source: parabix-LLVM/llvm_git/bindings/python/llvm/common.py @ 4078

Last change on this file since 4078 was 4078, checked in by linmengl, 5 years ago

checkin llvm-meng source

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