#

# Module which supports allocation of memory from an mmap

#

# multiprocessing/heap.py

#

# Copyright (c) 2007-2008, R Oudkerk --- see COPYING.txt

#

import bisect

import mmap

import tempfile

import os

import sys

import threading

import itertools

import _multiprocessing

from multiprocessing.util import Finalize, info

from multiprocessing.forking import assert_spawning

__all__ = ['BufferWrapper']

#

# Inheirtable class which wraps an mmap, and from which blocks can be allocated

#

if sys.platform == 'win32':

    from ._multiprocessing import win32

    class Arena(object):

        _counter = itertools.count()

        def __init__(self, size):

            self.size = size

            self.name = 'pym-%d-%d' % (os.getpid(), Arena._counter.next())

            self.buffer = mmap.mmap(-1, self.size, tagname=self.name)

            assert win32.GetLastError() == 0, 'tagname already in use'

            self._state = (self.size, self.name)

        def __getstate__(self):

            assert_spawning(self)

            return self._state

        def __setstate__(self, state):

            self.size, self.name = self._state = state

            self.buffer = mmap.mmap(-1, self.size, tagname=self.name)

            assert win32.GetLastError() == win32.ERROR_ALREADY_EXISTS

else:

    class Arena(object):

        def __init__(self, size):

            self.buffer = mmap.mmap(-1, size)

            self.size = size

            self.name = None

#

# Class allowing allocation of chunks of memory from arenas

#

class Heap(object):

    _alignment = 8

    def __init__(self, size=mmap.PAGESIZE):

        self._lastpid = os.getpid()

        self._lock = threading.Lock()

        self._size = size

        self._lengths = []

        self._len_to_seq = {}

        self._start_to_block = {}

        self._stop_to_block = {}

        self._allocated_blocks = set()

        self._arenas = []

    @staticmethod

    def _roundup(n, alignment):

        # alignment must be a power of 2

        mask = alignment - 1

        return (n + mask) & ~mask

    def _malloc(self, size):

        # returns a large enough block -- it might be much larger

        i = bisect.bisect_left(self._lengths, size)

        if i == len(self._lengths):

            length = self._roundup(max(self._size, size), mmap.PAGESIZE)

            self._size *= 2

            info('allocating a new mmap of length %d', length)

            arena = Arena(length)

            self._arenas.append(arena)

            return (arena, 0, length)

        else:

            length = self._lengths[i]

            seq = self._len_to_seq[length]

            block = seq.pop()

            if not seq:

                del self._len_to_seq[length], self._lengths[i]

        (arena, start, stop) = block

        del self._start_to_block[(arena, start)]

        del self._stop_to_block[(arena, stop)]

        return block

    def _free(self, block):

        # free location and try to merge with neighbours

        (arena, start, stop) = block

        try:

            prev_block = self._stop_to_block[(arena, start)]

        except KeyError:

            pass

        else:

            start, _ = self._absorb(prev_block)

        try:

            next_block = self._start_to_block[(arena, stop)]

        except KeyError:

            pass

        else:

            _, stop = self._absorb(next_block)

        block = (arena, start, stop)

        length = stop - start

        try:

            self._len_to_seq[length].append(block)

        except KeyError:

            self._len_to_seq[length] = [block]

            bisect.insort(self._lengths, length)

        self._start_to_block[(arena, start)] = block

        self._stop_to_block[(arena, stop)] = block

    def _absorb(self, block):

        # deregister this block so it can be merged with a neighbour

        (arena, start, stop) = block

        del self._start_to_block[(arena, start)]

        del self._stop_to_block[(arena, stop)]

        length = stop - start

        seq = self._len_to_seq[length]

        seq.remove(block)

        if not seq:

            del self._len_to_seq[length]

            self._lengths.remove(length)

        return start, stop

    def free(self, block):

        # free a block returned by malloc()

        assert os.getpid() == self._lastpid

        self._lock.acquire()

        try:

            self._allocated_blocks.remove(block)

            self._free(block)

        finally:

            self._lock.release()

    def malloc(self, size):

        # return a block of right size (possibly rounded up)

        assert 0 <= size < sys.maxint

        if os.getpid() != self._lastpid:

            self.__init__()                     # reinitialize after fork

        self._lock.acquire()

        try:

            size = self._roundup(max(size,1), self._alignment)

            (arena, start, stop) = self._malloc(size)

            new_stop = start + size

            if new_stop < stop:

                self._free((arena, new_stop, stop))

            block = (arena, start, new_stop)

            self._allocated_blocks.add(block)

            return block

        finally:

            self._lock.release()

#

# Class representing a chunk of an mmap -- can be inherited

#

class BufferWrapper(object):

    _heap = Heap()

    def __init__(self, size):

        assert 0 <= size < sys.maxint

        block = BufferWrapper._heap.malloc(size)

        self._state = (block, size)

        Finalize(self, BufferWrapper._heap.free, args=(block,))

    def get_address(self):

        (arena, start, stop), size = self._state

        address, length = _multiprocessing.address_of_buffer(arena.buffer)

        assert size <= length

        return address + start

    def get_size(self):

        return self._state[1]