}

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

		result->attDescs[i].name = pqResultStrdup(result,
												  conn->workBuffer.data);
		result->attDescs[i].typid = typid;
		result->attDescs[i].typlen = typlen;
		result->attDescs[i].atttypmod = atttypmod;
		/* XXX todo: save tableid/columnid, format too */
	}

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

/*
 * parseInput subroutine to read a '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, int msgLength)
{
	PGresult   *result = conn->result;
	int			nfields = result->numAttributes;
	PGresAttValue *tup;
	int			tupnfields;		/* # fields from tuple */
	int			vlen;			/* length of the current field value */
	int			i;

	/* 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((char *) conn->curTuple, 0, nfields * sizeof(PGresAttValue));
	}
	tup = conn->curTuple;

	/* Get the field count and make sure it's what we expect */
	if (pqGetInt(&tupnfields, 2, conn))
		return EOF;

	if (tupnfields != nfields)
	{
		/* Replace partially constructed result with an error result */
		printfPQExpBuffer(&conn->errorMessage,
						  libpq_gettext("unexpected field count in D message\n"));
		saveErrorResult(conn);
		/* Discard the failed message by pretending we read it */
		conn->inCursor = conn->inStart + 5 + msgLength;
		return 0;
	}

	/* Scan the fields */
	for (i = 0; i < nfields; i++)
	{
		/* get the value length */
		if (pqGetInt(&vlen, 4, conn))
			return EOF;
		if (vlen == -1)
		{
			/* null field */
			tup[i].value = result->null_field;
			tup[i].len = NULL_LEN;
			continue;
		}
		if (vlen < 0)
			vlen = 0;
		if (tup[i].value == NULL)
		{
			tup[i].value = (char *) pqResultAlloc(result, vlen + 1, false);
			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))
				return EOF;
		/* we have to terminate this ourselves */
		tup[i].value[vlen] = '\0';
	}

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

	return 0;

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

	/*
	 * we do NOT use saveErrorResult() here, because of the likelihood
	 * that there's not enough memory to concatenate messages.  Instead,
	 * discard the old result first to try to win back some memory.
	 */
	pqClearAsyncResult(conn);
	printfPQExpBuffer(&conn->errorMessage,
					  libpq_gettext("out of memory for query result\n"));
	conn->result = PQmakeEmptyPGresult(conn, PGRES_FATAL_ERROR);
	/* Discard the failed message by pretending we read it */
	conn->inCursor = conn->inStart + 5 + msgLength;
	return 0;
}


/*
 * PQisBusy
 *	 Return TRUE if PQgetResult would block waiting for input.
 */

int
PQisBusy(PGconn *conn)
{
	if (!conn)
		return FALSE;

	/* Parse any available data, if our state permits. */
	parseInput(conn);

	/* PQgetResult will return immediately in all states except BUSY. */
	return conn->asyncStatus == PGASYNC_BUSY;
}


/*
 * PQgetResult
 *	  Get the next PGresult produced by a query.
 *	  Returns NULL if and only if no query work remains.
 */

PGresult *
PQgetResult(PGconn *conn)
{
	PGresult   *res;

	if (!conn)
		return NULL;

	/* Parse any available data, if our state permits. */
	parseInput(conn);

	/* If not ready to return something, block until we are. */
	while (conn->asyncStatus == PGASYNC_BUSY)
	{
		/* Wait for some more data, and load it. */
		if (pqWait(TRUE, FALSE, conn) ||
			pqReadData(conn) < 0)
		{
			/*
			 * conn->errorMessage has been set by pqWait or pqReadData. We
			 * want to append it to any already-received error message.
			 */
			saveErrorResult(conn);
			conn->asyncStatus = PGASYNC_IDLE;
			return prepareAsyncResult(conn);
		}
		/* Parse it. */
		parseInput(conn);
	}

	/* Return the appropriate thing. */
	switch (conn->asyncStatus)
	{
		case PGASYNC_IDLE:
			res = NULL;			/* query is complete */
			break;
		case PGASYNC_READY:
			res = prepareAsyncResult(conn);
			/* Set the state back to BUSY, allowing parsing to proceed. */
			conn->asyncStatus = PGASYNC_BUSY;
			break;
		case PGASYNC_COPY_IN:
			res = PQmakeEmptyPGresult(conn, PGRES_COPY_IN);
			break;
		case PGASYNC_COPY_OUT:
			res = PQmakeEmptyPGresult(conn, PGRES_COPY_OUT);
			break;
		default:
			printfPQExpBuffer(&conn->errorMessage,
						   libpq_gettext("unexpected asyncStatus: %d\n"),
							  (int) conn->asyncStatus);
			res = PQmakeEmptyPGresult(conn, PGRES_FATAL_ERROR);
			break;
	}

	return res;
}


/*
 * PQexec
 *	  send a query to the backend and package up the result in a PGresult
 *
 * If the query was not even sent, return NULL; conn->errorMessage is set to
 * a relevant message.
 * If the query was sent, a new PGresult is returned (which could indicate
 * either success or failure).
 * The user is responsible for freeing the PGresult via PQclear()
 * when done with it.
 */

PGresult *
PQexec(PGconn *conn, const char *query)
{
	PGresult   *result;
	PGresult   *lastResult;
	bool		savedblocking;

	/*
	 * we assume anyone calling PQexec wants blocking behaviour, we force
	 * the blocking status of the connection to blocking for the duration
	 * of this function and restore it on return
	 */
	savedblocking = pqIsnonblocking(conn);
	if (PQsetnonblocking(conn, FALSE) == -1)
		return NULL;

	/*
	 * Silently discard any prior query result that application didn't
	 * eat. This is probably poor design, but it's here for backward
	 * compatibility.
	 */
	while ((result = PQgetResult(conn)) != NULL)
	{
		if (result->resultStatus == PGRES_COPY_IN ||
			result->resultStatus == PGRES_COPY_OUT)
		{
			PQclear(result);
			printfPQExpBuffer(&conn->errorMessage,
				 libpq_gettext("COPY state must be terminated first\n"));
			/* restore blocking status */
			goto errout;
		}
		PQclear(result);
	}

	/* OK to send the message */
	if (!PQsendQuery(conn, query))
		goto errout;			/* restore blocking status */

	/*
	 * For backwards compatibility, return the last result if there are
	 * more than one --- but merge error messages if we get more than one
	 * error result.
	 *
	 * We have to stop if we see copy in/out, however. We will resume parsing
	 * when application calls PQendcopy.
	 */
	lastResult = NULL;
	while ((result = PQgetResult(conn)) != NULL)
	{
		if (lastResult)
		{
			if (lastResult->resultStatus == PGRES_FATAL_ERROR &&
				result->resultStatus == PGRES_FATAL_ERROR)
			{
				pqCatenateResultError(lastResult, result->errMsg);
				PQclear(result);
				result = lastResult;
				/* Make sure PQerrorMessage agrees with concatenated result */
				resetPQExpBuffer(&conn->errorMessage);
				appendPQExpBufferStr(&conn->errorMessage, result->errMsg);
			}
			else
				PQclear(lastResult);
		}
		lastResult = result;
		if (result->resultStatus == PGRES_COPY_IN ||
			result->resultStatus == PGRES_COPY_OUT)
			break;
	}

	if (PQsetnonblocking(conn, savedblocking) == -1)
		return NULL;
	return lastResult;

errout:
	if (PQsetnonblocking(conn, savedblocking) == -1)
		return NULL;
	return NULL;
}


/*
 * 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 and length have already been consumed.
 * Exit: returns 0 if successfully consumed message.
 *		 returns EOF if not enough data.
 */
int
pqGetErrorNotice(PGconn *conn, bool isError)
{
	PGresult   *res;
	PQExpBufferData workBuf;
	char		id;

	/*
	 * Make a PGresult to hold the accumulated fields.  We temporarily
	 * lie about the result status, so that PQmakeEmptyPGresult doesn't
	 * uselessly copy conn->errorMessage.
	 */
	res = PQmakeEmptyPGresult(conn, PGRES_EMPTY_QUERY);
	res->resultStatus = PGRES_FATAL_ERROR;
	/*
	 * Since the fields 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.  We shouldn't
	 * use conn->errorMessage either, since this might be only a notice.
	 */
	initPQExpBuffer(&workBuf);

	/*
	 * Read the fields and save into res.
	 */
	for (;;)
	{
		if (pqGetc(&id, conn))
			goto fail;
		if (id == '\0')
			break;				/* terminator found */
		if (pqGets(&workBuf, conn))
			goto fail;
		switch (id)
		{
			case 'S':
				res->errSeverity = pqResultStrdup(res, workBuf.data);
				break;
			case 'C':
				res->errCode = pqResultStrdup(res, workBuf.data);
				break;
			case 'M':
				res->errPrimary = pqResultStrdup(res, workBuf.data);
				break;
			case 'D':
				res->errDetail = pqResultStrdup(res, workBuf.data);
				break;
			case 'H':
				res->errHint = pqResultStrdup(res, workBuf.data);
				break;
			case 'P':
				res->errPosition = pqResultStrdup(res, workBuf.data);
				break;
			case 'W':
				res->errContext = pqResultStrdup(res, workBuf.data);
				break;
			case 'F':
				res->errFilename = pqResultStrdup(res, workBuf.data);
				break;
			case 'L':
				res->errLineno = pqResultStrdup(res, workBuf.data);
				break;
			case 'R':
				res->errFuncname = pqResultStrdup(res, workBuf.data);
				break;
			default:
				/* silently ignore any other field type */
				break;
		}
	}

	/*
	 * Now build the "overall" error message for PQresultErrorMessage.
	 *
	 * XXX this should be configurable somehow.
	 */
	resetPQExpBuffer(&workBuf);
	if (res->errSeverity)
		appendPQExpBuffer(&workBuf, "%s:  ", res->errSeverity);
	if (res->errPrimary)
		appendPQExpBufferStr(&workBuf, res->errPrimary);
	/* translator: %s represents a digit string */
	if (res->errPosition)
		appendPQExpBuffer(&workBuf, libpq_gettext(" at character %s"),
						  res->errPosition);
	appendPQExpBufferChar(&workBuf, '\n');
	if (res->errDetail)
		appendPQExpBuffer(&workBuf, libpq_gettext("DETAIL:  %s\n"),
						  res->errDetail);
	if (res->errHint)
		appendPQExpBuffer(&workBuf, libpq_gettext("HINT:  %s\n"),
						  res->errHint);
	if (res->errContext)
		appendPQExpBuffer(&workBuf, libpq_gettext("CONTEXT:  %s\n"),
						  res->errContext);

	/*
	 * Either save error as current async result, or just emit the notice.
	 */
	if (isError)
	{
		res->errMsg = pqResultStrdup(res, workBuf.data);
		pqClearAsyncResult(conn);
		conn->result = res;
		resetPQExpBuffer(&conn->errorMessage);
		appendPQExpBufferStr(&conn->errorMessage, workBuf.data);
	}
	else
	{
		DONOTICE(conn, workBuf.data);
		PQclear(res);
	}

	termPQExpBuffer(&workBuf);
	return 0;

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

/*
 * Attempt to read a ParameterStatus message.
 * This is possible in several places, so we break it out as a subroutine.
 * Entry: 'S' message type and length have already been consumed.
 * Exit: returns 0 if successfully consumed message.
 *		 returns EOF if not enough data.
 */
static int
getParameterStatus(PGconn *conn)
{
	/* Get the parameter name */
	if (pqGets(&conn->workBuffer, conn))
		return EOF;
	/* Is it one we care about? */
	if (strcmp(conn->workBuffer.data, "client_encoding") == 0)
	{
		if (pqGets(&conn->workBuffer, conn))
			return EOF;
		conn->client_encoding = pg_char_to_encoding(conn->workBuffer.data);
	}
	else
	{
		/* Uninteresting parameter, ignore it */
		if (pqGets(&conn->workBuffer, conn))
			return EOF;
	}
	return 0;
}

/*
 * 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;
	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.
	 */
	newNotify = (PGnotify *) malloc(sizeof(PGnotify) +
									strlen(conn->workBuffer.data) +1);
	if (newNotify)
	{
		newNotify->relname = (char *) newNotify + sizeof(PGnotify);
		strcpy(newNotify->relname, conn->workBuffer.data);
		newNotify->be_pid = be_pid;
		DLAddTail(conn->notifyList, DLNewElem(newNotify));
	}

	/* Swallow extra string (not presently used) */
	if (pqGets(&conn->workBuffer, conn))
		return EOF;

	return 0;
}

/*
 * PQnotifies
 *	  returns a PGnotify* structure of the latest async notification
 * that has not yet been handled
 *
 * returns NULL, if there is currently
 * no unhandled async notification from the backend
 *
 * the CALLER is responsible for FREE'ing the structure returned
 */

PGnotify *
PQnotifies(PGconn *conn)
{
	Dlelem	   *e;
	PGnotify   *event;

	if (!conn)
		return NULL;

	/* Parse any available data to see if we can extract NOTIFY messages. */
	parseInput(conn);

	/* RemHead returns NULL if list is empty */
	e = DLRemHead(conn->notifyList);
	if (!e)
		return NULL;
	event = (PGnotify *) DLE_VAL(e);
	DLFreeElem(e);
	return event;
}

/*
 * PQgetline - gets a newline-terminated string from the backend.
 *
 * Chiefly here so that applications can use "COPY <rel> to stdout"
 * and read the output string.	Returns a null-terminated string in s.
 *
 * XXX this routine is now deprecated, because it can't handle binary data.
 * If called during a COPY BINARY we return EOF.
 *
 * PQgetline reads up to maxlen-1 characters (like fgets(3)) but strips
 * the terminating \n (like gets(3)).
 *
 * CAUTION: the caller is responsible for detecting the end-of-copy signal
 * (a line containing just "\.") when using this routine.
 *
 * RETURNS:
 *		EOF if error (eg, invalid arguments are given)
 *		0 if EOL is reached (i.e., \n has been read)
 *				(this is required for backward-compatibility -- this
 *				 routine used to always return EOF or 0, assuming that
 *				 the line ended within maxlen bytes.)
 *		1 in other cases (i.e., the buffer was filled before \n is reached)
 */
int
PQgetline(PGconn *conn, char *s, int maxlen)
{
	int			status;

	/* maxlen must be at least 3 to hold the \. terminator! */
	if (!conn || !s || maxlen < 3)
		return EOF;

	if (conn->sock < 0 ||
		conn->asyncStatus != PGASYNC_COPY_OUT ||
		conn->copy_is_binary)
	{
		printfPQExpBuffer(&conn->errorMessage,
					libpq_gettext("PQgetline: not doing text COPY OUT\n"));
		*s = '\0';
		return EOF;
	}

	while ((status = PQgetlineAsync(conn, s, maxlen-1)) == 0)
	{
		/* need to load more data */
		if (pqWait(TRUE, FALSE, conn) ||
			pqReadData(conn) < 0)
		{
			*s = '\0';
			return EOF;
		}
	}

	if (status < 0)
	{
		/* End of copy detected; gin up old-style terminator */
		strcpy(s, "\\.");
		return 0;
	}

	/* Add null terminator, and strip trailing \n if present */
	if (s[status-1] == '\n')
	{
		s[status-1] = '\0';
		return 0;
	}
	else
	{
		s[status] = '\0';
		return 1;
	}
}

/*
 * PQgetlineAsync - gets a COPY data row without blocking.
 *
 * This routine is for applications that want to do "COPY <rel> to stdout"
 * asynchronously, that is without blocking.  Having issued the COPY command
 * and gotten a PGRES_COPY_OUT response, the app should call PQconsumeInput
 * and this routine until the end-of-data signal is detected.  Unlike
 * PQgetline, this routine takes responsibility for detecting end-of-data.
 *
 * On each call, PQgetlineAsync will return data if a complete data row
 * is available in libpq's input buffer.  Otherwise, no data is returned
 * until the rest of the row arrives.
 *
 * If -1 is returned, the end-of-data signal has been recognized (and removed
 * from libpq's input buffer).  The caller *must* next call PQendcopy and
 * then return to normal processing.
 *
 * RETURNS:
 *	 -1    if the end-of-copy-data marker has been recognized
 *	 0	   if no data is available
 *	 >0    the number of bytes returned.
 *
 * The data returned will not extend beyond a data-row boundary.  If possible
 * a whole row will be returned at one time.  But if the buffer offered by
 * the caller is too small to hold a row sent by the backend, then a partial
 * data row will be returned.  In text mode this can be detected by testing
 * whether the last returned byte is '\n' or not.
 *
 * The returned data is *not* null-terminated.
 */

int
PQgetlineAsync(PGconn *conn, char *buffer, int bufsize)
{
	char		id;
	int			msgLength;
	int			avail;

	if (!conn || conn->asyncStatus != PGASYNC_COPY_OUT)
		return -1;				/* we are not doing a copy... */

	/*
	 * Recognize the next input message.  To make life simpler for async
	 * callers, we keep returning 0 until the next message is fully available
	 * even if it is not Copy Data.  This should keep PQendcopy from blocking.
	 */
	conn->inCursor = conn->inStart;
	if (pqGetc(&id, conn))
		return 0;
	if (pqGetInt(&msgLength, 4, conn))
		return 0;
	avail = conn->inEnd - conn->inCursor;
	if (avail < msgLength - 4)
		return 0;

	/*
	 * Cannot proceed unless it's a Copy Data message.  Anything else means
	 * end of copy mode.
	 */
	if (id != 'd')
		return -1;

	/*
	 * Move data from libpq's buffer to the caller's.  In the case where
	 * a prior call found the caller's buffer too small, we use
	 * conn->copy_already_done to remember how much of the row was already
	 * returned to the caller.
	 */
	conn->inCursor += conn->copy_already_done;
	avail = msgLength - 4 - conn->copy_already_done;
	if (avail <= bufsize)
	{
		/* Able to consume the whole message */
		memcpy(buffer, &conn->inBuffer[conn->inCursor], avail);
		/* Mark message consumed */
		conn->inStart = conn->inCursor + avail;
		/* Reset state for next time */
		conn->copy_already_done = 0;
		return avail;
	}
	else
	{
		/* We must return a partial message */
		memcpy(buffer, &conn->inBuffer[conn->inCursor], bufsize);
		/* The message is NOT consumed from libpq's buffer */
		conn->copy_already_done += bufsize;
		return bufsize;
	}
}

/*
 * PQputline -- sends a string to the backend.
 * Returns 0 if OK, EOF if not.
 *
 * This exists to support "COPY <rel> from stdin".  The backend will ignore
 * the string if not doing COPY.
 */
int
PQputline(PGconn *conn, const char *s)
{
	return PQputnbytes(conn, s, strlen(s));
}

/*
 * PQputnbytes -- like PQputline, but buffer need not be null-terminated.
 * Returns 0 if OK, EOF if not.
 */
int
PQputnbytes(PGconn *conn, const char *buffer, int nbytes)
{
	if (!conn || conn->sock < 0)
		return EOF;
	if (nbytes > 0)
	{
		if (pqPutMsgStart('d', conn) < 0 ||
			pqPutnchar(buffer, nbytes, conn) < 0 ||
			pqPutMsgEnd(conn) < 0)
			return EOF;
	}
	return 0;
}

/*
 * PQendcopy
 *		After completing the data transfer portion of a copy in/out,
 *		the application must call this routine to finish the command protocol.
 *
 * RETURNS:
 *		0 on success
 *		1 on failure
 */
int
PQendcopy(PGconn *conn)
{
	PGresult   *result;

	if (!conn)
		return 0;

	if (conn->asyncStatus != PGASYNC_COPY_IN &&
		conn->asyncStatus != PGASYNC_COPY_OUT)
	{
		printfPQExpBuffer(&conn->errorMessage,
						  libpq_gettext("no COPY in progress\n"));
		return 1;
	}

	/* Send the CopyDone message if needed */
	if (conn->asyncStatus == PGASYNC_COPY_IN)
	{
		if (pqPutMsgStart('c', conn) < 0 ||
			pqPutMsgEnd(conn) < 0)
			return 1;
	}

	/*
	 * make sure no data is waiting to be sent, abort if we are
	 * non-blocking and the flush fails
	 */
	if (pqFlush(conn) && pqIsnonblocking(conn))
		return (1);

	/* Return to active duty */
	conn->asyncStatus = PGASYNC_BUSY;
	resetPQExpBuffer(&conn->errorMessage);

	/*
	 * Non blocking connections may have to abort at this point.  If everyone
	 * played the game there should be no problem, but in error scenarios
	 * the expected messages may not have arrived yet.  (We are assuming that
	 * the backend's packetizing will ensure that CommandComplete arrives
	 * along with the CopyDone; are there corner cases where that doesn't
	 * happen?)
	 */
	if (pqIsnonblocking(conn) && PQisBusy(conn))
		return (1);

	/* Wait for the completion response */
	result = PQgetResult(conn);

	/* Expecting a successful result */
	if (result && result->resultStatus == PGRES_COMMAND_OK)
	{
		PQclear(result);
		return 0;
	}

	/*
	 * Trouble. For backwards-compatibility reasons, we issue the error
	 * message as if it were a notice (would be nice to get rid of this
	 * silliness, but too many apps probably don't handle errors from
	 * PQendcopy reasonably).  Note that the app can still obtain the
	 * error status from the PGconn object.
	 */
	if (conn->errorMessage.len > 0)
		DONOTICE(conn, conn->errorMessage.data);

	PQclear(result);

	return 1;
}


/* ----------------
 *		PQfn -	Send a function call to the POSTGRES backend.
 *
 *		conn			: backend connection
 *		fnid			: function id
 *		result_buf		: pointer to result buffer (&int if integer)
 *		result_len		: length of return value.
 *		actual_result_len: actual length returned. (differs from result_len
 *						  for varlena structures.)
 *		result_type		: If the result is an integer, this must be 1,
 *						  otherwise this should be 0
 *		args			: pointer to an array of function arguments.
 *						  (each has length, if integer, and value/pointer)
 *		nargs			: # of arguments in args array.
 *
 * RETURNS
 *		PGresult with status = PGRES_COMMAND_OK if successful.
 *			*actual_result_len is > 0 if there is a return value, 0 if not.
 *		PGresult with status = PGRES_FATAL_ERROR if backend returns an error.
 *		NULL on communications failure.  conn->errorMessage will be set.
 * ----------------
 */

PGresult *
PQfn(PGconn *conn,
	 int fnid,
	 int *result_buf,
	 int *actual_result_len,
	 int result_is_int,
	 const PQArgBlock *args,
	 int nargs)
{
	bool		needInput = false;
	ExecStatusType status = PGRES_FATAL_ERROR;
	char		id;
	int			msgLength;
	int			avail;
	int			i;

	*actual_result_len = 0;

	if (!conn)
		return NULL;

	/* clear the error string */
	resetPQExpBuffer(&conn->errorMessage);

	if (conn->sock < 0 || conn->asyncStatus != PGASYNC_IDLE ||
		conn->result != NULL)
	{
		printfPQExpBuffer(&conn->errorMessage,
						  libpq_gettext("connection in wrong state\n"));
		return NULL;
	}

	if (pqPutMsgStart('F', conn) < 0 ||		/* function call msg */
		pqPutInt(fnid, 4, conn) < 0 ||		/* function id */
		pqPutInt(1, 2, conn) < 0 ||			/* # of format codes */
		pqPutInt(1, 2, conn) < 0 ||			/* format code: BINARY */
		pqPutInt(nargs, 2, conn) < 0)		/* # of args */
	{
		handleSendFailure(conn);
		return NULL;
	}

	for (i = 0; i < nargs; ++i)
	{							/* len.int4 + contents	   */
		if (pqPutInt(args[i].len, 4, conn))
		{
			handleSendFailure(conn);
			return NULL;
		}
		if (args[i].len == -1)
			continue;			/* it's NULL */

		if (args[i].isint)
		{
			if (pqPutInt(args[i].u.integer, args[i].len, conn))
			{
				handleSendFailure(conn);
				return NULL;
			}
		}
		else
		{
			if (pqPutnchar((char *) args[i].u.ptr, args[i].len, conn))
			{
				handleSendFailure(conn);
				return NULL;
			}
		}
	}

	if (pqPutInt(1, 2, conn) < 0)		/* result format code: BINARY */
	{
		handleSendFailure(conn);
		return NULL;
	}

	if (pqPutMsgEnd(conn) < 0 ||
		pqFlush(conn))
	{
		handleSendFailure(conn);
		return NULL;
	}

	for (;;)
	{
		if (needInput)
		{
			/* Wait for some data to arrive (or for the channel to close) */
			if (pqWait(TRUE, FALSE, conn) ||
				pqReadData(conn) < 0)
				break;
		}

		/*
		 * Scan the message. If we run out of data, loop around to try
		 * again.
		 */
		needInput = true;

		conn->inCursor = conn->inStart;
		if (pqGetc(&id, conn))
			continue;
		if (pqGetInt(&msgLength, 4, conn))
			continue;

		/*
		 * 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);
			break;
		}
		if (msgLength > 30000 &&
			!(id == 'T' || id == 'D' || id == 'd' || id == 'V'))
		{
			handleSyncLoss(conn, id, msgLength);
			break;
		}

		/*
		 * Can't process if message body isn't all here yet.
		 */
		msgLength -= 4;
		avail = conn->inEnd - conn->inCursor;
		if (avail < msgLength)
		{
			/*
			 * Before looping, enlarge the input buffer if needed to hold
			 * the whole message.  See notes in parseInput.
			 */
			if (pqCheckInBufferSpace(conn->inCursor + msgLength, conn))
			{
				/*
				 * XXX add some better recovery code... plan is to skip
				 * over the message using its length, then report an error.
				 * For the moment, just treat this like loss of sync (which
				 * indeed it might be!)
				 */
				handleSyncLoss(conn, id, msgLength);
				break;
			}
			continue;
		}

		/*
		 * We should see V or E response to the command, but might get N
		 * and/or A notices first. We also need to swallow the final Z
		 * before returning.
		 */
		switch (id)
		{
			case 'V':			/* function result */
				if (pqGetInt(actual_result_len, 4, conn))
					continue;
				if (*actual_result_len != -1)
				{
					if (result_is_int)
					{
						if (pqGetInt(result_buf, *actual_result_len, conn))
							continue;
					}
					else
					{
						if (pqGetnchar((char *) result_buf,
									   *actual_result_len,
									   conn))
							continue;
					}
				}
				/* correctly finished function result message */
				status = PGRES_COMMAND_OK;
				break;
			case 'E':			/* error return */
				if (pqGetErrorNotice(conn, true))
					continue;
				status = PGRES_FATAL_ERROR;
				break;
			case 'A':			/* notify message */
				/* handle notify and go back to processing return values */
				if (getNotify(conn))
					continue;
				break;
			case 'N':			/* notice */
				/* handle notice and go back to processing return values */
				if (pqGetErrorNotice(conn, false))
					continue;
				break;
			case 'Z':			/* backend is ready for new query */
				if (pqGetc(&conn->xact_status, conn))
					continue;
				/* consume the message and exit */
				conn->inStart += 5 + msgLength;
				/* if we saved a result object (probably an error), use it */
				if (conn->result)
					return prepareAsyncResult(conn);
				return PQmakeEmptyPGresult(conn, status);
			case 'S':			/* parameter status */
				if (getParameterStatus(conn))
					continue;
				break;
			default:
				/* The backend violates the protocol. */
				printfPQExpBuffer(&conn->errorMessage,
							  libpq_gettext("protocol error: id=0x%x\n"),
								  id);
				saveErrorResult(conn);
				/* trust the specified message length as what to skip */
				conn->inStart += 5 + msgLength;
				return prepareAsyncResult(conn);
		}
		/* Completed this message, keep going */
		/* trust the specified message length as what to skip */
		conn->inStart += 5 + msgLength;
		needInput = false;
	}

	/*
	 * We fall out of the loop only upon failing to read data.
	 * conn->errorMessage has been set by pqWait or pqReadData. We want to
	 * append it to any already-received error message.
	 */
	saveErrorResult(conn);
	return prepareAsyncResult(conn);
}


/* ====== accessor funcs for PGresult ======== */

ExecStatusType
PQresultStatus(const PGresult *res)
{
	if (!res)
		return PGRES_NONFATAL_ERROR;
	return res->resultStatus;
}

char *
PQresStatus(ExecStatusType status)
{
	if (status < 0 || status >= sizeof pgresStatus / sizeof pgresStatus[0])
		return libpq_gettext("invalid ExecStatusType code");
	return pgresStatus[status];
}

char *
PQresultErrorMessage(const PGresult *res)
{
	if (!res || !res->errMsg)
		return "";
	return res->errMsg;
}

int
PQntuples(const PGresult *res)
{
	if (!res)
		return 0;
	return res->ntups;
}

int
PQnfields(const PGresult *res)
{
	if (!res)
		return 0;
	return res->numAttributes;
}

int
PQbinaryTuples(const PGresult *res)
{
	if (!res)
		return 0;
	return res->binary;
}

/*
 * Helper routines to range-check field numbers and tuple numbers.
 * Return TRUE if OK, FALSE if not
 */

static int
check_field_number(const PGresult *res, int field_num)
{
	char		noticeBuf[128];

	if (!res)
		return FALSE;			/* no way to display error message... */
	if (field_num < 0 || field_num >= res->numAttributes)
	{
		if (res->noticeHook)
		{
			snprintf(noticeBuf, sizeof(noticeBuf),
			   libpq_gettext("column number %d is out of range 0..%d\n"),
					 field_num, res->numAttributes - 1);
			DONOTICE(res, noticeBuf);
		}
		return FALSE;
	}
	return TRUE;
}

static int
check_tuple_field_number(const PGresult *res,
						 int tup_num, int field_num)
{
	char		noticeBuf[128];

	if (!res)
		return FALSE;			/* no way to display error message... */
	if (tup_num < 0 || tup_num >= res->ntups)
	{
		if (res->noticeHook)
		{
			snprintf(noticeBuf, sizeof(noticeBuf),
				  libpq_gettext("row number %d is out of range 0..%d\n"),
					 tup_num, res->ntups - 1);
			DONOTICE(res, noticeBuf);
		}
		return FALSE;
	}
	if (field_num < 0 || field_num >= res->numAttributes)
	{
		if (res->noticeHook)
		{
			snprintf(noticeBuf, sizeof(noticeBuf),
			   libpq_gettext("column number %d is out of range 0..%d\n"),
					 field_num, res->numAttributes - 1);
			DONOTICE(res, noticeBuf);
		}
		return FALSE;
	}
	return TRUE;
}

/*
   returns NULL if the field_num is invalid
*/
char *
PQfname(const PGresult *res, int field_num)
{
	if (!check_field_number(res, field_num))
		return NULL;
	if (res->attDescs)
		return res->attDescs[field_num].name;
	else
		return NULL;
}

/*
   returns -1 on a bad field name
*/
int
PQfnumber(const PGresult *res, const char *field_name)
{
	int			i;
	char	   *field_case;

	if (!res)
		return -1;

	if (field_name == NULL ||
		field_name[0] == '\0' ||
		res->attDescs == NULL)
		return -1;

	field_case = strdup(field_name);
	if (*field_case == '"')
	{
		strcpy(field_case, field_case + 1);
		*(field_case + strlen(field_case) - 1) = '\0';
	}
	else
		for (i = 0; field_case[i]; i++)
			if (isupper((unsigned char) field_case[i]))
				field_case[i] = tolower((unsigned char) field_case[i]);

	for (i = 0; i < res->numAttributes; i++)
	{
		if (strcmp(field_case, res->attDescs[i].name) == 0)
		{
			free(field_case);
			return i;
		}
	}
	free(field_case);
	return -1;
}

Oid
PQftype(const PGresult *res, int field_num)
{
	if (!check_field_number(res, field_num))
		return InvalidOid;
	if (res->attDescs)
		return res->attDescs[field_num].typid;
	else
		return InvalidOid;
}

int
PQfsize(const PGresult *res, int field_num)
{
	if (!check_field_number(res, field_num))
		return 0;
	if (res->attDescs)
		return res->attDescs[field_num].typlen;
	else
		return 0;
}

int
PQfmod(const PGresult *res, int field_num)
{
	if (!check_field_number(res, field_num))
		return 0;
	if (res->attDescs)
		return res->attDescs[field_num].atttypmod;
	else
		return 0;
}

char *
PQcmdStatus(PGresult *res)
{
	if (!res)
		return NULL;
	return res->cmdStatus;
}

/*
   PQoidStatus -
	if the last command was an INSERT, return the oid string
	if not, return ""
*/
char *
PQoidStatus(const PGresult *res)
{
	/*
	 * This must be enough to hold the result. Don't laugh, this is better
	 * than what this function used to do.
	 */
	static char buf[24];

	size_t		len;

	if (!res || !res->cmdStatus || strncmp(res->cmdStatus, "INSERT ", 7) != 0)
		return "";

	len = strspn(res->cmdStatus + 7, "0123456789");
	if (len > 23)
		len = 23;
	strncpy(buf, res->cmdStatus + 7, len);
	buf[len] = '\0';

	return buf;
}

/*
  PQoidValue -
	a perhaps preferable form of the above which just returns
	an Oid type
*/
Oid
PQoidValue(const PGresult *res)
{
	char	   *endptr = NULL;
	unsigned long result;

	if (!res || !res->cmdStatus || strncmp(res->cmdStatus, "INSERT ", 7) != 0)
		return InvalidOid;

#ifdef WIN32
	SetLastError(0);
#else
	errno = 0;
#endif
	result = strtoul(res->cmdStatus + 7, &endptr, 10);

	if (!endptr || (*endptr != ' ' && *endptr != '\0') || errno == ERANGE)
		return InvalidOid;
	else
		return (Oid) result;
}


/*
   PQcmdTuples -
	If the last command was an INSERT/UPDATE/DELETE/MOVE/FETCH, return a
	string containing the number of inserted/affected tuples. If not,
	return "".

	XXX: this should probably return an int
*/
char *
PQcmdTuples(PGresult *res)
{
	char		noticeBuf[128];
	char		*p;

	if (!res)
		return "";

	if (strncmp(res->cmdStatus, "INSERT ", 7) == 0)
	{
		p = res->cmdStatus + 6;
		p++;
		/* INSERT: skip oid */
		while (*p != ' ' && *p)
			p++;
	}
	else if (strncmp(res->cmdStatus, "DELETE ", 7) == 0 ||
			 strncmp(res->cmdStatus, "UPDATE ", 7) == 0)
		p = res->cmdStatus + 6;
	else if (strncmp(res->cmdStatus, "FETCH ", 6) == 0)
		p = res->cmdStatus + 5;
	else if (strncmp(res->cmdStatus, "MOVE ", 5) == 0)
		p = res->cmdStatus + 4;
	else
		return "";

	p++;

	if (*p == 0)
	{
		if (res->noticeHook)
		{
			snprintf(noticeBuf, sizeof(noticeBuf),
					 libpq_gettext("could not interpret result from server: %s\n"),
					 res->cmdStatus);
			DONOTICE(res, noticeBuf);
		}
		return "";
	}

	return p;
}

/*
   PQgetvalue:
	return the value of field 'field_num' of row 'tup_num'

	If res is binary, then the value returned is NOT a null-terminated
	ASCII string, but the binary representation in the server's native
	format.

	if res is not binary, a null-terminated ASCII string is returned.
*/
char *
PQgetvalue(const PGresult *res, int tup_num, int field_num)
{
	if (!check_tuple_field_number(res, tup_num, field_num))
		return NULL;
	return res->tuples[tup_num][field_num].value;
}

/* PQgetlength:
	 returns the length of a field value in bytes.	If res is binary,
	 i.e. a result of a binary portal, then the length returned does
	 NOT include the size field of the varlena.  (The data returned
	 by PQgetvalue doesn't either.)
*/
int
PQgetlength(const PGresult *res, int tup_num, int field_num)
{
	if (!check_tuple_field_number(res, tup_num, field_num))
		return 0;
	if (res->tuples[tup_num][field_num].len != NULL_LEN)
		return res->tuples[tup_num][field_num].len;
	else
		return 0;
}

/* PQgetisnull:
	 returns the null status of a field value.
*/
int
PQgetisnull(const PGresult *res, int tup_num, int field_num)
{
	if (!check_tuple_field_number(res, tup_num, field_num))
		return 1;				/* pretend it is null */
	if (res->tuples[tup_num][field_num].len == NULL_LEN)
		return 1;
	else
		return 0;
}

/* PQsetnonblocking:
	 sets the PGconn's database connection non-blocking if the arg is TRUE
	 or makes it non-blocking if the arg is FALSE, this will not protect
	 you from PQexec(), you'll only be safe when using the non-blocking
	 API
	 Needs to be called only on a connected database connection.
*/

int
PQsetnonblocking(PGconn *conn, int arg)
{
	arg = (arg == TRUE) ? 1 : 0;
	/* early out if the socket is already in the state requested */
	if (arg == conn->nonblocking)
		return (0);

	/*
	 * to guarantee constancy for flushing/query/result-polling behavior
	 * we need to flush the send queue at this point in order to guarantee
	 * proper behavior. this is ok because either they are making a
	 * transition _from_ or _to_ blocking mode, either way we can block
	 * them.
	 */
	/* if we are going from blocking to non-blocking flush here */
	if (pqFlush(conn))
		return (-1);

	conn->nonblocking = arg;

	return (0);
}

/* return the blocking status of the database connection, TRUE == nonblocking,
	 FALSE == blocking
*/
int
PQisnonblocking(const PGconn *conn)
{
	return (pqIsnonblocking(conn));
}

/* try to force data out, really only useful for non-blocking users */
int
PQflush(PGconn *conn)
{
	return (pqFlush(conn));
}


/*
 *		PQfreemem - safely frees memory allocated
 *
 * Needed mostly by Win32, unless multithreaded DLL (/MD in VC6)
 * Used for freeing memory from PQescapeByte()a/PQunescapeBytea()
 */
void PQfreemem(void *ptr)
{
	free(ptr);
}

/*
 * PQfreeNotify - free's the memory associated with a PGnotify
 *
 * This function is here only for binary backward compatibility.
 * New code should use PQfreemem().  A macro will automatically map
 * calls to PQfreemem.  It should be removed in the future.  bjm 2003-03-24
 */

#undef PQfreeNotify
void PQfreeNotify(PGnotify *notify);

void
PQfreeNotify(PGnotify *notify)
{
	PQfreemem(notify);
}


/* ---------------
 * Escaping arbitrary strings to get valid SQL strings/identifiers.
 *
 * Replaces "\\" with "\\\\" and "'" with "''".
 * length is the length of the buffer pointed to by
 * from.  The buffer at to must be at least 2*length + 1 characters
 * long.  A terminating NUL character is written.
 * ---------------
 */

size_t
PQescapeString(char *to, const char *from, size_t length)
{
	const char *source = from;
	char	   *target = to;
	unsigned int remaining = length;

	while (remaining > 0)
	{
		switch (*source)
		{
			case '\\':
				*target = '\\';
				target++;
				*target = '\\';
				/* target and remaining are updated below. */
				break;

			case '\'':
				*target = '\'';
				target++;
				*target = '\'';
				/* target and remaining are updated below. */
				break;

			default:
				*target = *source;
				/* target and remaining are updated below. */
		}
		source++;
		target++;
		remaining--;
	}

	/* Write the terminating NUL character. */
	*target = '\0';

	return target - to;
}

/*
 *		PQescapeBytea	- converts from binary string to the
 *		minimal encoding necessary to include the string in an SQL
 *		INSERT statement with a bytea type column as the target.
 *
 *		The following transformations are applied
 *		'\0' == ASCII  0 == \\000
 *		'\'' == ASCII 39 == \'
 *		'\\' == ASCII 92 == \\\\
 *		anything >= 0x80 ---> \\ooo (where ooo is an octal expression)
 */
unsigned char *
PQescapeBytea(const unsigned char *bintext, size_t binlen, size_t *bytealen)
{
	const unsigned char *vp;
	unsigned char *rp;
	unsigned char *result;
	size_t		i;
	size_t		len;

	/*
	 * empty string has 1 char ('\0')
	 */
	len = 1;

	vp = bintext;
	for (i = binlen; i > 0; i--, vp++)
	{
		if (*vp == 0 || *vp >= 0x80)
			len += 5;			/* '5' is for '\\ooo' */
		else if (*vp == '\'')
			len += 2;
		else if (*vp == '\\')
			len += 4;
		else
			len++;
	}

	rp = result = (unsigned char *) malloc(len);
	if (rp == NULL)
		return NULL;

	vp = bintext;
	*bytealen = len;

	for (i = binlen; i > 0; i--, vp++)
	{
		if (*vp == 0 || *vp >= 0x80)
		{
			(void) sprintf(rp, "\\\\%03o", *vp);
			rp += 5;
		}
		else if (*vp == '\'')
		{
			rp[0] = '\\';
			rp[1] = '\'';
			rp += 2;
		}
		else if (*vp == '\\')
		{
			rp[0] = '\\';
			rp[1] = '\\';
			rp[2] = '\\';
			rp[3] = '\\';
			rp += 4;
		}
		else
			*rp++ = *vp;
	}
	*rp = '\0';

	return result;
}

/*
 *		PQunescapeBytea - converts the null terminated string representation
 *		of a bytea, strtext, into binary, filling a buffer. It returns a
 *		pointer to the buffer which is NULL on error, and the size of the
 *		buffer in retbuflen. The pointer may subsequently be used as an
 *		argument to the function free(3). It is the reverse of PQescapeBytea.
 *
 *		The following transformations are reversed:
 *		'\0' == ASCII  0 == \000
 *		'\'' == ASCII 39 == \'
 *		'\\' == ASCII 92 == \\
 *
 *		States:
 *		0	normal		0->1->2->3->4
 *		1	\			   1->5
 *		2	\0			   1->6
 *		3	\00
 *		4	\000
 *		5	\'
 *		6	\\
 */
unsigned char *
PQunescapeBytea(const unsigned char *strtext, size_t *retbuflen)
{
	size_t		buflen;
	unsigned char *buffer,
			   *bp;
	const unsigned char *sp;
	unsigned int state = 0;

	if (strtext == NULL)
		return NULL;
	buflen = strlen(strtext);	/* will shrink, also we discover if
								 * strtext */
	buffer = (unsigned char *) malloc(buflen);	/* isn't NULL terminated */
	if (buffer == NULL)
		return NULL;
	for (bp = buffer, sp = strtext; *sp != '\0'; bp++, sp++)
	{
		switch (state)
		{
			case 0:
				if (*sp == '\\')
					state = 1;
				*bp = *sp;
				break;
			case 1:
				if (*sp == '\'')	/* state=5 */
				{				/* replace \' with 39 */
					bp--;
					*bp = '\'';
					buflen--;
					state = 0;
				}
				else if (*sp == '\\')	/* state=6 */
				{				/* replace \\ with 92 */
					bp--;
					*bp = '\\';
					buflen--;
					state = 0;
				}
				else
				{
					if (isdigit(*sp))
						state = 2;
					else
						state = 0;
					*bp = *sp;
				}
				break;
			case 2:
				if (isdigit(*sp))
					state = 3;
				else
					state = 0;
				*bp = *sp;
				break;
			case 3:
				if (isdigit(*sp))		/* state=4 */
				{
					int			v;

					bp -= 3;
					sscanf(sp - 2, "%03o", &v);
					*bp = v;
					buflen -= 3;
					state = 0;
				}
				else
				{
					*bp = *sp;
					state = 0;
				}
				break;
		}
	}
	buffer = realloc(buffer, buflen);
	if (buffer == NULL)
		return NULL;

	*retbuflen = buflen;
	return buffer;
}