Dilwyn Jones wrote:
> clr.w d0 ;position in linkage to set
Should be clr.w d1 of course. Though I think it doesn't really matter.
> clr.w d2 ;no bytes to be set (read only)
> moveq.w #-1,d3 ;infinite timeout
> ;find channel ID for window number passed and put in a0
> clr.l a1 ;pointer to data to set, in this case none as it's read only
> move.w #$6f,d0 ;iop.slnk ($6f=dec.111)
I suggest to *always* use symbolic names instead of direct numbers.
Especially with things like the PTR2 offset and flag later on.
In this case one would include the following files for example:
include 'dev8_keys_qdos_io'
include 'dev8_keys_con'
The command can then be written as
moveq #iop.slnk,d0
> trap #3
> tst.w d0 ;any error such as channel not open
Error returns are long. Though it doesn't make much difference in
practice, it'd be cleaner to use "tst.l d0".
> move.w #$128,d7 ;offset $128 in PE linkage block
> move.l 0(a1,d7.w),d6
Those two lines are equivalent to
move.l pt_ident(a1),d6 ; Flag that identifies GD2
Again, by using symbolic names the code gets much clearer. And
regarding the comment, the code already shows that something at
position $128 is taken out of the PE block. A comment should not
repeat what the code does, it should be one level higher and say /why/
the code does what it does.
Sorry for being so teacher like, but years of formal computer science
training do leave their traces ;-)
> This is completely off the top of my head with no testing, no real
> knowledge of what i'm doing, but filled with hope someone will read
> this and either complete it into something workable or at least tell
> me what i'm doing wrong!
You asked for it, you got my comments ;-)
It might be a good programing example to see how a clean, SMSQ/E
programing style conform implementation of all this could look like:
example_asm:
<--->
; Example basic extension V1.00 © 2003 me
section example
include 'dev8_keys_qdos_io'
include 'dev8_keys_con'
include 'dev8_keys_qlv'
include 'dev8_keys_err'
include 'dev8_mac_proc'
xref ut_chan1
xref ut_rtint
;+++
; Initialise SBASIC procedures
;---
ex_initp
lea ex_procs,a1 ; example procedures
move.w sb.inipr,a2
jmp (a2)
ex_procs
proc_stt
proc_end ; empty, no procedures, only functions
proc_stt
proc_ref PTR_ENV
proc_ref GD2
proc_end
;+++
; x = PTR_ENV (#ch)
;
; Returns 1 if the pointer environment is installed. Parameter Ch is
; optional.
;---
ptr_env
jsr ut_chan1 ; get a channel id
bne.s ex_rts
cmpa.l a3,a5 ; any more parameters?
bne.s ex_ipar ; yes, that's bad
moveq #-1,d3
moveq #iop.pinf,d0 ; test for PE
trap #3
moveq #1,d1 ; default to "PE installed"
tst.l d0 ; 0 = PE installed
beq.s ptr_ret
moveq #0,d1 ; no PE, return 0
ptr_ret
jmp ut_rtint ; return integer in D1
;+++
; x = GD2 (#ch)
;
; Returns 1 if the GD2 environment is available. Parameter Ch is
; optional.
;---
gd2
jsr ut_chan1 ; get a channel id
bne.s ex_rts
cmpa.l a3,a5 ; any more parameters?
bne.s ex_ipar ; yes, that's bad
clr.w d1 ; don't set anything, only get
clr.w d2 ; address of PE linkage block
moveq #-1,d3
moveq #iop.slnk,d0
trap #3
tst.l d0
bne.s ex_rts
moveq #1,d1 ; default to "GD2 available"
move.l pt_ident(a1),d0
cmp.l #pt.ident,d0 ; flag for GD2
beq.s gd2_ret
moveq #0,d1 ; no GD2 available
gd2_ret
jmp ut_rtint
ex_ipar
moveq #err.ipar,d0
ex_rts
rts
end
<--->
example_link:
<--->
program win2_example_cde
section example
section utils
input win2_example_rel
library dev8_sbsext_utq_lib
<--->
Please note that the current sbsext_ut_lib of the SMSQ/E sources are
*NOT* QDOS compatible anymore. Gave me some big headache when building
Qpac2. That's why I created sbsext_utq_lib, which replaces only the
problematic functions with ones that again run on all systems.
Will send the sources to Wolfgang to have it delivered with the
official distribution.
Marcel
