Add 2015/mills2/try.sh, update bugs, formatting
The bugs.md has a INABIAF section for 2015/mills2. The README.md file has been format and typo checked.
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@@ -5,6 +5,17 @@ make
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```
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### Bugs and (Mis)features:
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The current status of this entry is:
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```
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STATUS: INABIAF - please **DO NOT** fix
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```
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For more detailed information see [2015 mills2 in bugs.md](/bugs.md#2015-mills2).
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## To use:
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```sh
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@@ -15,16 +26,7 @@ make
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### Try:
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```sh
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printf '000I\236\f\31H\260\240\301\203' > ioccc.Z
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./prog ioccc.Z
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dd bs=1k count=4096 < /dev/urandom > test1
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compress < test1 > test1.Z
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time ./prog test1.Z | cmp - test1
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dd bs=1k count=4096 < /dev/zero > test2
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compress < test2 > test2.Z
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time ./prog test2.Z | cmp - test2
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./try.sh
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```
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@@ -32,11 +34,15 @@ time ./prog test2.Z | cmp - test2
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Without ASCII art, the source code of this entry would have been exactly 256
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bytes. Compared to [1990/jaw](http://ioccc.org/years.html#1990_jaw), it is very
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impressive, even taking into account the missing atob functionality. Now we wish
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for a compress(1)-like compressor using a similar idea.
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impressive, even taking into account the missing `atob` functionality. Now we wish
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for a `compress(1)`-like compressor using a similar idea.
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Why is the sad smiley on line 12 in that particular place?
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```c
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c=0) :( O
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```
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## Author's remarks:
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@@ -46,16 +52,17 @@ This program is an implementation of the unix `zcat(1)` command for printing
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compressed files that have been created by the `compress(1)` command.
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The adaptive [LZW](https://en.wikipedia.org/wiki/Lempel–Ziv–Welch) compression
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employed by `compress` usually requires a fairly large amount of memory to
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build the decompression tables (in fact, `compress` has a command-line option
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to control the size of the decompression tables, since some of the early
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systems to which it was ported (*cough*MS-DOS*cough*) did not have enough
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memory to use the full 16-bit codes). This version has no large static or
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dynamic tables. It is able to decompress 16-bit files using a single function
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and a few ints.
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employed by `compress(1)` usually requires a fairly large amount of memory to
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build the decompression tables (in fact, `compress(1)` has a command-line option
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to control the size of the decompression tables, since some of the early systems
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to which it was ported
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(\*cough\*[MS-DOS](https://computerhistory.org/blog/microsoft-ms-dos-early-source-code/?key=microsoft-ms-dos-early-source-code)\*cough\*)
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did not have enough memory to use the full 16-bit codes). This version has no
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large static or dynamic tables. It is able to decompress 16-bit files using a
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single function and a few `int`s.
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To run the program, take an existing compressed file and pass it to the program
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on the command line. On the odd chance you don't have `compress` hanging about
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on the command line. On the odd chance you don't have `compress(1)` hanging about
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on your system, I've provided compressed copies of this year's IOCCC rules
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and guidelines files. To print them, just do
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@@ -83,11 +90,11 @@ complicated by several issues:
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* Codes are at bit offsets within the stream, and must be extracted.
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* As codes are added to the dictionary, the code word size grows, so finding
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the offset to a particular code word is involved.
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* The `compress` encoder reserves a code word that clears the coding tables.
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* The `compress(1)` encoder reserves a code word that clears the coding tables.
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When this is encountered, the computation of offsets and bit sizes reset.
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* The `compress` decoder is designed to always read a block of eight code
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words at the same time, so that it need only read N bytes to get eight N-bit
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code words. When the "clear" code is encountered, the entire eight-word
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* The `compress(1)` decoder is designed to always read a block of eight code
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words at the same time, so that it need only read `N` bytes to get eight
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`N-bit` code words. When the "clear" code is encountered, the entire eight-word
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block is flushed (since the decoder didn't know the word size would change).
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The program needs to account for this extra flushing.
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* The end of the stream is not explicitly marked; the encoder just pads out
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@@ -106,9 +113,9 @@ compressed data, it's likely to crash in an interesting manner.
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In particular, it doesn't look at the third byte of the header, which encodes
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the maximum code word size and whether "block mode" was used when the encoder
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was run. If you use `compress` in its default mode, the maximum word size
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was run. If you use `compress(1)` in its default mode, the maximum word size
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will be 16 bits and "block mode" will be enabled. You are unlikely to find
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any files that don't use "block mode", since all versions of `compress` after
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any files that don't use "block mode", since all versions of `compress(1)` after
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2.0 (circa 1984) use it by default and have no documented way to disable it.
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Reducing the bit depth is still possibly by using the `-b` flag. Modern
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systems have no problem with the 200 KB or so needed for 16-bit decoder
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@@ -121,10 +128,11 @@ In the event that you don't supply an argument, or that argument doesn't name
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a readable file, the program will just silently exit. This is a feature.
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The program depends on having a little-endian system. On a big-endian system
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you will get a weird big-endian version of `compress`, which might have come to
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pass in an alternate universe where the vax on which `compress` was authored
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had been big-endian. Luckily for us, it wasn't, and neither are most of the
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systems you might want to compile this for.
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you will get a weird big-endian version of `compress(1)`, which might have come
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to pass in an alternate universe where the
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[VAX](https://en.wikipedia.org/wiki/VAX) on which `compress(1)` was authored had
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been big-endian. Luckily for us, it wasn't, and neither are most of the systems
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you might want to compile this for.
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## Copyright and CC BY-SA 4.0 License:
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Executable
+61
@@ -0,0 +1,61 @@
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#!/usr/bin/env bash
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#
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# try.sh - demonstrate IOCCC winner 2015/mills2
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#
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# make sure CC is set so that when we do make CC="$CC" it isn't empty. Doing it
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# this way allows us to have the user specify a different compiler in an easy
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# way.
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if [[ -z "$CC" ]]; then
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CC="cc"
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fi
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make CC="$CC" all >/dev/null || exit 1
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# clear screen after compilation so that only the entry is shown
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clear
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echo "$ printf '000I\236\f\31H\260\240\301\203' > ioccc.Z" 1>&2
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printf '000I\236\f\31H\260\240\301\203' > ioccc.Z
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echo 1>&2
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echo "$ ./prog ioccc.Z" 1>&2
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./prog ioccc.Z
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echo 1>&2
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echo "$ dd bs=512 count=128 < /dev/urandom > test1" 1>&2
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dd bs=512 count=128 < /dev/urandom > test1
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echo 1>&2
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echo "$ compress < test1 > test1.Z" 1>&2
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compress < test1 > test1.Z
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echo 1>&2
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echo "$ time ./prog test1.Z | cmp - test1" 1>&2
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time ./prog test1.Z | cmp - test1
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echo 1>&2
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echo "$ dd bs=512 count=128 < /dev/zero > test2" 1>&2
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dd bs=512 count=128 < /dev/zero > test2
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echo 1>&2
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echo "$ compress < test2 > test2.Z" 1>&2
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compress < test2 > test2.Z
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echo 1>&2
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echo "$ time ./prog test2.Z | cmp - test2" 1>&2
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time ./prog test2.Z | cmp - test2
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echo 1>&2
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echo "$ ./prog ioccc_guidelines.txt.Z" 1>&2
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read -r -n 1 -p "Press any key to continue (space = next page, q = quit): "
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echo 1>&2
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./prog ioccc_guidelines.txt.Z | less -EXF
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echo 1>&2
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echo "$ ./prog ioccc_rules.txt.Z" 1>&2
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read -r -n 1 -p "Press any key to continue (space = next page, q = quit): "
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echo 1>&2
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./prog ioccc_rules.txt.Z | less -EXF
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@@ -3059,7 +3059,17 @@ If you want to try and fix this (mis)feature, you are welcome to try.
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# 2015
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There are no known bugs and (Mis)features for entries in 2015.
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## 2015 mills2
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### STATUS: INABIAF - please **DO NOT** fix
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### Source code: [2015/mills2/prog.c](2015/mills2/prog.c)
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### Information: [2015/mills2/README.md](2015/mills2/README.md)
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The program doesn't look at the header of files so if it's passed something hat
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is not compressed data it's likely to crash.
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The program depends on little endian systems.
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# 2016
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@@ -3813,6 +3813,11 @@ also involves good eye-hand coordination and playing games like this in the
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past).
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## [2015/mills2](2015/mills2/prog.c) ([README.md](2015/mills2/README.md))
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[Cody](#cody) added the [try.sh](2015/mills2/try.sh) script.
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## [2015/muth](2015/muth/prog.c) ([README.md](2015/muth/README.md))
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[Cody](#cody) added the [try.sh](2015/muth/try.sh) script.
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