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Author SHA1 Message Date
AnachronautandClaude Opus 5 a13bbeb4db ls, a listing laid out to be read
> ls
  Copy.sbx   Say.sbx    Where.sbx  Walk.sbx   ls.sbx     Lander     where.sh

dir says what is there one line each, with sizes and a tally of the disk.
This says the names in columns and nothing else, which is what you want
ninety times in a hundred. Two programs rather than one with a switch,
because they answer different questions and neither answer is a worse
version of the other.

AND THIS IS A PROGRAM WHERE DIR IS BUILT IN, which is the difference that
matters when the disk is what you are doubting: dir is already in memory
and this has to be loaded off the disk it is about to list. The daily
driver and the diagnostic.

Two passes over the directory and no buffer at all. Columns need the
longest name before the first line can be printed, which usually means
holding every name - twenty four bytes each against a format that allows
1,024 entries. Walking twice costs a read of each directory block, into a
buffer that is already there.

Across and not down. Real listings go down the columns so that names next
to each other alphabetically are next to each other on the screen, and
that reason depends on sorting - which nothing here does. With the order
arbitrary, down-and-across buys nothing and costs a division.

Directories in blue and wearing a separator, unfinished saves in red,
everything else plain: whether a file is runnable cannot be known without
opening it, and opening every file in a directory to colour a listing is
a price nobody agreed to pay. The colour reaches a terminal as well as
the screen, so it is one mechanism and not two.

---- Three bugs, and one of them is this machine's oldest trap ----

nameLength answered in A, and a RET puts A back the way the caller had
it. So it answered with nothing, and every gap between the columns came
out the same width because the padding was subtracting whatever A
happened to hold. Q is the ALU's output and nothing puts it back, which
is why every answer here comes home in it.

The padding subtracted the other way round - the name from the cell -
which borrowed on every name that was not the longest, so all of them
took the "wider than its cell" path and the listing came out separated by
one space.

And padding after a name left trailing spaces on every line that did not
fill its last column. It goes before the next name now, so spaces only
ever fall between two things and a line ends on a name.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
2026-09-06 19:29:02 -04:00
AnachronautandClaude Opus 5 323d7a0330 A listing says what is left of the disk, and what will fit
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
2026-09-06 18:19:04 -04:00