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//////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga 2006-2012. Distributed under the Boost
// Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/libs/interprocess for documentation.
//
//////////////////////////////////////////////////////////////////////////////
//[doc_managed_allocation_command
#include <boost/interprocess/managed_shared_memory.hpp>
#include <cassert>
//<-
#include "../test/get_process_id_name.hpp"
//->
int main()
{
using namespace boost::interprocess;
//Remove shared memory on construction and destruction
struct shm_remove
{
//<-
#if 1
shm_remove() { shared_memory_object::remove(test::get_process_id_name()); }
~shm_remove(){ shared_memory_object::remove(test::get_process_id_name()); }
#else
//->
shm_remove() { shared_memory_object::remove("MySharedMemory"); }
~shm_remove(){ shared_memory_object::remove("MySharedMemory"); }
//<-
#endif
//->
} remover;
//<-
(void)remover;
//->
//Managed memory segment that allocates portions of a shared memory
//segment with the default management algorithm
//<-
#if 1
managed_shared_memory managed_shm(create_only, test::get_process_id_name(), 10000*sizeof(std::size_t));
#else
//->
managed_shared_memory managed_shm(create_only, "MySharedMemory", 10000*sizeof(std::size_t));
//<-
#endif
//->
//Allocate at least 100 bytes, 1000 bytes if possible
managed_shared_memory::size_type min_size = 100;
managed_shared_memory::size_type first_received_size = 1000;
std::size_t *hint = 0;
std::size_t *ptr = managed_shm.allocation_command<std::size_t>
(boost::interprocess::allocate_new, min_size, first_received_size, hint);
//Received size must be bigger than min_size
assert(first_received_size >= min_size);
//Get free memory
managed_shared_memory::size_type free_memory_after_allocation = managed_shm.get_free_memory();
//<-
(void)free_memory_after_allocation;
//->
//Now write the data
for(std::size_t i = 0; i < first_received_size; ++i) ptr[i] = i;
//Now try to triplicate the buffer. We won't admit an expansion
//lower to the double of the original buffer.
//This "should" be successful since no other class is allocating
//memory from the segment
min_size = first_received_size*2;
managed_shared_memory::size_type expanded_size = first_received_size*3;
std::size_t * ret = managed_shm.allocation_command
(boost::interprocess::expand_fwd, min_size, expanded_size, ptr);
//<-
(void)ret;
//->
//Check invariants
assert(ptr != 0);
assert(ret == ptr);
assert(expanded_size >= first_received_size*2);
//Get free memory and compare
managed_shared_memory::size_type free_memory_after_expansion = managed_shm.get_free_memory();
assert(free_memory_after_expansion < free_memory_after_allocation);
//<-
(void)free_memory_after_expansion;
//->
//Write new values
for(std::size_t i = first_received_size; i < expanded_size; ++i) ptr[i] = i;
//Try to shrink approximately to min_size, but the new size
//should be smaller than min_size*2.
//This "should" be successful since no other class is allocating
//memory from the segment
managed_shared_memory::size_type shrunk_size = min_size;
ret = managed_shm.allocation_command
(boost::interprocess::shrink_in_place, min_size*2, shrunk_size, ptr);
//Check invariants
assert(ptr != 0);
assert(ret == ptr);
assert(shrunk_size <= min_size*2);
assert(shrunk_size >= min_size);
//Get free memory and compare
managed_shared_memory::size_type free_memory_after_shrinking = managed_shm.get_free_memory();
assert(free_memory_after_shrinking > free_memory_after_expansion);
//<-
(void)free_memory_after_shrinking;
//->
//Deallocate the buffer
managed_shm.deallocate(ptr);
return 0;
}
//]
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