informix_backend.ec

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/*
**  gsql -- A simplified, unified interface to various SQL packages.
**  Copyright (C) 1999 John Schulien
**
**  This program is free software; you can redistribute it and/or modify
**  it under the terms of the GNU General Public License as published by
**  the Free Software Foundation; either version 2 of the License, or
**  (at your option) any later version.
**
**  This program is distributed in the hope that it will be useful,
**  but WITHOUT ANY WARRANTY; without even the implied warranty of
**  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
**  GNU General Public License for more details.
**
**  You should have received a copy of the GNU General Public License
**  along with this program; if not, write to the Free Software
**  Foundation, Inc.,  59 Temple Place - Suite 330, Cambridge, MA 02139, USA.
**
**  informix_backend.c -- the Informix database backend
**
**  BIG FAT WARNING !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
**
**  This module is not built by default and can only be distributed in 
**  source because of 2 reasons:
**
**  1. the GPL license of both this module and gxsnmp itself does not permit
**     a link against the proprietary Informix libraries.
**
**  2. a binary module would contain parts of Informix code (at least one
**     object file is always linked in - even if dynamic linkage is used),
**     so there would most likely a runtime license from Informix be needed
**     to distribute the binary code.
**
** This module is just a demonstration of how esql could be used with gxsnmp.
**
*/

#define DEBUG_QUERIES

EXEC SQL include sqltypes.h;

/* Grrr! Informix defines v_int, v_long etc., so undo this to make glib happy */

#undef v_int
#undef v_long
#undef v_float

#include <glib.h>
#include "plugins.h"

static int cursor_cnt = 0;

/*******************************************************************************
**
**  Private structure to represent an open database
**
**  The first two elements of this structure are mandatory.
**
**  The Informix backend currently only supports one connection at a time.
**  The syntax would be even more ugly (and a second *_cnt hack would be
**  needed to keep track of the distinct connections).
**
**  Informix keeps track of the connections internally, so we can just
**  limit the structure to the mandatory parts.
*******************************************************************************/

typedef struct _G_sql_connection
{
  struct _G_sql_backend * backend;	/* Pointer to the backend block */
  gint			  errno;	/* Last error reported on connection */
}
G_sql_connection;

/*******************************************************************************
**
**  Private structure to represent an open query
**
**  The first two elements of this structure are mandatory
**
*******************************************************************************/

typedef struct _G_sql_query
{
  struct _G_sql_connection * connection;  /* Pointer to the connection block */
  gint			     errno;	  /* Last error reported on query */

  char                       curname[20]; /* Name of cursor     */
  char                       desname[20]; /* Name of descriptor */
  char                       qidname[20]; /* Name of query id   */
}
G_sql_query;

/*
**  Next comes the public portion of the database interface definition.
**  G_sql_backend and G_sql_query must be defined before including g_sql.h.
**  with G_SQL_BACKEND defined.
*/

#define G_SQL_BACKEND
#include "g_sql.h"

/*
**  Forward references
*/

static gboolean           sql_initialize  (G_sql_backend    * dbb);
static gboolean           sql_terminate   (G_sql_backend    * dbb);
static G_sql_connection * sql_connect     (G_sql            * db);
static gboolean           sql_disconnect  (G_sql_connection * dbc);
static GList            * sql_enum_dbs    (G_sql_connection * dbc);
static gboolean	          sql_select      (G_sql_connection * dbc,
				           gchar 	    * database);
static G_sql_query      * sql_query       (G_sql_connection * dbc,
				      	   gchar            * query,
					   gint		      querylen);
static gboolean           sql_free_query  (G_sql_query      * dbq);
static gboolean           sql_next_row    (G_sql_query      * dbq);
static gchar            * sql_field       (G_sql_query      * dbq, 
					   void		   ** accel,
					   gchar            * field, 
				           gint             * length);

/*
**  The database backend control block for the Informix engine
*/

static struct _G_sql_backend backend =
{
  "Informix",                   /* Name of the database engine */
  NULL,				/* Private data pointer */
  sql_initialize,		/* "Initialize" handler */
  sql_terminate,		/* "Terminate" handler */
  sql_connect,                  /* "Connect" handler */
  sql_disconnect,		/* "Disconnect" handler */
  sql_enum_dbs,      		/* "Enumerate databases" handler */
  sql_select,			/* "Select" handler */
  sql_query,			/* "Query" handler */
  sql_free_query,		/* "Free-Query" handler */ 
  sql_next_row,			/* "Next Row" handler */
  sql_field			/* "Get Field" handler */
};

void
print_error()
{
  g_warning("%d - %s", SQLCODE, SQLSTATE);
}

/*******************************************************************************
**
**  sql_initialize ()  -- Perform database engine-specific initialization
**
**  Informix has no initialization function, so just return TRUE.
**
*******************************************************************************/

gboolean
sql_initialize (G_sql_backend * dbb)
{
  g_print ("Informix database plugin installed.\n");
  return TRUE;
}

/*******************************************************************************
**
**  sql_terminate ()  -- Perform database engine-specific termination
**
**  Informix has no termination function, so just return TRUE.
**
*******************************************************************************/

gboolean
sql_terminate (G_sql_backend *dbb)
{
  g_print ("Informix database plugin terminated.\n");
  return TRUE;
}

/*******************************************************************************
**
**  sql_connect ()  --  Connect to a Informix database server
**
*******************************************************************************/

static G_sql_connection *
sql_connect (G_sql * db)
{
  G_sql_connection *dbc;
  int len;

EXEC SQL BEGIN DECLARE SECTION;
  char *user, *pwd;
  char host[256];
EXEC SQL END DECLARE SECTION;

  dbc = (G_sql_connection *) g_new0 (G_sql_connection, 1);
  if (!dbc)
      return NULL;

  dbc->backend = &backend;

  g_snprintf(host, sizeof(host), "@%s", db->host);

  if (db->user && db->password && strcmp(db->user, ""))
    {
      user = db->user;
      pwd  = db->password;

      EXEC SQL CONNECT TO :host USER :user USING :pwd;
    }
  else
    {
      EXEC SQL CONNECT TO :host;
    }

  if(!SQLCODE)
    {
      dbc->errno = 0;
      return dbc;
    }

  g_warning("CONNECT to database host '%s' failed.", db->host);
  print_error();
  g_free(dbc);
  return NULL;
}

/*******************************************************************************
**
**  sql_disconnect ()  --  Close a connection to a MySQL database server
**
**  Close the open connection, then free the control block.
**
**  Returns:  TRUE  -- if the operation was successful
**            FALSE -- if the operation failed
**
*******************************************************************************/

static gboolean
sql_disconnect (G_sql_connection * dbc)
{

  EXEC SQL DISCONNECT ALL;

  g_free (dbc);
  return TRUE;
}

/*******************************************************************************
**
**  sql_enum_dbs ()  --  Enumerate the available databases
**
**  Use the mysql_list_dbs() function to list the available databases on the
**  connection.
**
**  Returns:  GList of databases if the operation succeeded
**            NULL if the operation failed.       
**
*******************************************************************************/

static GList * 
sql_enum_dbs (G_sql_connection * dbc)
{
  EXEC SQL BEGIN DECLARE SECTION;
  char name[256];
  EXEC SQL END DECLARE SECTION;
  char *nname;
  GList *result = NULL;

  EXEC SQL DATABASE sysmaster;
  if (SQLCODE)
    {
      g_warning("Selecting sysmaster database failed.");
      print_error();
      return NULL;
    }
  EXEC SQL DECLARE data_cur CURSOR FOR 
    SELECT name into :name FROM informix.sysdatabases;

  if (SQLCODE)
    {
      g_warning("Query failed.");
      print_error();
      return NULL;
    }
  EXEC SQL OPEN data_cur;

  for(;;)
    {
      EXEC SQL FETCH data_cur;
      if (SQLCODE)
        break;
      nname = g_strdup(name);
      result = g_list_append(result, nname);
    }     

  EXEC SQL CLOSE data_cur;
  EXEC SQL FREE data_cur;
  return result;
}

/*******************************************************************************
**
**  db_select ()  --  Select a database on an open Informix server connection
**
**  Returns:  TRUE  -- if the select operation was successful
**            FALSE -- if the select operation failed
**
*******************************************************************************/

static gboolean
sql_select (G_sql_connection * dbc, gchar *database) 
{
  EXEC SQL BEGIN DECLARE SECTION;
  char *execstr;
  EXEC SQL END DECLARE SECTION;
  int len;
  
  len = strlen(database) + 15;
  execstr = g_malloc(len);
  g_snprintf(execstr, len, "DATABASE '%s';", database);

  EXEC SQL PREPARE data_id FROM :execstr;
  EXEC SQL EXECUTE data_id;
  EXEC SQL FREE data_id;

  g_free(execstr);

  if(!SQLCODE)
    {