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EMS.PAS
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Pascal/Delphi Source File
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1993-10-21
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5KB
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198 lines
{**************************************************************************
* EMS - unit of EMS functions *
* Copyright (c) 1991,1993 Kim Kokkonen, TurboPower Software. *
* May be freely distributed and used but not sold except by permission. *
* *
* Version 3.0 9/24/91 *
* first release *
* Version 3.1 11/4/91 *
* no change *
* Version 3.2 11/22/91 *
* no change *
* Version 3.3 1/8/92 *
* no change *
* Version 3.4 2/14/92 *
* no change *
* Version 3.5 10/18/93 *
* add RestorePageMap function *
* change FreeEms to return a Byte status code *
***************************************************************************}
{$R-,S-,I-,V-,B-,F-,A-,E-,N-,G-,X-}
unit Ems;
{-EMS functions needed for MAPMEM, MARKNET, RELNET}
interface
const
MaxHandles = 255;
EmsDevice : string[8] = 'EMMXXXX0';
type
HandlePageRecord =
record
Handle : Word;
NumPages : Word;
end;
PageArray = array[1..MaxHandles] of HandlePageRecord;
PageArrayPtr = ^PageArray;
function EmsPresent : Boolean;
{-Return true if EMS memory manager is present}
function EmsPagesAvailable : LongInt;
{-Return Total pages in high word, Available pages in low word}
function EmsHandles(var PageMap : PageArray) : Word;
{-Return number of handles allocated and page map}
function EmsVersion : Byte;
{-Return EMM version number}
procedure GetHandleName(Handle : Word; var Name : String);
{-Return name of EMS block, if any}
function FreeEms(Handle : Word) : Byte;
{-Deallocate EMS handle}
function RestorePageMap(Handle : Word) : Byte;
{-Restore page map}
{=========================================================================}
implementation
function EMSpresent : Boolean; assembler;
{-Return true if EMS memory manager is present}
asm
mov ax,$3567
int $21
mov ax,es
or ax,bx {is int $67 nil?}
jz @AbsentNoClose
cmp byte ptr es:[bx],$CF {does int $67 point to iret?}
je @AbsentNoClose
mov dx,offset EmsDevice+1
mov ax,$3D02
int $21 {can we open EMM device?}
mov bx,ax
jc @AbsentNoClose
mov ax,$4400
int $21 {can we get its device properties?}
jc @Absent
and dx,$80 {does bit 7 = 1?}
jz @Absent
mov ax,$4407
int $21 {device ready for output?}
jc @Absent
or al,al
jz @Absent
push bx
mov ah,$30
int $21
pop bx
xchg ah,al
cmp ax,$030A
jb @Present
mov ax,$440A
int $21 {local device?}
jc @Present
and dx,$8000
jnz @Absent
@Present:
mov ah,$3E {close handle}
int $21
mov al,1
jmp @Done
@Absent:
mov ah,$3E {close handle}
int $21
@AbsentNoClose:
xor ax,ax
@Done:
end;
function EmsPagesAvailable : LongInt; assembler;
{-Return Total pages in high word, Available pages in low word}
asm
mov ah, $42
int $67
or ah,ah
jnz @error
mov ax,bx {available pages now in ax}
jmp @done
@error:
xor ax,ax
mov dx,ax
@done:
end;
function EmsHandles(var PageMap : PageArray) : Word; assembler;
{-Return number of handles allocated and page map}
asm
mov ah,$4D
les di,PageMap
xor bx,bx
int $67
or ah,ah
mov ax,bx
jz @done
xor ax,ax
@done:
end;
function EmsVersion : Byte; assembler;
{-Return EMM version number}
asm
mov ah,$46
int $67
or ah,ah
jz @Done
xor al,al
@Done:
end;
procedure GetHandleName(Handle : Word; var Name : String); assembler;
{-Return name of EMS block, if any}
asm
mov dx,Handle
les di,Name
mov si,di {save offset}
inc di {point past length byte}
mov ax,$5300
int $67
mov al,0 {assume zero length}
or ah,ah
jnz @Done
mov cx,8
xor al,al
cld {scan for null terminator}
repne scasb
mov al,8 {assume all 8 chars significant}
jne @Done
sub al,cl
dec al
@Done:
mov es:[si],al {store length byte}
end;
function FreeEms(Handle : Word) : Byte; assembler;
{-Deallocate EMS handle}
asm
mov ah,$45
mov dx,Handle
int $67
mov al,ah
end;
function RestorePageMap(Handle : Word) : Byte; assembler;
{-Restore page map}
asm
mov ah,$48
mov dx,HAndle
int $67
mov al,ah
end;
end.