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This backports the recent optimization to search_n back to so_6. The only major difference is that it doesn't use find_if in the predicated case. It never did, and to enable this would involve copying a bunch of framework. Tested on powerpc-darwin Chris
Index: stl_algo.h =================================================================== RCS file: /cvsroot/gcc/gcc/libstdc++-v3/include/bits/stl_algo.h,v retrieving revision 1.57 diff -u -r1.57 stl_algo.h --- stl_algo.h 17 Aug 2005 02:12:56 -0000 1.57 +++ stl_algo.h 10 Sep 2005 15:20:41 -0000 @@ -607,6 +607,92 @@ } /** + * @if maint + * This is an uglified + * search_n(_ForwardIterator, _ForwardIterator, _Integer, const _Tp&) + * overloaded for forward iterators. + * @endif + */ + template<typename _ForwardIterator, typename _Integer, typename _Tp> + _ForwardIterator + __search_n(_ForwardIterator __first, _ForwardIterator __last, + _Integer __count, const _Tp& __val, + std::forward_iterator_tag) + { + __first = std::find(__first, __last, __val); + while (__first != __last) + { + typename iterator_traits<_ForwardIterator>::difference_type + __n = __count; + _ForwardIterator __i = __first; + ++__i; + while (__i != __last && __n != 1 && *__i == __val) + { + ++__i; + --__n; + } + if (__n == 1) + return __first; + if (__i == __last) + return __last; + __first = std::find(++__i, __last, __val); + } + return __last; + } + + /** + * @if maint + * This is an uglified + * search_n(_ForwardIterator, _ForwardIterator, _Integer, const _Tp&) + * overloaded for random access iterators. + * @endif + */ + template<typename _RandomAccessIter, typename _Integer, typename _Tp> + _RandomAccessIter + __search_n(_RandomAccessIter __first, _RandomAccessIter __last, + _Integer __count, const _Tp& __val, + std::random_access_iterator_tag) + { + + typedef typename std::iterator_traits<_RandomAccessIter>::difference_type + _DistanceType; + + _DistanceType __tailSize = __last - __first; + const _DistanceType __pattSize = __count; + + if (__tailSize < __pattSize) + return __last; + + const _DistanceType __skipOffset = __pattSize - 1; + _RandomAccessIter __lookAhead = __first + __skipOffset; + __tailSize -= __pattSize; + + while (1) // the main loop... + { + // __lookAhead here is always pointing to the last element of next + // possible match. + while (!(*__lookAhead == __val)) // the skip loop... + { + if (__tailSize < __pattSize) + return __last; // Failure + __lookAhead += __pattSize; + __tailSize -= __pattSize; + } + _DistanceType __remainder = __skipOffset; + for (_RandomAccessIter __backTrack = __lookAhead - 1; + *__backTrack == __val; --__backTrack) + { + if (--__remainder == 0) + return (__lookAhead - __skipOffset); // Success + } + if (__remainder > __tailSize) + return __last; // Failure + __lookAhead += __remainder; + __tailSize -= __remainder; + } + } + + /** * @brief Search a sequence for a number of consecutive values. * @param first A forward iterator. * @param last A forward iterator. @@ -632,27 +718,104 @@ if (__count <= 0) return __first; - else + if (__count == 1) + return std::find(__first, __last, __val); + return std::__search_n(__first, __last, __count, __val, + std::__iterator_category(__first)); + } + + /** + * @if maint + * This is an uglified + * search_n(_ForwardIterator, _ForwardIterator, _Integer, const _Tp&, + * _BinaryPredicate) + * overloaded for forward iterators. + * @endif + */ + template<typename _ForwardIterator, typename _Integer, typename _Tp, + typename _BinaryPredicate> + _ForwardIterator + __search_n(_ForwardIterator __first, _ForwardIterator __last, + _Integer __count, const _Tp& __val, + _BinaryPredicate __binary_pred, std::forward_iterator_tag) + { + while (__first != __last && !__binary_pred(*__first, __val)) + ++__first; + + while (__first != __last) + { + typename iterator_traits<_ForwardIterator>::difference_type + __n = __count; + _ForwardIterator __i = __first; + ++__i; + while (__i != __last && __n != 1 && *__i == __val) { - __first = std::find(__first, __last, __val); - while (__first != __last) - { - typename iterator_traits<_ForwardIterator>::difference_type - __n = __count; - _ForwardIterator __i = __first; - ++__i; - while (__i != __last && __n != 1 && *__i == __val) - { - ++__i; - --__n; - } - if (__n == 1) - return __first; - else - __first = std::find(__i, __last, __val); - } + ++__i; + --__n; + } + if (__n == 1) + return __first; + if (__i == __last) return __last; + __first = ++__i; + while (__first != __last && !__binary_pred(*__first, __val)) + ++__first; + } + return __last; + } + + /** + * @if maint + * This is an uglified + * search_n(_ForwardIterator, _ForwardIterator, _Integer, const _Tp&, + * _BinaryPredicate) + * overloaded for random access iterators. + * @endif + */ + template<typename _RandomAccessIter, typename _Integer, typename _Tp, + typename _BinaryPredicate> + _RandomAccessIter + __search_n(_RandomAccessIter __first, _RandomAccessIter __last, + _Integer __count, const _Tp& __val, + _BinaryPredicate __binary_pred, std::random_access_iterator_tag) + { + + typedef typename std::iterator_traits<_RandomAccessIter>::difference_type + _DistanceType; + + _DistanceType __tailSize = __last - __first; + const _DistanceType __pattSize = __count; + + if (__tailSize < __pattSize) + return __last; + + const _DistanceType __skipOffset = __pattSize - 1; + _RandomAccessIter __lookAhead = __first + __skipOffset; + __tailSize -= __pattSize; + + while (1) // the main loop... + { + // __lookAhead here is always pointing to the last element of next + // possible match. + while (!__binary_pred(*__lookAhead, __val)) // the skip loop... + { + if (__tailSize < __pattSize) + return __last; // Failure + __lookAhead += __pattSize; + __tailSize -= __pattSize; + } + _DistanceType __remainder = __skipOffset; + for (_RandomAccessIter __backTrack = __lookAhead - 1; + __binary_pred(*__backTrack, __val); --__backTrack) + { + if (--__remainder == 0) + return (__lookAhead - __skipOffset); // Success } + if (__remainder > __tailSize) + return __last; // Failure + __lookAhead += __remainder; + __tailSize -= __remainder; + } } /** @@ -685,40 +848,14 @@ if (__count <= 0) return __first; - else - { - while (__first != __last) - { - if (__binary_pred(*__first, __val)) - break; - ++__first; - } - while (__first != __last) - { - typename iterator_traits<_ForwardIterator>::difference_type - __n = __count; - _ForwardIterator __i = __first; - ++__i; - while (__i != __last && __n != 1 && __binary_pred(*__i, __val)) - { - ++__i; - --__n; - } - if (__n == 1) - return __first; - else - { - while (__i != __last) - { - if (__binary_pred(*__i, __val)) - break; - ++__i; - } - __first = __i; - } - } - return __last; - } + if (__count == 1) + { + while (__first != __last && !__binary_pred(*__first, __val)) + ++__first; + return __first; + } + return std::__search_n(__first, __last, __count, __val, __binary_pred, + std::__iterator_category(__first)); } /**
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