fe-misc.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

/*-------------------------------------------------------------------------
 *
 *	 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/pqcomprim.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) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/interfaces/libpq/fe-misc.c,v 1.122.2.1 2005/11/22 18:23:30 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */

#include "postgres_fe.h"

#include <errno.h>
#include <signal.h>
#include <time.h>

#ifndef WIN32_CLIENT_ONLY
#include <netinet/in.h>
#include <arpa/inet.h>
#endif

#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_POLL_H
#include <sys/poll.h>
#endif
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif

#include "libpq-fe.h"
#include "libpq-int.h"
#include "pqsignal.h"
#include "mb/pg_wchar.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);


/*
 * 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++];

	if (conn->Pfdebug)
		fprintf(conn->Pfdebug, "From backend> %c\n", *result);

	return 0;
}


/*
 * pqPutc: write 1 char to the current message
 */
int
pqPutc(char c, PGconn *conn)
{
	if (pqPutMsgBytes(&c, 1, conn))
		return EOF;

	if (conn->Pfdebug)
		fprintf(conn->Pfdebug, "To backend> %c\n", c);

	return 0;
}


/*
 * pqGets:
 * 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.
 */
int
pqGets(PQExpBuffer buf, PGconn *conn)
{
	/* 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;

	resetPQExpBuffer(buf);
	appendBinaryPQExpBuffer(buf, inBuffer + conn->inCursor, slen);

	conn->inCursor = ++inCursor;

	if (conn->Pfdebug)
		fprintf(conn->Pfdebug, "From backend> \"%s\"\n",
				buf->data);

	return 0;
}


/*
 * 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;

	if (conn->Pfdebug)
		fprintf(conn->Pfdebug, "To backend> \"%s\"\n", s);

	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 < 0 || len > (size_t) (conn->inEnd - conn->inCursor))
		return EOF;

	memcpy(s, conn->inBuffer + conn->inCursor, len);
	/* no terminating null */

	conn->inCursor += len;

	if (conn->Pfdebug)
		fprintf(conn->Pfdebug, "From backend (%lu)> %.*s\n",
				(unsigned long) len, (int) len, s);

	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;

	if (conn->Pfdebug)
		fprintf(conn->Pfdebug, "To backend> %.*s\n", (int) len, s);

	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) ntohs(tmp2);
			break;
		case 4:
			if (conn->inCursor + 4 > conn->inEnd)
				return EOF;
			memcpy(&tmp4, conn->inBuffer + conn->inCursor, 4);
			conn->inCursor += 4;
			*result = (int) ntohl(tmp4);
			break;
		default:
			pqInternalNotice(&conn->noticeHooks,
							 "integer of size %lu not supported by pqGetInt",
							 (unsigned long) bytes);
			return EOF;
	}

	if (conn->Pfdebug)
		fprintf(conn->Pfdebug, "From backend (#%lu)> %d\n", (unsigned long) bytes, *result);

	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 = htons((uint16) value);
			if (pqPutMsgBytes((const char *) &tmp2, 2, conn))
				return EOF;
			break;
		case 4:
			tmp4 = htonl((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;
	}

	if (conn->Pfdebug)
		fprintf(conn->Pfdebug, "To backend (%lu#)> %d\n", (unsigned long) bytes, value);

	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(int bytes_needed, PGconn *conn)
{
	int			newsize = conn->outBufSize;
	char	   *newbuf;

	if (bytes_needed <= 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 (bytes_needed > newsize && newsize > 0);

	if (bytes_needed <= 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 (bytes_needed > newsize && newsize > 0);

	if (bytes_needed <= newsize)
	{
		newbuf = realloc(conn->outBuffer, newsize);
		if (newbuf)
		{
			/* realloc succeeded */
			conn->outBuffer = newbuf;
			conn->outBufSize = newsize;
			return 0;
		}
	}

	/* realloc failed. Probably out of memory */
	printfPQExpBuffer(&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(int bytes_needed, PGconn *conn)
{
	int			newsize = conn->inBufSize;
	char	   *newbuf;

	if (bytes_needed <= 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 (bytes_needed > newsize && newsize > 0);

	if (bytes_needed <= 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 (bytes_needed > newsize && newsize > 0);

	if (bytes_needed <= newsize)
	{
		newbuf = realloc(conn->inBuffer, newsize);
		if (newbuf)
		{
			/* realloc succeeded */
			conn->inBuffer = newbuf;
			conn->inBufSize = newsize;
			return 0;
		}
	}

	/* realloc failed. Probably out of memory */
	printfPQExpBuffer(&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)
 *
 * force_len forces the message to have a length word; otherwise, we add
 * a length word if protocol 3.
 *
 * 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.  If we are sending a message without length word
 * (pre protocol 3.0 only), then outMsgStart is -1.  The state variable
 * conn->outMsgEnd is the end of the data collected so far.
 */
int
pqPutMsgStart(char msg_type, bool force_len, 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? */
	if (force_len || PG_PROTOCOL_MAJOR(conn->pversion) >= 3)
	{
		lenPos = endPos;
		/* allow room for message length */
		endPos += 4;
	}
	else
		lenPos = -1;

	/* 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 */

	if (conn->Pfdebug)
		fprintf(conn->Pfdebug, "To backend> Msg %c\n",
				msg_type ? msg_type : ' ');

	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)
{
	if (conn->Pfdebug)
		fprintf(conn->Pfdebug, "To backend> Msg complete, length %u\n",
				conn->outMsgEnd - conn->outCount);

	/* Fill in length word if needed */
	if (conn->outMsgStart >= 0)
	{
		uint32		msgLen = conn->outMsgEnd - conn->outMsgStart;

		msgLen = htonl(msgLen);
		memcpy(conn->outBuffer + conn->outMsgStart, &msgLen, 4);
	}

	/* 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;
	char		sebuf[256];

	if (conn->sock < 0)
	{
		printfPQExpBuffer(&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 + 8192, conn))
		{