# 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.

def unique(g):

    seen = {}

    for f in g:

        if f not in seen:

            seen[f] = 1

            yield f

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.WSTOPSIG(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)

def copytree(src, dst, copyfile):

    """Copy a directory tree, files are copied using 'copyfile'."""

    names = os.listdir(src)

    os.mkdir(dst)

    for name in names:

        srcname = os.path.join(src, name)

        dstname = os.path.join(dst, name)

        if os.path.isdir(srcname):

            copytree(srcname, dstname, copyfile)

        elif os.path.isfile(srcname):

            copyfile(srcname, dstname)

        else:

            raise IOError("Not a regular file: %r" % srcname)

# 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("\\", "/")

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):

    def readlock(pathname):