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Improve libpgeasy API for multiple result sets, add example.
This commit is contained in:
Bruce Momjian
parent
e7db8fa80e
commit
b2aade0e4b
@ -1,5 +1,5 @@
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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/Attic/libpgeasy.sgml,v 2.8 2002/01/07 02:29:12 petere Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/Attic/libpgeasy.sgml,v 2.9 2002/03/04 18:50:20 momjian Exp $
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-->
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<chapter id="pgeasy">
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@ -11,7 +11,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/Attic/libpgeasy.sgml,v 2.8 2002/01/07 02:29
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<para>
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Written by Bruce Momjian
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(<email>pgman@candle.pha.pa.us</email>)
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and last updated 2000-03-30
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and last updated 2002-03-04
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</para>
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</note>
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@ -19,13 +19,12 @@ $Header: /cvsroot/pgsql/doc/src/sgml/Attic/libpgeasy.sgml,v 2.8 2002/01/07 02:29
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<application>pgeasy</application> allows you to cleanly interface
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to the <application>libpq</application> library, more like a 4GL
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SQL interface. Refer to <xref linkend="libpq"> for more
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information about <application>libpq</application>
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information about <application>libpq</application>.
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</para>
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<para>
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It consists of set of simplified C functions that encapsulate the
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functionality of <application>libpq</application>.
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The functions are:
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It consists of a set of simplified C functions that encapsulate the
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functionality of <application>libpq</application>. The functions are:
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<itemizedlist>
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<listitem>
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@ -88,53 +87,50 @@ void set_result(PGresult *newres);
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</synopsis>
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</listitem>
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<listitem>
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<synopsis>
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void unset_result(PGresult *oldres);
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</synopsis>
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</listitem>
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</itemizedlist>
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</para>
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<para>
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Many functions return a structure or value, so you can do more work
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Many functions return a structure or value, so you can work
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with the result if required.
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</para>
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<para>
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You basically connect to the database with <function>connectdb</function>,
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issue your query with <function>doquery</function>,
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fetch the results with <function>fetch</function>,
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and finish with <function>disconnectdb</function>.
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You basically connect to the database with
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<function>connectdb</function>, issue your query with
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<function>doquery</function>, fetch the results with
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<function>fetch</function>, and finish with
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<function>disconnectdb</function>.
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</para>
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<para>
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For <literal>SELECT</literal> queries, <function>fetch</function>
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allows you to pass pointers as parameters, and on return the variables
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are filled with data from the binary cursor you opened. These binary
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cursors cannot be used if you are running the
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<application>pgeasy</application>
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client on a system with a different architecture than the database
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server. If you pass a NULL pointer parameter, the column is skipped.
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<function>fetchwithnulls</function> allows you to retrieve the NULL
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status of the field by passing an <literal>int*</literal>
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after each result pointer, which returns true or false if the field is null.
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You can always use <application>libpq</application> functions on the <structname>PGresult</structname> pointer returned
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by <function>doquery</function>.
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<function>reset_fetch</function> starts the fetch back at the beginning.
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allows you to pass pointers as parameters, and on return the
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variables are filled with data from the binary cursor you opened.
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These binary cursors cannot be used if you are running the
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<application>pgeasy</application> client on a system with a different
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architecture than the database server. If you pass a NULL pointer
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parameter, the column is skipped. <function>fetchwithnulls</function>
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allows you to retrieve the NULL status of the field by passing an
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<literal>int*</literal> after each result pointer, which returns true
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or false to indicate if the field is null. You can always use
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<application>libpq</application> functions on the
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<structname>PGresult</structname> pointer returned by
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<function>doquery</function>. <function>reset_fetch</function> starts
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the fetch back at the beginning.
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</para>
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<para>
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<function>get_result</function>,
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<function>set_result</function>,
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and
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<function>unset_result</function>
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allow you to handle multiple result sets at the same time.
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<function>get_result</function> and <function>set_result</function>
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allow you to handle multiple open result sets. Use
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<function>get_result</function> to save a result into an application
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variable. You can then later use <function>set_result</function> to
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return to the previously save result.
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</para>
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<para>
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There are several demonstration programs in the
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source directory.
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There are several demonstration programs in
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<filename>pgsql/src/interfaces/libpgeasy/examples</>.
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</para>
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</chapter>
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@ -4,23 +4,17 @@
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# Makefile for pgeasy examples
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#
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# IDENTIFICATION
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# $Header: /cvsroot/pgsql/src/interfaces/libpgeasy/examples/Attic/Makefile,v 1.2 2000/05/18 14:24:37 momjian Exp $
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# $Header: /cvsroot/pgsql/src/interfaces/libpgeasy/examples/Attic/Makefile,v 1.3 2002/03/04 18:50:21 momjian Exp $
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#
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#-------------------------------------------------------------------------
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CFLAGS=-I/usr/local/pgsql/include
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TARGET = pginsert pgwordcount pgnulltest
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TARGET = pginsert pgwordcount pgnulltest pgmultiresult
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LDFLAGS = -L/usr/local/pgsql/lib -lpgeasy
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all : $(TARGET)
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pginsert:
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gcc -o $@ $(CFLAGS) $@.c $(PGEASY) $(LDFLAGS)
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pgwordcount:
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gcc -o $@ $(CFLAGS) $@.c $(PGEASY) $(LDFLAGS)
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pgnulltest:
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%: %.c
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gcc -o $@ $(CFLAGS) $@.c $(PGEASY) $(LDFLAGS)
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clean:
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@ -6,6 +6,7 @@
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#include <stdio.h>
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#include <string.h>
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#include <stdarg.h>
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#include <stdlib.h>
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#include "libpq-fe.h"
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#include "halt.h"
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@ -16,31 +17,33 @@
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#endif
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#ifndef TRUE
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#define TRUE 1
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#define TRUE 1
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#endif
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#ifndef FALSE
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#define FALSE 0
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#define FALSE 0
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#endif
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/* GLOBAL VARIABLES */
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static PGconn *conn;
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static PGresult *res = NULL;
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static int tuple; /* stores fetch location */
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static int tuple; /* stores fetch location */
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#define ON_ERROR_STOP 0
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#define ON_ERROR_CONTINUE 1
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#define ON_ERROR_STOP 0
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#define ON_ERROR_CONTINUE 1
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static int on_error_state = ON_ERROR_STOP; /* halt on errors? */
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static int on_error_state = ON_ERROR_STOP; /* halt on errors? */
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static int user_has_res = FALSE;
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static void add_res_tuple(void);
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static void get_res_tuple(void);
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static void del_res_tuple(void);
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static int in_result_block = FALSE;
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static int was_get_unset_result = FALSE;
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/*
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*
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* connectdb - returns PGconn structure
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*
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*/
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PGconn *
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connectdb(char *options)
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@ -53,17 +56,14 @@ connectdb(char *options)
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return conn;
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}
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/*
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*
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* disconnectdb
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*
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*/
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void
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disconnectdb()
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{
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if (res != NULL &&
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in_result_block == FALSE &&
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was_get_unset_result == FALSE)
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if (res != NULL && user_has_res == FALSE)
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{
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PQclear(res);
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res = NULL;
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@ -72,20 +72,17 @@ disconnectdb()
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PQfinish(conn);
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}
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/*
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*
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* doquery - returns PGresult structure
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*
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*/
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PGresult *
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doquery(char *query)
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{
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if (res != NULL &&
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in_result_block == FALSE &&
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was_get_unset_result == FALSE)
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if (res != NULL && user_has_res == FALSE)
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PQclear(res);
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was_get_unset_result = FALSE;
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user_has_res = FALSE;
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res = PQexec(conn, query);
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if (on_error_state == ON_ERROR_STOP &&
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@ -105,11 +102,10 @@ doquery(char *query)
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return res;
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}
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/*
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*
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* fetch - returns tuple number (starts at 0), or the value END_OF_TUPLES
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* NULL pointers are skipped
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*
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*/
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int
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fetch(void *param,...)
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@ -142,8 +138,8 @@ fetch(void *param,...)
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return tuple++;
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}
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/*
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*
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* fetchwithnulls - returns tuple number (starts at 0),
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* or the value END_OF_TUPLES
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* Returns TRUE or FALSE into null indicator variables
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@ -185,10 +181,19 @@ fetchwithnulls(void *param,...)
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return tuple++;
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}
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/*
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* reset_fetch
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*/
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void
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reset_fetch()
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{
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tuple = 0;
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}
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/*
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*
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* on_error_stop
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*
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*/
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void
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on_error_stop()
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@ -196,10 +201,9 @@ on_error_stop()
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on_error_state = ON_ERROR_STOP;
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}
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/*
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*
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* on_error_continue
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*
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*/
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void
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on_error_continue()
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@ -209,92 +213,132 @@ on_error_continue()
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/*
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*
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* get_result
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*
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*/
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PGresult *
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get_result()
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{
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char *cmdstatus = PQcmdStatus(res);
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if (res == NULL)
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halt("get_result called with no result pointer used\n");
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was_get_unset_result = TRUE;
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/* delete it if it is already there; we are about to re-add it */
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del_res_tuple();
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/* we have to store the fetch location somewhere */
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/* XXX THIS IS A NO-NO */
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cmdstatus[0] = NUL;
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memcpy(&cmdstatus[1], &tuple, sizeof(tuple));
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/* we have to store the fetch location */
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add_res_tuple();
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user_has_res = TRUE;
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return res;
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}
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/*
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*
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* set_result
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*
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*/
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void
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set_result(PGresult *newres)
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{
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char *cmdstatus = PQcmdStatus(res);
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if (newres == NULL)
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halt("set_result called with null result pointer\n");
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if (res != NULL && was_get_unset_result == FALSE)
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if (res != NULL && user_has_res == FALSE)
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{
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if (in_result_block == FALSE)
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PQclear(res);
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else
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{
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/* XXX THIS IS A NO-NO */
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cmdstatus[0] = NUL;
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memcpy(&cmdstatus[1], &tuple, sizeof(tuple));
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}
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/*
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* Basically, throw away res. We can't return to it because the
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* user doesn't have the res pointer.
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*/
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del_res_tuple();
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PQclear(res);
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}
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in_result_block = TRUE;
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was_get_unset_result = FALSE;
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cmdstatus = PQcmdStatus(newres);
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memcpy(&tuple, &cmdstatus[1], sizeof(tuple));
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user_has_res = FALSE;
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res = newres;
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get_res_tuple();
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}
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/*
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*
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* unset_result
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*
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* Routines to store res/tuple mapping
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* This is used to keep track of fetch locations while using get/set on
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* result sets.
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* Auto-growing array is used, with empty slots marked by res == NULL
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*/
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void
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unset_result(PGresult *oldres)
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static struct res_tuple
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{
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char *cmdstatus = PQcmdStatus(oldres);
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PGresult *res;
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int tuple;
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} *res_tuple = NULL;
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if (oldres == NULL)
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halt("unset_result called with null result pointer\n");
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static int res_tuple_len = 0;
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if (in_result_block == FALSE)
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halt("Unset of result without being set.\n");
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was_get_unset_result = TRUE;
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/* XXX THIS IS A NO-NO */
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cmdstatus[0] = NUL;
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memcpy(&cmdstatus[1], &tuple, sizeof(tuple));
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in_result_block = FALSE;
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}
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/*
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*
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* reset_fetch
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*
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* add_res_tuple
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*/
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void
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reset_fetch()
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static void
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add_res_tuple(void)
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{
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tuple = 0;
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int i,
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new_res_tuple_len = res_tuple_len ? res_tuple_len * 2 : 1;
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for (i = 0; i < res_tuple_len; i++)
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/* Put it in an empty slot */
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if (res_tuple[i].res == NULL)
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{
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res_tuple[i].res = res;
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res_tuple[i].tuple = tuple;
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}
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/* Need to grow array */
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res_tuple = realloc(res_tuple, new_res_tuple_len * sizeof(struct res_tuple));
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/* clear new elements */
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for (i = res_tuple_len; i < new_res_tuple_len; i++)
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{
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res_tuple[i].res = NULL;
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res_tuple[i].tuple = 0;
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}
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/* recursion to add entry */
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add_res_tuple();
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}
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/*
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* get_res_tuple
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*/
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static void
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get_res_tuple(void)
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{
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int i;
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for (i = 0; i < res_tuple_len; i++)
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if (res_tuple[i].res == res)
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{
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tuple = res_tuple[i].tuple;
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return;
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}
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halt("get_res_tuple called with invalid result pointer\n");
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}
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/*
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* del_res_tuple
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*/
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static void
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del_res_tuple(void)
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{
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int i;
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for (i = 0; i < res_tuple_len; i++)
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if (res_tuple[i].res == res)
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{
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res_tuple[i].res = NULL;
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return;
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}
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return;
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}
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