Hello,
Here you have a unit for calling XMS services in the same way as you
normally call interrupt services, using the REG register buffer.
I hope it will be useful, especially for programmers not accustomed to
assembly language and using pointers. You may save yourself from having
to buy a library to access XMS services. Of course you have to know wich
XMS services are available. You will find them in Ralph Brown's
interrupt list under interrupt 2Fh, function 4310h (get XMS driver
address).
'*****************************************************************************
*
' Unit CallXMS.bas
' Copyright (C) 1996 by Hans Lunsing.  All Rights Reserved.
'*****************************************************************************
*
$COMPILE        UNIT    'Destination of compilation
'Compiler directives for code generation
$CPU            80386   'Generate code for processor {8086 | 80286 | 80386}
$DIM            ALL     'Declararations required for {ALL | ARRAY | NONE}
$EVENT          OFF     'Generate event checking code
$FLOAT          EMULATE 'FP math package '{EMULATE | NPX | PROCEDURE}
$OPTIMIZE       SPEED   'Optimize code for {SPEED | SIZE}
$OPTION GOSUB   OFF     'Preserve GOSUB stack if a runtime error occurs
$OPTION SIGNED  OFF     'Return addresses by VARSEG etc. as signed integers
'Compiler directives for debugging and testing
$DEBUG UNIT     OFF     'Attach debug information to unit file
$ERROR ALL      OFF     'Generate test code for all types of errors
'*****************************************************************************
*
DEFINT A-Z
$INCLUDE "regnames.inc"
FUNCTION CallXMS () PUBLIC AS INTEGER
' ----------------------------------------------------------------------
' Function: to call XMS services in the same way as interrupt services:
'           - fill REG register buffer
'           - call service procedure
'           - read REG register buffer
' XMS services are available only if an appropriate driver is loaded.
' If that is not the case, the function returns 1 instead of 0, and
' REG(%AX) = 0 and REG(%BX) = -1.
' ----------------------------------------------------------------------
DIM XMSEntry    AS STATIC DWORD PTR     'Saved value of XMS entry point
DIM Entry       AS DWORD PTR            'Local (stack) value of XMS entry 
point
DIM rAX         AS WORD                 'All relevant registers on the stack
DIM rBX         AS WORD
DIM rCX         AS WORD
DIM rDX         AS WORD
DIM rDS         AS WORD
DIM rES         AS WORD
DIM rSI         AS WORD
DIM rDI         AS WORD
DIM rFlags      AS WORD                 'Flags on the stack
FUNCTION = 0
IF XMSEntry = 0 THEN
  ' XMSEntry not yet known. We'll try to get it.
  ' First test if driver is available. If not, return
  '   FUNCTION = 1, REG(%AX) = 0, REG(%BX) = -1
  ASM   MOV     AX, &h4300
  ASM   INT     &h2F
  ASM   MOV     rAX, AX
  IF (rAX AND &hFF)  &h80 THEN        'Driver not available
    REG %AX, 0
    REG %BX, -1
    FUNCTION = 1
    EXIT FUNCTION
  ELSE                                  'Driver available. Get entry point.
    ASM MOV     AX, &h4310
    ASM INT     &h2F
    ASM MOV     XMSEntry, BX
    ASM MOV     AX, ES
    ASM MOV     XMSEntry[2], AX
  END IF
END IF
' Place register buffer on the local stack
rAX = REG(%AX)
rBX = REG(%BX)
rCX = REG(%CX)
rDX = REG(%DX)
rDS = REG(%DS)
rES = REG(%ES)
rSI = REG(%SI)
rDI = REG(%DI)
' Place entry point vector on the local stack
Entry = XMSEntry
' Save adressing registers
ASM     PUSH    DS
ASM     PUSH    ES
ASM     PUSH    SI
ASM     PUSH    DI
' Fill registers from register buffer on stack
ASM     MOV     AX, rDS
ASM     MOV     DS, AX
ASM     MOV     AX, rES
ASM     MOV     ES, AX
ASM     MOV     SI, rSI
ASM     MOV     DI, rDI
ASM     MOV     AX, rAX
ASM     MOV     BX, rBX
ASM     MOV     CX, rCX
ASM     MOV     DX, rDX
' Call XMS service
ASM     CALL    DWORD PTR Entry
' Fill register buffer on stack from registers
ASM     PUSHF
ASM     POP     rFlags
ASM     MOV     rAX, AX
ASM     MOV     rBX, BX
ASM     MOV     rCX, CX
ASM     MOV     rDX, DX
ASM     MOV     AX, DS
ASM     MOV     rDS, AX
ASM     MOV     AX, ES
ASM     MOV     rES, AX
ASM     MOV     rSI, SI
ASM     MOV     rDI, DI
>>> Continued to next message
Friendly greeting you,
Hans Lunsing,           Fido     : 2:281/607.214, 2:282/610.12
                        Internet : jlunsing@doge.nl
--- Terminate 4.00/Pro
 # Origin: BBS De Lauwers For BASIC Programmers! ++31594688407 (2:282/610.12)
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