testlibpq3.c File Reference

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <sys/types.h>
#include "libpq-fe.h"
#include <netinet/in.h>
#include <arpa/inet.h>

Include dependency graph for testlibpq3.c:

Go to the source code of this file.

Functions
static void	exit_nicely (PGconn *conn)
static void	show_binary_results (PGresult *res)
int	main (int argc, char **argv)

Function Documentation

exit_nicely()

static void exit_nicely ( PGconn *  conn )

static

Definition at line 48 of file testlibpq3.c.

{
    PQfinish(conn);
    exit(1);
}

References conn, and PQfinish().

Referenced by main().

main()

int main	(	int	argc,
		char **	argv
	)

Definition at line 115 of file testlibpq3.c.

{
    const char *conninfo;
    PGconn     *conn;
    PGresult   *res;
    const char *paramValues[1];
    int         paramLengths[1];
    int         paramFormats[1];
    uint32_t    binaryIntVal;
 
    /*
     * If the user supplies a parameter on the command line, use it as the
     * conninfo string; otherwise default to setting dbname=postgres and using
     * environment variables or defaults for all other connection parameters.
     */
    if (argc > 1)
        conninfo = argv[1];
    else
        conninfo = "dbname = postgres";
 
    /* Make a connection to the database */
    conn = PQconnectdb(conninfo);
 
    /* Check to see that the backend connection was successfully made */
    if (PQstatus(conn) != CONNECTION_OK)
    {
        fprintf(stderr, "%s", PQerrorMessage(conn));
        exit_nicely(conn);
    }
 
    /* Set always-secure search path, so malicious users can't take control. */
    res = PQexec(conn, "SET search_path = testlibpq3");
    if (PQresultStatus(res) != PGRES_COMMAND_OK)
    {
        fprintf(stderr, "SET failed: %s", PQerrorMessage(conn));
        PQclear(res);
        exit_nicely(conn);
    }
    PQclear(res);
 
    /*
     * The point of this program is to illustrate use of PQexecParams() with
     * out-of-line parameters, as well as binary transmission of data.
     *
     * This first example transmits the parameters as text, but receives the
     * results in binary format.  By using out-of-line parameters we can avoid
     * a lot of tedious mucking about with quoting and escaping, even though
     * the data is text.  Notice how we don't have to do anything special with
     * the quote mark in the parameter value.
     */
 
    /* Here is our out-of-line parameter value */
    paramValues[0] = "joe's place";
 
    res = PQexecParams(conn,
                       "SELECT * FROM test1 WHERE t = $1",
                       1,       /* one param */
                       NULL,    /* let the backend deduce param type */
                       paramValues,
                       NULL,    /* don't need param lengths since text */
                       NULL,    /* default to all text params */
                       1);      /* ask for binary results */
 
    if (PQresultStatus(res) != PGRES_TUPLES_OK)
    {
        fprintf(stderr, "SELECT failed: %s", PQerrorMessage(conn));
        PQclear(res);
        exit_nicely(conn);
    }
 
    show_binary_results(res);
 
    PQclear(res);
 
    /*
     * In this second example we transmit an integer parameter in binary form,
     * and again retrieve the results in binary form.
     *
     * Although we tell PQexecParams we are letting the backend deduce
     * parameter type, we really force the decision by casting the parameter
     * symbol in the query text.  This is a good safety measure when sending
     * binary parameters.
     */
 
    /* Convert integer value "2" to network byte order */
    binaryIntVal = htonl((uint32_t) 2);
 
    /* Set up parameter arrays for PQexecParams */
    paramValues[0] = (char *) &binaryIntVal;
    paramLengths[0] = sizeof(binaryIntVal);
    paramFormats[0] = 1;        /* binary */
 
    res = PQexecParams(conn,
                       "SELECT * FROM test1 WHERE i = $1::int4",
                       1,       /* one param */
                       NULL,    /* let the backend deduce param type */
                       paramValues,
                       paramLengths,
                       paramFormats,
                       1);      /* ask for binary results */
 
    if (PQresultStatus(res) != PGRES_TUPLES_OK)
    {
        fprintf(stderr, "SELECT failed: %s", PQerrorMessage(conn));
        PQclear(res);
        exit_nicely(conn);
    }
 
    show_binary_results(res);
 
    PQclear(res);
 
    /* close the connection to the database and cleanup */
    PQfinish(conn);
 
    return 0;
}

References conn, CONNECTION_OK, exit_nicely(), fprintf, PGRES_COMMAND_OK, PGRES_TUPLES_OK, PQclear, PQconnectdb(), PQerrorMessage(), PQexec(), PQexecParams(), PQfinish(), PQresultStatus, PQstatus(), and show_binary_results().

show_binary_results()

static void show_binary_results ( PGresult *  res )

static

Definition at line 60 of file testlibpq3.c.

{
    int         i,
                j;
    int         i_fnum,
                t_fnum,
                b_fnum;
 
    /* Use PQfnumber to avoid assumptions about field order in result */
    i_fnum = PQfnumber(res, "i");
    t_fnum = PQfnumber(res, "t");
    b_fnum = PQfnumber(res, "b");
 
    for (i = 0; i < PQntuples(res); i++)
    {
        char       *iptr;
        char       *tptr;
        char       *bptr;
        int         blen;
        int         ival;
 
        /* Get the field values (we ignore possibility they are null!) */
        iptr = PQgetvalue(res, i, i_fnum);
        tptr = PQgetvalue(res, i, t_fnum);
        bptr = PQgetvalue(res, i, b_fnum);
 
        /*
         * The binary representation of INT4 is in network byte order, which
         * we'd better coerce to the local byte order.
         */
        ival = ntohl(*((uint32_t *) iptr));
 
        /*
         * The binary representation of TEXT is, well, text, and since libpq
         * was nice enough to append a zero byte to it, it'll work just fine
         * as a C string.
         *
         * The binary representation of BYTEA is a bunch of bytes, which could
         * include embedded nulls so we have to pay attention to field length.
         */
        blen = PQgetlength(res, i, b_fnum);
 
        printf("tuple %d: got\n", i);
        printf(" i = (%d bytes) %d\n",
               PQgetlength(res, i, i_fnum), ival);
        printf(" t = (%d bytes) '%s'\n",
               PQgetlength(res, i, t_fnum), tptr);
        printf(" b = (%d bytes) ", blen);
        for (j = 0; j < blen; j++)
            printf("\\%03o", bptr[j]);
        printf("\n\n");
    }
}

References i, j, PQfnumber(), PQgetlength, PQgetvalue, PQntuples, and printf.

Referenced by main().