
/*
* dlfcn-win32
* Copyright (c) 2007 Ramiro Polla
*
* dlfcn-win32 is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* dlfcn-win32 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with dlfcn-win32; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <windows.h>
#include <stdio.h>
#include "dlfcn.h"
/* Note:
* MSDN says these functions are not thread-safe. We make no efforts to have
* any kind of thread safety.
*/
typedef struct global_object {
	HMODULE hModule;
	struct global_object *previous;
	struct global_object *next;
} global_object;
static global_object first_object;
/* These functions implement a double linked list for the global objects. */
static global_object *global_search( HMODULE hModule )
{
	global_object *pobject;
	if( hModule == NULL )
		return NULL;
	for( pobject = &first_object; pobject ; pobject = pobject->next )
		if( pobject->hModule == hModule )
			return pobject;
		return NULL;
	}
	static void global_add( HMODULE hModule )
	{
		global_object *pobject;
		global_object *nobject;
		if( hModule == NULL )
			return;
		pobject = global_search( hModule );
/* Do not add object again if it's already on the list */
		if( pobject )
			return;
		for( pobject = &first_object; pobject->next ; pobject = pobject->next );
			nobject = malloc( sizeof(global_object) );
/* Should this be enough to fail global_add, and therefore also fail
* dlopen?
*/
if( !nobject )
	return;
pobject->next = nobject;
nobject->next = NULL;
nobject->previous = pobject;
nobject->hModule = hModule;
}
static void global_rem( HMODULE hModule )
{
	global_object *pobject;
	if( hModule == NULL )
		return;
	pobject = global_search( hModule );
	if( !pobject )
		return;
	if( pobject->next )
		pobject->next->previous = pobject->previous;
	if( pobject->previous )
		pobject->previous->next = pobject->next;
	free( pobject );
}
/* POSIX says dlerror( ) doesn't have to be thread-safe, so we use one
* static buffer.
* MSDN says the buffer cannot be larger than 64K bytes, so we set it to
* the limit.
*/
static char error_buffer[65535];
static char *current_error;
static int copy_string( char *dest, int dest_size, const char *src )
{
	int i = 0;
/* gcc should optimize this out */
	if( !src || !dest )
		return 0;
	for( i = 0 ; i < dest_size-1 ; i++ )
	{
		if( !src[i] )
			break;
		else
			dest[i] = src[i];
	}
	dest[i] = '\0';
	return i;
}
static void save_err_str( const char *str )
{
	DWORD dwMessageId;
	DWORD pos;
	dwMessageId = GetLastError( );
	if( dwMessageId == 0 )
		return;
/* Format error message to:
* "<argument to function that failed>": <Windows localized error message>
*/
pos = copy_string( error_buffer, sizeof(error_buffer), "\"" );
pos += copy_string( error_buffer+pos, sizeof(error_buffer)-pos, str );
pos += copy_string( error_buffer+pos, sizeof(error_buffer)-pos, "\": " );
pos += FormatMessage( FORMAT_MESSAGE_FROM_SYSTEM, NULL, dwMessageId,
	MAKELANGID( LANG_NEUTRAL, SUBLANG_DEFAULT ),
	error_buffer+pos, sizeof(error_buffer)-pos, NULL );
if( pos > 1 )
{
/* POSIX says the string must not have trailing <newline> */
	if( error_buffer[pos-2] == '\r' && error_buffer[pos-1] == '\n' )
		error_buffer[pos-2] = '\0';
}
current_error = error_buffer;
}
static void save_err_ptr_str( const void *ptr )
{
char ptr_buf[19]; /* 0x<pointer> up to 64 bits. */
	sprintf( ptr_buf, "0x%p", ptr );
	save_err_str( ptr_buf );
}
void *dlopen( const char *file, int mode )
{
	HMODULE hModule;
	UINT uMode;
	current_error = NULL;
/* Do not let Windows display the critical-error-handler message box */
	uMode = SetErrorMode( SEM_FAILCRITICALERRORS );
	if( file == 0 )
	{
/* POSIX says that if the value of file is 0, a handle on a global
* symbol object must be provided. That object must be able to access
* all symbols from the original program file, and any objects loaded
* with the RTLD_GLOBAL flag.
* The return value from GetModuleHandle( ) allows us to retrieve
* symbols only from the original program file. For objects loaded with
* the RTLD_GLOBAL flag, we create our own list later on.
*/
hModule = GetModuleHandle( NULL );
if( !hModule )
	save_err_ptr_str( file );
}
else
{
	char lpFileName[MAX_PATH];
	int i;
/* MSDN says backslashes *must* be used instead of forward slashes. */
	for( i = 0 ; i < sizeof(lpFileName)-1 ; i++ )
	{
		if( !file[i] )
			break;
		else if( file[i] == '/' )
			lpFileName[i] = '\\';
		else
			lpFileName[i] = file[i];
	}
	lpFileName[i] = '\0';
/* POSIX says the search path is implementation-defined.
* LOAD_WITH_ALTERED_SEARCH_PATH is used to make it behave more closely
* to UNIX's search paths (start with system folders instead of current
* folder).
*/
hModule = LoadLibraryEx( (LPSTR) lpFileName, NULL,
	LOAD_WITH_ALTERED_SEARCH_PATH );
/* If the object was loaded with RTLD_GLOBAL, add it to list of global
* objects, so that its symbols may be retrieved even if the handle for
* the original program file is passed. POSIX says that if the same
* file is specified in multiple invocations, and any of them are
* RTLD_GLOBAL, even if any further invocations use RTLD_LOCAL, the
* symbols will remain global.
*/
if( !hModule )
	save_err_str( lpFileName );
else if( (mode & RTLD_GLOBAL) )
	global_add( hModule );
}
/* Return to previous state of the error-mode bit flags. */
SetErrorMode( uMode );
return (void *) hModule;
}
int dlclose( void *handle )
{
	HMODULE hModule = (HMODULE) handle;
	BOOL ret;
	current_error = NULL;
	ret = FreeLibrary( hModule );
/* If the object was loaded with RTLD_GLOBAL, remove it from list of global
* objects.
*/
if( ret )
	global_rem( hModule );
else
	save_err_ptr_str( handle );
/* dlclose's return value in inverted in relation to FreeLibrary's. */
ret = !ret;
return (int) ret;
}
void *dlsym( void *handle, const char *name )
{
	FARPROC symbol;
	current_error = NULL;
	symbol = GetProcAddress( handle, name );
	if( symbol == NULL )
	{
		HMODULE hModule;
/* If the handle for the original program file is passed, also search
* in all globally loaded objects.
*/
hModule = GetModuleHandle( NULL );
if( hModule == handle )
{
	global_object *pobject;
	for( pobject = &first_object; pobject ; pobject = pobject->next )
	{
		if( pobject->hModule )
		{
			symbol = GetProcAddress( pobject->hModule, name );
			if( symbol != NULL )
				break;
		}
	}
}
}
if( symbol == NULL )
	save_err_str( name );
return (void*) symbol;
}
char *dlerror( void )
{
	char *error_pointer = current_error;
/* POSIX says that invoking dlerror( ) a second time, immediately following
* a prior invocation, shall result in NULL being returned.
*/
current_error = NULL;
return error_pointer;
}