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