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from __future__ import absolute_import

from __future__ import unicode_literals

import io

import os.path

import shlex

import string

from pre_commit import five

printable = frozenset(string.printable)

class ExecutableNotFoundError(OSError):

pass

def parse_bytesio(bytesio):

"""Parse the shebang from a file opened for reading binary."""

if bytesio.read(2) != b'#!':

return ()

first_line = bytesio.readline()

try:

first_line = first_line.decode('US-ASCII')

except UnicodeDecodeError:

return ()

# Require only printable ascii

for c in first_line:

if c not in printable:

return ()

# shlex.split is horribly broken in py26 on text strings

cmd = tuple(shlex.split(five.n(first_line)))

if cmd[0] == '/usr/bin/env':

cmd = cmd[1:]

return cmd

def parse_filename(filename):

"""Parse the shebang given a filename."""

if not os.path.exists(filename) or not os.access(filename, os.X_OK):

return ()

with io.open(filename, 'rb') as f:

return parse_bytesio(f)

def find_executable(exe, _environ=None):

exe = os.path.normpath(exe)

if os.sep in exe:

return exe

environ = _environ if _environ is not None else os.environ

if 'PATHEXT' in environ:

possible_exe_names = (exe,) + tuple(

exe + ext.lower() for ext in environ['PATHEXT'].split(os.pathsep)

)

else:

possible_exe_names = (exe,)

for path in environ.get('PATH', '').split(os.pathsep):

for possible_exe_name in possible_exe_names:

joined = os.path.join(path, possible_exe_name)

if os.path.isfile(joined) and os.access(joined, os.X_OK):

return joined

else:

return None

def normexe(orig_exe):

if os.sep not in orig_exe:

exe = find_executable(orig_exe)

if exe is None:

raise ExecutableNotFoundError(

'Executable `{0}` not found'.format(orig_exe),

)

return exe

else:

return orig_exe

def normalize_cmd(cmd):

"""Fixes for the following issues on windows

- http://bugs.python.org/issue8557

- windows does not parse shebangs

This function also makes deep-path shebangs work just fine

"""

# Use PATH to determine the executable

exe = normexe(cmd[0])

# Figure out the shebang from the resulting command

cmd = parse_filename(exe) + (exe,) + cmd[1:]

# This could have given us back another bare executable

exe = normexe(cmd[0])

return (exe,) + cmd[1:]

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