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//////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga 2006-2007. 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.
//
//////////////////////////////////////////////////////////////////////////////
#include <boost/interprocess/detail/config_begin.hpp>
//[doc_managed_allocation_command
#include <boost/interprocess/managed_shared_memory.hpp>
#include <cassert>
int main()
{
using namespace boost::interprocess;
//Managed memory segment that allocates portions of a shared memory
//segment with the default management algorithm
shared_memory_object::remove("MyManagedShm");
try{
managed_shared_memory managed_shm(create_only, "MyManagedShm", 10000*sizeof(std::size_t));
//Allocate at least 100 bytes, 1000 bytes if possible
std::size_t received_size, min_size = 100, preferred_size = 1000;
std::size_t *ptr = managed_shm.allocation_command<std::size_t>
(allocate_new, min_size, preferred_size, received_size).first;
//Received size must be bigger than min_size
assert(received_size >= min_size);
//Get free memory
std::size_t free_memory_after_allocation = managed_shm.get_free_memory();
//Now write the data
for(std::size_t i = 0; i < 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
std::size_t expanded_size;
std::pair<std::size_t *, bool> ret = managed_shm.allocation_command
(expand_fwd, received_size*2, received_size*3, expanded_size, ptr);
//Check invariants
assert(ret.second == true);
assert(ret.first == ptr);
assert(expanded_size >= received_size*2);
//Get free memory and compare
std::size_t free_memory_after_expansion = managed_shm.get_free_memory();
assert(free_memory_after_expansion < free_memory_after_allocation);
//Write new values
for(std::size_t i = 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
std::size_t shrunk_size;
ret = managed_shm.allocation_command
(shrink_in_place, min_size*2, min_size, shrunk_size, ptr);
//Check invariants
assert(ret.second == true);
assert(ret.first == ptr);
assert(shrunk_size <= min_size*2);
assert(shrunk_size >= min_size);
//Get free memory and compare
std::size_t free_memory_after_shrinking = managed_shm.get_free_memory();
assert(free_memory_after_shrinking > free_memory_after_expansion);
//Deallocate the buffer
managed_shm.deallocate(ptr);
}
catch(...){
shared_memory_object::remove("MyManagedShm");
throw;
}
shared_memory_object::remove("MyManagedShm");
return 0;
}
//]
#include <boost/interprocess/detail/config_end.hpp>
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