/*
 *  Copyright (C) 2002-2019  The DOSBox Team
 *
 *  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.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */


#include <stdlib.h>
#include <string.h>
#include <stddef.h>
#include "dosbox.h"
#include "callback.h"
#include "mem.h"
#include "regs.h"
#include "dos_inc.h"
#include "setup.h"
#include "inout.h"
#include "xms.h"
#include "bios.h"

#define XMS_HANDLES							50		/* 50 XMS Memory Blocks */ 
#define XMS_VERSION    						0x0300	/* version 3.00 */
#define XMS_DRIVER_VERSION					0x0301	/* my driver version 3.01 */

#define	XMS_GET_VERSION						0x00
#define	XMS_ALLOCATE_HIGH_MEMORY			0x01
#define	XMS_FREE_HIGH_MEMORY				0x02
#define	XMS_GLOBAL_ENABLE_A20				0x03
#define	XMS_GLOBAL_DISABLE_A20				0x04
#define	XMS_LOCAL_ENABLE_A20				0x05
#define	XMS_LOCAL_DISABLE_A20				0x06
#define	XMS_QUERY_A20						0x07
#define	XMS_QUERY_FREE_EXTENDED_MEMORY		0x08
#define	XMS_ALLOCATE_EXTENDED_MEMORY		0x09
#define	XMS_FREE_EXTENDED_MEMORY			0x0a
#define	XMS_MOVE_EXTENDED_MEMORY_BLOCK		0x0b
#define	XMS_LOCK_EXTENDED_MEMORY_BLOCK		0x0c
#define	XMS_UNLOCK_EXTENDED_MEMORY_BLOCK	0x0d
#define	XMS_GET_EMB_HANDLE_INFORMATION		0x0e
#define	XMS_RESIZE_EXTENDED_MEMORY_BLOCK	0x0f
#define	XMS_ALLOCATE_UMB					0x10
#define	XMS_DEALLOCATE_UMB					0x11
#define XMS_QUERY_ANY_FREE_MEMORY			0x88
#define XMS_ALLOCATE_ANY_MEMORY				0x89
#define	XMS_GET_EMB_HANDLE_INFORMATION_EXT	0x8e
#define XMS_RESIZE_ANY_EXTENDED_MEMORY_BLOCK 0x8f

#define	XMS_FUNCTION_NOT_IMPLEMENTED		0x80
#define	HIGH_MEMORY_NOT_EXIST				0x90
#define	HIGH_MEMORY_IN_USE					0x91
#define	HIGH_MEMORY_NOT_ALLOCATED			0x93
#define XMS_OUT_OF_SPACE					0xa0
#define XMS_OUT_OF_HANDLES					0xa1
#define XMS_INVALID_HANDLE					0xa2
#define XMS_INVALID_SOURCE_HANDLE			0xa3
#define XMS_INVALID_SOURCE_OFFSET			0xa4
#define XMS_INVALID_DEST_HANDLE				0xa5
#define XMS_INVALID_DEST_OFFSET				0xa6
#define XMS_INVALID_LENGTH					0xa7
#define XMS_BLOCK_NOT_LOCKED				0xaa
#define XMS_BLOCK_LOCKED					0xab
#define	UMB_ONLY_SMALLER_BLOCK				0xb0
#define	UMB_NO_BLOCKS_AVAILABLE				0xb1

struct XMS_Block {
	Bitu	size;
	MemHandle mem;
	Bit8u	locked;
	bool	free;
};

#ifdef _MSC_VER
#pragma pack (1)
#endif
struct XMS_MemMove{
	Bit32u length;
	Bit16u src_handle;
	union {
		RealPt realpt;
		Bit32u offset;
	} src;
	Bit16u dest_handle;
	union {
		RealPt realpt;
		Bit32u offset;
	} dest;

} GCC_ATTRIBUTE(packed);
#ifdef _MSC_VER
#pragma pack ()
#endif


Bitu XMS_EnableA20(bool enable) {
	Bit8u val = IO_Read	(0x92);
	if (enable) IO_Write(0x92,val | 2);
	else		IO_Write(0x92,val & ~2);
	return 0;
}

Bitu XMS_GetEnabledA20(void) {
	return (IO_Read(0x92)&2)>0;
}

static RealPt xms_callback;
static bool umb_available;

static XMS_Block xms_handles[XMS_HANDLES];

static INLINE bool InvalidHandle(Bitu handle) {
	return (!handle || (handle>=XMS_HANDLES) || xms_handles[handle].free);
}

Bitu XMS_QueryFreeMemory(Bit16u& largestFree, Bit16u& totalFree) {
	/* Scan the tree for free memory and find largest free block */
	totalFree=(Bit16u)(MEM_FreeTotal()*4);
	largestFree=(Bit16u)(MEM_FreeLargest()*4);
	if (!totalFree) return XMS_OUT_OF_SPACE;
	return 0;
}

Bitu XMS_AllocateMemory(Bitu size, Bit16u& handle) {	// size = kb
	/* Find free handle */
	Bit16u index=1;
	while (!xms_handles[index].free) {
		if (++index>=XMS_HANDLES) return XMS_OUT_OF_HANDLES;
	}
	MemHandle mem;
	if (size!=0) {
		Bitu pages=(size/4) + ((size & 3) ? 1 : 0);
		mem=MEM_AllocatePages(pages,true);
		if (!mem) return XMS_OUT_OF_SPACE;
	} else {
		mem=MEM_GetNextFreePage();
		if (mem==0) LOG(LOG_MISC,LOG_ERROR)("XMS:Allocate zero pages with no memory left");
	}
	xms_handles[index].free=false;
	xms_handles[index].mem=mem;
	xms_handles[index].locked=0;
	xms_handles[index].size=size;
	handle=index;
	return 0;
}

Bitu XMS_FreeMemory(Bitu handle) {
	if (InvalidHandle(handle)) return XMS_INVALID_HANDLE;
	MEM_ReleasePages(xms_handles[handle].mem);
	xms_handles[handle].mem=-1;
	xms_handles[handle].size=0;
	xms_handles[handle].free=true;
	return 0;
}

Bitu XMS_MoveMemory(PhysPt bpt) {
	/* Read the block with mem_read's */
	Bitu length=mem_readd(bpt+offsetof(XMS_MemMove,length));
	Bitu src_handle=mem_readw(bpt+offsetof(XMS_MemMove,src_handle));
	union {
		RealPt realpt;
		Bit32u offset;
	} src,dest;
	src.offset=mem_readd(bpt+offsetof(XMS_MemMove,src.offset));
	Bitu dest_handle=mem_readw(bpt+offsetof(XMS_MemMove,dest_handle));
	dest.offset=mem_readd(bpt+offsetof(XMS_MemMove,dest.offset));
	PhysPt srcpt,destpt;
	if (src_handle) {
		if (InvalidHandle(src_handle)) {
			return XMS_INVALID_SOURCE_HANDLE;
		}
		if (src.offset>=(xms_handles[src_handle].size*1024U)) {
			return XMS_INVALID_SOURCE_OFFSET;
		}
		if (length>xms_handles[src_handle].size*1024U-src.offset) {
			return XMS_INVALID_LENGTH;
		}
		srcpt=(xms_handles[src_handle].mem*4096)+src.offset;
	} else {
		srcpt=Real2Phys(src.realpt);
	}
	if (dest_handle) {
		if (InvalidHandle(dest_handle)) {
			return XMS_INVALID_DEST_HANDLE;
		}
		if (dest.offset>=(xms_handles[dest_handle].size*1024U)) {
			return XMS_INVALID_DEST_OFFSET;
		}
		if (length>xms_handles[dest_handle].size*1024U-dest.offset) {
			return XMS_INVALID_LENGTH;
		}
		destpt=(xms_handles[dest_handle].mem*4096)+dest.offset;
	} else {
		destpt=Real2Phys(dest.realpt);
	}
//	LOG_MSG("XMS move src %X dest %X length %X",srcpt,destpt,length);
	mem_memcpy(destpt,srcpt,length);
	return 0;
}

Bitu XMS_LockMemory(Bitu handle, Bit32u& address) {
	if (InvalidHandle(handle)) return XMS_INVALID_HANDLE;
	if (xms_handles[handle].locked<255) xms_handles[handle].locked++;
	address = xms_handles[handle].mem*4096;
	return 0;
}

Bitu XMS_UnlockMemory(Bitu handle) {
 	if (InvalidHandle(handle)) return XMS_INVALID_HANDLE;
	if (xms_handles[handle].locked) {
		xms_handles[handle].locked--;
		return 0;
	}
	return XMS_BLOCK_NOT_LOCKED;
}

Bitu XMS_GetHandleInformation(Bitu handle, Bit8u& lockCount, Bit8u& numFree, Bit16u& size) {
	if (InvalidHandle(handle)) return XMS_INVALID_HANDLE;
	lockCount = xms_handles[handle].locked;
	/* Find available blocks */
	numFree=0;
	for (Bitu i=1;i<XMS_HANDLES;i++) {
		if (xms_handles[i].free) numFree++;
	}
	size=(Bit16u)(xms_handles[handle].size);
	return 0;
}

Bitu XMS_ResizeMemory(Bitu handle, Bitu newSize) {
	if (InvalidHandle(handle)) return XMS_INVALID_HANDLE;	
	// Block has to be unlocked
	if (xms_handles[handle].locked>0) return XMS_BLOCK_LOCKED;
	Bitu pages=newSize/4 + ((newSize & 3) ? 1 : 0);
	if (MEM_ReAllocatePages(xms_handles[handle].mem,pages,true)) {
		xms_handles[handle].size = newSize;
		return 0;
	} else return XMS_OUT_OF_SPACE;
}

static bool multiplex_xms(void) {
	switch (reg_ax) {
	case 0x4300:					/* XMS installed check */
			reg_al=0x80;
			return true;
	case 0x4310:					/* XMS handler seg:offset */
			SegSet16(es,RealSeg(xms_callback));
			reg_bx=RealOff(xms_callback);
			return true;			
	}
	return false;

}

INLINE void SET_RESULT(Bitu res,bool touch_bl_on_succes=true) {
	if(touch_bl_on_succes || res) reg_bl = (Bit8u)res;
	reg_ax = (res==0);
}

Bitu XMS_Handler(void) {
//	LOG(LOG_MISC,LOG_ERROR)("XMS: CALL %02X",reg_ah);
	switch (reg_ah) {
	case XMS_GET_VERSION:										/* 00 */
		reg_ax=XMS_VERSION;
		reg_bx=XMS_DRIVER_VERSION;
		reg_dx=0;	/* No we don't have HMA */
		break;
	case XMS_ALLOCATE_HIGH_MEMORY:								/* 01 */
		reg_ax=0;
		reg_bl=HIGH_MEMORY_NOT_EXIST;
		break;
	case XMS_FREE_HIGH_MEMORY:									/* 02 */
		reg_ax=0;
		reg_bl=HIGH_MEMORY_NOT_EXIST;
		break;
		
	case XMS_GLOBAL_ENABLE_A20:									/* 03 */
	case XMS_LOCAL_ENABLE_A20:									/* 05 */
		SET_RESULT(XMS_EnableA20(true));
		break;
	case XMS_GLOBAL_DISABLE_A20:								/* 04 */
	case XMS_LOCAL_DISABLE_A20:									/* 06 */
		SET_RESULT(XMS_EnableA20(false));
		break;	
	case XMS_QUERY_A20:											/* 07 */
		reg_ax = XMS_GetEnabledA20();
		reg_bl = 0;
		break;
	case XMS_QUERY_FREE_EXTENDED_MEMORY:						/* 08 */
		reg_bl = XMS_QueryFreeMemory(reg_ax,reg_dx);
		break;
	case XMS_ALLOCATE_ANY_MEMORY:								/* 89 */
		reg_edx &= 0xffff;
		// fall through
	case XMS_ALLOCATE_EXTENDED_MEMORY:							/* 09 */
		{
		Bit16u handle = 0;
		SET_RESULT(XMS_AllocateMemory(reg_dx,handle));
		reg_dx = handle;
		}; break;
	case XMS_FREE_EXTENDED_MEMORY:								/* 0a */
		SET_RESULT(XMS_FreeMemory(reg_dx));
		break;
	case XMS_MOVE_EXTENDED_MEMORY_BLOCK:						/* 0b */
		SET_RESULT(XMS_MoveMemory(SegPhys(ds)+reg_si),false);
		break;
	case XMS_LOCK_EXTENDED_MEMORY_BLOCK: {						/* 0c */
		Bit32u address;
		Bitu res = XMS_LockMemory(reg_dx, address);
		if(res) reg_bl = (Bit8u)res;
		reg_ax = (res==0);
		if (res==0) { // success
			reg_bx=(Bit16u)(address & 0xFFFF);
			reg_dx=(Bit16u)(address >> 16);
		};
		}; break;
	case XMS_UNLOCK_EXTENDED_MEMORY_BLOCK:						/* 0d */
		SET_RESULT(XMS_UnlockMemory(reg_dx));
		break;
	case XMS_GET_EMB_HANDLE_INFORMATION:  						/* 0e */
		SET_RESULT(XMS_GetHandleInformation(reg_dx,reg_bh,reg_bl,reg_dx),false);
		break;
	case XMS_RESIZE_ANY_EXTENDED_MEMORY_BLOCK:					/* 0x8f */
		if(reg_ebx > reg_bx) LOG_MSG("64MB memory limit!");
		//fall through
	case XMS_RESIZE_EXTENDED_MEMORY_BLOCK:						/* 0f */
		SET_RESULT(XMS_ResizeMemory(reg_dx, reg_bx));
		break;
	case XMS_ALLOCATE_UMB: {									/* 10 */
		if (!umb_available) {
			reg_ax=0;
			reg_bl=XMS_FUNCTION_NOT_IMPLEMENTED;
			break;
		}
		Bit16u umb_start=dos_infoblock.GetStartOfUMBChain();
		if (umb_start==0xffff) {
			reg_ax=0;
			reg_bl=UMB_NO_BLOCKS_AVAILABLE;
			reg_dx=0;	// no upper memory available
			break;
		}
		/* Save status and linkage of upper UMB chain and link upper
		   memory to the regular MCB chain */
		Bit8u umb_flag=dos_infoblock.GetUMBChainState();
		if ((umb_flag&1)==0) DOS_LinkUMBsToMemChain(1);
		Bit8u old_memstrat=DOS_GetMemAllocStrategy()&0xff;
		DOS_SetMemAllocStrategy(0x40);	// search in UMBs only

		Bit16u size=reg_dx;Bit16u seg;
		if (DOS_AllocateMemory(&seg,&size)) {
			reg_ax=1;
			reg_bx=seg;
		} else {
			reg_ax=0;
			if (size==0) reg_bl=UMB_NO_BLOCKS_AVAILABLE;
			else reg_bl=UMB_ONLY_SMALLER_BLOCK;
			reg_dx=size;	// size of largest available UMB
		}

		/* Restore status and linkage of upper UMB chain */
		Bit8u current_umb_flag=dos_infoblock.GetUMBChainState();
		if ((current_umb_flag&1)!=(umb_flag&1)) DOS_LinkUMBsToMemChain(umb_flag);
		DOS_SetMemAllocStrategy(old_memstrat);
		}
		break;
	case XMS_DEALLOCATE_UMB:									/* 11 */
		if (!umb_available) {
			reg_ax=0;
			reg_bl=XMS_FUNCTION_NOT_IMPLEMENTED;
			break;
		}
		if (dos_infoblock.GetStartOfUMBChain()!=0xffff) {
			if (DOS_FreeMemory(reg_dx)) {
				reg_ax=0x0001;
				break;
			}
		}
		reg_ax=0x0000;
		reg_bl=UMB_NO_BLOCKS_AVAILABLE;
		break;
	case XMS_QUERY_ANY_FREE_MEMORY:								/* 88 */
		reg_bl = XMS_QueryFreeMemory(reg_ax,reg_dx);
		reg_eax &= 0xffff;
		reg_edx &= 0xffff;
		reg_ecx = (MEM_TotalPages()*MEM_PAGESIZE)-1;			// highest known physical memory address
		break;
	case XMS_GET_EMB_HANDLE_INFORMATION_EXT: {					/* 8e */
		Bit8u free_handles;
		Bitu result = XMS_GetHandleInformation(reg_dx,reg_bh,free_handles,reg_dx);
		if (result != 0) reg_bl = result;
		else {
			reg_edx &= 0xffff;
			reg_cx = free_handles;
		}
		reg_ax = (result==0);
		} break;
	default:
		LOG(LOG_MISC,LOG_ERROR)("XMS: unknown function %02X",reg_ah);
		reg_ax=0;
		reg_bl=XMS_FUNCTION_NOT_IMPLEMENTED;
	}
//	LOG(LOG_MISC,LOG_ERROR)("XMS: CALL Result: %02X",reg_bl);
	return CBRET_NONE;
}

Bitu GetEMSType(Section_prop * section);

class XMS: public Module_base {
private:
	CALLBACK_HandlerObject callbackhandler;
public:
	XMS(Section* configuration):Module_base(configuration){
		Section_prop * section=static_cast<Section_prop *>(configuration);
		umb_available=false;
		if (!section->Get_bool("xms")) return;
		Bitu i;
		BIOS_ZeroExtendedSize(true);
		DOS_AddMultiplexHandler(multiplex_xms);

		/* place hookable callback in writable memory area */
		xms_callback=RealMake(DOS_GetMemory(0x1)-1,0x10);
		callbackhandler.Install(&XMS_Handler,CB_HOOKABLE,Real2Phys(xms_callback),"XMS Handler");
		// pseudocode for CB_HOOKABLE:
		//	jump near skip
		//	nop,nop,nop
		//	label skip:
		//	callback XMS_Handler
		//	retf
	   
		for (i=0;i<XMS_HANDLES;i++) {
			xms_handles[i].free=true;
			xms_handles[i].mem=-1;
			xms_handles[i].size=0;
			xms_handles[i].locked=0;
		}
		/* Disable the 0 handle */
		xms_handles[0].free	= false;

		/* Set up UMB chain */
		umb_available=section->Get_bool("umb");
		bool ems_available = GetEMSType(section)>0;
		DOS_BuildUMBChain(section->Get_bool("umb"),ems_available);
	}

	~XMS(){
		Section_prop * section = static_cast<Section_prop *>(m_configuration);
		/* Remove upper memory information */
		dos_infoblock.SetStartOfUMBChain(0xffff);
		if (umb_available) {
			dos_infoblock.SetUMBChainState(0);
			umb_available=false;
		}

		if (!section->Get_bool("xms")) return;
		/* Undo biosclearing */
		BIOS_ZeroExtendedSize(false);

		/* Remove Multiplex */
		DOS_DelMultiplexHandler(multiplex_xms);

		/* Free used memory while skipping the 0 handle */
		for (Bitu i = 1;i<XMS_HANDLES;i++) 
			if(!xms_handles[i].free) XMS_FreeMemory(i);
	}

};
static XMS* test;

void XMS_ShutDown(Section* /*sec*/) {
	delete test;	
}

void XMS_Init(Section* sec) {
	test = new XMS(sec);
	sec->AddDestroyFunction(&XMS_ShutDown,true);
}
