# util.py - utility functions and platform specfic implementations

#

# Copyright 2005 K. Thananchayan <thananck@yahoo.com>

#

# This software may be used and distributed according to the terms

# of the GNU General Public License, incorporated herein by reference.

import os

class CommandError(Exception): pass

def explain_exit(code):

    """return a 2-tuple (desc, code) describing a process's status"""

    if os.WIFEXITED(code):

        val = os.WEXITSTATUS(code)

        return "exited with status %d" % val, val

    elif os.WIFSIGNALED(code):

        val = os.WTERMSIG(code)

        return "killed by signal %d" % val, val

    elif os.WIFSTOPPED(code):

        val = os.STOPSIG(code)

        return "stopped by signal %d" % val, val

    raise ValueError("invalid exit code")

def system(cmd, errprefix=None):

    """execute a shell command that must succeed"""

    rc = os.system(cmd)

    if rc:

        errmsg = "%s %s" % (os.path.basename(cmd.split(None, 1)[0]),

                            explain_exit(rc)[0])

        if errprefix:

            errmsg = "%s: %s" % (errprefix, errmsg)

        raise CommandError(errmsg)

def rename(src, dst):

    try:

        os.rename(src, dst)

    except:

        os.unlink(dst)

        os.rename(src, dst)

# Platfor specific varients

if os.name == 'nt':

    nulldev = 'NUL:'

    def is_exec(f, last):

        return last

    def set_exec(f, mode):

        pass

    def pconvert(path):

        return path.replace("\\", "/")

    def makelock(info, pathname):

        ld = os.open(pathname, os.O_CREAT | os.O_WRONLY | os.O_EXCL)

        os.write(ld, info)

        os.close(ld)

    def readlock(pathname):

        return file(pathname).read()

else:

    nulldev = '/dev/null'

    def is_exec(f, last):

        return (os.stat(f).st_mode & 0100 != 0)

    def set_exec(f, mode):

        s = os.stat(f).st_mode

        if (s & 0100 != 0) == mode:

            return

        if mode:

            # Turn on +x for every +r bit when making a file executable

            # and obey umask.

            umask = os.umask(0)

            os.umask(umask)

            os.chmod(f, s | (s & 0444) >> 2 & ~umask)

        else:

            os.chmod(f, s & 0666)

    def pconvert(path):

        return path

    def makelock(info, pathname):

        os.symlink(info, pathname)

    def readlock(pathname):

        return os.readlink(pathname)