/**

 * vim: set ts=4 :

 * =============================================================================

 * SourceMod SDKTools Extension

 * Copyright (C) 2004-2008 AlliedModders LLC.  All rights reserved.

 * =============================================================================

 *

 * This program is free software; you can redistribute it and/or modify it under

 * the terms of the GNU General Public License, version 3.0, as published by the

 * Free Software Foundation.

 * 

 * 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, see <http://www.gnu.org/licenses/>.

 *

 * As a special exception, AlliedModders LLC gives you permission to link the

 * code of this program (as well as its derivative works) to "Half-Life 2," the

 * "Source Engine," the "SourcePawn JIT," and any Game MODs that run on software

 * by the Valve Corporation.  You must obey the GNU General Public License in

 * all respects for all other code used.  Additionally, AlliedModders LLC grants

 * this exception to all derivative works.  AlliedModders LLC defines further

 * exceptions, found in LICENSE.txt (as of this writing, version JULY-31-2007),

 * or <http://www.sourcemod.net/license.php>.

 *

 * Version: $Id$

 */

#ifndef _INCLUDE_SOURCEMOD_DETOURS_H_

#define _INCLUDE_SOURCEMOD_DETOURS_H_

#if defined PLATFORM_POSIX

#include <sys/mman.h>

#define	PAGE_SIZE	4096

#define ALIGN(ar) ((long)ar & ~(PAGE_SIZE-1))

#define	PAGE_EXECUTE_READWRITE	PROT_READ|PROT_WRITE|PROT_EXEC

#endif

struct patch_t

{

	patch_t()

	{

		patch[0] = 0;

		bytes = 0;

	}

	unsigned char patch[20];

	size_t bytes;

};

inline void ProtectMemory(void *addr, int length, int prot)

{

#if defined PLATFORM_LINUX

	void *addr2 = (void *)ALIGN(addr);

	mprotect(addr2, sysconf(_SC_PAGESIZE), prot);

#elif defined PLATFORM_WINDOWS

	DWORD old_prot;

	VirtualProtect(addr, length, prot, &old_prot);

#endif

}

inline void SetMemPatchable(void *address, size_t size)

{

	ProtectMemory(address, (int)size, PAGE_EXECUTE_READWRITE);

}

inline void DoGatePatch(unsigned char *target, void *callback)

{

	SetMemPatchable(target, 20);

	target[0] = 0xFF;	/* JMP */

	target[1] = 0x25;	/* MEM32 */

	*(void **)(&target[2]) = callback;

}

inline void ApplyPatch(void *address, int offset, const patch_t *patch, patch_t *restore)

{

	ProtectMemory(address, 20, PAGE_EXECUTE_READWRITE);

	unsigned char *addr = (unsigned char *)address + offset;

	if (restore)

	{

		for (size_t i=0; i<patch->bytes; i++)

		{

			restore->patch[i] = addr[i];

		}

		restore->bytes = patch->bytes;

	}

	for (size_t i=0; i<patch->bytes; i++)

	{

		addr[i] = patch->patch[i];

	}

}

#endif //_INCLUDE_SOURCEMOD_DETOURS_H_