#

# 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]

