Tuesday, November 23, 2010

The Lonely Programmer (Hacker)

I've been noticing books on the market (and some blogs too) that speak of our newly emerging "Maker" culture -- a culture where people fed up with intangible abstract work (do you sit in a cubicle pushing numbers?) are turning to the gratification of hands on creation. They say that working on physical things can give you a deep sense of accomplishment that nurtures our primordial tool building minds.

I put forth that some programmers can get this feeling from the intangible and abstract.  I grew up working with my hands (art, electronics, and just generally building stuff).  Programming became an extension of that. It my mind, my code held the same sense of accomplishment and gratification as building something with my hands.  I became enamored with virtual worlds!

Nowadays, however, I find that a lot off programmers spend significant time worrying about languages, syntax, test coverage and code re-use. These are topics of varying importance, but they are just about honing your skills.  At some point you have to produce something. Hopefully it is beautiful (not just on the outside but inside too).  How you managed to create it (the language, test approach, etc) is secondary to the thing itself. And, oh, if it is malleable and can be adapted to do new exciting things, is that proof enough you used good coding techniques?

We spend so much time talking about the tools, we forget that it is the result that matters. We forget about the joy and awe of working code.  We instead tend to form language advocacy groups, cult-like methodologies and obsess over software licensing.

Really, if someone were to create a fully aware artificial being capable of not only passing the Turing test but able to engage us in deep conversation, would we (the programmers) nitpick over how poorly the code is structured, the lack of test coverage and how terrible it is that it was implemented in a crappy programing language?

Thursday, November 11, 2010

MP3 ID3v1 tag reading in Perl and in Haskell

I am building an MP3 jukebox for my home...

I know that I am supposed to use ID3v2, but my MP3 collection (CD ripped, Amazon and Emusic) still sports ID3v1 tags, so I thought it would be a safe  bet to just parse it.

I quickly wrote an ID3v1 tag parser in Perl (yes, I know CPAN has several solutions for this but I wanted to write my own just for the fun). Here is what it looks like:

use strict;
use warnings;
use Fcntl qw(:seek);

my @genre = (
'Blues','Classic Rock','Country','Dance',
'Jazz','Metal','New Ag(e','Oldies',
'Alternative','Ska','Death Metal','Pranks',
'Game','Sound Clip','Gospel','Noise',
'Space','Meditative','Instrumental Pop','Instrumental Rock',
'Southern Rock','Cult','Gangsta','Top 40',
'Christian Rap','Pop/Funk','Jungle','Native American',
'Cabaret','New Wave','Psychadelic','Rave',
'Acid Punk','Acid Jazz','Polka','Retro',
'Musical','Rock &','Hard Rock','Folk',
'Folk-Rock','National Folk','Swing','Fast Fusion',
'Bluegrass','Avantgarde','Gothic Rock','Progressive Rock',
'Psychedelic Rock','Symphonic Rock','Slow Rock','Big Band',
'Chorus','Easy Listening','Acoustic','Humour',
'Speech','Chanson','Opera','Chamber Music',
'Symphony','Booty Brass','Primus','Porn Groove',
'Satire','Slow Jam','Club','Tango',
'Samba','Folklore','Ballad','Power Ballad',
'Rhytmic Soul','Freestyle','Duet','Punk Rock',
'Drum Solo','A Capela','Euro-House','Dance Hall' );

my $id3v1;
my $id3v1_tmpl = "A3 A30 A30 A30 A4 A28 C C C";

while (my $filename = ) {
    chomp $filename;
    open my $fh, '<', $filename or next;
    binmode $fh;
    seek $fh, -128, SEEK_END and read $fh, $id3v1, 128;
    close $fh;
    my (undef,$title,$artist,$album,$year,$comment,undef,$trk,$genr) =
    print "$filename|$title|$artist|$album|$year|$trk|".$genre[$genr]."\n";

Basically it takes a stream of MP3 filenames over stdin, opens them and dumps out a pipe delimited summary of what it found. Here is how it is run:

$ find /home/todd/music -name "*.mp3" | perl mp3info.pl >mp3_data.txt

Here is a line from the output (mp3_data.txt):
/home/todd/music/Charles Mingus/Ah Um/Charles Mingus_10_Pedal Point Blues.mp3|Pedal Point Blues|Charles Mingus|Ah Um|1959|10|Jazz

I am considering using Haskell for my jukebox, so I was curious what this would look like in Haskell.  Here is my newbie Haskell implementation:

import Text.Printf
import Data.Array
import Char
import System.Environment
import System.IO

-- Create a array of genres
genres = listArray (0, l-1) genres_l 
           genres_l = [
             "Blues", "Classic Rock","Country","Dance",
             "Jazz","Metal","New Age","Oldies",
             "Alternative","Ska","Death Metal","Pranks",
             "Game","Sound Clip","Gospel","Noise",
             "Space","Meditative","Instrumental Pop","Instrumental Rock",
             "Southern Rock","Cult","Gangsta","Top 40",
             "Christian Rap","Pop/Funk","Jungle","Native American",
             "Cabaret","New Wave","Psychadelic","Rave",
             "Acid Punk","Acid Jazz","Polka","Retro",
             "Musical","Rock &","Hard Rock","Folk",
             "Folk-Rock","National Folk","Swing","Fast Fusion",
             "Bluegrass","Avantgarde","Gothic Rock","Progressive Rock",
             "Psychedelic Rock","Symphonic Rock","Slow Rock","Big Band",
             "Chorus","Easy Listening","Acoustic","Humour",
             "Speech","Chanson","Opera","Chamber Music",
             "Symphony","Booty Brass","Primus","Porn Groove",
             "Satire","Slow Jam","Club","Tango",
             "Samba","Folklore","Ballad","Power Ballad",
             "Rhytmic Soul","Freestyle","Duet","Punk Rock",
             "Drum Solo","A Capela","Euro-House","Dance Hall" ]
           l = length genres_l

main = do

  hSetEncoding stdin latin1
  hSetEncoding stdout latin1

  fname <- getContents          -- lazily read list of files from stdin
  mapM print_id3v1 (lines fname)
print_id3v1 fname = do
  print fname
  inh <- openBinaryFile fname ReadMode
  hSeek inh SeekFromEnd (-128)
  dat <- hGetContents inh
  printf "%s|%s|%s|%s|%s|%d|%s\n"
       (extract 3 30 dat)      -- Title
       (extract 33 30 dat)     -- Artist
       (extract 63 30 dat)     -- Album
       (extract 93 4 dat)                              -- Year
       (Char.ord (head (extract 126 1 dat)))           -- Track
       (genres !(Char.ord (head (extract 127 1 dat)))) -- Genre
  hClose inh

-- extract and trim a range of elements from list
extract idx ln s = 
    trim0 (take ln (drop idx s))

-- Trim nulls from list
trim0 s = filter (/= '\0') s

You run it similarly. Frustratingly, it isn't very happy with filenames with non-ASCII characters :-(

$ find /home/todd/music/ -name "*.mp3" -print | ./mp3info >mp3_files.txt 
mp3info: /home/todd/Music/music/Ch�ying Drolma & Steve Tibbetts/Selwa/Ch�ying Drolma & Steve Tibbetts_05_Gayatri.mp3: openBinaryFile: does not exist (No such file or directory)

I am not a Haskell expert, but I didn't expect it to choke there...

EDIT: Fixed the filename problem by adding:

  hSetEncoding stdin latin1
  hSetEncoding stdout latin1