Source code for multiprocessing.sharedctypes

#
# Module which supports allocation of ctypes objects from shared memory
#
# multiprocessing/sharedctypes.py
#
# Copyright (c) 2006-2008, R Oudkerk
# Licensed to PSF under a Contributor Agreement.
#

import ctypes
import weakref

from . import heap
from . import get_context

from .context import assert_spawning
from .reduction import ForkingPickler

__all__ = ['RawValue', 'RawArray', 'Value', 'Array', 'copy', 'synchronized']

#
#
#

typecode_to_type = {
    'c': ctypes.c_char,  'u': ctypes.c_wchar,
    'b': ctypes.c_byte,  'B': ctypes.c_ubyte,
    'h': ctypes.c_short, 'H': ctypes.c_ushort,
    'i': ctypes.c_int,   'I': ctypes.c_uint,
    'l': ctypes.c_long,  'L': ctypes.c_ulong,
    'f': ctypes.c_float, 'd': ctypes.c_double
    }

#
#
#

def _new_value(type_):
    size = ctypes.sizeof(type_)
    wrapper = heap.BufferWrapper(size)
    return rebuild_ctype(type_, wrapper, None)

[docs]def RawValue(typecode_or_type, *args): ''' Returns a ctypes object allocated from shared memory ''' type_ = typecode_to_type.get(typecode_or_type, typecode_or_type) obj = _new_value(type_) ctypes.memset(ctypes.addressof(obj), 0, ctypes.sizeof(obj)) obj.__init__(*args) return obj
[docs]def RawArray(typecode_or_type, size_or_initializer): ''' Returns a ctypes array allocated from shared memory ''' type_ = typecode_to_type.get(typecode_or_type, typecode_or_type) if isinstance(size_or_initializer, int): type_ = type_ * size_or_initializer obj = _new_value(type_) ctypes.memset(ctypes.addressof(obj), 0, ctypes.sizeof(obj)) return obj else: type_ = type_ * len(size_or_initializer) result = _new_value(type_) result.__init__(*size_or_initializer) return result
[docs]def Value(typecode_or_type, *args, lock=True, ctx=None): ''' Return a synchronization wrapper for a Value ''' obj = RawValue(typecode_or_type, *args) if lock is False: return obj if lock in (True, None): ctx = ctx or get_context() lock = ctx.RLock() if not hasattr(lock, 'acquire'): raise AttributeError("'%r' has no method 'acquire'" % lock) return synchronized(obj, lock, ctx=ctx)
[docs]def Array(typecode_or_type, size_or_initializer, *, lock=True, ctx=None): ''' Return a synchronization wrapper for a RawArray ''' obj = RawArray(typecode_or_type, size_or_initializer) if lock is False: return obj if lock in (True, None): ctx = ctx or get_context() lock = ctx.RLock() if not hasattr(lock, 'acquire'): raise AttributeError("'%r' has no method 'acquire'" % lock) return synchronized(obj, lock, ctx=ctx)
[docs]def copy(obj): new_obj = _new_value(type(obj)) ctypes.pointer(new_obj)[0] = obj return new_obj
[docs]def synchronized(obj, lock=None, ctx=None): assert not isinstance(obj, SynchronizedBase), 'object already synchronized' ctx = ctx or get_context() if isinstance(obj, ctypes._SimpleCData): return Synchronized(obj, lock, ctx) elif isinstance(obj, ctypes.Array): if obj._type_ is ctypes.c_char: return SynchronizedString(obj, lock, ctx) return SynchronizedArray(obj, lock, ctx) else: cls = type(obj) try: scls = class_cache[cls] except KeyError: names = [field[0] for field in cls._fields_] d = dict((name, make_property(name)) for name in names) classname = 'Synchronized' + cls.__name__ scls = class_cache[cls] = type(classname, (SynchronizedBase,), d) return scls(obj, lock, ctx) # # Functions for pickling/unpickling #
def reduce_ctype(obj): assert_spawning(obj) if isinstance(obj, ctypes.Array): return rebuild_ctype, (obj._type_, obj._wrapper, obj._length_) else: return rebuild_ctype, (type(obj), obj._wrapper, None) def rebuild_ctype(type_, wrapper, length): if length is not None: type_ = type_ * length ForkingPickler.register(type_, reduce_ctype) buf = wrapper.create_memoryview() obj = type_.from_buffer(buf) obj._wrapper = wrapper return obj # # Function to create properties # def make_property(name): try: return prop_cache[name] except KeyError: d = {} exec(template % ((name,)*7), d) prop_cache[name] = d[name] return d[name] template = ''' def get%s(self): self.acquire() try: return self._obj.%s finally: self.release() def set%s(self, value): self.acquire() try: self._obj.%s = value finally: self.release() %s = property(get%s, set%s) ''' prop_cache = {} class_cache = weakref.WeakKeyDictionary() # # Synchronized wrappers # class SynchronizedBase(object): def __init__(self, obj, lock=None, ctx=None): self._obj = obj if lock: self._lock = lock else: ctx = ctx or get_context(force=True) self._lock = ctx.RLock() self.acquire = self._lock.acquire self.release = self._lock.release def __reduce__(self): assert_spawning(self) return synchronized, (self._obj, self._lock) def get_obj(self): return self._obj def get_lock(self): return self._lock def __repr__(self): return '<%s wrapper for %s>' % (type(self).__name__, self._obj) class Synchronized(SynchronizedBase): value = make_property('value') class SynchronizedArray(SynchronizedBase): def __len__(self): return len(self._obj) def __getitem__(self, i): self.acquire() try: return self._obj[i] finally: self.release() def __setitem__(self, i, value): self.acquire() try: self._obj[i] = value finally: self.release() def __getslice__(self, start, stop): self.acquire() try: return self._obj[start:stop] finally: self.release() def __setslice__(self, start, stop, values): self.acquire() try: self._obj[start:stop] = values finally: self.release() class SynchronizedString(SynchronizedArray): value = make_property('value') raw = make_property('raw')