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comparison level2/cmds/mfree.asm @ 3194:2ecebda8716b

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mfree.asm: Fix zero-day Block Map entry bug Previously, code assumed that the final entry in the block map would be used. This was true for CoCo but is not necessarily true (and is not true for mc09). Slight mod removes that implicit assumption; the code now works correctly on both platforms.
author Neal Crook <foofoobedoo@gmail.com>
date Tue, 30 May 2017 23:59:46 +0100
parents 489617e567c5
children
comparison
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3193:489617e567c5 3194:2ecebda8716b
6 * Edt/Rev YYYY/MM/DD Modified by 6 * Edt/Rev YYYY/MM/DD Modified by
7 * Comment 7 * Comment
8 * ------------------------------------------------------------------ 8 * ------------------------------------------------------------------
9 * 2 ????/??/?? 9 * 2 ????/??/??
10 * Original Tandy/Microware version. 10 * Original Tandy/Microware version.
11 * 3 2017/05/30 Neal Crook
12 * Original version misbehaved if final block in the map was free.
13 * That situation never occurs on coco, but it does occur on the mc09
14 * target. Inferred behaviour and added comments as a side-effect of
15 * debugging effort.
11 16
12 nam Mfree 17 nam Mfree
13 ttl Show free memory 18 ttl Show free memory
14 19
15 * Disassembled 98/09/11 12:07:32 by Disasm v1.6 (C) 1988 by RML 20 * Disassembled 98/09/11 12:07:32 by Disasm v1.6 (C) 1988 by RML
19 endc 24 endc
20 25
21 tylg set Prgrm+Objct 26 tylg set Prgrm+Objct
22 atrv set ReEnt+rev 27 atrv set ReEnt+rev
23 rev set $00 28 rev set $00
24 edition set 2 29 edition set 3
25 30
26 mod eom,name,tylg,atrv,start,size 31 mod eom,name,tylg,atrv,start,size
27 32
28 freeblks rmb 2 33 freeblks rmb 2
29 mapsiz rmb 2 34 mapsiz rmb 2
76 loop ldu #$0000 number of free blocks in this sequence 81 loop ldu #$0000 number of free blocks in this sequence
77 L00AD tst ,x+ is this block 0? 82 L00AD tst ,x+ is this block 0?
78 beq L00BA yes - found a free block 83 beq L00BA yes - found a free block
79 leay $01,y total number of blocks we have inspected 84 leay $01,y total number of blocks we have inspected
80 cmpy <mapsiz at the end of the map? 85 cmpy <mapsiz at the end of the map?
81 bcs L00AD no, so carry on looking 86 bne L00AD no, so carry on looking
82 bra alldone yes, and the last block was not free, so we're done. 87 bra alldone yes, and the last block was not free, so we're done.
83 88
84 * Block number in Y is the first free block of a sequence (tho maybe a sequence of 1) 89 * Block number in Y is the first free block of a sequence (tho maybe a sequence of 1)
85 L00BA tfr y,d 90 L00BA tfr y,d
86 bsr buf4hex append start block, in hex, to output buffer 91 bsr buf4hex append start block, in hex, to output buffer
98 103
99 * Look for the last free block in this sequence 104 * Look for the last free block in this sequence
100 L00D2 leau $01,u 105 L00D2 leau $01,u
101 leay $01,y 106 leay $01,y
102 cmpy <mapsiz 107 cmpy <mapsiz
103 beq alldone ??should never exit at this point, but 108 beq last
104 * on mc09 we do - terminate part-way through an entry. 109
105 tst ,x+ 110 tst ,x+
106 beq L00D2 haven't found it yet.. 111 beq L00D2 haven't found it yet..
107 last lda <ppblk 112 last lda <ppblk
108 pshs y,a 113 pshs y,a
109 clra 114 clra
116 std <u0006 2 MS bytes of block end address 121 std <u0006 2 MS bytes of block end address
117 lda #$FF 122 lda #$FF
118 sta <u0008 1 LS byte of block end address is $FF 123 sta <u0008 1 LS byte of block end address is $FF
119 bsr buf6hex append block end address in hex, to output buffer 124 bsr buf6hex append block end address in hex, to output buffer
120 leax -$01,x 125 leax -$01,x
121 tfr u,d 126 tfr u,d number of blocks in this sequence u->d
122 bsr buf4hex append number of blocks, in hex, to output buffer 127 bsr buf4hex append number of blocks, in hex, to output buffer
123 lbsr L0199 append size, in decimal, to output buffer 128 lbsr L0199 append size, in decimal, to output buffer
124 129
125 addd <freeblks 130 addd <freeblks
126 std <freeblks total number of blocks 131 std <freeblks total number of blocks
127 bsr wrbuf print this entry 132 bsr wrbuf print this entry
128 bra loop loop for next entry 133 cmpy <mapsiz
134 bne loop loop for next entry
129 135
130 * All of the entries have been printed. Print the trailer and totals. 136 * All of the entries have been printed. Print the trailer and totals.
131 * Bug: if the last block is unused, it and any unused blocks before it will
132 * not get reported, *and* the formatting of the last entry will be messed up.
133 * That never happens on the Coco, because the last block is always used.
134 * It does happen on mc09 though.
135 alldone leay >Ftr,pcr 137 alldone leay >Ftr,pcr
136 bsr tobuf 1st line of footer to output buffer 138 bsr tobuf 1st line of footer to output buffer
137 bsr wrbuf ..print it 139 bsr wrbuf ..print it
138 bsr tobuf 2nd line of footer to output buffer 140 bsr tobuf 2nd line of footer to output buffer
139 tfr u,d ..add total #blocks, total memory size 141 ldd <freeblks get total number of blocks
140 addd <freeblks
141 std <freeblks
142 bsr buf4hex append total number of blocks, in hex, to output buffer 142 bsr buf4hex append total number of blocks, in hex, to output buffer
143 bsr L0199 append total size, in decimal, to output buffer 143 bsr L0199 append total size, in decimal, to output buffer
144 bsr wrbuf ..print it 144 bsr wrbuf ..print it
145 * Successful exit 145 * Successful exit
146 clrb 146 clrb