(f)utility

29th January 2011

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Migrated to Posterous

This site has migrated to Posterous.

16th April 2010

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Compiling SYSV_IPC python module with GCC on AIX 5.2

I had a need to use good old SYSV message queues to interoperate with a bunch of old C programs, straight from python. Come in sysv_ipc module to the rescue, which works great on a variety of systems, but I need it on AIX.

Using Perzl wonderful rpm packages for AIX, I was able to compile it with GCC 4.2 and setup it into Python 2.6.

Modify common.h to unset SHM_SIZE (Obsolete step as of sysv_ipc 0.6):

#undef SHM_SIZE

enum GET_SET_IDENTIFIERS {

Export those two vars:

LDSHARED="/opt/freeware/lib/python2.6/config/ld_so_aix gcc -bI:/opt/freeware/lib/python2.6/config/python.exp"
CC="gcc"

You can then go on and:

python setup.py install [--user]

Update: common.h should not be modified anymore.

7th April 2010

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Play a MP3 file with pymad and pyaudio

Based on the wave example from pyaudio:

import pyaudio
import mad
import sys

if len(sys.argv) < 2:
    print "Plays a wave file.\n\n" +\
          "Usage: %s filename.wav" % sys.argv[0]
    sys.exit(-1)

mf = mad.MadFile(sys.argv[1])

p = pyaudio.PyAudio()

# open stream
stream = p.open(format =
                p.get_format_from_width(pyaudio.paInt32),
                channels = 2,
                rate = mf.samplerate(),
                output = True)

# read data
data = mf.read()

# play stream
while data != None:
    stream.write(data)
    data = mf.read()

stream.close()
p.terminate()

7th April 2010

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Play an MP3 file with pymad and pyao

This is for Mac OS X, adapt to your needs:

import mad, ao, sys

mf = mad.MadFile(sys.argv[1])
dev = ao.AudioDevice('macosx', bits=32, rate=mf.samplerate(), channels=2)
buf = mf.read()
while buf != None:
    dev.play(buf, len(buf))
    buf = mf.read()

7th April 2010

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Crash on object deletion in pyao and pyogg

The author of pyogg goofed up on python object deletion in the wrapper. This was reported.

Unfortunately libao (0.82) is also affected, and there’s no action even on the previous pyogg bug. It causes a “glibc double-free” on Linux and a “pointer being freed was not allocated” on Mac OS X.

The project seems quite dead, but is merely a wrapper to the C libs where the real action takes place, so there’s not much of a fuss to have it unmaintained.

Here is the patch against pyao:

--- src/aomodule.c.orig 2010-04-07 19:06:45.000000000 +0200
+++ src/aomodule.c  2010-04-07 19:06:56.000000000 +0200
@@ -150,7 +150,7 @@
 py_ao_dealloc(ao_Object *self)
 {
   ao_close(self->dev);
-  PyMem_DEL(self);
+  PyObject_DEL(self);
 }

 static PyObject *

And for reference, the patch against pyogg:

Index: legacy/pyvorbis/pyvorbisfile.c
===================================================================
--- legacy/pyvorbis/pyvorbisfile.c  (revision 20)
+++ legacy/pyvorbis/pyvorbisfile.c  (working copy)
@@ -173,8 +173,7 @@
   if (ret == NULL) {
     PyMem_DEL(newobj);
     return NULL;
-  } else
-    Py_DECREF(ret);
+  }

   return (PyObject *) newobj;
 }
@@ -191,11 +190,13 @@
        close */
     Py_DECREF(py_self->py_file);
   } else {
-    /* Otherwise, we opened the file and should close it. */
-    fclose(py_self->c_file);
+    /* Do NOT close the file -- ov_open() takes ownership of the FILE*,
+       and ov_close() is responsible for closing it. */
   }

-  PyMem_DEL(self);
+  free(py_self->ovf);
+
+  PyObject_DEL(self);
 }

 static PyObject *

2nd April 2010

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Uninstalling ActivePython and ActiveTCL

Little script to easily uninstall either. Take care to adapt to your needs.

#activepython
sudo rm -R /Library/Frameworks/Python.framework /Applications/Python\ 3.1 /usr/local/bin/{2to3*,py*,idle*}

#activetcl
sudo rm -R /Library/Frameworks/{Tcl,Tk}.framework /Applications/Utilities/Wish\ 8.5.app /usr/local/bin/{tclsh8.5,wish8.5} /Library/Documentation/Help/ActiveTcl-8.5

29th March 2010

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Lovely command to obtain the processes (or rather, PID) using a socket port (here 23) on AIX:

$ netstat -Aan  | egrep '\.23 ' | awk '{print $1}' | \
    sed -e 's/^\(.*\)$/sockinfo \1 tcpcb/' | kdb | egrep '^pvproc' | awk '{print $4}'  | sort | uniq | \
    sed 's/^\(.*\)$/hcal \1/' | kdb | grep Value | awk '{print $6}'

Useful when you don’t have lsof at hand.