projects / ceph.git / blame
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|---|---|---|
| 7c673cae FG |
1 | // -*- C++ -*- |
| 2 | ||
| 3 | // Copyright (C) 2007 Douglas Gregor <doug.gregor@gmail.com> | |
| 4 | ||
| 5 | // Use, modification and distribution is subject to the Boost Software | |
| 6 | // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at | |
| 7 | // http://www.boost.org/LICENSE_1_0.txt) | |
| 8 | #ifndef BOOST_GRAPH_DISTRIBUTED_TAG_ALLOCATOR_HPP | |
| 9 | #define BOOST_GRAPH_DISTRIBUTED_TAG_ALLOCATOR_HPP | |
| 10 | ||
| 11 | #ifndef BOOST_GRAPH_USE_MPI | |
| 12 | #error "Parallel BGL files should not be included unless <boost/graph/use_mpi.hpp> has been included" | |
| 13 | #endif | |
| 14 | ||
| 15 | #include <vector> | |
| 16 | ||
| 17 | namespace boost { namespace graph { namespace distributed { namespace detail { | |
| 18 | ||
| 19 | /** | |
| 20 | * \brief The tag allocator allows clients to request unique tags that | |
| 21 | * can be used for one-time communications. | |
| 22 | * | |
| 23 | * The tag allocator hands out tag values from a predefined maximum | |
| 24 | * (given in the constructor) moving downward. Tags are provided one | |
| 25 | * at a time via a @c token. When the @c token goes out of scope, the | |
| 26 | * tag is returned and may be reallocated. These tags should be used, | |
| 27 | * for example, for one-time communication of values. | |
| 28 | */ | |
| 29 | class tag_allocator { | |
| 30 | public: | |
| 31 | class token; | |
| 32 | friend class token; | |
| 33 | ||
| 34 | /** | |
| 35 | * Construct a new tag allocator that provides unique tags starting | |
| 36 | * with the value @p top_tag and moving lower, as necessary. | |
| 37 | */ | |
| 38 | explicit tag_allocator(int top_tag) : bottom(top_tag) { } | |
| 39 | ||
| 40 | /** | |
| 41 | * Retrieve a new tag. The token itself holds onto the tag, which | |
| 42 | * will be released when the token is destroyed. | |
| 43 | */ | |
| 44 | token get_tag(); | |
| 45 | ||
| 46 | private: | |
| 47 | int bottom; | |
| 48 | std::vector<int> freed; | |
| 49 | }; | |
| 50 | ||
| 51 | /** | |
| 52 | * A token used to represent an allocated tag. | |
| 53 | */ | |
| 54 | class tag_allocator::token { | |
| 55 | public: | |
| 56 | /// Transfer ownership of the tag from @p other. | |
| 57 | token(const token& other); | |
| 58 | ||
| 59 | /// De-allocate the tag, if this token still owns it. | |
| 60 | ~token(); | |
| 61 | ||
| 62 | /// Retrieve the tag allocated for this task. | |
| 63 | operator int() const { return tag_; } | |
| 64 | ||
| 65 | private: | |
| 66 | /// Create a token with a specific tag from the given tag_allocator | |
| 67 | token(tag_allocator* allocator, int tag) | |
| 68 | : allocator(allocator), tag_(tag) { } | |
| 69 | ||
| 70 | /// Undefined: tokens are not copy-assignable | |
| 71 | token& operator=(const token&); | |
| 72 | ||
| 73 | /// The allocator from which this tag was allocated. | |
| 74 | tag_allocator* allocator; | |
| 75 | ||
| 76 | /// The stored tag flag. If -1, this token does not own the tag. | |
| 77 | mutable int tag_; | |
| 78 | ||
| 79 | friend class tag_allocator; | |
| 80 | }; | |
| 81 | ||
| 82 | } } } } // end namespace boost::graph::distributed::detail | |
| 83 | ||
| 84 | #endif // BOOST_GRAPH_DISTRIBUTED_TAG_ALLOCATOR_HPP |