"I am only an egg."

motd

Fri, 04 Dec 2009 13:29:27 GMT

Simon Peyton-Jones gracefully shunts some haskell-cafe thread:

Friends
One of the absolutely best things about the Haskell community is that it is almost invariably respectful and usually friendly. People often remark on this when they join the community. Beginner questions are greeted with polite and helpful replies. Category theory and elementary type errors show up in successive messages. Etc.
But thread is an exception.
If you think someone is talking nonsense, I think the best policy is to ignore it or reply privately (not to the list); then the thread dies. I find derogatory discussion of a particular person quite discouraging. It is likely to be unjust, and it encourages more of the same. It's like littering your own house.
Respect, guys, please.

cabal-install haddock documentation - another round of workarounds

Sun, 08 Nov 2009 21:19:02 GMT

Today I've found a way to cabal-install offline documentation – with source hyperlinks! – for a Haskell package.

(The reddit link was quite helpful by pushing me in right direction.)

To obtain documentation without source hyperlinks you just

run `cabal install' with `--enable-documentation' option ...or
enable `documentation' parameter in ~/.cabal/config

Then reinstall the package with `cabal install --reinstall' command. Documentation will appear in ~/.cabal/share/doc/PACKAGE-VERSION/html/ directory.

But if you want proper documentation – with `Source' links to the right of declarations – try these commands (replacing `iteratee' with your favourite package):

$ cd /tmp
$ tar -xzf ~/.cabal/packages/hackage.haskell.org/iteratee/0.2.4/iteratee-0.2.4.tar.gz
$ cd iteratee-0.2.4
$ cabal configure
$ cabal haddock --hyperlink-source

## NOTE:
##  * Make sure `documentation' is *disabled* in ~/.cabal/config.
##  * Don't use `--enable-documentation' in `cabal install' command.
## Otherwise links to source code will be omitted from documentation.

$ cabal install --reinstall

That's almost it. But source code pages will not be syntax-highlighted, because hscolour.css is missing. I've used a workaround:

$ cd ~/.cabal/share/doc/iteratee-0.2.4/html/src
$ ln -s /usr/share/doc/ghc6-doc/libraries/Cabal/src/hscolour.css

Now everything is sweet (i.e., documented and hyperlinked to sources).

This post is a reminder to myself, which may possibly help some other haskeller.

Making Motorola playlists (.pla files), part 3

Sun, 01 Nov 2009 18:16:39 GMT

(See part 1 and part 2.)

Motorola SLVR7e L7e phone has FAT16 filesystem on its memory card. Using wikipedia article on FAT16 design we will locate .mp3 entries in the filesystem and try to correlate them with .pla file (the playlist).

FAT16 consists of boot sector (1 sector is 512 bytes), two File Allocation Tables (FATs), root directory, and data region. Boot sector specifies various parameters of the filesystem. The ones of our interest are:

[number of] sectors per cluster,
sectors per FAT,
maximum number of root directory entries.

Note that FAT16 entries – including boot sector parameters – are little endian.

We will use this helper function to read values from the filesystem:

read_at() {
    case "$2" in
        1) t='C';;
        2) t='v';;
        *) echo 'Usage: read_at OFFSET SIZE' >&2; return 1;;
    esac
    dd if=/dev/sdb1 bs=1 skip=$1 count=$2 2>/dev/null | \
        perl -wspe '$_ = unpack("'$t'") . "\n"'
}

And these are the boot sector values we need:

$ read_at $((0xd)) 1   # sectors_per_cluster
32
$ read_at $((0x16)) 2  # sectors_per_FAT
239
$ read_at $((0x11)) 2  # max_root_entry
512

So far so good. Now let's skip over boot sector and FATs and go right to the root directory.

root_directory_offset = size_of_boot_sector + size_of_FATs = = (1 + 2 * sectors_per_FAT) * 512 = (1 + 2*239) * 512 = = 0x3be00

Here we are:

0003BE00   41 6D 00 6F 00 62 00 69 00 6C 00 0F 00 60 65 00   Am.o.b.i.l...`e.
0003BE10   00 00 FF FF FF FF FF FF FF FF 00 00 FF FF FF FF   ................
0003BE20   4D 4F 42 49 4C 45 20 20 20 20 20 10 00 00 00 00   MOBILE     .....
0003BE30   00 00 A8 38 00 00 62 79 2C 36 02 00 00 00 00 00   ...8..by,6......
0003BE40   41 64 00 00 00 FF FF FF FF FF FF 0F 00 41 FF FF   Ad...........A..
0003BE50   FF FF FF FF FF FF FF FF FF FF 00 00 FF FF FF FF   ................
0003BE60   44 20 20 20 20 20 20 20 20 20 20 10 00 64 62 8F   D          ..db.
0003BE70   4F 3B 4F 3B 00 00 62 8F 4F 3B 22 00 00 00 00 00   O;O;..b.O;".....
0003BE80   E5 6D 00 70 00 33 00 70 00 6C 00 0F 00 CB 61 00   .m.p.3.p.l....a.
0003BE90   79 00 65 00 72 00 2E 00 6D 00 00 00 64 00 62 00   y.e.r...m...d.b.
0003BEA0   E5 50 33 50 4C 41 7E 31 4D 44 42 20 00 00 00 00   .P3PLA~1MDB ....
0003BEB0   00 00 6F 39 00 00 0B 51 0B 39 07 06 FD 01 00 00   ..o9...Q.9......
0003BEC0   E5 4C 00 4F 00 47 00 2E 00 67 00 0F 00 E7 7A 00   .L.O.G...g....z.
0003BED0   00 00 FF FF FF FF FF FF FF FF 00 00 FF FF FF FF   ................
0003BEE0   E5 4F 47 20 20 20 20 20 47 5A 20 20 00 64 57 95   .OG     GZ  .dW.
0003BEF0   3E 3B 3E 3B 00 00 57 95 3E 3B 61 02 15 2A 00 00   >;>;..W.>;a..*..
0003BF00   E5 45 43 53 45 50 7E 31 54 41 52 20 00 64 FB 0A   .ECSEP~1TAR .d..
0003BF10   21 3B 21 3B 00 00 FB 0A 21 3B 87 20 00 38 3F 06   !;!;....!;. .8?.
0003BF20   E5 4C 00 4F 00 47 00 2E 00 67 00 0F 00 E7 7A 00   .L.O.G...g....z.
0003BF30   00 00 FF FF FF FF FF FF FF FF 00 00 FF FF FF FF   ................
0003BF40   E5 4F 47 20 20 20 20 20 47 5A 20 20 00 64 0E 0B   .OG     GZ  .d..
0003BF50   21 3B 21 3B 00 00 0E 0B 21 3B 84 39 F6 23 00 00   !;!;....!;.9.#..
0003BF60   E5 7A 00 00 00 FF FF FF FF FF FF 0F 00 9D FF FF   .z..............
0003BF70   FF FF FF FF FF FF FF FF FF FF 00 00 FF FF FF FF   ................
0003BF80   E5 52 00 65 00 63 00 53 00 65 00 0F 00 9D 70 00   .R.e.c.S.e....p.
0003BF90   2E 00 68 00 74 00 6D 00 6C 00 00 00 2E 00 67 00   ..h.t.m.l.....g.
0003BFA0   E5 45 43 53 45 50 7E 31 47 5A 20 20 00 00 9A A2   .ECSEP~1GZ  ....
0003BFB0   1F 3B 1F 3B 00 00 9A A2 1F 3B 99 20 B9 04 00 00   .;.;.....;. ....
0003BFC0   E5 45 43 59 43 4C 45 52 20 20 20 17 00 9C 5C 89   .ECYCLER   ...\.
0003BFD0   44 3B 44 3B 00 00 5D 89 44 3B 42 55 00 00 00 00   D;D;..].D;BU....
0003BFE0   E5 55 54 4F 52 55 4E 20 49 4E 46 07 18 00 00 74   .UTORUN INF....t
0003BFF0   38 2D 44 3B 00 00 00 74 38 2D 4E 55 AA E7 00 00   8-D;...t8-NU....
0003C000   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
0003C010   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
0003C020   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
0003C030   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
0003C040   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
0003C050   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
0003C060   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
0003C070   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
0003C080   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
0003C090   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
0003C0A0   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
0003C0B0   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
0003C0C0   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
0003C0D0   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
   TWEAK 3.01: /dev/sdb1          (LOOK)   posn=0x3BE00    size=0x3B86FE00

You see the output of tweak hex editor. <ADVERTISEMENT>Very nice tool indeed. Due to its lazy nature it can open huge files instantly, supports cut-n-paste, searches for byte sequences, and has Emacs-like shortcuts. By the author of PuTTY.</ADVERTISEMENT>

Root directory is just ``a Directory Table that stores information about the files and directories located in the root directory. It is only used with FAT12 and FAT16''.^[src] Rootdir's hex dump is hardly readable (yet) but we can mount and list it:

$ mount /mnt/winstick
$ ls -AlgG /mnt/winstick
total 32
drwxrwxrwx  3 16384 2009-10-15 20:59 d
drwxrwxrwx 17 16384 2007-01-12 17:11 mobile

This `mobile' directory was created by phone when it formatted memory card, and `d' was made by me.

Dentries

A directory table consists of directory entries or dentries as kernel source calls them. ``Each entry records the name, extension, attributes (archive, directory, hidden, read-only, system and volume), the date and time of creation, the address of the first cluster of the file/directory's data and finally the size of the file/directory. Aside from the Root Directory Table in FAT12 and FAT16 file systems, which occupies the special Root Directory Region location, all Directory Tables are stored in the Data Region.''^[src]

Dentry for `mobile' directory has offset 0x3be20, and `d' is at 0x3be60. If you follow the addresses, you can see that DOS file names are uppercase, contrary to the output of ls command. Let's ignore this fact for a while.

At this point you may wonder how do all these dentries relate to our original intention to locate .mp3 files. The answer is — indirectly. :) Dentries are kind of road signs that one can follow to get from root to destination file. Each dentry has a "pointer" to its contents — number of first cluster, encoded in two bytes starting at 0x1a (dentry's offset).

To be finished...

Быстрый нудный пост (про проблемы с Иксами)

Sat, 24 Oct 2009 22:29:00 GMT

Итак, проблема

Тормозит отрисовка окон: scroll и при перетягивании мышью. (Изначально "проблем с Иксами" было больше, но я вам про них не расскажу, чтоб не сбить нарратив.)

Решение

Поставить драйвер NVIDIA.

Реализация

...Затрудняется тем, что драйвер из пакета `nvidia-kernel-source' не собирается для ядер старше 2.6.26. Я его пропатчил, как мог (чтобы собрался с двумя директориями linux-headers-*-686 и linux-headers-*-common, и свежим API), но Xserver отказался с запускаться с тем, что получилось.

Решение

На работе времени мало. Значит, надо принести туда исправный ноутбук из дому, а глючную Тошибу взять на выходные на "debug с пристрастием".

...Пятничным утром, благородно дав мне возможность ввести в строй замену (перебросить почту, всё такое), ноутбук-с-тормозящими-исками перестал реагировать на клавиатуру. За что был выключен кнопкой (в последствии — неоднократно).

Новые симптомы

Xserver перестаёт реагировать на клавиатуру. Мышка лазит, но толку с неё. "Подвисаем" по-разному: один раз не смог даже username вбить при входе в сессию, другой раз только успело xterm нарисовать; обычно — вскоре после начала работы.

Отладка

Есть два полезных документа: ServerDebugging на Xorg Wiki и Xserver Debugging Hints. Они убедили меня поставить пакет с отладочной информацией, `xserver-xorg-core-dbg'.

После этого оставалось:

дождаться зависания иксов,
зайти с другого компьютера по ssh,
gdb /usr/lib/debug/usr/bin/Xorg `pgrep X`,
увидеть бесконечный цикл внутри модуля `nv' (пакет `xserver-xorg-video-nv').

Победа

Исправляем в /etc/X11/xorg.conf драйвер с "nv" на "vesa". Рестартуем xdm (всё в том же ssh). И прекрасно работаем – стабильно и достаточно быстро – с vesa драйвером.

Резюме

Посылаю драйвера nv и nvidia в виртуальную задницу. (Сидеть им там не пересидеть, в 3D игры я не играю.)

Из полезного: настроил русский язык в текстовой консоли. (Всего-то и надо `console-cyrillic' поставить.)

Пост получился ослепительно нудным, но я предупреждал. Удачи!

Hackage is down

Mon, 19 Oct 2009 12:59:30 GMT

$ nc -w5 -vz haskell.hackage.org
haskell.hackage.org: forward host lookup failed: Host name lookup failure

Let's tune to #haskell IRC channel...

$ wget -qO- 'http://tunes.org/~nef/logs/haskell/09.10.19' | \ grep -i hackage 00:00:07 --- quit: hackagebot (Remote closed the connection) 00:01:07 --- join: hackagebot (n=hackageb@joyful.com) joined #haskell 00:23:44 <ksf> can't the galois guys at least put up a page that says that hackage is down? 00:25:18 * arcatan waits for ishackageup.com 00:27:46 <RichardO> hackage is down? 00:29:56 <dmwit> Down with Hackage! 00:31:16 <ksf> Ha! It's her! lambdabot hacked hackage and uses it to plot her plans for world domination, faster! 01:10:50 <Baughn> So, um.. hackage... 01:54:41 <huntse> So I have the day off work with a cold, perfect for some haskell hacking and hackage is down. *sigh* 02:05:12 <endojelly> hackage down? 02:05:47 <fasta> Someone implement HTorrentHackage, please. 02:05:50 <ziman> but there's the alternative hackage vith the reverse deps... 02:30:12 <aleator> Hmm.. http://hackage.haskell.org/ is down :( 02:31:20 <paolino> still, is there anyone with a tarball of hackage or part of it ? 02:34:09 <ziman> http://bifunctor.homelinux.net/~roel/hackage/packages/hackage.html 02:50:27 <jkff> Oh hell, hackage is still down... 02:50:32 <endojelly> http://hackage.haskell.org/platform/2009.2.0.2/haskell-platform-2009.2.0.2.tar.gz 02:51:39 <ivanm> jkff: let me go check hackage for one... :p 02:51:51 <mux> but hackage seems ot be down 02:52:12 <jkff> ivanm: Well, I already see parsedate, and it has a darcs repo outside hackage. Let's see if it can handle bytestrings.. 02:55:17 <ivanm> endojelly: since hackage.haskell is down... how can I check? ;-) 02:57:34 <HugoDaniel> what is wrong with hackage ? :( 03:07:01 <ivanm> dancor: check hackage :p 03:17:06 <mylh> hi all :) anyone knows what have happend to hackage? I've been on vacation last week now i'm back and it doesn't works 03:18:44 <endojelly> Downloading the latest package list from hackage.haskell.org 03:57:03 <Raevel> hackage status? 03:57:39 <mylh> Raeve: hackage is down for me 03:57:43 <ivanm> STOP ASKING ABOUT HACKAGE! 03:58:39 <ivanm> and then people will ask "is hackage still down?" 04:04:22 <Raevel> oh , i rememberd i had all the hackage packages i need on my server \o/ 04:04:35 <Cale> Why is hackage down? 04:08:54 <mxc> as someone who lives in SE Asia now, and has been called a bad person many times in the past, why is hackage down now? 04:11:12 <huntse_> mxc: hackage is down because someone captured all the special magical haskell fairies that keep it running. 04:23:24 <endojelly> soooo... what *is* wrong with hackage? 04:25:19 <Saizan> @topic-cons "Hackage is down, server problems." 04:25:19 <lambdabot> I do not know the channel "Hackage 04:25:29 <Saizan> @topic-cons #haskell "Hackage is down, server problems." 04:25:29 --- topic: set to '["\"Hackage is down, server problems.\"","The Monad.Reader issue #14 out now: http://themonadreader.wordpress.com/","#haskell-in-depth launched!","Haskell News: http://reddit.com/r/haskell","The Haskell programming language","http://haskell.org","Paste: http://moonpatio.com","Logs: http://tunes.org/~nef/logs/haskell/"]' by lambdabot 04:28:14 <profmakx> what happened to hackage 04:31:40 <profmakx> broken hackage is no good :( 04:39:17 <jkramer> Is hackage down? 04:49:41 <mercury^> Saizan_: Now would be the moment for me to bitch about hackage being down. :> 04:58:08 <ivanm> Saizan_: cohackage? :p 04:58:44 <Saizan_> ivanm: cohackage is the one that downloads packages from you :) 05:00:51 <HugoDaniel> hackage :( 05:01:37 <profmakx> we need hackage mirrors! 05:01:39 <HugoDaniel> i can mirror hackage 05:26:54 <dmwit> raim0_: Hackage is down just now, so unless your distro has a package for it... 05:32:40 <Axman6> when hackage is back up >_> 05:35:26 <dmwit> raim0_: Nah, I just mean installing the latest GHC and cabal-installing the packages you want straight from Hackage. 05:36:22 <dmwit> I thought Hackage wouldn't even let you upload packages with -Werror enabled. 05:37:21 <dcoutts> ksf: that's why we banned -werror on hackage 05:52:42 <raim0_> dmwit: how do I install cabal as the cabal-install's bootstrap.sh tries to fetch needed package from the hackage 05:53:17 <dcoutts> raim0_: you're out of luck until hackage is back online 05:55:48 <Axman6> raim0_: do you think someone's getting paid to look after hackage? 06:08:39 <burp> hackage can't have high requiremenets, it's all static, right? 06:10:54 <byorgey> medfly: for hackage, or in general? 06:12:19 <medfly> I suppose that for hackage. 06:13:53 <fnord123> how much traffic does hackage get? 06:33:38 <fasta> You can always do Hackage over Freenet. 06:50:17 <yitz> when hackage come back up. sigh. 06:53:41 <SamB_XP_> dcoutts: what does it take to mirror hackage ? 06:53:56 <SamB_XP_> dcoutts: do we need to switch to hackage2 ? 07:03:37 <nha_> hmm hackage is still down? 07:03:48 <ksf> as a peer, you could say "pull all packages that are signed by that author or the other". in such a way, an official hackage could pull everything from registered authors, without limiting others to distribute their stuff. 07:17:38 <ksf> hackage.haskell.org could distribute between the mirrors, and then some special domain could be used for the real master server that you can push to. 07:18:08 <SamB_XP_> ksf: that's called you mean master.hackage.haskell.org? 07:19:20 <yitz> jystic1: nowhere, until hackage comes back up. :( 07:21:15 <SamB_XP_> fasta: we still need some better way of authenticating packages than "it's on hackage.haskell.org" ... 07:23:06 <ksf> SamB_XP_, he might happen to trust main hackage, and hackage.haskell.org will only offer stuff from trusted keys. 07:31:31 <FunctorSalad> anyone upped the hackage tarball yet? ;) 07:35:36 <SamB_XP_> JaffaCake: can you get MSR to set up a hackage mirror? 07:36:19 <ksf> as is hackage. 08:04:55 <yairchu_> I can't understand why hackage is broken, wasn't the bailout supposed to prevent this? 08:12:42 <sproingie> still no hackage i see 08:13:08 <roconnor_> http://bifunctor.homelinux.net/~roel/hackage/packages/hackage.html 08:14:13 <nothingmuch> is hackage.haskell.org down? 08:16:24 <nothingmuch> http://bifunctor.homelinux.net/~roel/hackage/packages/archive/cabal-install/0.6.2/cabal-install-0.6.2.tar.gz # 404 09:12:50 <pumpkin> pity hackage is dead 10:20:25 <a_guest> what has happened to hackage.haskell.org?? 10:20:42 <c_wraith> hackage has been down over 24 hours, now 10:20:48 <a_guest> for me, hackage.haskell.org, is down 10:23:23 <a_guest> I can't read the api doc because of hackage down 10:24:48 <shapr> Anyway.... what's up with Hackage? 10:25:38 <tommd> @quote hackage 10:25:39 <lambdabot> dons says: [on whether a library is wanted] *yes* put it on Hackage! 10:25:41 <tommd> @quote hackage 10:25:42 <lambdabot> dcoutts says: remember, if it's not on hackage it doesn't exist! 10:30:36 <dons> Heinlein is fscking the disks on hackage 10:35:29 <codm`> Hey, so is hackage lost? Was hoping a server just needed to be rebooted on Monday morning. But still no hackage, and nothing on haskell.org explaining the situation. 10:54:25 <paolino> any news on hackage ? 10:54:44 <FcoX> (hackage is down? oh! I was blaming my ISP!!) 10:55:48 <roconnor_> http://bifunctor.homelinux.net/~roel/hackage/packages/hackage.html 11:23:54 <FunctorSalad> there are too many type-level integers on hackage 11:24:35 <Berengal> FunctorSalad, the solution is simple: Write your own (then upload it to hackage so others don't face your problem) 11:43:37 <HugoDaniel> hackage anyone ? :D 11:43:56 <HugoDaniel> (maybe if i keep pressuring hackage might start working...) 11:56:44 * heatsink searches the logs for "hackage" instead of asking 12:00:05 <heatsink> Wow, hackage was a popular subject yesterday. 12:10:47 <sproingie> we should provide daily torrents of the hackage tarball 12:17:54 <FunctorSalad> still no hackage torrent? 12:19:43 <Berengal> Man, haskell is awesome (even with hackage down) 12:20:11 <sproingie> i have a week-old or so tarball of hackage 12:27:04 <tommd> dcoutts: Has anyone proposed an API matcher to enforce versioning on Hackage? Something that will compare function names / types and decide if the package follows versioning rules. 12:29:12 <tommd> But I'm always wanting to hack on hackage-server more. 12:33:34 <yakov> what is up with hackage? 12:48:42 <HairyDude> is hackage down?

Болею

Sun, 18 Oct 2009 18:14:13 GMT

С лицом, измученным и серым,
На белой смятой простыне,
Как жертва бешеной холеры,
Лежит коленками к стене.
Протяжно стонет, как при родах.
Трясется градусник в руках.
Вся вековая боль народов
Застыла в суженных зрачках.
По волевому подбородку
Струится за слезой слеза.
Он шепчет, жалобно и робко:
"Как ты с детьми теперь – одна?.."
В квартире стихли разговоры
Ночник горит едва-едва.
Темно. Опущены все шторы.
У мужа – тридцать семь и два...

Это про меня.

(Списал отсюда. Автор неизвестен.)

Fixing dosbox arrow keys

Tue, 13 Oct 2009 22:44:12 GMT

Problem

Arrow keys don't work in dosbox-0.72 .

Details

`dosbox -startmapper' shows that `left' key has become `right alt', `up' — `print screen'; `down' and `right' keys are not recognized.

Solution

Unset `usescancodes' in your ~/.dosboxrc.

$ cat ~/.dosboxrc
[sdl]
usescancodes=false

NOTE: This bug may be fixed in 0.73 (there is evdev mentioned in the changelog).

Very Public или Всесмывающий поток семантики

Mon, 12 Oct 2009 13:54:59 GMT

В C++ не хватает степеней "публичности" для элементов классов. В [больном на голову] коде часто встречается такое:

class Foo : public Bar {
public:
  enum One { one = 1 };
  enum Two { two = 2 };

public:
  Foo(int n);
  virtual ~Foo(); // the empty body is defined elsewere

public:
  int val;

protected:
  enum Three { three = /* a lot */ one + two };
};

C+++ должен понимать, что перечисления One и Two — публичные, конструктор и деструктор — очень публичные, а переменная(-член) — совсем публичная(-чный).

Write, think, learn

Sat, 10 Oct 2009 21:37:41 GMT

``How to Write More Clearly, Think More Clearly, and Learn Complex Material More Easily.''
Wonderful presentation by Michael A. Covington.

I like it up to the last slide (especially the last slide).

[ via Chung-chieh Shan's blog entry ]

()

Sat, 10 Oct 2009 20:48:20 GMT

Надо же! Оказывается, доклады на тему ``Business-Critical System vs. Your Favourite Functional Language'' популярны.

Making Motorola playlists (.pla files), part 2

Tue, 06 Oct 2009 15:20:33 GMT

(See part 1.)

As long as .pla file is binary, we will view it in hex. Here's a hex dump of a playlist containing first three tracks of Led Zeppelin IV:

$ hd lz4.pla
00000000  00 03 00 01 00 00 00 00  01 40 00 04 00 00 3d 60  |.........@....=`|
00000010  01 40 00 0e 00 00 3d 60  01 40 00 02 00 00 3d 5f  |.@....=`.@....=_|
00000020

This playlist is named `lz4.pla'. We will refer to it below.

Header

I've created several playlists "manually" and noticed that the second byte is always equal to the number of tracks in playlist (`03' in lz4.pla). Bytes with offsets 0 and 2–7 are the same for all playlists I've seen. Thus we can guess the format of .pla file header:

00 <nn> 00 01 00 00 00 00,

where <nn> is number of tracks in playlist.

Entry

Playlist header is followed by entries — 8-byte-long track specifications. There are as many entries as there are tracks in a playlist (lz4.pla file has three: address ranges 0x8–0xf, 0x10–0x17, and 0x18–0x1f).

When we open playlist in Motorola, we see the names of tracks included. But there is no chance for 8 bytes of .pla entry to contain the name of track: the third track is displayed as `03 - The Battle of Evermore' making a string of 27 characters.

Thus, we can assume that .pla entry encodes position of .mp3 file within the underlying filesystem.

Continued...

Making Motorola playlists (.pla files), part 1

Thu, 01 Oct 2009 21:04:10 GMT

I've got Motorola SLVR L7e mobile phone. The device is capable of playing MP3 audio files, and I use this feature occasionally.

Once a musical album is uploaded to phone's microSD, it is better to create playlist, otherwise playback will stop as soon as the first track finishes.

And while uploading albums is very simple (you just copy directories like you do with ordinary USB memory stick), creating playlists on L7e is pain.

You go to `Multimedia/Sounds' menu item, choose `New Playlist', then `Audio Files' and start selecting those belonging to your album. There are two inconveniences: 1) tracks are not sorted (i.e., you see the list of `03.Baz, and `01.Foo, and `02.Bar'), and 2) the list includes all the tracks stored on your memory card (and 1Gb flash may contain lots of them). Thus making a playlist is a laborious process of consulting track listing (from computer folder or wikipedia) and hunting tracks that are scattered over a huge list.

You think you've added files and you are done? Not so fast. You need to reorder them now. That's right, remember they were unsorted in the previous step. And here is Motorola playlist files' reordering procedure: choose playlist, select `Options' then `Reorder', go to track #1, select and pull it to the top, put it there; go to track #2, place it right after the first; repeat until it's time for pressing `Done'.

Phew!

But what a hell, none of human beings deserve being involved in such a stupid activity! What are these playlists?..

The result of suffering is a .pla file, stored in `mobile/audio' directory. The file is easy to see, copy, and delete, but it's not quite obvious how to create it -- the darn file is binary with format unknown.

Continued...

LtU-Kiev: Haskell experience

Tue, 29 Sep 2009 19:52:29 GMT

В эту субботу LtU-Kiev собирается, вы в курсе?

whois ltu-kiev

Sat, 26 Sep 2009 20:23:21 GMT

Что такое LtU-Kiev и как оно началось?

The main thing uniting us is our interest in programming languages...

[joke alert]

Thu, 10 Sep 2009 20:17:26 GMT

Try this command in your xterm (don't worry, it's harmless):

(trap 'xrandr -o normal' 0; xrandr -o inverted; sleep 20)

(-:

[Inspired by `Changing X11 resolution on the fly' article.]

%-/

Mon, 07 Sep 2009 14:09:33 GMT

(Re: Daily WTF to Ultimate Refactoring?)

Чувствую себя лейтенантом Рипли, которая забежала с зажжённым огнемётом в склизкую колонию "чужих" с благородной целью (сделать на этом месте солнечную лужайку с бабочками), но постепенно начала осознавать масштабы. Подлая "матка" загадила яйцами невообразимые площадя...

Daily WTF to Ultimate Refactoring?

Fri, 04 Sep 2009 08:51:05 GMT

It ain't easy to profile 2.6K SLOC program made of 3 functions.

PS: I've narrowed the problem: 99.1% time is spent in one of these functions; just 1000 lines of code.

``Gromit, that's it! Cheese!''

Thu, 06 Aug 2009 07:53:12 GMT

Using Debian's required package, you can learn a lot about French cheeses:

  $ aptitude changelog login | awk -F\" '/The ".+" release/ {print $2}'
  Tome des Bauges
  Chevrotin
  Banonet
  Banon
  Chambérat
  Le Puant Macéré
  Rocamadour
  Morbier
  Bleu des Causses
  Bleu d'Auvergne
  ...

Without Debian the command would be longer:

  wget -qO - http://packages.debian.org/changelogs/pool/main/s/shadow/current/changelog.txt | awk -F\" '/The ".+" release/ {print $2}'

utility of the day

Fri, 10 Jul 2009 12:48:58 GMT

gcov coverage testing tool

        -:         -:         -:         -:         -:

The lines marked with `#####' were never executed.

Compile with `--coverage' and run yer program:

 $ vi /tmp/1.c $ cd /tmp $ gcc --coverage -g -Wall -W -o 1 1.c $ ./1 >/dev/null $ gcov /tmp/1.c File '/tmp/1.c' Lines executed:63.64% of 11 /tmp/1.c:creating '1.c.gcov'

GCC only.

Update: gcov with `-b'

word of the day

Sat, 04 Jul 2009 07:10:44 GMT

$ dict braino
2 definitions found

From The Free On-line Dictionary of Computing (4 April 2009) [foldoc]:

thinko
braino

    /thing'koh/ (Or "braino", by analogy with "typo") A
   momentary, correctable glitch in mental processing,
   especially one involving recall of information learned by
   rote; a bubble in the stream of consciousness.

   See also brain fart.  Compare mouso.

   [Jargon File]

   (1996-04-20)


From The Jargon File (version 4.4.7, 29 Dec 2003) [jargon]:

braino
 /bray'no/, n.

        Syn. for thinko. See also brain fart.

`work-log-hide-inactive' via "d-a-i" sequences

Fri, 03 Jul 2009 23:32:17 GMT

It works!

Sorry, but no explanations right now -- I'll better have some sleep...

Anyway, the picture is nice, isn't it? :)

* * *

Update: the description of above screenshot.

все профессии нужны

Mon, 22 Jun 2009 10:14:09 GMT

Очень не хватает опыта работы в службе знакомств.

Передо мной выложен ряд из 7 почти неотличимых чёрных носков. Нужно разбить их на пары.

CS152-Lecture_14-Kernighan.pdf

Mon, 22 Jun 2009 08:03:48 GMT

Не могу удержаться, чтобы не порекомендовать:

Brian Kernighan, "Random Thoughts on Scripting Languages" (PDF)

Как говорила наша учительница русского языка и литературы: ``Бальзам на раны''. А если проще -- ржак полнейший (достигается умелой расстановкой цитат Ларри Уолла).

Хакеры, наслаждайтесь!

"I am only an egg."

motd

cabal-install haddock documentation - another round of workarounds

Рекомендую почитать

Making Motorola playlists (.pla files), part 3

Dentries

Быстрый нудный пост (про проблемы с Иксами)

Итак, проблема

Решение

Реализация

Решение

Новые симптомы

Отладка

Победа

Резюме

Hackage is down

Болею

Fixing dosbox arrow keys

Problem

Details

Solution

See also

Very Public или Всесмывающий поток семантики

Write, think, learn

()

Making Motorola playlists (.pla files), part 2

Header

Entry

Making Motorola playlists (.pla files), part 1

LtU-Kiev: Haskell experience

whois ltu-kiev

[joke alert]

%-/

Daily WTF to Ultimate Refactoring?

``Gromit, that's it! Cheese!''

utility of the day

word of the day

`work-log-hide-inactive' via "d-a-i" sequences

все профессии нужны

CS152-Lecture_14-Kernighan.pdf