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Commit b2aade0e authored by Bruce Momjian's avatar Bruce Momjian
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Improve libpgeasy API for multiple result sets, add example.

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doc/src/sgml/libpgeasy.sgml
+ 31
− 35
View file @ b2aade0e
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/Attic/libpgeasy.sgml,v 2.8 2002/01/07 02:29:12 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/Attic/libpgeasy.sgml,v 2.9 2002/03/04 18:50:20 momjian Exp $
-->
<chapter id="pgeasy">
......@@ -11,7 +11,7 @@ $Header: /cvsroot/pgsql/doc/src/sgml/Attic/libpgeasy.sgml,v 2.8 2002/01/07 02:29
<para>
Written by Bruce Momjian
(<email>pgman@candle.pha.pa.us</email>)
and last updated 2000-03-30
and last updated 2002-03-04
</para>
</note>
......@@ -19,13 +19,12 @@ $Header: /cvsroot/pgsql/doc/src/sgml/Attic/libpgeasy.sgml,v 2.8 2002/01/07 02:29
<application>pgeasy</application> allows you to cleanly interface
to the <application>libpq</application> library, more like a 4GL
SQL interface. Refer to <xref linkend="libpq"> for more
information about <application>libpq</application>
information about <application>libpq</application>.
</para>
<para>
It consists of set of simplified C functions that encapsulate the
functionality of <application>libpq</application>.
The functions are:
It consists of a set of simplified C functions that encapsulate the
functionality of <application>libpq</application>. The functions are:
<itemizedlist>
<listitem>
......@@ -88,53 +87,50 @@ void set_result(PGresult *newres);
</synopsis>
</listitem>
<listitem>
<synopsis>
void unset_result(PGresult *oldres);
</synopsis>
</listitem>
</itemizedlist>
</para>
<para>
Many functions return a structure or value, so you can do more work
Many functions return a structure or value, so you can work
with the result if required.
</para>
<para>
You basically connect to the database with <function>connectdb</function>,
issue your query with <function>doquery</function>,
fetch the results with <function>fetch</function>,
and finish with <function>disconnectdb</function>.
You basically connect to the database with
<function>connectdb</function>, issue your query with
<function>doquery</function>, fetch the results with
<function>fetch</function>, and finish with
<function>disconnectdb</function>.
</para>
<para>
For <literal>SELECT</literal> queries, <function>fetch</function>
allows you to pass pointers as parameters, and on return the variables
are filled with data from the binary cursor you opened. These binary
cursors cannot be used if you are running the
<application>pgeasy</application>
client on a system with a different architecture than the database
server. If you pass a NULL pointer parameter, the column is skipped.
<function>fetchwithnulls</function> allows you to retrieve the NULL
status of the field by passing an <literal>int*</literal>
after each result pointer, which returns true or false if the field is null.
You can always use <application>libpq</application> functions on the <structname>PGresult</structname> pointer returned
by <function>doquery</function>.
<function>reset_fetch</function> starts the fetch back at the beginning.
allows you to pass pointers as parameters, and on return the
variables are filled with data from the binary cursor you opened.
These binary cursors cannot be used if you are running the
<application>pgeasy</application> client on a system with a different
architecture than the database server. If you pass a NULL pointer
parameter, the column is skipped. <function>fetchwithnulls</function>
allows you to retrieve the NULL status of the field by passing an
<literal>int*</literal> after each result pointer, which returns true
or false to indicate if the field is null. You can always use
<application>libpq</application> functions on the
<structname>PGresult</structname> pointer returned by
<function>doquery</function>. <function>reset_fetch</function> starts
the fetch back at the beginning.
</para>
<para>
<function>get_result</function>,
<function>set_result</function>,
and
<function>unset_result</function>
allow you to handle multiple result sets at the same time.
<function>get_result</function> and <function>set_result</function>
allow you to handle multiple open result sets. Use
<function>get_result</function> to save a result into an application
variable. You can then later use <function>set_result</function> to
return to the previously save result.
</para>
<para>
There are several demonstration programs in the
source directory.
There are several demonstration programs in
<filename>pgsql/src/interfaces/libpgeasy/examples</>.
</para>
</chapter>
......
src/interfaces/libpgeasy/examples/Makefile
+ 3
− 9
View file @ b2aade0e
......@@ -4,23 +4,17 @@
# Makefile for pgeasy examples
#
# IDENTIFICATION
# $Header: /cvsroot/pgsql/src/interfaces/libpgeasy/examples/Attic/Makefile,v 1.2 2000/05/18 14:24:37 momjian Exp $
# $Header: /cvsroot/pgsql/src/interfaces/libpgeasy/examples/Attic/Makefile,v 1.3 2002/03/04 18:50:21 momjian Exp $
#
#-------------------------------------------------------------------------
CFLAGS=-I/usr/local/pgsql/include
TARGET = pginsert pgwordcount pgnulltest
TARGET = pginsert pgwordcount pgnulltest pgmultiresult
LDFLAGS = -L/usr/local/pgsql/lib -lpgeasy
all : $(TARGET)
pginsert:
gcc -o $@ $(CFLAGS) $@.c $(PGEASY) $(LDFLAGS)
pgwordcount:
gcc -o $@ $(CFLAGS) $@.c $(PGEASY) $(LDFLAGS)
pgnulltest:
%: %.c
gcc -o $@ $(CFLAGS) $@.c $(PGEASY) $(LDFLAGS)
clean:
......
src/interfaces/libpgeasy/libpgeasy.c
+ 120
− 76
View file @ b2aade0e
......@@ -6,6 +6,7 @@
#include <stdio.h>
#include <string.h>
#include <stdarg.h>
#include <stdlib.h>
#include "libpq-fe.h"
#include "halt.h"
......@@ -16,31 +17,33 @@
#endif
#ifndef TRUE
#define TRUE 1
#define TRUE 1
#endif
#ifndef FALSE
#define FALSE 0
#define FALSE 0
#endif
/* GLOBAL VARIABLES */
static PGconn *conn;
static PGresult *res = NULL;
static int tuple; /* stores fetch location */
static int tuple; /* stores fetch location */
#define ON_ERROR_STOP 0
#define ON_ERROR_CONTINUE 1
#define ON_ERROR_STOP 0
#define ON_ERROR_CONTINUE 1
static int on_error_state = ON_ERROR_STOP; /* halt on errors? */
static int on_error_state = ON_ERROR_STOP; /* halt on errors? */
static int user_has_res = FALSE;
static void add_res_tuple(void);
static void get_res_tuple(void);
static void del_res_tuple(void);
static int in_result_block = FALSE;
static int was_get_unset_result = FALSE;
/*
*
* connectdb - returns PGconn structure
*
*/
PGconn *
connectdb(char *options)
......@@ -53,17 +56,14 @@ connectdb(char *options)
return conn;
}
/*
*
* disconnectdb
*
*/
void
disconnectdb()
{
if (res != NULL &&
in_result_block == FALSE &&
was_get_unset_result == FALSE)
if (res != NULL && user_has_res == FALSE)
{
PQclear(res);
res = NULL;
......@@ -72,20 +72,17 @@ disconnectdb()
PQfinish(conn);
}
/*
*
* doquery - returns PGresult structure
*
*/
PGresult *
doquery(char *query)
{
if (res != NULL &&
in_result_block == FALSE &&
was_get_unset_result == FALSE)
if (res != NULL && user_has_res == FALSE)
PQclear(res);
was_get_unset_result = FALSE;
user_has_res = FALSE;
res = PQexec(conn, query);
if (on_error_state == ON_ERROR_STOP &&
......@@ -105,11 +102,10 @@ doquery(char *query)
return res;
}
/*
*
* fetch - returns tuple number (starts at 0), or the value END_OF_TUPLES
* NULL pointers are skipped
*
*/
int
fetch(void *param,...)
......@@ -142,8 +138,8 @@ fetch(void *param,...)
return tuple++;
}
/*
*
* fetchwithnulls - returns tuple number (starts at 0),
* or the value END_OF_TUPLES
* Returns TRUE or FALSE into null indicator variables
......@@ -185,10 +181,19 @@ fetchwithnulls(void *param,...)
return tuple++;
}
/*
* reset_fetch
*/
void
reset_fetch()
{
tuple = 0;
}
/*
*
* on_error_stop
*
*/
void
on_error_stop()
......@@ -196,10 +201,9 @@ on_error_stop()
on_error_state = ON_ERROR_STOP;
}
/*
*
* on_error_continue
*
*/
void
on_error_continue()
......@@ -209,92 +213,132 @@ on_error_continue()
/*
*
* get_result
*
*/
PGresult *
get_result()
{
char *cmdstatus = PQcmdStatus(res);
if (res == NULL)
halt("get_result called with no result pointer used\n");
was_get_unset_result = TRUE;
/* delete it if it is already there; we are about to re-add it */
del_res_tuple();
/* we have to store the fetch location somewhere */
/* XXX THIS IS A NO-NO */
cmdstatus[0] = NUL;
memcpy(&cmdstatus[1], &tuple, sizeof(tuple));
/* we have to store the fetch location */
add_res_tuple();
user_has_res = TRUE;
return res;
}
/*
*
* set_result
*
*/
void
set_result(PGresult *newres)
{
char *cmdstatus = PQcmdStatus(res);
if (newres == NULL)
halt("set_result called with null result pointer\n");
if (res != NULL && was_get_unset_result == FALSE)
if (res != NULL && user_has_res == FALSE)
{
if (in_result_block == FALSE)
PQclear(res);
else
{
/* XXX THIS IS A NO-NO */
cmdstatus[0] = NUL;
memcpy(&cmdstatus[1], &tuple, sizeof(tuple));
}
/*
* Basically, throw away res. We can't return to it because the
* user doesn't have the res pointer.
*/
del_res_tuple();
PQclear(res);
}
in_result_block = TRUE;
was_get_unset_result = FALSE;
cmdstatus = PQcmdStatus(newres);
memcpy(&tuple, &cmdstatus[1], sizeof(tuple));
user_has_res = FALSE;
res = newres;
get_res_tuple();
}
/*
*
* unset_result
*
* Routines to store res/tuple mapping
* This is used to keep track of fetch locations while using get/set on
* result sets.
* Auto-growing array is used, with empty slots marked by res == NULL
*/
void
unset_result(PGresult *oldres)
static struct res_tuple
{
char *cmdstatus = PQcmdStatus(oldres);
PGresult *res;
int tuple;
} *res_tuple = NULL;
if (oldres == NULL)
halt("unset_result called with null result pointer\n");
static int res_tuple_len = 0;
if (in_result_block == FALSE)
halt("Unset of result without being set.\n");
was_get_unset_result = TRUE;
/*
* add_res_tuple
*/
static void
add_res_tuple(void)
{
int i,
new_res_tuple_len = res_tuple_len ? res_tuple_len * 2 : 1;
for (i = 0; i < res_tuple_len; i++)
/* Put it in an empty slot */
if (res_tuple[i].res == NULL)
{
res_tuple[i].res = res;
res_tuple[i].tuple = tuple;
}
/* Need to grow array */
res_tuple = realloc(res_tuple, new_res_tuple_len * sizeof(struct res_tuple));
/* clear new elements */
for (i = res_tuple_len; i < new_res_tuple_len; i++)
{
res_tuple[i].res = NULL;
res_tuple[i].tuple = 0;
}
/* XXX THIS IS A NO-NO */
cmdstatus[0] = NUL;
memcpy(&cmdstatus[1], &tuple, sizeof(tuple));
in_result_block = FALSE;
/* recursion to add entry */
add_res_tuple();
}
/*
*
* reset_fetch
*
* get_res_tuple
*/
void
reset_fetch()
static void
get_res_tuple(void)
{
tuple = 0;
int i;
for (i = 0; i < res_tuple_len; i++)
if (res_tuple[i].res == res)
{
tuple = res_tuple[i].tuple;
return;
}
halt("get_res_tuple called with invalid result pointer\n");
}
/*
* del_res_tuple
*/
static void
del_res_tuple(void)
{
int i;
for (i = 0; i < res_tuple_len; i++)
if (res_tuple[i].res == res)
{
res_tuple[i].res = NULL;
return;
}
return;
}
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