file/python/magic.py

#!/usr/bin/env python
'''
Python bindings for libmagic
'''

import ctypes

from ctypes import *
from ctypes.util import find_library

def _init():
    """
    Loads the shared library through ctypes and returns a library
    L{ctypes.CDLL} instance 
    """
    return ctypes.cdll.LoadLibrary(find_library('magic'))

_libraries = {}
_libraries['magic'] = _init()

# Flag constants for open and setflags
MAGIC_NONE = NONE = 0
MAGIC_DEBUG = DEBUG = 1
MAGIC_SYMLINK = SYMLINK = 2
MAGIC_COMPRESS = COMPRESS = 4
MAGIC_DEVICES = DEVICES = 8
MAGIC_MIME_TYPE = MIME_TYPE = 16
MAGIC_CONTINUE = CONTINUE = 32
MAGIC_CHECK = CHECK = 64
MAGIC_PRESERVE_ATIME = PRESERVE_ATIME = 128
MAGIC_RAW = RAW = 256
MAGIC_ERROR = ERROR = 512
MAGIC_MIME_ENCODING = MIME_ENCODING = 1024
MAGIC_MIME = MIME = 1040
MAGIC_APPLE = APPLE = 2048

MAGIC_NO_CHECK_COMPRESS = NO_CHECK_COMPRESS = 4096
MAGIC_NO_CHECK_TAR = NO_CHECK_TAR = 8192
MAGIC_NO_CHECK_SOFT = NO_CHECK_SOFT = 16384
MAGIC_NO_CHECK_APPTYPE = NO_CHECK_APPTYPE = 32768
MAGIC_NO_CHECK_ELF = NO_CHECK_ELF = 65536
MAGIC_NO_CHECK_TEXT = NO_CHECK_TEXT = 131072
MAGIC_NO_CHECK_CDF = NO_CHECK_CDF = 262144
MAGIC_NO_CHECK_TOKENS = NO_CHECK_TOKENS = 1048576
MAGIC_NO_CHECK_ENCODING = NO_CHECK_ENCODING = 2097152

MAGIC_NO_CHECK_BUILTIN = NO_CHECK_BUILTIN = 4173824

class magic_set(Structure):
    pass
magic_set._fields_ = []
magic_t = POINTER(magic_set)

_open = _libraries['magic'].magic_open
_open.restype = magic_t
_open.argtypes = [c_int]

_close = _libraries['magic'].magic_close
_close.restype = None
_close.argtypes = [magic_t]

_file = _libraries['magic'].magic_file
_file.restype = c_char_p
_file.argtypes = [magic_t, c_char_p]

_descriptor = _libraries['magic'].magic_descriptor
_descriptor.restype = c_char_p
_descriptor.argtypes = [magic_t, c_int]

_buffer = _libraries['magic'].magic_buffer
_buffer.restype = c_char_p
_buffer.argtypes = [magic_t, c_void_p, c_size_t]

_error = _libraries['magic'].magic_error
_error.restype = c_char_p
_error.argtypes = [magic_t]

_setflags = _libraries['magic'].magic_setflags
_setflags.restype = c_int
_setflags.argtypes = [magic_t, c_int]

_load = _libraries['magic'].magic_load
_load.restype = c_int
_load.argtypes = [magic_t, c_char_p]

_compile = _libraries['magic'].magic_compile
_compile.restype = c_int
_compile.argtypes = [magic_t, c_char_p]

_check = _libraries['magic'].magic_check
_check.restype = c_int
_check.argtypes = [magic_t, c_char_p]

_list = _libraries['magic'].magic_list
_list.restype = c_int
_list.argtypes = [magic_t, c_char_p]

_errno = _libraries['magic'].magic_errno
_errno.restype = c_int
_errno.argtypes = [magic_t]

class Magic(object):
    def __init__(self, ms):
        self._magic_t = ms

    def close(self):
        """
        Closes the magic database and deallocates any resources used.
        """
        _close(self._magic_t)

    def file(self, filename):
        """
        Returns a textual description of the contents of the argument passed
        as a filename or None if an error occurred and the MAGIC_ERROR flag
        is set.  A call to errno() will return the numeric error code.
        """
        try: # attempt python3 approach first
            bi = bytes(filename, 'utf-8')
            return str(_file(self._magic_t, bi), 'utf-8')
        except:
            return _file(self._magic_t, filename.encode('utf-8'))

    def descriptor(self, fd):
        """
        Like the file method, but the argument is a file descriptor.
        """
        return _descriptor(self._magic_t, fd)

    def buffer(self, buf):
        """
        Returns a textual description of the contents of the argument passed
        as a buffer or None if an error occurred and the MAGIC_ERROR flag
        is set. A call to errno() will return the numeric error code.
        """
        try: # attempt python3 approach first
            return str(_buffer(self._magic_t, buf, len(buf)), 'utf-8')
        except:
            return _buffer(self._magic_t, buf, len(buf))

    def error(self):
        """
        Returns a textual explanation of the last error or None
        if there was no error.
        """
        try: # attempt python3 approach first
            return str(_error(self._magic_t), 'utf-8')
        except:
            return _error(self._magic_t)
  
    def setflags(self, flags):
        """
        Set flags on the magic object which determine how magic checking behaves;
        a bitwise OR of the flags described in libmagic(3), but without the MAGIC_
        prefix.

        Returns -1 on systems that don't support utime(2) or utimes(2)
        when PRESERVE_ATIME is set.
        """
        return _setflags(self._magic_t, flags)

    def load(self, filename=None):
        """
        Must be called to load entries in the colon separated list of database files
        passed as argument or the default database file if no argument before
        any magic queries can be performed.
        
        Returns 0 on success and -1 on failure.
        """
        return _load(self._magic_t, filename)

    def compile(self, dbs):
        """
        Compile entries in the colon separated list of database files
        passed as argument or the default database file if no argument.
        Returns 0 on success and -1 on failure.
        The compiled files created are named from the basename(1) of each file
        argument with ".mgc" appended to it.
        """
        return _compile(self._magic_t, dbs)

    def check(self, dbs):
        """
        Check the validity of entries in the colon separated list of
        database files passed as argument or the default database file
        if no argument.
        Returns 0 on success and -1 on failure.
        """
        return _check(self._magic_t, dbs)

    def list(self, dbs):
        """
        Check the validity of entries in the colon separated list of
        database files passed as argument or the default database file
        if no argument.
        Returns 0 on success and -1 on failure.
        """
        return _list(self._magic_t, dbs)
    
    def errno(self):
        """
        Returns a numeric error code. If return value is 0, an internal
        magic error occurred. If return value is non-zero, the value is
        an OS error code. Use the errno module or os.strerror() can be used
        to provide detailed error information.
        """
        return _errno(self._magic_t)

def open(flags):
    """
    Returns a magic object on success and None on failure.
    Flags argument as for setflags.
    """
    return Magic(_open(flags))