;*=*=*
;	xtrsmous/cmd
;	LS-DOS driver for xtrs emulation of mouse
;
;	Copyright (c) 1998, Timothy Mann
;       $Id: xtrsmous.z80,v 1.2 2008/06/26 04:39:56 mann Exp $
;
;	This software may be copied, modified, and used for any
;	purpose without fee, provided that (1) the above copyright
;	notice is retained, and (2) modified versions are clearly
;	marked as having been modified, with the modifier's name and
;	the date included.  
;
;	Usage:
;	  xtrsmous		To load driver in high memory.
;	  xtrsmous (low) 	To load driver in low memory if possible,
;				  or in high memory if low memory is full.
;
;	The default is to use high memory because MDRAW/BAS contains a
;	PEEK in the first line of code that looks for the driver in
;	high memory; if it is in low memory, MDRAW thinks the driver
;	is not installed and exits.  If you edit this line of code to
;	remove the test, the driver will work fine in low memory.
;*=*=*


; ASCII chars
LF      equ     10
CR	equ	13
ETX	equ	3

; Model 4 SVC numbers
@high   equ     100
@dsply  equ     10
@flags  equ     101
@logot  equ     12
@gtdcb  equ	82 
@gtmod	equ	83
@keyin	equ	9
@param	equ	17
@mouse	equ     120     ;unofficial value

svcvec	equ	100h + 2*@mouse

; xtrs emts (byte-reversed)
emt_mouse  equ	029edh

	org	3000h
;*=*=*
; 	Relocator for disk driver
;*=*=*
instal:	ld	de,prmtab
	ld	a,@param	;Parse parameters
	rst	40
	jp	nz,prmerr
	ld      hl,hello_
	ld      a,@dsply        ;Display hello
	rst     40
;*=*=*
;       Check if driver already loaded
;*=*=*
	ld	de,modnam
	ld	a,@gtmod
	rst	40
	jp	z,loaded	;Already loaded
;*=*=*
;	Check if OK to use low memory.
;*=*=*
lparm:	ld	bc,0
	ld	a,b
	or	c
	jr	z,usehi
;*=*=*
;       Obtain low memory driver pointer.  Bizarre API here!
;*=*=*
        ld      e,'K'           ;Locate pointer to *KI DCB
	ld	d,'I'		;  via @GTDCB SVC
        ld      a,@gtdcb        
        rst     40
        jp      nz,curdl        ;No error unless KI clobbered!
        dec     hl              ;Decrement to driver pointer
        ld      d,(hl)          ;P/u hi-order of pointer,
        dec     hl              ;  decrement to and p/u
        ld      e,(hl)          ;  lo-order of pointer
;*=*=*
;       Check if driver will fit into [(LCPTR), X'12FF']
;*=*=*
	push	hl		;Save address of pointer
        ld      hl,length	;New pointer will be
        add     hl,de		;  pointer + LENGTH
	ld	d,h		;Save a copy in DE
	ld	e,l
        ld      bc,1301h        ;If > 1300H, driver won't fit
        sub     a               ;Reset carry flag
        sbc     hl,bc
	pop	hl		;Get back address of pointer
        jr      nc,usehi        ;Go if driver won't fit
	ld	(hl),e		;Store new value of pointer
	inc	hl
	ld	(hl),d
	dec	de		;Last byte of driver goes here
	ld      (newend),de
	jr	dorelo
;*=*=*
;       Put in high memory instead.
;*=*=*
usehi:	ld      hl,0            ;Get current HIGH$
	ld      b,l
	ld      a,@high 
	rst     40
	jp      nz,nomem
	ld      (newend),hl	;Last byte of driver goes here
	ld	de,length
	sub	a		;Reset carry flag
	sbc	hl,de		;Compute new HIGH$
	ld      a,@high         ;Set new HIGH$ into the system
	rst     40
;*=*=*
;       Relocate internal references in driver.
;	HL = address for last byte of driver.
;*=*=*
dorelo:	call	relo
;*=*=*
;	Link to @ICNFG (must follow address relocation and precede movement)
;*=*=*
	ld      a,@flags        ;Get flags pointer into IY
	rst     40
        ld      a,(iy+28)       ;Copy current @ICNFG into LINK
        ld      l,(iy+29)
        ld      h,(iy+30)
	ld	(link),a
        ld      (link+1),hl
	ld	hl,dvrcfg	;Get relocated init address
rx01	equ	$-2
        ld      (iy+29),l       ;Save in @ICNFG vector
        ld      (iy+30),h
	ld	(iy+28),0c3h	;Insert JP opcode
;*=*=*
;       Move driver into low or high memory.
;*=*=*
move:
	ld      de,(newend)     ;Destination address
	ld      hl,dvrend       ;Last byte of module
	ld      bc,length       ;Length of filter
	lddr
	ex      de,hl
	inc     hl              ;Bump to driver entry
;*=*=*
;	Driver is loaded; finish up.
;*=*=*
	call	dvrini		;Hook into SVC table

	ld      hl,0            ;Successful completion
	sub	a
	ret

;*=*=*
;	Error vectors
;*=*=*
prmerr:	ld	hl,prmerr_
	defb	0ddh
loaded:	ld	hl,loaded_
	defb	0ddh
curdl:	ld	hl,curdl_
	defb	0ddh
nomem:  ld      hl,nomem_
logot:	ld	a,@logot 
	rst	40
	ld      hl,-1            ;Unuccessful completion
	ret

;*=*=*
;       Relocate internal references in driver.
;	HL = address for last byte of driver.
;*=*=*
relo:	ld	hl,(newend)
	ld      iy,reltab       ;Point to relocation tbl
	ld      de,dvrend
	sub     a               ;Clear carry flag
	sbc     hl,de
	ld      b,h             ;Move to BC
	ld      c,l
rloop:  ld      l,(iy)          ;Get address to change
	ld      h,(iy+1)
	ld      a,h
	or      l
	ret	z
	ld      e,(hl)          ;P/U address
	inc     hl
	ld      d,(hl)
	ex      de,hl           ;Offset it
	add     hl,bc
	ex      de,hl
	ld      (hl),d          ;And put back
	dec     hl
	ld      (hl),e
	inc     iy
	inc     iy
	jr      rloop           ;Loop till done

;*=*=*
;	Messages and globals
;*=*=*
hello_: defb    'XTRSMOUS - Emulated mouse driver for xtrs - 9/28/98',CR
curdl_:	defb	'LS-DOS is curdled!',CR
nomem_: defb    'High memory is not available!',CR
loaded_:defb	'Mouse driver is already loaded!',CR
prmerr_:defb	'Bad parameters!',CR
lcptr:	defw	0
newend:	defw	0

;*=*=*
;	Parameter table
;*=*=*
prmtab:	defb	'LOW   '
	defw	lparm+1
	defb	'L     '
	defw	lparm+1
	defb	0

;*=*=*
;	Driver
;*=*=*
entry:  jr      begin           ;The driver starts with the
	defw    dvrend          ;  DOS standard header
rx00	equ	$-2
	defb    modptr-modnam   ;Length of name
modnam:	defb    '$MOUSE'        ;Name for @GTMOD requests
modptr: defw    0               ;These pointers are unused, but 1st byte MBZ
	defw    0
;*=*=*
;	Do the real work using an emulator trap
;*=*=*
begin:	defw	emt_mouse
	ret
;*=*=*
;	Boot-time initialization
;*=*=*
dvrcfg:				;@ICNFG chains in here
	call	dvrini
rx02	equ	$-2	
link:	defb	'Tim'		;Replaced by next link in @ICNFG chain
;*=*=*
;	Hook into SVC table
;*=*=*
dvrini:	ld	hl,entry
rx03	equ	$-2
	ld	(svcvec),hl
	ret

dvrend  equ     $-1
length  equ     $-entry
reltab: defw    rx00,rx01,rx02,rx03,0
	end     instal
