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[wxWidgets.git] / src / iodbc / dlf.c

/** dynamic library loader (mapping to svr4)
 
    Copyright (C) 1995 by Ke Jin <kejin@empress.com> 

    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.
**/

#include  "wx/setup.h"

#include	<../iodbc/dlf.h>
#include	<errno.h>

#ifdef	DLDAPI_DEFINED	
# undef DLDAPI_DEFINED
#endif

#ifdef DLDAPI_SVR4_DLFCN
# define DLDAPI_DEFINED
static	char sccsid[] = "@(#)dynamic load interface -- SVR4 dlfcn";
#endif

/********************************* 
 *
 *	HP/UX 
 *
 *********************************/
#ifdef	DLDAPI_HP_SHL
# define	DLDAPI_DEFINED
# include	<dl.h>

static	char sccsid[] = "@(#)dynamic load interface -- HP/UX dl(shl)";

void*	dlopen(char* path, int mode)
{
	return (void*)shl_load((char*)(path), BIND_DEFERRED, 0L);
}

void*	dlsym(void* hdll, char* sym)
{
	void*	symaddr = 0;
	int	ret;

	if( ! hdll )
		hdll = (void*)PROG_HANDLE;

	/* Remember, a driver may export calls as function pointers 
	 * (i.e. with type TYPE_DATA) rather than as functions 
	 * (i.e. with type TYPE_PROCEDURE). Thus, to be safe, we 
	 * uses TYPE_UNDEFINED to cover all of them. 
	 */
	ret = shl_findsym((shl_t*)&hdll, sym, TYPE_UNDEFINED, &symaddr);

	if( ret == -1 )
		return 0;

	return symaddr;
}

char*	dlerror()
{
	extern char*	strerror();

	return strerror(errno);
}

int	dlclose(void* hdll)
{
	return shl_unload((shl_t)hdll);
}

#endif	/* end of HP/UX Seection */

/*********************************
 *
 *	IBM AIX
 *
 *********************************/
#ifdef	DLDAPI_AIX_LOAD
# define	DLDAPI_DEFINED
# include	<sys/types.h>
# include	<sys/ldr.h>
# include	<sys/stat.h>
# include	<nlist.h>

/*
 *   Following id sting is a copyright mark. Removing(i.e. use the 
 *   source code in this .c file without include it or make it not
 *   appear in the final object file of AIX platform) or modifing 
 *   it without permission from original author(kejin@empress.com) 
 *   are copyright violation.
 */
static  char sccsid[]
	= "@(#)dynamic load interface, Copyright(c) 1995 by Ke Jin";

# ifndef	HTAB_SIZE
#  define	HTAB_SIZE	256
# endif

# define	FACTOR		0.618039887 /* i.e. (sqrt(5) - 1)/2 */

# ifndef	ENTRY_SYM
#  define	ENTRY_SYM	".__start" /* default entry point for aix */
# endif

typedef struct slot_s
{
	char*		sym;
	long		fdesc[3]; /* 12 bytes function descriptor */
	struct slot_s* 	next;
} slot_t;

/* Note: on AIX, a function pointer actually points to a
 * function descriptor, a 12 bytes data. The first 4 bytes
 * is the virtual address of the function. The next 4 bytes 
 * is the virtual address of TOC (Table of Contents) of the
 * object module the function belong to. The last 4 bytes 
 * are always 0 for C and Fortran functions. Every object 
 * module has an entry point (which can be specified at link
 * time by -e ld option). iODBC driver manager requires ODBC
 * driver shared library always use the default entry point
 * (so you shouldn't use -e ld option when creating a driver
 * share library). load() returns the function descriptor of 
 * a module's entry point. From which we can calculate function
 * descriptors of other functions in the same module by using
 * the fact that the load() doesn't change the relative 
 * offset of functions to their module entry point(i.e the 
 * offset in memory loaded by load() will be as same as in 
 * the module library file). 
 */

typedef	slot_t*		hent_t;
typedef struct nlist	nlist_t;
typedef struct stat	stat_t;	

typedef struct obj 
{
	int	dev;	/* device id */
	int	ino;	/* inode number */
	char*	path;	/* file name */
	int	(*pentry)();	/* entry point of this share library */
	int	refn;	/* number of reference */
	hent_t	htab[HTAB_SIZE];
	struct obj*
		next;
} obj_t;

static char*	errmsg = 0;

static void init_htab(hent_t* ht)
/* initate a hashing table */
{
	int	i;

	for(i=0; i<HTAB_SIZE; i++)
		ht[i] = (slot_t*)0;

	return;
}

static void clean_htab(hent_t* ht)
/* free all slots */
{
	int	i;
	slot_t*	ent;
	slot_t* tent;

	for(i = 0; i< HTAB_SIZE; i++)
	{
		for( ent = ht[i]; ent; )
		{
			tent = ent->next;
			
			free(ent->sym);
			free(ent);

			ent = tent;
		}

		ht[i] = 0;
	}

	return;
}

static int	hash(char* sym )
{
	int	a, key;
	double	f;

	if( !sym || !*sym )
		return 0;

	for(key=*sym;*sym;sym++)
        {
		key += *sym;
                a = key;

		key = (int)( (a<<8) + (key>>8) );
		key = (key>0)? key:-key;
        }

	f = key*FACTOR;
	a = (int)f;

	return (int)((HTAB_SIZE - 1)*( f - a ));
}

static hent_t	search(hent_t* htab, char* sym)
/* search hashing table to find a matched slot */
{
	int	key;
	slot_t*	ent;

	key = hash(sym);

	for(ent = htab[key]; ent; ent = ent->next )
	{
		if(!strcmp(ent->sym, sym))
			return ent;
	}

	return 0;	/* no match */
}

static void	insert(hent_t* htab, slot_t* ent)
/* insert a new slot to hashing table */
{
	int	key;

	key = hash(ent->sym);

	ent->next = htab[key];
	htab[key] = ent;

	return;
}

static slot_t*	slot_alloc(char* sym)
/* allocate a new slot with symbol */
{
	slot_t*	ent;

	ent = (slot_t*)malloc(sizeof(slot_t));

	ent->sym = (char*)malloc(strlen(sym)+1);

	if( ! ent->sym )
	{
		free(ent);
		return 0;
	}

	strcpy( ent->sym, sym );

	return ent;
}

static obj_t* obj_list = 0;

void*	dlopen(char* file, int mode )
{
	stat_t	st;
	obj_t*	pobj;
	char	buf[1024];
	
	if( ! file || ! *file )
	{
		errno = EINVAL;
		return 0;
	}

	errno = 0;
	errmsg = 0;

#if 0
	if( file[0] != '/' && file[0] != '.' )
	{
		for(;;)
		{
			sprintf(buf, "/lib/%s", file);

			if( stat( buf, &st ) )
			{
				file = buf;
				break;
			}
			
			sprintf(buf, "/usr/lib/%s", file);

			if( stat( buf, &st ) )
			{
				file = buf;
				break; 
			}

			if( stat( file, &st ) )
				break;

			return 0;
		}
	}
	else 
#endif
	if( stat( file, &st ) )
		return 0;

	for( pobj = obj_list; pobj; pobj = pobj->next )
	/* find a match object */
	{
		if( pobj->ino == st.st_ino 
		 && pobj->dev == st.st_dev )
		{
			/* found a match. increase its
			 * reference count and return 
			 * its address */
			pobj->refn ++;
			return pobj;
		}
	}

	pobj = (obj_t*)malloc( sizeof(obj_t) );

	if( ! pobj )
		return 0;

	pobj->path = (char*)malloc( strlen(file) + 1);

	if( ! pobj->path )
	{
		free( pobj );
		return 0;
	}

	strcpy( pobj->path, file );

	pobj->dev = st.st_dev;
	pobj->ino = st.st_ino;
	pobj->refn = 1;

	pobj->pentry = (int(*)())load(file, 0, 0);

	if( ! pobj->pentry )
	{
		free( pobj->path );
		free( pobj );
		return 0;
	}

	init_htab(pobj->htab);

	pobj->next = obj_list;
	obj_list = pobj;

	return pobj;
}

int	dlclose(void* hobj)
{
	obj_t*	pobj = (obj_t*)hobj;
	obj_t*	tpobj;
	int	match = 0;

	if( ! hobj )
	{
		errno = EINVAL;
		return -1;
	}

	errno = 0;
	errmsg = 0;

	if( pobj == obj_list )
	{
		pobj->refn --;

		if( pobj->refn )
			return 0;

		match = 1;
		obj_list = pobj->next;
	}

	for( tpobj = obj_list; !match && tpobj; tpobj = tpobj->next )
	{
		if( tpobj->next == pobj )
		{
			pobj->refn --;

			if( pobj->refn )
				return 0;

			match = 1;
			tpobj->next = pobj->next;
		}
	}

	if(match)
	{
		unload((void*)(pobj->pentry));
		clean_htab(pobj->htab);
		free(pobj->path);
		free(pobj);
	}

	return 0;
}

char*	dlerror()
{
	extern char*	sys_errlist[];

	if( ! errmsg || ! errmsg[0] )
	{
		if( errno >= 0 )
			return sys_errlist[errno];
		
		return "";
	}

	return errmsg;
}

void*	dlsym(void* hdl, char* sym)
{
	nlist_t	nl[3];
	obj_t*	pobj = (obj_t*)hdl;
	slot_t*	ent;
	int	(*fp)();
	long	lbuf[3];

	if( !hdl || !(pobj->htab) || !sym || ! *sym )
	{
		errno = EINVAL;
		return 0;
	}

	errno = 0;
	errmsg = 0;

	ent = search( pobj->htab, sym );

	if( ent )
		return ent->fdesc;

#define	n_name	_n._n_name

	nl[0].n_name = ENTRY_SYM;
	nl[1].n_name = sym;
	nl[2].n_name = 0;

	/* There is a potential problem here. If application
	 * did not pass a full path name, and changed the
	 * working directory after the load(), then nlist()
	 * will be unable to open the original shared library
	 * file to resolve the symbols. there are 3 ways to working 
	 * round this: 1. convert to full pathname in driver
	 * manager. 2. applications always pass driver's full 
	 * path name. 3. if driver itself don't support 
	 * SQLGetFunctions(), call it with SQL_ALL_FUNCTIONS
	 * as flag immidately after SQLConnect(), SQLDriverConnect()
	 * and SQLBrowseConnect() to force the driver manager
	 * resolving all will be used symbols. 
	 */
	if( nlist( pobj->path, nl) == -1 )
		return 0;

	if( ! nl[0].n_type && ! nl[0].n_value )
	{
		errmsg = "can't locate module entry symbol";
		return 0;
	}

	/* Note: On AIX 3.x if the object library is not
	 * built with -g compiling option, .n_type field
	 * is always 0. While on 4.x it will be 32. 
	 * On AIX 4.x, if the symbol is a entry point,
	 * n_value will be 0. However, one thing is for sure 
	 * that if a symbol is not existance in the file,
	 * both .n_type and .n_value would be 0.
	 */

	if( ! nl[1].n_type && ! nl[1].n_value )
	{
		errmsg = "symbol not existance in this module";
		return 0;
	}

	ent = slot_alloc(sym);

	if( ! ent )
		return 0;

	/* catch it with a slot in the hashing table */
	insert(pobj->htab, ent);

	memcpy(ent->fdesc, pobj->pentry, sizeof(ent->fdesc));

	/* now ent->fdesc[0] is the virtual address of entry point
	 * and ent->fdesc[1] is the TOC of the module
	 */

	/* let's calculate the virtual address of the symbol 
	 * by adding a relative offset getting from the module 
	 * file symbol table, i.e
	 *
	 *  functin virtual address = entry point virtual address +
	 *     + ( function offset in file - entry point offset in file )
	 */

	(ent->fdesc)[0] = (ent->fdesc)[0] + 	
		( nl[1].n_value - nl[0].n_value ); 

	/* return the function descriptor */
	return ent->fdesc;
}

#endif	/* end of IBM AIX Section */


/********************************* 
 *
 *	Windows 3.x, 95, NT
 *
 *********************************/
#ifdef	DLDAPI_WINDOWS
# define	DLDAPI_DEFINED
# include	<windows.h>

void FAR*	dlopen(char FAR* dll, int mode)
{
	HINSTANCE	hint;

	if( dll == NULL )
	{
		return GetWindowWord( NULL, GWW_HINSTANCE );
	}

	hint = LoadLibrary(dll);

	if( hint < HINSTANCE_ERROR )
	{
		return NULL;
	}

	return (void FAR*)hint;
}

void FAR*	dlsym( void FAR* hdll, char FAR* sym )
{
	return (void FAR*)GetProcAddress(hdll, sym);
}

char FAR*	dlerror()
{
	return 0L; /* unimplemented yet */
}

int	dlclose(void FAR* hdll)
{
	FreeLibrary((HINSTANCE)hdll);
}

#endif	/* end of Windows family */

/***********************************
 *
 * 	other platforms
 *
 ***********************************/
#ifdef DLDAPI_OS2
# define	DLDAPI_DEFINED
/*
 *	DosLoadModule(), DosQueryProcAddress(), DosFreeModule(), ...
 */
#endif

#ifdef	DLDAPI_MAC
# define	DLDAPI_DEFINED
#endif

#ifdef DLDAPI_NEXT
# define	DLDAPI_DEFINED
#endif

#ifndef DLDAPI_DEFINED
# error	"dynamic load editor undefined"
#endif