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- // -*- C++ -*-
- // Copyright (C) 2007 Douglas Gregor <doug.gregor@gmail.com>
- // Use, modification and distribution is subject to 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)
- #ifndef BOOST_GRAPH_DISTRIBUTED_TAG_ALLOCATOR_HPP
- #define BOOST_GRAPH_DISTRIBUTED_TAG_ALLOCATOR_HPP
- #ifndef BOOST_GRAPH_USE_MPI
- #error "Parallel BGL files should not be included unless <boost/graph/use_mpi.hpp> has been included"
- #endif
- #include <vector>
- namespace boost { namespace graph { namespace distributed { namespace detail {
- /**
- * \brief The tag allocator allows clients to request unique tags that
- * can be used for one-time communications.
- *
- * The tag allocator hands out tag values from a predefined maximum
- * (given in the constructor) moving downward. Tags are provided one
- * at a time via a @c token. When the @c token goes out of scope, the
- * tag is returned and may be reallocated. These tags should be used,
- * for example, for one-time communication of values.
- */
- class tag_allocator {
- public:
- class token;
- friend class token;
- /**
- * Construct a new tag allocator that provides unique tags starting
- * with the value @p top_tag and moving lower, as necessary.
- */
- explicit tag_allocator(int top_tag) : bottom(top_tag) { }
- /**
- * Retrieve a new tag. The token itself holds onto the tag, which
- * will be released when the token is destroyed.
- */
- token get_tag();
- private:
- int bottom;
- std::vector<int> freed;
- };
- /**
- * A token used to represent an allocated tag.
- */
- class tag_allocator::token {
- public:
- /// Transfer ownership of the tag from @p other.
- token(const token& other);
- /// De-allocate the tag, if this token still owns it.
- ~token();
- /// Retrieve the tag allocated for this task.
- operator int() const { return tag_; }
- private:
- /// Create a token with a specific tag from the given tag_allocator
- token(tag_allocator* allocator, int tag)
- : allocator(allocator), tag_(tag) { }
- /// Undefined: tokens are not copy-assignable
- token& operator=(const token&);
- /// The allocator from which this tag was allocated.
- tag_allocator* allocator;
- /// The stored tag flag. If -1, this token does not own the tag.
- mutable int tag_;
- friend class tag_allocator;
- };
- } } } } // end namespace boost::graph::distributed::detail
- #endif // BOOST_GRAPH_DISTRIBUTED_TAG_ALLOCATOR_HPP
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