A2osX/ProDOS.FX/ProDOS.S.XDOS.B.txt
2019-11-04 08:21:40 +01:00

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NEW
AUTO 3,1
* create file
create jsr lookfile check for duplicate, get free entry
bcs tstfnf error code may be 'file not found'
lda #MLI.E.DUPFILE name already exists
crerr1 sec
rts
tstfnf cmp #MLI.E.FNOTFND 'file not found' is ok
bne crerr1 otherwise exit with error.
ldy #$07 test for tree or directory file,
lda (A3L),y no other kinds are legal.
cmp #$04 is it seed, sapling or tree?
bcc tstdspc branch if it is
cmp #$0D
bne ctyperr report type error if not directory.
tstdspc lda devnum make sure destination device
jsr twrprot1 is not write protected.
bcs H351D
lda nofree is there space in directory to
beq xtndir add this file? branch if not
jmp creat1 otherwise, go create file.
ctyperr lda #MLI.E.UNSUPST filetype error
sec
H351D rts
xtndir lda own_blk before extending directory,
ora own_blk+1 make sure it's a subdirectory.
bne H352A
lda #MLI.E.DIRFULL otherwise, directory full error
sec
rts
H352A lda bloknml preserve disk address of current (last)
pha directory link, before allocating an
lda bloknml+1 extended block.
pha
jsr alc1blk allocate a block for extending directory
plx
stx bloknml+1 restore block addr of dir info in gbuf
plx
stx bloknml
bcs H351D unable to allocate.
sta gbuf+2 save block address in y,a to
sty gbuf+3 current directory.
jsr wrtgbuf update directory block with new link.
bcs H351D if error
ldx #$01
swpbloks lda bloknml,x prepare new directory block
sta gbuf,x using current block as back link
lda gbuf+2,x
sta bloknml,x and save new block as next to be written
dex
bpl swpbloks
inx
txa x and a = 0
clrdir sta gbuf+2,x
sta gbuf+$100,x
inx
bne clrdir
jsr wrtgbuf write prepared directory extension.
bcs H351D if error
lda own_blk
ldx own_blk+1
jsr rdblk read in parent directory block
ldx own_ent and calc entry address.
lda /gbuf
sta zpt+1
lda #$04
ocalc clc
dex has entry address been calulated?
beq H3584 if yes.
adc own_len next entry address
bcc ocalc
inc zpt+1 entry must be in 2nd 256 bytes of block
bcs ocalc always taken.
H3584 sta zpt
ldy #$13 index to block count
H3588 lda (zpt),y
adc dinctbl-$13,y add 1 to block count and
sta (zpt),y
iny
tya $200 to the directory's eof.
eor #$18 done with usage/eof update?
bne H3588 branch if not.
jsr wrtgbuf go update parent.
bcs crerr2
jmp create
crerr2 rts return and report errors
creat1 ldx #$00 zero out gbuf
H35A0 stz gbuf,x
stz gbuf+$100,x and data block of file.
inx
bne H35A0
ldy #$0B move user specified date/time
cmvtime lda (A3L),y to directory.
sta d_filid,y
txa if all 4 bytes of date/time = 0
ora (A3L),y then use built-in date/time.
tax
dey
cpy #$07
bne cmvtime
txa does user want default time?
bne cmvname if not.
ldx #$03
mvdftime lda p8date,x move current default date/time
sta d_credt,x
dex
bpl mvdftime
cmvname lda (A3L),y y = index to file kind.
cmp #$04
lda #$10 assume tree type
bcc csvfkind
lda #$D0 it's directory.
csvfkind ldx namptr index to local name of pathname.
ora pathbuf,x combine file kind with name length.
sta d_stor sos calls this 'storage type'.
and #$0F strip back to name length
tay and use as counter for move.
clc
adc namptr calc end of name
tax
crname lda pathbuf,x move local name as filename
sta d_stor,y
dex
dey
bne crname
ldy #$03 index to 'access' parameter
lda (A3L),y
sta d_attr
iny also move 'file identification'
lda (A3L),y
sta d_filid
cmvauxid iny move auxillary identification bytes
lda (A3L),y
sta d_auxid-5,y
cpy #$06
bne cmvauxid
lda xdosver save current xdos version #
sta d_sosver
lda compat and backward compatibility #
sta d_comp
lda #$01 usage is always 1 block
sta d_usage
lda d_head place back pointer to header block
sta d_dhdr
lda d_head+1
sta d_dhdr+1
lda d_stor storage type.
and #$E0 is it a directory?
beq cralcblk branch if seed file.
ldx #$1E move header to data block
cmvheadr lda d_stor,x
sta gbuf+4,x
dex
bpl cmvheadr
eor #$30
sta gbuf+4 make it a directory header mark.
ldx #$07 overwrite password area and other
cmvpass lda pass,x header info.
sta gbuf+20,x
lda xdosver,x
sta gbuf+32,x
dex
bpl cmvpass
ldx #$02 and include info about parent directory
stx d_eof+1
cmvparnt lda d_entblk,x
sta gbuf+39,x
dex
bpl cmvparnt
lda h_entln lastly, the length of parent's
sta gbuf+42 directory entries.
cralcblk jsr alc1blk get address of file's data block
bcs crerr3
sta d_frst
sty d_frst+1
sta bloknml
sty bloknml+1
jsr wrtgbuf go write data block of file
bcs crerr3
inc h_fcnt add 1 to total # of files in this dir
bne credone
inc h_fcnt+1
credone jsr drevise go revise directories with new file
bcs crerr3
jmp upbmap lastly, update volume bitmap
entcalc lda /gbuf set high address of dir entry
sta zpt+1 index pointer.
lda #$04 calc address of entry based
ldx d_entnum on the entry #.
H3689 clc
H368A dex addr = gbuf + ((d_entnum-1) * h_entln)
beq H3696 branch with carry clear = no errors.
adc h_entln
bcc H368A
inc zpt+1 inc hi address.
bcs H3689 always.
H3696 sta zpt newly calculated low address.
crerr3 rts carry set if error.
drevise lda p8date
beq drevise1 if no clock, then don't mod date/time.
ldx #$03
modtime lda p8date,x move last modification date/time
sta d_moddt,x to entry being updated.
dex
bpl modtime
drevise1 lda d_attr mark entry as backupable
ora bkbitflg (bit 5 = backup needed)
sta d_attr
lda d_dev get device # of directory
sta devnum to be revised
lda d_entblk and address of direcotry block.
ldx d_entblk+1
jsr rdblk read block into general purpose buffer
bcs crerr3
jsr entcalc fix up ptr to entry location within gbuf.
ldy h_entln now move 'd.' info to directory.
dey
H36CA lda d_stor,y
sta (zpt),y
dey
bpl H36CA
lda d_head is the entry block same as
cmp bloknml the entry's header block?
bne H36E0 if no, go save entry block
lda d_head+1 then maybe, so test high addresses.
cmp bloknml+1
beq uphead branch if they are the same block.
H36E0 jsr wrtgbuf go write updated directory block.
bcs crerr3
lda d_head get address of header block and
ldx d_head+1
jsr rdblk go read in header block to modify.
bcs crerr3
uphead ldy #$01 update current # of files in this dir.
H36F2 lda h_fcnt,y
sta gbuf+37,y (current entry count)
dey
bpl H36F2
lda h_attr also update header's attributes.
sta gbuf+34
jsr wrtgbuf go write updated header
bcs H375A
ripple lda gbuf+4 test for 'root' directory because
and #$F0 if it is, then directory revision
eor #$F0 is complete (leaves carry clear).
beq H3770 branch if done.
lda gbuf+41 get entry #
sta d_entnum
lda gbuf+42 and the length of ertries in that dir
sta h_entln
lda gbuf+39 get addr of parent entry's dir block
ldx gbuf+40
jsr rdblk read it
bcs H375A
jsr entcalc get indirect ptr to parent entry in gbuf
lda p8date don't touch mod
beq H373B if no clock...
ldx #$03 update the modification date & time
ldy #$24 for this entry too
H3732 lda p8date,x
sta (zpt),y
dey
dex
bpl H3732
H373B jsr wrtgbuf write updated entry back to disk.
bcs H375A if error.
ldy #$25 compare current block # to this
lda (zpt),y entry's header block.
iny
cmp bloknml are low addresses the same?
sta bloknml
bne H3751 branch if entry doesn't reside in same
lda (zpt),y block as header.
cmp bloknml+1 are high address the same?
beq ripple they are the same, continue to root dir.
H3751 lda (zpt),y not same so read in this dir's header.
sta bloknml+1
jsr rdgbuf
bcc ripple continue if read was good
H375A rts
tsterr lda #$52 not tree or dir, unrecognized type
sec
rts
tstsos lda gbuf pointer to previous dir block
ora gbuf+1 must be null
bne tsterr
lda gbuf+4 test for header
and #$E0
cmp #$E0
bne tsterr
H3770 clc no error
rts
findfile jsr lookfile see if file exists
bcs nofind
moventry ldy h_entln
H377A lda (zpt),y move entry into storage
sta d_stor,y
dey
bpl H377A
lda #$00 no errors
nofind rts
lookfile jsr preproot go find volume
bcs fnderr
bne lookfil0 branch if more than root
lda /gbuf otherwise, report a bad path error
sta zpt+1 (but 1st create a phantom entry
lda #$04 for open)
sta zpt
ldy #$1F move in id and date info
phantm1 lda (zpt),y
sta d_stor,y
dey
cpy #$17
bne phantm1
phantm2 lda rootstuf-$10,y
sta d_stor,y
dey
cpy #$0F
bne phantm2
lda #$D0 fake directory file
sta d_stor
lda gbuf+2 check forward link.
ora gbuf+3 if non-zero, assume full sized directory
bne H37C2 else assume it's the slot 3 /RAM volume
lda #$02 so reset eof and blocks_used fields
sta d_eof+1
lda #$01
sta d_usage
H37C2 lda #MLI.E.INVPATH bad path (carry set)
rts
lookfil0 stz nofree reset free entry indicator.
sec dir to be searched has header in this block.
L37C9 stz totent reset entry counter.
jsr looknam look for name pointed to by pnptr.
bcc namfound if name was found.
lda entcntl have we looked at all of the
sbc totent entries in this directory?
bcc L37E2 maybe, check hi count.
bne L37EB no, read next directory block.
cmp entcnth has the last entry been looked at?
beq errfnf yes, give 'file not found' error
bne L37EB or branch always.
L37E2 dec entcnth should be at least one
bpl L37EB so this should be branch always...
errdir lda #MLI.E.BADDIR directory error
fnderr sec
rts
L37EB sta entcntl keep a running count.
lda /gbuf reset indirect pointer
sta zpt+1
lda gbuf+2 get link to next dir block
bne L37FC (if there is one).
cmp gbuf+3 are both zero, i.e. no link? if so,
beq errdir then not all entries were acct'd for.
L37FC ldx gbuf+3 acc has value for block# (low).
jsr rdblk go read the next linked directory.
bcc L37C9 if no error.
rts return error in acc.
errfnf lda nofree was any free entry found?
bne fnf0
lda gbuf+2 test link
bne L3814
cmp gbuf+3 if both are 0 then give up.
beq fnf0 report 'not found'.
L3814 sta d_entblk
lda gbuf+3
sta d_entblk+1 assume 1st entry of next block
lda #$01 is free for use.
sta d_entnum mark as valid (for create)
sta nofree
fnf0 jsr nxtpnam1 'file not found' or 'path not found'?
errpath1 sec if non-zero then 'path not found'
beq fnf1
lda #MLI.E.PNOTFND path not found
rts
fnf1 lda #MLI.E.FNOTFND file not found
rts
namfound jsr nxtpname adj index to next name in path.
beq filfound branch if that was the last name.
ldy #$00 be sure this is a directory entry.
lda (zpt),y high nibble will tell.
and #$F0
cmp #$D0 is it a subdirectory?
bne errpath1 error if not.
ldy #$11 get address of 1st subdirectory block
lda (zpt),y
sta bloknml (no checking done for a valid block#)
iny
sta d_head save as file's header block too
lda (zpt),y
sta bloknml+1
sta d_head+1
jsr rdgbuf read subdirectory into gbuf.
bcs fnderr1 if error.
lda gbuf+37 get the # of files contained in this
sta entcntl directory.
lda gbuf+38
sta entcnth
lda gbuf+20 make sure password is disabled
ldx #$00
sec
rol
L3869 bcc L386C
inx
L386C asl
bne L3869
cpx #$05 is password disabled?
beq movhead
lda #MLI.E.INCFF directory is not compatible
fnderr1 sec
rts
movhead jsr movhed0 move directory info.
jmp lookfil0 do next local pathname.
movhed0 ldx #$0A move this directory info
L387F lda gbuf+28,x
sta h_credt,x
dex
bpl L387F
lda gbuf+4 if this is root, then nothing to do
and #$F0
eor #$F0 test header type.
beq L389C branch if root
ldx #$03 otherwise, save owner info about
L3893 lda gbuf+39,x this header.
sta own_blk,x
dex
bpl L3893
L389C rts
filfound lda h_maxent figure out which entry # this is
sec
sbc cntent max entries - count entries + 1
adc #$00 = entry # (carry was set)
sta d_entnum
lda bloknml and indicate block # of this directory
sta d_entblk
lda bloknml+1
sta d_entblk+1
clc
rts
looknam lda h_maxent reset count of files per block
sta cntent
lda /gbuf
sta zpt+1
lda #$04
L38C1 sta zpt reset indirect pointer to gbuf
bcs L38F8 branch if this block contains a header
ldy #$00
lda (zpt),y get length of name in directory.
bne isname branch if there is a name.
lda nofree test if a free entry has been declared.
bne L38F8 yes, inc to next entry.
jsr filfound set address for current entry.
inc nofree indicate a free spot has been found.
bne L38F8 always.
isname and #$0F strip byte (is checked by 'filfound')
inc totent inc count of valid files found.
sta namcnt save name length as counter.
ldx namptr get index to current path.
cmp pathbuf,x are both names the same length?
bne L38F8 no, inc to next entry.
cmpname inx (first) next letter index
iny
lda (zpt),y compare names letter by letter
cmp pathbuf,x
bne L38F8
dec namcnt all letters compared?
bne cmpname no, continue.
clc a match is found.
noname rts
L38F8 dec cntent checked all entries in this block?
sec
beq noname yes, no name match.
lda h_entln add entry length to current pointer
clc
adc zpt
bcc L38C1 branch if still in 1st page.
inc zpt+1 look on 2nd page.
clc carry should always be clear before
bcc L38C1 looking at next.
preproot jsr findvol search vcb's and dev's for spec'd volume
bcs novolume
lda #$00 zero out directory temps
ldy #$42
L3914 sta own_blk,y and owner info
dey
bpl L3914
lda devnum setup device # for this directory
sta d_dev
jsr movhed0 setup other header info from directory
ldy #$01 in gbuf and clean up misc info.
ldx vcbptr
inx
L3929 lda vcbbuf+18,x misc info includes
sta h_tblk,y total # of blocks,
lda vcbbuf+26,x the address of the 1st bitmap,
sta h_bmap,y
lda bloknml,y directory's disk address,
sta d_head,y
lda h_fcnt,y and setting up a counter for the # of
sta entcntl,y files in this directory.
dex
dey
bpl L3929
nxtpname jsr nxtpnam1 get new namptr in y and namlen in acc.
sty namptr save new pathname pointer.
rts (status reg according to accumulator)
nxtpnam1 ldy namptr inc pathname pointer to next name
lda pathbuf,y in the path.
sec
adc namptr if this addition results in zero,
tay then prefixed directory has been moved
bne L395F to another device. branch if not.
lda devnum revise devnum for prefixed directory
sta p_dev
L395F lda pathbuf,y test for end of name.
clc no errors
novolume rts
findvol lda #$00
ldy preflag use prefix volume name to look up vcb.
bit prfxflg is this a prefixed path?
bpl L396F branch if it is
tay set ptr to volume name
L396F sty vnptr and save.
sta devnum zero out dev# until vcb located.
L3975 pha acc now used as vcb lookup index.
tax index pointer to x.
lda vcbbuf,x get vcb volume name length.
bne L3987 branch if claimed vcb to be tested.
L397C ldy vnptr restore pointer to requested vol name.
pla now adj vcb index to next vcb entry.
clc
adc #$20
bcc L3975 branch if more vcb's to check
bcs L39D4 otherwise go look for unlogged volumes.
L3987 sta namcnt save length of vol name to be compared.
L398A cmp pathbuf,y is it the same as requested vol name?
bne L397C branch if not
inx
iny next character
lda vcbbuf,x
dec namcnt last character?
bpl L398A if not.
plx restore pointer to matching vcb.
stx vcbptr save it for future reference.
lda vcbbuf+16,x get it's device #
sta devnum and save it.
stz bloknml+1 assume prefix is not used and
lda #$02 that root directory is to be used.
sta bloknml
lda vnptr = 0 if no prefix.
L39AC tay if prefix then find ptr to prefixed
sta namptr dir name. save path ptr.
beq L39C2 branch if no prefix.
sec
adc pathbuf,y inc to next dir in prefix path.
bcc L39AC branch if another dir in prefix.
lda p_blok volume verification will occur at
sta bloknml subdirectory level.
lda p_blok+1
sta bloknml+1
* verify volume name
L39C2 jsr rdgbuf read in directory (or prefix dir)
bcs L39CC if error then look on other devices.
jsr cmppnam compare dir name with path name.
bcc L39F0 if they match, stop looking.
L39CC ldx vcbptr check if current (matched) vcb is active
lda vcbbuf+17,x i.e. does it have open files?
bmi L39ED report not found if active.
L39D4 lda vnptr make path ptr same as volume ptr
sta namptr
jsr mvdevnums copy all device #'s to be examined.
lda devnum log current device 1st before searching
bne L39F1 others.
L39E2 ldx GP.numdevs scan look list for devices we need
L39E5 lda loklst,x to search for the requested volume.
bne L39F4 branch if we've a device to look at.
dex
bpl L39E5 look at next one.
L39ED lda #MLI.E.VNOTFND no mounted volume
sec error
L39F0 rts
L39F1 ldx GP.numdevs now remove the device from the list
L39F4 cmp loklst,x of prospective devices.
beq L39FE branch if match.
dex look until found.
bpl L39F4 always taken (usually) unless
bmi L39ED if dev was removed from devlst (/RAM).
L39FE sta devnum preserve device to be checked next.
stz loklst,x mark this one as tested.
jsr fnddvcb find vcb that claims this dev (if any).
bcs L3A29 branch if vcb full.
ldx vcbptr did fndvcb find it or return free vcb?
lda vcbbuf,x
beq L3A16 if free vcb.
lda vcbbuf+17,x is this volume active?
bmi L39E2 if so, no need to re-log.
L3A16 lda #$02 go read root dir into gbuf
ldx #$00
jsr rdblk
bcs L39E2 ignore if unable to read.
jsr logvcb go log in volume name.
bcs L39E2 look at next if non-xdos disk mounted.
jsr cmppnam is this the volume ?
bcs L39E2 if not
L3A29 rts
mvdevnums ldx GP.numdevs copy all dev #'s to be checked.
L3A2D lda devlist,x active device list.
and #$F0 strip device type info.
sta loklst,x copy them to a temp workspace
dex
bpl L3A2D
ldx GP.numdevs
rts
fnddvcb lda #$00 look for vcb with this device#
ldy #$FF
L3A40 tax new index to next vcb
lda vcbbuf+16,x check all devnums
cmp devnum is this the vcb?
bne L3A4E if not
stx vcbptr
clc indicates found
rts
L3A4E lda vcbbuf,x is this a free vcb?
bne L3A57 if not
iny
stx vcbptr
L3A57 txa
clc inc index to next vcb
adc #$20
bne L3A40
tya any free vcb's available?
bpl L3A79 yes
lda #$00 look for an entry to kick out
L3A62 tax
lda vcbbuf+17,x any open files?
bpl L3A70 no, kick this one out.
txa next vcb
clc
adc #$20 (vcb entry size)
bne L3A62
beq L3A7A all vcb entries have open files
L3A70 stx vcbptr save entry index.
stz vcbbuf,x free this entry
stz vcbbuf+16,x
L3A79 clc no error.
L3A7A lda #$55 # vcb full error
rts
cmppnam ldx #$00 index to directory name.
ldy namptr index to pathname.
lda gbuf+4 get dir name length and type.
cmp #$E0 is it a directory?
bcc L3A90 if not.
and #$0F isolate name length and
sta namcnt save as a counter.
bne L3A95 branch if valid length.
L3A90 sec indicate not found
rts
L3A92 lda gbuf+4,x next char
L3A95 cmp pathbuf,y
bne L3A90 if not the same.
inx check next char
iny
dec namcnt
bpl L3A92 if more to compare.
clc match found
rts
logvcb ldx vcbptr previously logged in volume?
lda vcbbuf,x (acc = 0?)
beq logvcb1 no, go prepare vcb.
jsr cmpvcb does vcb match vol read?
bcc L3B05 yes, do not disturb.
logvcb1 ldy #$1F zero out vcb entry
L3AB2 stz vcbbuf,x
inx
dey
bpl L3AB2
jsr tstsos make sure it's an xdos disk
bcs L3B05 if not, return carry set.
jsr tstdupvol does a duplicate with open files
bcs L3B04 already exist? branch if yes.
lda gbuf+4 move volume name to vcb.
and #$0F strip root marker
tay
pha
ora vcbptr
tax
L3ACE lda gbuf+4,y
sta vcbbuf,x
dex
dey
bne L3ACE
pla get length again
sta vcbbuf,x and save.
lda devnum last device used.
sta vcbbuf+16,x save device # and
lda gbuf+41 total # of blocks on this unit.
sta vcbbuf+18,x
lda gbuf+42
sta vcbbuf+19,x
lda bloknml save address of root directory.
sta vcbbuf+22,x
lda bloknml+1
sta vcbbuf+23,x
lda gbuf+39 save address of the 1st bitmap.
sta vcbbuf+26,x
lda gbuf+40
sta vcbbuf+27,x
L3B04 clc indicate logged if possible
L3B05 rts
cmpvcb lda gbuf+4 with name in directory.
and #$0F
cmp vcbbuf,x are they the same length?
stx xvcbptr (see rev note #23)
bne L3B1E if not the same.
tay
ora xvcbptr
tax
L3B18 lda gbuf+4,y
cmp vcbbuf,x
L3B1E sec anticipate different names.
bne L3B26 if not the same.
dex
dey
bne L3B18
clc indicate match.
L3B26 ldx xvcbptr offset to start of vcb (rev note #23)
rts
tstdupvol lda #$00 check for other logged in volumes with the same name.
L3B2C tax
jsr cmpvcb
bcs L3B41 if no match.
lda vcbbuf+17,x test for any open files.
bmi L3B4B cannot look at this volume.
lda #$00 take duplicate offline if no open files
sta vcbbuf,x
sta vcbbuf+16,x
beq L3B49 ok to log in new volume.
L3B41 txa index to next vcb
clc
and #$E0 strip odd stuff.
adc #$20 inc to next entry.
bcc L3B2C branch if more to check
L3B49 clc
rts
L3B4B sta duplflag duplicate has been found.
stx vcbentry save pointer to conflicting vcb.
sec error.
rts
tstfrblk ldx vcbptr test if enough free blocks available for request.
lda vcbbuf+21,x check if proper count for this volume.
ora vcbbuf+20,x
bne L3BAD branch if count is non-zero.
tkfrecnt jsr cntbms get # of bitmaps
sta bmcnt and save.
stz scrtch start count at 0
stz scrtch+1
lda #$FF mark 'first free' temp as unknown
sta nofree
jsr upbmap update volume bitmap.
bcs L3BC1 if error.
ldx vcbptr get address of 1st bitmap
lda vcbbuf+26,x
sta bloknml
lda vcbbuf+27,x
sta bloknml+1
L3B81 jsr rdgbuf use general buffer for temp space to
bcs L3BC1 count free blocks (bits).
jsr count
dec bmcnt was that the last bitmap?
bmi L3B96 if so, go change fcb so not done again.
inc bloknml
bne L3B81
inc bloknml+1
bra L3B81
L3B96 ldx vcbptr mark which block had 1st free space
lda nofree
bmi L3BBE if no free space was found.
sta vcbbuf+28,x update the free count.
lda scrtch+1
sta vcbbuf+21,x update volume control byte.
lda scrtch
sta vcbbuf+20,x
L3BAD lda vcbbuf+20,x compare total available free blocks
sec on this volume.
sbc reql
lda vcbbuf+21,x
sbc reqh
bcc L3BBE
clc
rts
L3BBE lda #MLI.E.VOLFULL
sec
L3BC1 rts
count ldy #$00
L3BC4 lda gbuf,y bit pattern.
beq L3BCC don't count
jsr cntfree
L3BCC lda gbuf+$100,y do both pages with same loop
beq L3BD4
jsr cntfree
L3BD4 iny
bne L3BC4 loop until all 512 bytes counted.
bit nofree has 1st block w/free space been found?
bpl L3BEE if yes.
lda scrtch test to see if any blocks were counted
ora scrtch+1
beq L3BEE branch if none counted.
jsr cntbms get total # of maps.
sec subtract countdown from total bitmaps
sbc bmcnt
sta nofree
L3BEE rts
cntfree asl count the # of bits in this byte
bcc L3BFA
inc scrtch
bne L3BFA
inc scrtch+1
L3BFA ora #$00
bne cntfree loop until all bits counted
rts
cntbms ldx vcbptr
ldy vcbbuf+19,x return the # of bitmaps
lda vcbbuf+18,x possible with the total count
bne L3C0B found in the vcb.
dey adj for bitmap block boundary
L3C0B tya
lsr divide by 16. the result is
lsr the # of bitmaps.
lsr
lsr
rts
MAN
SAVE USR/SRC/PRODOS.FX/PRODOS.S.XDOS.B
LOAD USR/SRC/PRODOS.FX/PRODOS.S
ASM