OBJNAM FREESP.SBR ; Created 3-Nov-85, Last modified 2-Jan-86
; Subroutine to free up freespace reserved by FREESP command
; by Irv Bromberg, Medic/OS Consultants, Toronto, CANADA
RADIX 10
VEDIT=7
VMINOR=0
VMAJOR=2
VSUB=0
IF EQ,1
Calling syntax: XCALL FREESP {,Bytes}
Assembled under AMOS/L 1.3 FREESP.SBR version 2.0(7) size=138 bytes,
hash=477-617-264-136.
Frees up the freespace reserved by FREESP command used to invoke the
calling BASIC program. Optionally returns the number of free bytes to
floating variable. Method used: If the user's partition contains a
command file and the pending line contains only "!" followed by line
terminator then the command file and terminal status words are saved,
silence (NO trace) mode and line input mode are set, a KBD monitor call
is executed to flush the FREESP command file, and then the command file
and terminal status words are restored. Otherwise no action is taken
except to optionally return the number of free bytes.
The freespace remains free (and its contents unmodified) even when you
chain from one compiled BASIC program to another. This allows you to
create a common data module in the freespace and chain to another
program which will have access to the common data.
To return the freespace or reserve even more your program must return to
monitor level. At this time any files or programs which were LOADed
will slide down to the base of the user's memory partition.
SCALE is supported (scaled floating values) so that the bytes count
floating parameter returned to BASIC is properly scaled.
Edit history:
1-Jan-86 1.2(5) Put back flushed line if it's not empty; removed
conditional assembly of SCALE, always supported.
2-Jan-86 1.3(6) Simplify & improve. Always try to get more freespace
unless no CMD file pending -- if flushed line is not
"!<cr>" then put it back.
2-Jan-86 2.0(7) Simplify further. Don't flush line if it is not "!", thus
avoiding the need to be prepared to put it back.
ENDC
SCALE=128 ; =offset to SCALE value in BASIC impure area
PHDR -1,0,PH$REE!PH$REU ; re-entrant & re-usable
jobidx JCB
tstw JOBCMZ(JCB) ; command file pending?
beq NoMore ; no, can't clear any more
mov JOBBAS(JCB),Buffer ; find beginning of current cmd file
add JOBSIZ(JCB),Buffer
subw JOBCMZ(JCB),Buffer ; now pointing to next byte
cmpb (Buffer)+,#'! ; must be exclamation here
bne NoMore ; else can't flush for freespace
lin ; must be followed by line terminator
bne NoMore
pushw JOBCMS(JCB) ; save command file status
movw #c.sil,JOBCMS(JCB) ; silence mode (suppress !<cr><lf>)
mov JOBTRM(JCB),TCB ; yes, flush first line of command file
pushw T.STS(TCB) ; save terminal status word
andw #^c<T$IMI!T$DAT>,T.STS(TCB) ; force line input mode
kbd ; flush FREESP cmd file
popw Dtemp ; recall saved terminal status word
andw #^c<T$OIP>,Dtemp ; clear old OIP bit
orw Dtemp,T.STS(TCB) ; restore T.STS bits originally set
popw JOBCMS(JCB) ; restore command file status
NoMore: tstw @ArgBas ; parameter passed?
beq Done ; no, done
cmpb 2(ArgBas),#4 ; floating?
bne Done ; no, ignore it
usrend Free ; get new user end
usrfre Atemp
sub Atemp,Free
add #4,Free ; because USRFRE goes 1 LWORD beyond
sub #8,sp ; get some workspace on user stack
mov sp,Worksp
fltof Free,@Worksp
mov Scale(Impure),D7 ; SCALE factor in use?
beq 10$ ; 0=no SCALE factor in use
fpwr @Worksp,D7 ; yes, scale the number
10$: mov 4(ArgBas),Atemp
movb (Worksp)+,(Atemp)+ ; move byte-by-byte in case on
movb (Worksp)+,(Atemp)+ ; odd memory address
movb (Worksp)+,(Atemp)+
movb (Worksp)+,(Atemp)+
movb (Worksp)+,(Atemp)+
movb (Worksp)+,(Atemp)+
add #8,sp ; restore SP
Done: RTN ; return to BASIC
END
