Adding upstream version 15.4.upstream/15.4upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1282 insertions, 0 deletions

diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
new file mode 100644
index 0000000..d76bb39
--- /dev/null
+++ b/src/interfaces/libpq/fe-misc.c
@@ -0,0 +1,1282 @@
+/*-------------------------------------------------------------------------
+ *
+ *	 FILE
+ *		fe-misc.c
+ *
+ *	 DESCRIPTION
+ *		 miscellaneous useful functions
+ *
+ * The communication routines here are analogous to the ones in
+ * backend/libpq/pqcomm.c and backend/libpq/pqformat.c, but operate
+ * in the considerably different environment of the frontend libpq.
+ * In particular, we work with a bare nonblock-mode socket, rather than
+ * a stdio stream, so that we can avoid unwanted blocking of the application.
+ *
+ * XXX: MOVE DEBUG PRINTOUT TO HIGHER LEVEL.  As is, block and restart
+ * will cause repeat printouts.
+ *
+ * We must speak the same transmitted data representations as the backend
+ * routines.
+ *
+ *
+ * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/interfaces/libpq/fe-misc.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres_fe.h"
+
+#include <signal.h>
+#include <time.h>
+
+#ifdef WIN32
+#include "win32.h"
+#else
+#include <unistd.h>
+#include <sys/time.h>
+#endif
+
+#ifdef HAVE_POLL_H
+#include <poll.h>
+#endif
+#ifdef HAVE_SYS_SELECT_H
+#include <sys/select.h>
+#endif
+
+#include "libpq-fe.h"
+#include "libpq-int.h"
+#include "mb/pg_wchar.h"
+#include "pg_config_paths.h"
+#include "port/pg_bswap.h"
+
+static int	pqPutMsgBytes(const void *buf, size_t len, PGconn *conn);
+static int	pqSendSome(PGconn *conn, int len);
+static int	pqSocketCheck(PGconn *conn, int forRead, int forWrite,
+						  time_t end_time);
+static int	pqSocketPoll(int sock, int forRead, int forWrite, time_t end_time);
+
+/*
+ * PQlibVersion: return the libpq version number
+ */
+int
+PQlibVersion(void)
+{
+	return PG_VERSION_NUM;
+}
+
+
+/*
+ * pqGetc: get 1 character from the connection
+ *
+ *	All these routines return 0 on success, EOF on error.
+ *	Note that for the Get routines, EOF only means there is not enough
+ *	data in the buffer, not that there is necessarily a hard error.
+ */
+int
+pqGetc(char *result, PGconn *conn)
+{
+	if (conn->inCursor >= conn->inEnd)
+		return EOF;
+
+	*result = conn->inBuffer[conn->inCursor++];
+
+	return 0;
+}
+
+
+/*
+ * pqPutc: write 1 char to the current message
+ */
+int
+pqPutc(char c, PGconn *conn)
+{
+	if (pqPutMsgBytes(&c, 1, conn))
+		return EOF;
+
+	return 0;
+}
+
+
+/*
+ * pqGets[_append]:
+ * get a null-terminated string from the connection,
+ * and store it in an expansible PQExpBuffer.
+ * If we run out of memory, all of the string is still read,
+ * but the excess characters are silently discarded.
+ */
+static int
+pqGets_internal(PQExpBuffer buf, PGconn *conn, bool resetbuffer)
+{
+	/* Copy conn data to locals for faster search loop */
+	char	   *inBuffer = conn->inBuffer;
+	int			inCursor = conn->inCursor;
+	int			inEnd = conn->inEnd;
+	int			slen;
+
+	while (inCursor < inEnd && inBuffer[inCursor])
+		inCursor++;
+
+	if (inCursor >= inEnd)
+		return EOF;
+
+	slen = inCursor - conn->inCursor;
+
+	if (resetbuffer)
+		resetPQExpBuffer(buf);
+
+	appendBinaryPQExpBuffer(buf, inBuffer + conn->inCursor, slen);
+
+	conn->inCursor = ++inCursor;
+
+	return 0;
+}
+
+int
+pqGets(PQExpBuffer buf, PGconn *conn)
+{
+	return pqGets_internal(buf, conn, true);
+}
+
+int
+pqGets_append(PQExpBuffer buf, PGconn *conn)
+{
+	return pqGets_internal(buf, conn, false);
+}
+
+
+/*
+ * pqPuts: write a null-terminated string to the current message
+ */
+int
+pqPuts(const char *s, PGconn *conn)
+{
+	if (pqPutMsgBytes(s, strlen(s) + 1, conn))
+		return EOF;
+
+	return 0;
+}
+
+/*
+ * pqGetnchar:
+ *	get a string of exactly len bytes in buffer s, no null termination
+ */
+int
+pqGetnchar(char *s, size_t len, PGconn *conn)
+{
+	if (len > (size_t) (conn->inEnd - conn->inCursor))
+		return EOF;
+
+	memcpy(s, conn->inBuffer + conn->inCursor, len);
+	/* no terminating null */
+
+	conn->inCursor += len;
+
+	return 0;
+}
+
+/*
+ * pqSkipnchar:
+ *	skip over len bytes in input buffer.
+ *
+ * Note: this is primarily useful for its debug output, which should
+ * be exactly the same as for pqGetnchar.  We assume the data in question
+ * will actually be used, but just isn't getting copied anywhere as yet.
+ */
+int
+pqSkipnchar(size_t len, PGconn *conn)
+{
+	if (len > (size_t) (conn->inEnd - conn->inCursor))
+		return EOF;
+
+	conn->inCursor += len;
+
+	return 0;
+}
+
+/*
+ * pqPutnchar:
+ *	write exactly len bytes to the current message
+ */
+int
+pqPutnchar(const char *s, size_t len, PGconn *conn)
+{
+	if (pqPutMsgBytes(s, len, conn))
+		return EOF;
+
+	return 0;
+}
+
+/*
+ * pqGetInt
+ *	read a 2 or 4 byte integer and convert from network byte order
+ *	to local byte order
+ */
+int
+pqGetInt(int *result, size_t bytes, PGconn *conn)
+{
+	uint16		tmp2;
+	uint32		tmp4;
+
+	switch (bytes)
+	{
+		case 2:
+			if (conn->inCursor + 2 > conn->inEnd)
+				return EOF;
+			memcpy(&tmp2, conn->inBuffer + conn->inCursor, 2);
+			conn->inCursor += 2;
+			*result = (int) pg_ntoh16(tmp2);
+			break;
+		case 4:
+			if (conn->inCursor + 4 > conn->inEnd)
+				return EOF;
+			memcpy(&tmp4, conn->inBuffer + conn->inCursor, 4);
+			conn->inCursor += 4;
+			*result = (int) pg_ntoh32(tmp4);
+			break;
+		default:
+			pqInternalNotice(&conn->noticeHooks,
+							 "integer of size %lu not supported by pqGetInt",
+							 (unsigned long) bytes);
+			return EOF;
+	}
+
+	return 0;
+}
+
+/*
+ * pqPutInt
+ * write an integer of 2 or 4 bytes, converting from host byte order
+ * to network byte order.
+ */
+int
+pqPutInt(int value, size_t bytes, PGconn *conn)
+{
+	uint16		tmp2;
+	uint32		tmp4;
+
+	switch (bytes)
+	{
+		case 2:
+			tmp2 = pg_hton16((uint16) value);
+			if (pqPutMsgBytes((const char *) &tmp2, 2, conn))
+				return EOF;
+			break;
+		case 4:
+			tmp4 = pg_hton32((uint32) value);
+			if (pqPutMsgBytes((const char *) &tmp4, 4, conn))
+				return EOF;
+			break;
+		default:
+			pqInternalNotice(&conn->noticeHooks,
+							 "integer of size %lu not supported by pqPutInt",
+							 (unsigned long) bytes);
+			return EOF;
+	}
+
+	return 0;
+}
+
+/*
+ * Make sure conn's output buffer can hold bytes_needed bytes (caller must
+ * include already-stored data into the value!)
+ *
+ * Returns 0 on success, EOF if failed to enlarge buffer
+ */
+int
+pqCheckOutBufferSpace(size_t bytes_needed, PGconn *conn)
+{
+	int			newsize = conn->outBufSize;
+	char	   *newbuf;
+
+	/* Quick exit if we have enough space */
+	if (bytes_needed <= (size_t) newsize)
+		return 0;
+
+	/*
+	 * If we need to enlarge the buffer, we first try to double it in size; if
+	 * that doesn't work, enlarge in multiples of 8K.  This avoids thrashing
+	 * the malloc pool by repeated small enlargements.
+	 *
+	 * Note: tests for newsize > 0 are to catch integer overflow.
+	 */
+	do
+	{
+		newsize *= 2;
+	} while (newsize > 0 && bytes_needed > (size_t) newsize);
+
+	if (newsize > 0 && bytes_needed <= (size_t) newsize)
+	{
+		newbuf = realloc(conn->outBuffer, newsize);
+		if (newbuf)
+		{
+			/* realloc succeeded */
+			conn->outBuffer = newbuf;
+			conn->outBufSize = newsize;
+			return 0;
+		}
+	}
+
+	newsize = conn->outBufSize;
+	do
+	{
+		newsize += 8192;
+	} while (newsize > 0 && bytes_needed > (size_t) newsize);
+
+	if (newsize > 0 && bytes_needed <= (size_t) newsize)
+	{
+		newbuf = realloc(conn->outBuffer, newsize);
+		if (newbuf)
+		{
+			/* realloc succeeded */
+			conn->outBuffer = newbuf;
+			conn->outBufSize = newsize;
+			return 0;
+		}
+	}
+
+	/* realloc failed. Probably out of memory */
+	appendPQExpBufferStr(&conn->errorMessage,
+						 "cannot allocate memory for output buffer\n");
+	return EOF;
+}
+
+/*
+ * Make sure conn's input buffer can hold bytes_needed bytes (caller must
+ * include already-stored data into the value!)
+ *
+ * Returns 0 on success, EOF if failed to enlarge buffer
+ */
+int
+pqCheckInBufferSpace(size_t bytes_needed, PGconn *conn)
+{
+	int			newsize = conn->inBufSize;
+	char	   *newbuf;
+
+	/* Quick exit if we have enough space */
+	if (bytes_needed <= (size_t) newsize)
+		return 0;
+
+	/*
+	 * Before concluding that we need to enlarge the buffer, left-justify
+	 * whatever is in it and recheck.  The caller's value of bytes_needed
+	 * includes any data to the left of inStart, but we can delete that in
+	 * preference to enlarging the buffer.  It's slightly ugly to have this
+	 * function do this, but it's better than making callers worry about it.
+	 */
+	bytes_needed -= conn->inStart;
+
+	if (conn->inStart < conn->inEnd)
+	{
+		if (conn->inStart > 0)
+		{
+			memmove(conn->inBuffer, conn->inBuffer + conn->inStart,
+					conn->inEnd - conn->inStart);
+			conn->inEnd -= conn->inStart;
+			conn->inCursor -= conn->inStart;
+			conn->inStart = 0;
+		}
+	}
+	else
+	{
+		/* buffer is logically empty, reset it */
+		conn->inStart = conn->inCursor = conn->inEnd = 0;
+	}
+
+	/* Recheck whether we have enough space */
+	if (bytes_needed <= (size_t) newsize)
+		return 0;
+
+	/*
+	 * If we need to enlarge the buffer, we first try to double it in size; if
+	 * that doesn't work, enlarge in multiples of 8K.  This avoids thrashing
+	 * the malloc pool by repeated small enlargements.
+	 *
+	 * Note: tests for newsize > 0 are to catch integer overflow.
+	 */
+	do
+	{
+		newsize *= 2;
+	} while (newsize > 0 && bytes_needed > (size_t) newsize);
+
+	if (newsize > 0 && bytes_needed <= (size_t) newsize)
+	{
+		newbuf = realloc(conn->inBuffer, newsize);
+		if (newbuf)
+		{
+			/* realloc succeeded */
+			conn->inBuffer = newbuf;
+			conn->inBufSize = newsize;
+			return 0;
+		}
+	}
+
+	newsize = conn->inBufSize;
+	do
+	{
+		newsize += 8192;
+	} while (newsize > 0 && bytes_needed > (size_t) newsize);
+
+	if (newsize > 0 && bytes_needed <= (size_t) newsize)
+	{
+		newbuf = realloc(conn->inBuffer, newsize);
+		if (newbuf)
+		{
+			/* realloc succeeded */
+			conn->inBuffer = newbuf;
+			conn->inBufSize = newsize;
+			return 0;
+		}
+	}
+
+	/* realloc failed. Probably out of memory */
+	appendPQExpBufferStr(&conn->errorMessage,
+						 "cannot allocate memory for input buffer\n");
+	return EOF;
+}
+
+/*
+ * pqPutMsgStart: begin construction of a message to the server
+ *
+ * msg_type is the message type byte, or 0 for a message without type byte
+ * (only startup messages have no type byte)
+ *
+ * Returns 0 on success, EOF on error
+ *
+ * The idea here is that we construct the message in conn->outBuffer,
+ * beginning just past any data already in outBuffer (ie, at
+ * outBuffer+outCount).  We enlarge the buffer as needed to hold the message.
+ * When the message is complete, we fill in the length word (if needed) and
+ * then advance outCount past the message, making it eligible to send.
+ *
+ * The state variable conn->outMsgStart points to the incomplete message's
+ * length word: it is either outCount or outCount+1 depending on whether
+ * there is a type byte.  The state variable conn->outMsgEnd is the end of
+ * the data collected so far.
+ */
+int
+pqPutMsgStart(char msg_type, PGconn *conn)
+{
+	int			lenPos;
+	int			endPos;
+
+	/* allow room for message type byte */
+	if (msg_type)
+		endPos = conn->outCount + 1;
+	else
+		endPos = conn->outCount;
+
+	/* do we want a length word? */
+	lenPos = endPos;
+	/* allow room for message length */
+	endPos += 4;
+
+	/* make sure there is room for message header */
+	if (pqCheckOutBufferSpace(endPos, conn))
+		return EOF;
+	/* okay, save the message type byte if any */
+	if (msg_type)
+		conn->outBuffer[conn->outCount] = msg_type;
+	/* set up the message pointers */
+	conn->outMsgStart = lenPos;
+	conn->outMsgEnd = endPos;
+	/* length word, if needed, will be filled in by pqPutMsgEnd */
+
+	return 0;
+}
+
+/*
+ * pqPutMsgBytes: add bytes to a partially-constructed message
+ *
+ * Returns 0 on success, EOF on error
+ */
+static int
+pqPutMsgBytes(const void *buf, size_t len, PGconn *conn)
+{
+	/* make sure there is room for it */
+	if (pqCheckOutBufferSpace(conn->outMsgEnd + len, conn))
+		return EOF;
+	/* okay, save the data */
+	memcpy(conn->outBuffer + conn->outMsgEnd, buf, len);
+	conn->outMsgEnd += len;
+	/* no Pfdebug call here, caller should do it */
+	return 0;
+}
+
+/*
+ * pqPutMsgEnd: finish constructing a message and possibly send it
+ *
+ * Returns 0 on success, EOF on error
+ *
+ * We don't actually send anything here unless we've accumulated at least
+ * 8K worth of data (the typical size of a pipe buffer on Unix systems).
+ * This avoids sending small partial packets.  The caller must use pqFlush
+ * when it's important to flush all the data out to the server.
+ */
+int
+pqPutMsgEnd(PGconn *conn)
+{
+	/* Fill in length word if needed */
+	if (conn->outMsgStart >= 0)
+	{
+		uint32		msgLen = conn->outMsgEnd - conn->outMsgStart;
+
+		msgLen = pg_hton32(msgLen);
+		memcpy(conn->outBuffer + conn->outMsgStart, &msgLen, 4);
+	}
+
+	/* trace client-to-server message */
+	if (conn->Pfdebug)
+	{
+		if (conn->outCount < conn->outMsgStart)
+			pqTraceOutputMessage(conn, conn->outBuffer + conn->outCount, true);
+		else
+			pqTraceOutputNoTypeByteMessage(conn,
+										   conn->outBuffer + conn->outMsgStart);
+	}
+
+	/* Make message eligible to send */
+	conn->outCount = conn->outMsgEnd;
+
+	if (conn->outCount >= 8192)
+	{
+		int			toSend = conn->outCount - (conn->outCount % 8192);
+
+		if (pqSendSome(conn, toSend) < 0)
+			return EOF;
+		/* in nonblock mode, don't complain if unable to send it all */
+	}
+
+	return 0;
+}
+
+/* ----------
+ * pqReadData: read more data, if any is available
+ * Possible return values:
+ *	 1: successfully loaded at least one more byte
+ *	 0: no data is presently available, but no error detected
+ *	-1: error detected (including EOF = connection closure);
+ *		conn->errorMessage set
+ * NOTE: callers must not assume that pointers or indexes into conn->inBuffer
+ * remain valid across this call!
+ * ----------
+ */
+int
+pqReadData(PGconn *conn)
+{
+	int			someread = 0;
+	int			nread;
+
+	if (conn->sock == PGINVALID_SOCKET)
+	{
+		appendPQExpBufferStr(&conn->errorMessage,
+							 libpq_gettext("connection not open\n"));
+		return -1;
+	}
+
+	/* Left-justify any data in the buffer to make room */
+	if (conn->inStart < conn->inEnd)
+	{
+		if (conn->inStart > 0)
+		{
+			memmove(conn->inBuffer, conn->inBuffer + conn->inStart,
+					conn->inEnd - conn->inStart);
+			conn->inEnd -= conn->inStart;
+			conn->inCursor -= conn->inStart;
+			conn->inStart = 0;
+		}
+	}
+	else
+	{
+		/* buffer is logically empty, reset it */
+		conn->inStart = conn->inCursor = conn->inEnd = 0;
+	}
+
+	/*
+	 * 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 + (size_t) 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)
+	{
+		switch (SOCK_ERRNO)
+		{
+			case EINTR:
+				goto retry3;
+
+				/* Some systems return EAGAIN/EWOULDBLOCK for no data */
+#ifdef EAGAIN
+			case EAGAIN:
+				return someread;
+#endif
+#if defined(EWOULDBLOCK) && (!defined(EAGAIN) || (EWOULDBLOCK != EAGAIN))
+			case EWOULDBLOCK:
+				return someread;
+#endif
+
+				/* We might get ECONNRESET etc here if connection failed */
+			case ALL_CONNECTION_FAILURE_ERRNOS:
+				goto definitelyFailed;
+
+			default:
+				/* pqsecure_read set the error message for us */
+				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, but the second
+	 * SSL_read() could still say WANT_READ because the data received was not
+	 * a complete SSL record.  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_in_use)
+		return 0;
+#endif
+
+	switch (pqReadReady(conn))
+	{
+		case 0:
+			/* definitely no data available */
+			return 0;
+		case 1:
+			/* ready for read */
+			break;
+		default:
+			/* we override pqReadReady's message with something more useful */
+			goto definitelyEOF;
+	}
+
+	/*
+	 * 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)
+	{
+		switch (SOCK_ERRNO)
+		{
+			case EINTR:
+				goto retry4;
+
+				/* Some systems return EAGAIN/EWOULDBLOCK for no data */
+#ifdef EAGAIN
+			case EAGAIN:
+				return 0;
+#endif
+#if defined(EWOULDBLOCK) && (!defined(EAGAIN) || (EWOULDBLOCK != EAGAIN))
+			case EWOULDBLOCK:
+				return 0;
+#endif
+
+				/* We might get ECONNRESET etc here if connection failed */
+			case ALL_CONNECTION_FAILURE_ERRNOS:
+				goto definitelyFailed;
+
+			default:
+				/* pqsecure_read set the error message for us */
+				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.
+	 */
+definitelyEOF:
+	appendPQExpBufferStr(&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"));
+
+	/* Come here if lower-level code already set a suitable errorMessage */
+definitelyFailed:
+	/* Do *not* drop any already-read data; caller still wants it */
+	pqDropConnection(conn, false);
+	conn->status = CONNECTION_BAD;	/* No more connection to backend */
+	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.
+ *
+ * Note that this is also responsible for consuming data from the socket
+ * (putting it in conn->inBuffer) in any situation where we can't send
+ * all the specified data immediately.
+ *
+ * If a socket-level write failure occurs, conn->write_failed is set and the
+ * error message is saved in conn->write_err_msg, but we clear the output
+ * buffer and return zero anyway; this is because callers should soldier on
+ * until we have read what we can from the server and checked for an error
+ * message.  write_err_msg should be reported only when we are unable to
+ * obtain a server error first.  Much of that behavior is implemented at
+ * lower levels, but this function deals with some edge cases.
+ */
+static int
+pqSendSome(PGconn *conn, int len)
+{
+	char	   *ptr = conn->outBuffer;
+	int			remaining = conn->outCount;
+	int			result = 0;
+
+	/*
+	 * If we already had a write failure, we will never again try to send data
+	 * on that connection.  Even if the kernel would let us, we've probably
+	 * lost message boundary sync with the server.  conn->write_failed
+	 * therefore persists until the connection is reset, and we just discard
+	 * all data presented to be written.  However, as long as we still have a
+	 * valid socket, we should continue to absorb data from the backend, so
+	 * that we can collect any final error messages.
+	 */
+	if (conn->write_failed)
+	{
+		/* conn->write_err_msg should be set up already */
+		conn->outCount = 0;
+		/* Absorb input data if any, and detect socket closure */
+		if (conn->sock != PGINVALID_SOCKET)
+		{
+			if (pqReadData(conn) < 0)
+				return -1;
+		}
+		return 0;
+	}
+
+	if (conn->sock == PGINVALID_SOCKET)
+	{
+		conn->write_failed = true;
+		/* Store error message in conn->write_err_msg, if possible */
+		/* (strdup failure is OK, we'll cope later) */
+		conn->write_err_msg = strdup(libpq_gettext("connection not open\n"));
+		/* Discard queued data; no chance it'll ever be sent */
+		conn->outCount = 0;
+		return 0;
+	}
+
+	/* while there's still data to send */
+	while (len > 0)
+	{
+		int			sent;
+
+#ifndef WIN32
+		sent = pqsecure_write(conn, ptr, len);
+#else
+
+		/*
+		 * Windows can fail on large sends, per KB article Q201213. The
+		 * failure-point appears to be different in different versions of
+		 * Windows, but 64k should always be safe.
+		 */
+		sent = pqsecure_write(conn, ptr, Min(len, 65536));
+#endif
+
+		if (sent < 0)
+		{
+			/* Anything except EAGAIN/EWOULDBLOCK/EINTR is trouble */
+			switch (SOCK_ERRNO)
+			{
+#ifdef EAGAIN
+				case EAGAIN:
+					break;
+#endif
+#if defined(EWOULDBLOCK) && (!defined(EAGAIN) || (EWOULDBLOCK != EAGAIN))
+				case EWOULDBLOCK:
+					break;
+#endif
+				case EINTR:
+					continue;
+
+				default:
+					/* Discard queued data; no chance it'll ever be sent */
+					conn->outCount = 0;
+
+					/* Absorb input data if any, and detect socket closure */
+					if (conn->sock != PGINVALID_SOCKET)
+					{
+						if (pqReadData(conn) < 0)
+							return -1;
+					}
+
+					/*
+					 * Lower-level code should already have filled
+					 * conn->write_err_msg (and set conn->write_failed) or
+					 * conn->errorMessage.  In the former case, we pretend
+					 * there's no problem; the write_failed condition will be
+					 * dealt with later.  Otherwise, report the error now.
+					 */
+					if (conn->write_failed)
+						return 0;
+					else
+						return -1;
+			}
+		}
+		else
+		{
+			ptr += sent;
+			len -= sent;
+			remaining -= sent;
+		}
+
+		if (len > 0)
+		{
+			/*
+			 * We didn't send it all, wait till we can send more.
+			 *
+			 * 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.
+			 *
+			 * In non-blocking mode, we don't wait here directly, but return 1
+			 * to indicate that data is still pending.  The caller should wait
+			 * for both read and write ready conditions, and call
+			 * PQconsumeInput() on read ready, but just in case it doesn't, we
+			 * call pqReadData() ourselves before returning.  That's not
+			 * enough if the data has not arrived yet, but it's the best we
+			 * can do, and works pretty well in practice.  (The documentation
+			 * used to say that you only need to wait for write-ready, so
+			 * there are still plenty of applications like that out there.)
+			 *
+			 * Note that errors here don't result in write_failed becoming
+			 * set.
+			 */
+			if (pqReadData(conn) < 0)
+			{
+				result = -1;	/* error message already set up */
+				break;
+			}
+
+			if (pqIsnonblocking(conn))
+			{
+				result = 1;
+				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.
+ * (See pqSendSome comments about how failure should be handled.)
+ */
+int
+pqFlush(PGconn *conn)
+{
+	if (conn->outCount > 0)
+	{
+		if (conn->Pfdebug)
+			fflush(conn->Pfdebug);
+
+		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.
+ *
+ * finish_time = ((time_t) -1) disables the wait limit.
+ *
+ * Returns -1 on failure, 0 if the socket is readable/writable, 1 if it timed out.
+ */
+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 -1;				/* errorMessage is already set */
+
+	if (result == 0)
+	{
+		appendPQExpBufferStr(&conn->errorMessage,
+							 libpq_gettext("timeout expired\n"));
+		return 1;
+	}
+
+	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 == PGINVALID_SOCKET)
+	{
+		appendPQExpBufferStr(&conn->errorMessage,
+							 libpq_gettext("invalid socket\n"));
+		return -1;
+	}
+
+#ifdef USE_SSL
+	/* Check for SSL library buffering read bytes */
+	if (forRead && conn->ssl_in_use && pgtls_read_pending(conn))
+	{
+		/* 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[PG_STRERROR_R_BUFLEN];
+
+		appendPQExpBuffer(&conn->errorMessage,
+						  libpq_gettext("%s() failed: %s\n"),
+						  "select",
+						  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 character beginning at s, using the
+ * specified encoding.
+ *
+ * Caution: when dealing with text that is not certainly valid in the
+ * specified encoding, the result may exceed the actual remaining
+ * string length.  Callers that are not prepared to deal with that
+ * should use PQmblenBounded() instead.
+ */
+int
+PQmblen(const char *s, int encoding)
+{
+	return pg_encoding_mblen(encoding, s);
+}
+
+/*
+ * Returns the byte length of the character beginning at s, using the
+ * specified encoding; but not more than the distance to end of string.
+ */
+int
+PQmblenBounded(const char *s, int encoding)
+{
+	return strnlen(s, pg_encoding_mblen(encoding, s));
+}
+
+/*
+ * Returns the display length of the character beginning at s, using the
+ * specified encoding.
+ */
+int
+PQdsplen(const char *s, int encoding)
+{
+	return pg_encoding_dsplen(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);
+		if (encoding < 0)
+			encoding = PG_SQL_ASCII;
+	}
+	return encoding;
+}
+
+
+#ifdef ENABLE_NLS
+
+static void
+libpq_binddomain(void)
+{
+	/*
+	 * If multiple threads come through here at about the same time, it's okay
+	 * for more than one of them to call bindtextdomain().  But it's not okay
+	 * for any of them to return to caller before bindtextdomain() is
+	 * complete, so don't set the flag till that's done.  Use "volatile" just
+	 * to be sure the compiler doesn't try to get cute.
+	 */
+	static volatile bool already_bound = false;
+
+	if (!already_bound)
+	{
+		/* bindtextdomain() does not preserve errno */
+#ifdef WIN32
+		int			save_errno = GetLastError();
+#else
+		int			save_errno = errno;
+#endif
+		const char *ldir;
+
+		/* No relocatable lookup here because the binary could be anywhere */
+		ldir = getenv("PGLOCALEDIR");
+		if (!ldir)
+			ldir = LOCALEDIR;
+		bindtextdomain(PG_TEXTDOMAIN("libpq"), ldir);
+		already_bound = true;
+#ifdef WIN32
+		SetLastError(save_errno);
+#else
+		errno = save_errno;
+#endif
+	}
+}
+
+char *
+libpq_gettext(const char *msgid)
+{
+	libpq_binddomain();
+	return dgettext(PG_TEXTDOMAIN("libpq"), msgid);
+}
+
+char *
+libpq_ngettext(const char *msgid, const char *msgid_plural, unsigned long n)
+{
+	libpq_binddomain();
+	return dngettext(PG_TEXTDOMAIN("libpq"), msgid, msgid_plural, n);
+}
+
+#endif							/* ENABLE_NLS */