Attached is proof-of-concept code for a sentinel iterator adapter. It turns a pointer to sentinel terminated sequence, such as a C-style string, into a forward iterator with a conforming end iterator.
This is more efficient than doing a separate sequence traversal just to find the end.
No, it is not. :-) PS: #include <boost/functional/hash.hpp> #include <algorithm> #include <iostream> #include <windows.h> static size_t test_strlen( char const * s ); static size_t test_sentinel( char const * s ); int main() { int const N = 10000000; DWORD t1 = timeGetTime(); size_t m1 = 0; for( int i = 0; i < N; ++i ) { m1 += test_strlen( "This is a test." ); } DWORD t2 = timeGetTime(); size_t m2 = 0; for( int i = 0; i < N; ++i ) { m2 += test_sentinel( "This is a test." ); } DWORD t3 = timeGetTime(); std::cout << t2 - t1 << " (" << m1 << "); " << t3 - t2 << " (" << m2 << ")\n"; } static size_t test_strlen( char const * s ) { return boost::hash_range( s, s + strlen( s ) ); } // sentinel terminated sequence iterator proof-of-concept // Copyright Beman Dawes, 2009 #include <cassert> // sentinel terminated sequence iterator template < class T, T Sentinel = T() > class sentinel_iterator { public: sentinel_iterator() : m_ptr(0) {} // construct end iterator sentinel_iterator( T * p ) : m_ptr( (p && *p != m_sentinel) ? p : 0 ) {} sentinel_iterator & operator++() { assert(m_ptr); if ( *++m_ptr == m_sentinel ) m_ptr = 0; return *this; } T & operator*() const { assert(m_ptr); return *m_ptr; } bool operator==( const sentinel_iterator & rhs ) const { return m_ptr == rhs.m_ptr; } bool operator!=( const sentinel_iterator & rhs ) const { return m_ptr != rhs.m_ptr; } private: T * m_ptr; // 0 == the end iterator static const T m_sentinel = Sentinel; }; static size_t test_sentinel( char const * s ) { return boost::hash_range( sentinel_iterator< char const >( s ), sentinel_iterator< char const >() ); }