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Add 2015/mills2/try.sh, update bugs, formatting

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The bugs.md has a INABIAF section for 2015/mills2.

The README.md file has been format and typo checked.
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Cody Boone Ferguson committed 2023-12-06 12:01:56 -08:00
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2015/mills2/README.md
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@@ -5,6 +5,17 @@ make
```
### Bugs and (Mis)features:
The current status of this entry is:
```
STATUS: INABIAF - please **DO NOT** fix
```
For more detailed information see [2015 mills2 in bugs.md](/bugs.md#2015-mills2).
## To use:
```sh
@@ -15,16 +26,7 @@ make
### Try:
```sh
printf '000I\236\f\31H\260\240\301\203' > ioccc.Z
./prog ioccc.Z
dd bs=1k count=4096 < /dev/urandom > test1
compress < test1 > test1.Z
time ./prog test1.Z | cmp - test1
dd bs=1k count=4096 < /dev/zero > test2
compress < test2 > test2.Z
time ./prog test2.Z | cmp - test2
./try.sh
```
@@ -32,11 +34,15 @@ time ./prog test2.Z | cmp - test2
Without ASCII art, the source code of this entry would have been exactly 256
bytes. Compared to [1990/jaw](http://ioccc.org/years.html#1990_jaw), it is very
impressive, even taking into account the missing atob functionality. Now we wish
for a compress(1)-like compressor using a similar idea.
impressive, even taking into account the missing `atob` functionality. Now we wish
for a `compress(1)`-like compressor using a similar idea.
Why is the sad smiley on line 12 in that particular place?
```c
c=0) :( O
```
## Author's remarks:
@@ -46,16 +52,17 @@ This program is an implementation of the unix `zcat(1)` command for printing
compressed files that have been created by the `compress(1)` command.
The adaptive [LZW](https://en.wikipedia.org/wiki/Lempel–Ziv–Welch) compression
employed by `compress` usually requires a fairly large amount of memory to
build the decompression tables (in fact, `compress` has a command-line option
to control the size of the decompression tables, since some of the early
systems to which it was ported (*cough*MS-DOS*cough*) did not have enough
memory to use the full 16-bit codes). This version has no large static or
dynamic tables. It is able to decompress 16-bit files using a single function
and a few ints.
employed by `compress(1)` usually requires a fairly large amount of memory to
build the decompression tables (in fact, `compress(1)` has a command-line option
to control the size of the decompression tables, since some of the early systems
to which it was ported
(\*cough\*[MS-DOS](https://computerhistory.org/blog/microsoft-ms-dos-early-source-code/?key=microsoft-ms-dos-early-source-code)\*cough\*)
did not have enough memory to use the full 16-bit codes). This version has no
large static or dynamic tables. It is able to decompress 16-bit files using a
single function and a few `int`s.
To run the program, take an existing compressed file and pass it to the program
on the command line. On the odd chance you don't have `compress` hanging about
on the command line. On the odd chance you don't have `compress(1)` hanging about
on your system, I've provided compressed copies of this year's IOCCC rules
and guidelines files. To print them, just do
@@ -83,11 +90,11 @@ complicated by several issues:
* Codes are at bit offsets within the stream, and must be extracted.
* As codes are added to the dictionary, the code word size grows, so finding
the offset to a particular code word is involved.
* The `compress` encoder reserves a code word that clears the coding tables.
* The `compress(1)` encoder reserves a code word that clears the coding tables.
When this is encountered, the computation of offsets and bit sizes reset.
* The `compress` decoder is designed to always read a block of eight code
words at the same time, so that it need only read N bytes to get eight N-bit
code words. When the "clear" code is encountered, the entire eight-word
* The `compress(1)` decoder is designed to always read a block of eight code
words at the same time, so that it need only read `N` bytes to get eight
`N-bit` code words. When the "clear" code is encountered, the entire eight-word
block is flushed (since the decoder didn't know the word size would change).
The program needs to account for this extra flushing.
* The end of the stream is not explicitly marked; the encoder just pads out
@@ -106,9 +113,9 @@ compressed data, it's likely to crash in an interesting manner.
In particular, it doesn't look at the third byte of the header, which encodes
the maximum code word size and whether "block mode" was used when the encoder
was run. If you use `compress` in its default mode, the maximum word size
was run. If you use `compress(1)` in its default mode, the maximum word size
will be 16 bits and "block mode" will be enabled. You are unlikely to find
any files that don't use "block mode", since all versions of `compress` after
any files that don't use "block mode", since all versions of `compress(1)` after
2.0 (circa 1984) use it by default and have no documented way to disable it.
Reducing the bit depth is still possibly by using the `-b` flag. Modern
systems have no problem with the 200 KB or so needed for 16-bit decoder
@@ -121,10 +128,11 @@ In the event that you don't supply an argument, or that argument doesn't name
a readable file, the program will just silently exit. This is a feature.
The program depends on having a little-endian system. On a big-endian system
you will get a weird big-endian version of `compress`, which might have come to
pass in an alternate universe where the vax on which `compress` was authored
had been big-endian. Luckily for us, it wasn't, and neither are most of the
systems you might want to compile this for.
you will get a weird big-endian version of `compress(1)`, which might have come
to pass in an alternate universe where the
[VAX](https://en.wikipedia.org/wiki/VAX) on which `compress(1)` was authored had
been big-endian. Luckily for us, it wasn't, and neither are most of the systems
you might want to compile this for.
## Copyright and CC BY-SA 4.0 License:
2015/mills2/try.sh
Executable
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@@ -0,0 +1,61 @@
#!/usr/bin/env bash
#
# try.sh - demonstrate IOCCC winner 2015/mills2
#
# make sure CC is set so that when we do make CC="$CC" it isn't empty. Doing it
# this way allows us to have the user specify a different compiler in an easy
# way.
if [[ -z "$CC" ]]; then
CC="cc"
fi
make CC="$CC" all >/dev/null || exit 1
# clear screen after compilation so that only the entry is shown
clear
echo "$ printf '000I\236\f\31H\260\240\301\203' > ioccc.Z" 1>&2
printf '000I\236\f\31H\260\240\301\203' > ioccc.Z
echo 1>&2
echo "$ ./prog ioccc.Z" 1>&2
./prog ioccc.Z
echo 1>&2
echo "$ dd bs=512 count=128 < /dev/urandom > test1" 1>&2
dd bs=512 count=128 < /dev/urandom > test1
echo 1>&2
echo "$ compress < test1 > test1.Z" 1>&2
compress < test1 > test1.Z
echo 1>&2
echo "$ time ./prog test1.Z | cmp - test1" 1>&2
time ./prog test1.Z | cmp - test1
echo 1>&2
echo "$ dd bs=512 count=128 < /dev/zero > test2" 1>&2
dd bs=512 count=128 < /dev/zero > test2
echo 1>&2
echo "$ compress < test2 > test2.Z" 1>&2
compress < test2 > test2.Z
echo 1>&2
echo "$ time ./prog test2.Z | cmp - test2" 1>&2
time ./prog test2.Z | cmp - test2
echo 1>&2
echo "$ ./prog ioccc_guidelines.txt.Z" 1>&2
read -r -n 1 -p "Press any key to continue (space = next page, q = quit): "
echo 1>&2
./prog ioccc_guidelines.txt.Z | less -EXF
echo 1>&2
echo "$ ./prog ioccc_rules.txt.Z" 1>&2
read -r -n 1 -p "Press any key to continue (space = next page, q = quit): "
echo 1>&2
./prog ioccc_rules.txt.Z | less -EXF