/oct2py/_utils.py

"""

.. module:: _utils

   :synopsis: Miscellaneous helper constructs



.. moduleauthor:: Steven Silvester <steven.silvester@ieee.org>



"""

import os

import time

import subprocess

import random

import atexit

import inspect

import dis

import re

import sys

from glob import glob



sys.path.append('..')





def _open():

    """

    Start an octave session in a subprocess.



    Returns

    =======

    out : fid

        File descriptor for the Octave subprocess



    Raises

    ======

    Oct2PyError

        If the session is not opened sucessfully.



    Notes

    =====

    Options sent to Octave: -q is quiet startup, --braindead is

    Matlab compatibilty mode.

    On Windows, it attempts to find octave in c:\Octave if it is not

    on the path.



    """

    session = None

    if 'linux' in sys.platform:

        session = subprocess.Popen('octave -q --braindead', 

                                 shell=True,

                                 stderr=subprocess.STDOUT,

                                 stdin=subprocess.PIPE,

                                 stdout=subprocess.PIPE,

                                 preexec_fn=os.setsid)

    else:

        try:

            session = subprocess.Popen('octave -q --braindead', 

                                 stderr=subprocess.STDOUT,

                                 stdin=subprocess.PIPE,

                                 stdout=subprocess.PIPE)

        except OSError:

            msg = ('\n\nPlease install octave and put it in your path:\n'

                         'setx PATH "%PATH%;<path-to-octave-bin-dir>"\n\n')

            raise Oct2PyError(msg)

    return session





def _register_del(fname):

    """

    Register a MAT file for deletion at program exit.



    Parameters

    ==========

    fname : str

        Name of file to register.



    """

    atexit.register(lambda filename=fname: _remove_files(filename))





def _remove_files(filename=''):

    """

    Remove the desired file and any old MAT files.



    All MAT files in the current working directory over a minute old are

    deleted.

    This helps clean up orphaned HDF files in case the previous session did

    not close properly.



    Parameters

    ==========

    filename : str, optional

        Specific file to delete.



    """

    try:

        os.remove(filename)

    except OSError:

        pass

    files = os.listdir(os.getcwd())

    for fname in files:

        if re.match(r'(load|save)_.{10}\.(mat|hdf)', fname):

            try:

                atime = os.path.getatime(fname)

            except OSError:

                continue

            if (time.time() - atime > 60):

                try:

                    os.remove(fname)

                except OSError:

                    pass





def _get_nout():

    """

    Return the number of return values the caller is expecting.



    Adapted from the ompc project.



    Returns

    =======

    out : int

        Number of arguments expected by caller, default is 1.



    """

    frame = inspect.currentframe()

    # step into the function that called us

    # nout is two frames back

    frame = frame.f_back.f_back

    bytecode = frame.f_code.co_code

    try:

        instruction = ord(bytecode[frame.f_lasti + 3])

    except TypeError:

        instruction = ord(chr(bytecode[frame.f_lasti + 3]))

    if instruction == dis.opmap['UNPACK_SEQUENCE']:

        try:

            howmany = ord(bytecode[frame.f_lasti + 4])

        except TypeError:

            howmany = ord(chr(bytecode[frame.f_lasti + 4]))

        return howmany

    elif instruction == dis.opmap['POP_TOP']:

        # OCTAVE always assumes at least 1 value

        return 1

    return 1





def _create_file(type_, ext):

    """

    Create a file of the given type and extension with a random name.



    Parameters

    ==========

    type_ : str {'load', 'save'}

        Type of file to create (used for Octave 'save' or 'load' commands).

    ext : str {'mat', 'hdf'}

        File extension.



    Returns

    =======

    out : str

        Random MAT file name e.g. 'load_4932048302.mat'.



    """

    name = [type_, '_']

    name.extend([str(random.choice(range(10))) for x in range(10)])

    name.append('.{0}'.format(ext))

    return ''.join(name)





class Oct2PyError(Exception):

    """ Called when we can't open Octave or Octave throws an error

    """

    pass





class Struct(dict):

    """

    Octave style struct, enhanced.



    Supports dictionary and attribute style access.



    Examples

    ========

    >>> from oct2py import Struct

    >>> a = Struct()

    >>> a.b = 'spam'  # a["b"] == 'spam'

    >>> a.c["d"] = 'eggs'  # a.c.d == 'eggs'

    >>> print(a)

    {'c': {'d': 'eggs'}, 'b': 'spam'}



    """

    def __getattr__(self, attr):

        try:

            return self[attr]

        except KeyError:

            if not attr.startswith('_'):

                self[attr] = Struct()

                return self[attr]

    __setattr__ = dict.__setitem__

    __delattr__ = dict.__delitem__





def _test():

    """Run the doctests for this module

    """

    doctest.testmod()





if __name__ == "__main__":

    import doctest

    _test()