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A listing says what is left of the disk, and what will fit

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dir said what was there and nothing about what was left. SplitDisk has
printed the free figure since it was written, so the machine's own
listing was the poorer of the two implementations at describing the same
disk.

  43 files, 3 directories
  46 of 64 entries, 1893 blocks free

Entries first, because they are the ceiling nobody notices until they hit
it: a disk of small files runs out of directory slots long before it runs
out of blocks.

COUNTED RATHER THAN ASKED. The superblock keeps a free count and this
file calls it "a note rather than the truth" in three places. sbfsSpace
reads the whole directory table instead, which costs a read per directory
block and is the answer rather than a guess. SplitDisk goes on reading
the note and saying when it is stale, which is the right place for that
check - the host tool is what you audit a disk with.

---- And it is a fact about the disk, not about where you are ----

The first version added the blocks up as the LISTING walked past them,
which cost no extra read and was wrong: that walk stops only on entries
in the working directory, so the same disk came out as 1,996 blocks free
from the root and 2,025 from /Apps. Comparing against SplitDisk is what
said so, which is what having two implementations is for.

---- The longest run, which is what decides whether a file fits ----

  4 of 16 entries, 37 blocks free
  the longest run is 25

Files are laid down contiguously, so the free total does not say whether
a file will fit. Both implementations learn it, from one specification.

Said only when it differs from the free total. Deleting is what fragments
a contiguous store, and a disk that has only been appended to has one gap
at the end - so on a healthy disk this is silent, and a line that appears
only when something is wrong is a line somebody reads.

There is no sort on this machine and the entries are in no order, so a
candidate walks the disk: each pass finds the used extent nearest at or
after it, and anything the candidate stands inside pushes it to the far
end and starts the pass again. The same trick allocating uses. So it
costs a pass per gap rather than per file - nearly nothing on a disk with
one gap, more the more fragmented the disk is, which is the right way
round.

holes.img is six files with the second and fourth deleted, because no
other disk here can show any of this: none of them has ever had anything
deleted from it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
This commit is contained in:
Anachronaut
2026-09-06 18:19:04 -04:00
co-authored by Claude Opus 5
parent 2ad8edf9bc
commit 323d7a0330
32 changed files with 649 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files
Tests/expected/cfgFallback.out
+1
View File
@@ -15,6 +15,7 @@ made
> cd Notes
/Notes> dir
0 files
8 of 32 entries, 308 blocks free
/Notes> exit
halted
Execution halted.
Tests/expected/cosmos.out
+1
View File
@@ -29,6 +29,7 @@ across.txt 700
empty.txt 0
aName22CharactersLong! 22
12 files
12 of 16 entries, 48 blocks free
>
> frobnicate
I do not know: frobnicate
Tests/expected/cosmosBuild.out
+5
View File
@@ -1,6 +1,7 @@
CosmOS
> dir
0 files
0 of 16 entries, 125 blocks free
> mkdir Apps
made
> mkdir Apps/Deep
@@ -11,10 +12,12 @@ made
Apps <dir>
Notes <dir>
0 files, 2 directories
3 of 16 entries, 125 blocks free
> cd Apps
/Apps> dir
Deep <dir>
0 files, 1 directory
3 of 16 entries, 125 blocks free
/Apps> mkdir Deep
cannot make that: check the path, the name, and whether it is taken
/Apps> mkdir /Notes/Deep
@@ -23,6 +26,7 @@ made
/Notes> dir
Deep <dir>
0 files, 1 directory
4 of 16 entries, 125 blocks free
/Notes> rmdir /Apps
cannot remove that: it must be a directory, and empty
/Notes> rmdir /Apps/Deep
@@ -44,6 +48,7 @@ removed
removed
> dir
0 files
0 of 16 entries, 125 blocks free
> exit
halted
Execution halted.
Tests/expected/cosmosClaim.out
+1
View File
@@ -7,6 +7,7 @@ finished
Claim.sbx 580
claim.dat 266
2 files
2 of 16 entries, 56 blocks free
> exit
halted
Execution halted.
Tests/expected/cosmosCrossDisk.out
+1
View File
@@ -51,6 +51,7 @@ pass.script 20
holds.script 87
crossed.txt 560
36 files, 2 directories
47 of 64 entries, 1890 blocks free
> exit
halted
Execution halted.
Tests/expected/cosmosCwd.out
+4
View File
@@ -4,11 +4,13 @@ Apps <dir>
A <dir>
B <dir>
0 files, 3 directories
9 of 32 entries, 240 blocks free
> cd /A
/A> dir
Say.sbx 53
notes.txt 25
2 files
9 of 32 entries, 240 blocks free
/A> Type notes.txt
these are the notes in A
finished
@@ -29,6 +31,7 @@ Apps <dir>
A <dir>
B <dir>
0 files, 3 directories
9 of 32 entries, 240 blocks free
> cd /B
/B> Type ../A/notes.txt
these are the notes in A
@@ -50,6 +53,7 @@ Apps <dir>
A <dir>
B <dir>
0 files, 3 directories
9 of 32 entries, 240 blocks free
> exit
halted
Execution halted.
Tests/expected/cosmosDrives.out
+2
View File
@@ -40,6 +40,7 @@ args.script 64
pass.script 20
holds.script 87
35 files, 2 directories
46 of 64 entries, 1893 blocks free
> drive 1
> dir
other.txt 28
@@ -47,6 +48,7 @@ notes <dir>
2things <dir>
twoblocks.txt 560
2 files, 2 directories
4 of 32 entries, 503 blocks free
> cd /notes
/notes> drive 0
> drive 1
Tests/expected/cosmosFault.out
+1
View File
@@ -57,6 +57,7 @@ args.script 64
pass.script 20
holds.script 87
35 files, 2 directories
46 of 64 entries, 1893 blocks free
> exit
halted
Execution halted.
Tests/expected/cosmosFiles.out
+4
View File
@@ -3,17 +3,21 @@ CosmOS
one.txt 13
two.txt 14
2 files
2 of 8 entries, 28 blocks free
> rename one.txt first.txt
renamed
> dir
first.txt 13
two.txt 14
2 files
2 of 8 entries, 28 blocks free
> delete first.txt
gone
> dir
two.txt 14
1 file
1 of 8 entries, 29 blocks free
the longest run is 28
> delete first.txt
no such file
> rename two.txt
Tests/expected/cosmosFlip.out
+1
View File
@@ -47,6 +47,7 @@ args.script 64
pass.script 20
holds.script 87
35 files, 2 directories
46 of 64 entries, 1893 blocks free
> exit
halted
Execution halted.
Tests/expected/cosmosGrid.out
+1
View File
@@ -47,6 +47,7 @@ args.script 64
pass.script 20
holds.script 87
35 files, 2 directories
46 of 64 entries, 1893 blocks free
> exit
halted
Execution halted.
Tests/expected/cosmosInvoke.out
+1
View File
@@ -17,6 +17,7 @@ notes.sbx 21
hello.sh 38
Apps <dir>
6 files, 1 directory
8 of 16 entries, 54 blocks free
> Greet a program with no extension
it says: a program with no extension
finished
Tests/expected/cosmosMonitor.out
+1
View File
@@ -133,6 +133,7 @@ args.script 64
pass.script 20
holds.script 87
35 files, 2 directories
46 of 64 entries, 1893 blocks free
> exit
halted
Execution halted.
Tests/expected/cosmosMonitorRun.out
+1
View File
@@ -52,6 +52,7 @@ args.script 64
pass.script 20
holds.script 87
35 files, 2 directories
46 of 64 entries, 1893 blocks free
> exit
halted
Execution halted.
Tests/expected/cosmosRamDisk.out
+2
View File
@@ -2,12 +2,14 @@ CosmOS
> drive 1
> dir
0 files
0 of 128 entries, 2031 blocks free
> Copy 0:/Say.sbx 1:/Say.sbx
copied
finished
> dir
Say.sbx 156
1 file
1 of 128 entries, 2030 blocks free
> drive
1
> exit
Tests/expected/cosmosRun.out
+1
View File
@@ -40,6 +40,7 @@ args.script 64
pass.script 20
holds.script 87
35 files, 2 directories
46 of 64 entries, 1893 blocks free
> load
load what?
> load nosuch.sbx
Tests/expected/cosmosSlowDisk.out
+1
View File
@@ -38,6 +38,7 @@ args.script 64
pass.script 20
holds.script 87
35 files, 2 directories
46 of 64 entries, 1893 blocks free
> load Say.sbx
loaded, starting at 5000
> run the disk took its time
Tests/expected/cosmosSpace.out
+55
View File
@@ -0,0 +1,55 @@
CosmOS
> dir
greet.sbx 211
hello.sbx 53
Life.sbx 1396
Snake.sbx 2164
Keys.sbx 664
Say.sbx 156
Where.sbx 827
Break.sbx 149
Grid.sbx 571
Press.sbx 872
Mode.sbx 48
Flip.sbx 173
Sprite.sbx 442
Depth.sbx 672
Packages <dir>
Pad.sbx 264
Crash.sbx 632
vars.script 50
blocks.script 343
loops.script 272
tune.sbx 318
Play.sbx 2526
notes.txt 21
Apps <dir>
hi.script 121
bad.script 45
plain.script 24
cross.script 280
nonl.script 38
outer.script 376
inner.script 44
loop.script 35
hush.script 42
aloud.script 59
args.script 64
pass.script 20
holds.script 87
35 files, 2 directories
46 of 64 entries, 1893 blocks free
> drive 1
> dir
f1.txt 1500
f3.txt 1500
f5.txt 1500
f6.txt 1500
4 files
4 of 16 entries, 37 blocks free
the longest run is 25
> drive 0
> exit
halted
Execution halted.
[exit 0]
Tests/expected/cosmosSprite.out
+1
View File
@@ -47,6 +47,7 @@ args.script 64
pass.script 20
holds.script 87
35 files, 2 directories
46 of 64 entries, 1893 blocks free
> exit
halted
Execution halted.
Tests/expected/cosmosTree.out
+3
View File
@@ -3,6 +3,7 @@ CosmOS
Apps <dir>
rooted.txt 21
1 file, 1 directory
5 of 32 entries, 248 blocks free
> load /Apps/Say.sbx
loaded, starting at 5000
> run the shallow one
@@ -43,6 +44,8 @@ gone
Apps <dir>
rooted.txt 21
1 file, 1 directory
4 of 32 entries, 249 blocks free
the longest run is 248
> exit
halted
Execution halted.
Tests/expected/cosmosTreeWrite.out
+2
View File
@@ -3,6 +3,7 @@ CosmOS
Folder <dir>
Edit.sbx 2243
1 file, 1 directory
3 of 16 entries, 244 blocks free
> load Edit.sbx
loaded, starting at 5000
> run note.txt
@@ -20,6 +21,7 @@ Folder <dir>
Edit.sbx 2243
note.txt 67
2 files, 1 directory
4 of 16 entries, 243 blocks free
> exit
halted
Execution halted.
Tests/expected/onceAsked.out
+1
View File
@@ -6,6 +6,7 @@ finished
System <dir>
Apps <dir>
0 files, 2 directories
8 of 32 entries, 305 blocks free
> exit
halted
Execution halted.
Tests/expected/romBoot.out
+1
View File
@@ -13,6 +13,7 @@ made
> cd Notes
/Notes> dir
0 files
7 of 32 entries, 309 blocks free
/Notes> exit
halted
Execution halted.
Tests/expected/selfBoot.out
+1
View File
@@ -13,6 +13,7 @@ made
> cd Notes
/Notes> dir
0 files
7 of 32 entries, 309 blocks free
/Notes> exit
halted
Execution halted.
Tests/input/cosmosSpace.in
+5
View File
@@ -0,0 +1,5 @@
dir
drive 1
dir
drive 0
exit
Tests/makedisks.sh
+20
View File
@@ -230,6 +230,26 @@ printf '#! script\nfor a in 1 2\n for b in x y\n echo $a$b\n end\nend\nset
printf 'this is not a program' > notes.txt
"$TOOL" put "$DISKS/cosmos.img" notes.txt >/dev/null
# ---- A disk with holes in it ----
#
# Six files laid down one after another, then the second and the fourth taken away. Files are
# laid down CONTIGUOUSLY on this format, so what is left is thirty seven free blocks in three
# pieces - two of six between the survivors and twenty five at the end - and the largest file
# that will fit is twenty five blocks, not thirty seven.
#
# That gap between "how much is free" and "how much will fit" is the whole reason a listing
# says the longest run, and it is invisible on every other disk here: a disk that has only
# been appended to has one gap, at the end, and the two numbers are the same. Deleting is what
# fragments a contiguous store, so a disk that has never had anything deleted from it cannot
# demonstrate any of this.
"$TOOL" format "$DISKS/holes.img" 64 2 >/dev/null
python3 -c "open('holey.txt','w').write('x' * 1500)"
for i in 1 2 3 4 5 6; do
"$TOOL" put "$DISKS/holes.img" holey.txt "f$i.txt" >/dev/null
done
"$TOOL" delete "$DISKS/holes.img" f2.txt >/dev/null
"$TOOL" delete "$DISKS/holes.img" f4.txt >/dev/null
# ---- A second disk, for the second drive ----
#
# Deliberately nothing like the first: its own file and its own directory, so that a test
Tests/manifest
+18
View File
@@ -1033,6 +1033,24 @@ cosmosWhere | CosmOS/Source/cosmos.asm | run | cosmosWhe
# a name twice. Then the same walk in /Apps, because a walk that only ever ran at the root
# would not have proved it walks where you are.
cosmosWalk | CosmOS/Source/cosmos.asm | run | cosmosWalk.in | 200000000 | disks/cosmos.img
# ---- What a listing says about the disk it is listing ----
#
# dir said what was there and nothing about what was left. SplitDisk has printed the free
# figure since it was written, so the machine's own listing was the poorer of the two
# implementations at describing the same disk.
#
# COUNTED RATHER THAN ASKED. The superblock keeps a free count and sbfs.asm calls it "a note
# rather than the truth" in three places; this reads the whole directory table instead. The
# first version added the blocks up as the LISTING walked past them, which cost nothing extra
# and was wrong - that walk stops only on entries in the working directory, so the same disk
# came out as 1,996 blocks free from the root and 2,025 from /Apps. Listing both directories
# here is what would say so again.
#
# And then a disk with holes in it, which is the case the longest run exists for: thirty seven
# blocks free in three pieces, so the largest file that will fit is twenty five. Said only
# when it differs from the free total, so the first listing is silent about it and the second
# is not - a line that appears only when something is wrong is a line somebody reads.
cosmosSpace | CosmOS/Source/cosmos.asm | run | cosmosSpace.in | 200000000 | disks/cosmos.img+disks/holes.img
# ---- Starting itself ----
#
# /System/Boot/startup.sh runs before anybody can type. This one is also the check on #quiet