bindings/python/llvm/common.py

   1 #===- common.py - Python LLVM Bindings -----------------------*- python -*--===#
   2 #
   3 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 # See https://llvm.org/LICENSE.txt for license information.
   5 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 #
   7 #===------------------------------------------------------------------------===#
   8
   9 from ctypes import POINTER
  10 from ctypes import c_void_p
  11 from ctypes import cdll
  12
  13 import ctypes.util
  14 import platform
  15
  16 # LLVM_VERSION: sync with PACKAGE_VERSION in autoconf/configure.ac and CMakeLists.txt
  17 #               but leave out the 'svn' suffix.
  18 LLVM_VERSION = '3.4'
  19
  20 __all__ = [
  21     'c_object_p',
  22     'get_library',
  23 ]
  24
  25 c_object_p = POINTER(c_void_p)
  26
  27 class LLVMObject(object):
  28     """Base class for objects that are backed by an LLVM data structure.
  29
  30     This class should never be instantiated outside of this package.
  31     """
  32     def __init__(self, ptr, ownable=True, disposer=None):
  33         assert isinstance(ptr, c_object_p)
  34
  35         self._ptr = self._as_parameter_ = ptr
  36
  37         self._self_owned = True
  38         self._ownable = ownable
  39         self._disposer = disposer
  40
  41         self._owned_objects = []
  42
  43     def take_ownership(self, obj):
  44         """Take ownership of another object.
  45
  46         When you take ownership of another object, you are responsible for
  47         destroying that object. In addition, a reference to that object is
  48         placed inside this object so the Python garbage collector will not
  49         collect the object while it is still alive in libLLVM.
  50
  51         This method should likely only be called from within modules inside
  52         this package.
  53         """
  54         assert isinstance(obj, LLVMObject)
  55
  56         self._owned_objects.append(obj)
  57         obj._self_owned = False
  58
  59     def from_param(self):
  60         """ctypes function that converts this object to a function parameter."""
  61         return self._as_parameter_
  62
  63     def __del__(self):
  64         if not hasattr(self, '_self_owned') or not hasattr(self, '_disposer'):
  65             return
  66
  67         if self._self_owned and self._disposer:
  68             self._disposer(self)
  69
  70 class CachedProperty(object):
  71     """Decorator that caches the result of a property lookup.
  72
  73     This is a useful replacement for @property. It is recommended to use this
  74     decorator on properties that invoke C API calls for which the result of the
  75     call will be idempotent.
  76     """
  77     def __init__(self, wrapped):
  78         self.wrapped = wrapped
  79         try:
  80             self.__doc__ = wrapped.__doc__
  81         except: # pragma: no cover
  82             pass
  83
  84     def __get__(self, instance, instance_type=None):
  85         if instance is None:
  86             return self
  87
  88         value = self.wrapped(instance)
  89         setattr(instance, self.wrapped.__name__, value)
  90
  91         return value
  92
  93 def get_library():
  94     """Obtain a reference to the llvm library."""
  95
  96     # On Linux, ctypes.cdll.LoadLibrary() respects LD_LIBRARY_PATH
  97     # while ctypes.util.find_library() doesn't.
  98     # See http://docs.python.org/2/library/ctypes.html#finding-shared-libraries
  99     #
 100     # To make it possible to run the unit tests without installing the LLVM shared
 101     # library into a default linker search path.  Always Try ctypes.cdll.LoadLibrary()
 102     # with all possible library names first, then try ctypes.util.find_library().
 103
 104     names = ['LLVM-' + LLVM_VERSION, 'LLVM-' + LLVM_VERSION + 'svn']
 105     t = platform.system()
 106     if t == 'Darwin':
 107         pfx, ext = 'lib', '.dylib'
 108     elif t == 'Windows':
 109         pfx, ext = '', '.dll'
 110     else:
 111         pfx, ext = 'lib', '.so'
 112
 113     for i in names:
 114         try:
 115             lib = cdll.LoadLibrary(pfx + i + ext)
 116         except OSError:
 117             pass
 118         else:
 119             return lib
 120
 121     for i in names:
 122         t = ctypes.util.find_library(i)
 123         if t:
 124             return cdll.LoadLibrary(t)
 125     raise Exception('LLVM shared library not found!')