projects / ceph.git / blame
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1 | [/ |
| 2 | Copyright 2010 Neil Groves | |
| 3 | Distributed under the Boost Software License, Version 1.0. | |
| 4 | (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
| 5 | /] | |
| 6 | [section:any_range any_range] | |
| 7 | ||
| 8 | [heading Description] | |
| 9 | ||
| 10 | `any_range` is a range that has the type information erased hence a `any_range<int, boost::forward_traversal_tag, int, std::ptrdiff_t>` | |
| 11 | can be used to represent a `std::vector<int>`, a `std::list<int>` or many other types. | |
| 12 | ||
| 13 | The __type_erasure_article__ covers the motivation and goals of type erasure in this context. Clearly | |
| 14 | my implementation is building upon a lot of prior art created by others. Thomas Becker's `any_iterator` was a strong | |
| 15 | influence. Adobe also have an `any_iterator` implementation, but this has very tight coupling to other parts of the | |
| 16 | library that precluded it from use in Boost.Range. | |
| 17 | Early development versions of this Range Adaptor directly used Thomas Becker's any_iterator implementation. | |
| 18 | Subsequently I discovered that the heap allocations of this and many other implementations cause poor | |
| 19 | speed performance particularly at the tails of the distribution. To solve this required a new design that | |
| 20 | incorporated the embedded buffer optimization. | |
| 21 | ||
| 22 | Despite the underlying `any_iterator` being the fastest available implementation, the performance overhead of `any_range` is still appreciable due to the cost of virtual function calls required to implement `increment`, `decrement`, `advance`, `equal` etc. Frequently a better design choice is to convert to a canonical form. | |
| 23 | ||
| 24 | Please see the __range_adaptors_type_erased__ for a Range Adaptor that returns `any_range` instances. | |
| 25 | ||
| 26 | [heading Synopsis] | |
| 27 | ||
| 28 | `` | |
| 29 | template< | |
| 30 | class Value | |
| 31 | , class Traversal | |
| 32 | , class Reference | |
| 33 | , class Difference | |
| 34 | , class Buffer = any_iterator_default_buffer | |
| 35 | > | |
| 36 | class any_range | |
| 37 | : public iterator_range< | |
| 38 | range_detail::any_iterator< | |
| 39 | Value | |
| 40 | , Traversal | |
| 41 | , Reference | |
| 42 | , Difference | |
| 43 | , Buffer | |
| 44 | > | |
| 45 | > | |
| 46 | { | |
| 47 | typedef range_detail::any_iterator< | |
| 48 | Value | |
| 49 | , Traversal | |
| 50 | , Reference | |
| 51 | , Difference | |
| 52 | , Buffer | |
| 53 | > any_iterator_type; | |
| 54 | ||
| 55 | typedef iterator_range<any_iterator_type> base_type; | |
| 56 | ||
| 57 | struct enabler {}; | |
| 58 | struct disabler {}; | |
| 59 | public: | |
| 60 | typedef any_iterator_type iterator; | |
| 61 | typedef any_iterator_type const_iterator; | |
| 62 | ||
| 63 | any_range() | |
| 64 | { | |
| 65 | } | |
| 66 | ||
| 67 | any_range(const any_range& other) | |
| 68 | : base_type(other) | |
| 69 | { | |
| 70 | } | |
| 71 | ||
| 72 | template<class WrappedRange> | |
| 73 | any_range(WrappedRange& wrapped_range) | |
| 74 | : base_type(boost::begin(wrapped_range), | |
| 75 | boost::end(wrapped_range)) | |
| 76 | { | |
| 77 | } | |
| 78 | ||
| 79 | template<class WrappedRange> | |
| 80 | any_range(const WrappedRange& wrapped_range) | |
| 81 | : base_type(boost::begin(wrapped_range), | |
| 82 | boost::end(wrapped_range)) | |
| 83 | { | |
| 84 | } | |
| 85 | ||
| 86 | template< | |
| 87 | class OtherValue | |
| 88 | , class OtherTraversal | |
| 89 | , class OtherReference | |
| 90 | , class OtherDifference | |
| 91 | > | |
| 92 | any_range(const any_range< | |
| 93 | OtherValue | |
| 94 | , OtherTraversal | |
| 95 | , OtherReference | |
| 96 | , OtherDifference | |
| 97 | , Buffer | |
| 98 | >& other) | |
| 99 | : base_type(boost::begin(other), boost::end(other)) | |
| 100 | { | |
| 101 | } | |
| 102 | ||
| 103 | template<class Iterator> | |
| 104 | any_range(Iterator first, Iterator last) | |
| 105 | : base_type(first, last) | |
| 106 | { | |
| 107 | } | |
| 108 | }; | |
| 109 | `` | |
| 110 | ||
| 111 | [heading Definition] | |
| 112 | ||
| 113 | Defined in header file `boost/range/any_range.hpp` | |
| 114 | ||
| 115 | [endsect] |