/* Lazy evaluation support Mark Jenkinson, FMRIB Image Analysis Group Copyright (C) 2000 University of Oxford */ /* Part of FSL - FMRIB's Software Library http://www.fmrib.ox.ac.uk/fsl fsl@fmrib.ox.ac.uk Developed at FMRIB (Oxford Centre for Functional Magnetic Resonance Imaging of the Brain), Department of Clinical Neurology, Oxford University, Oxford, UK LICENCE FMRIB Software Library, Release 5.0 (c) 2012, The University of Oxford (the "Software") The Software remains the property of the University of Oxford ("the University"). The Software is distributed "AS IS" under this Licence solely for non-commercial use in the hope that it will be useful, but in order that the University as a charitable foundation protects its assets for the benefit of its educational and research purposes, the University makes clear that no condition is made or to be implied, nor is any warranty given or to be implied, as to the accuracy of the Software, or that it will be suitable for any particular purpose or for use under any specific conditions. Furthermore, the University disclaims all responsibility for the use which is made of the Software. It further disclaims any liability for the outcomes arising from using the Software. 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You are not permitted under this Licence to use this Software commercially. Use for which any financial return is received shall be defined as commercial use, and includes (1) integration of all or part of the source code or the Software into a product for sale or license by or on behalf of Licensee to third parties or (2) use of the Software or any derivative of it for research with the final aim of developing software products for sale or license to a third party or (3) use of the Software or any derivative of it for research with the final aim of developing non-software products for sale or license to a third party, or (4) use of the Software to provide any service to an external organisation for which payment is received. If you are interested in using the Software commercially, please contact Isis Innovation Limited ("Isis"), the technology transfer company of the University, to negotiate a licence. Contact details are: innovation@isis.ox.ac.uk quoting reference DE/9564. */ #if !defined(__lazy_h) #define __lazy_h #include #include #include #ifndef NO_NAMESPACE using namespace std; namespace LAZY { #endif typedef std::map > mapclass; typedef std::map >::iterator mapiterator; //-------------------------------------------------------------------------// template class lazy { private: mutable T storedval; unsigned int tag; const S *iptr; T (*calc_fn)(const S &); private: const T& value() const; T calculate_val() const { return (*calc_fn)(*iptr); } public: lazy() { tag = 0; } void init(const S *, T (*fnptr)(const S &)); void copy(const lazy &, const S *); const T& force_recalculation() const; const T& operator() () const { return this->value(); } }; //-------------------------------------------------------------------------// class lazymanager { template friend class lazy; private: mutable bool validflag; mutable mapclass validcache; mutable unsigned int tagnum; private: unsigned int getnewtag() const { return tagnum++; } const bool is_whole_cache_valid() const { return validflag; } const bool is_cache_entry_valid(const unsigned int tag) const { return validcache[tag]; } void set_cache_entry_validity(const unsigned int tag, const bool newflag) const { validcache[tag] = newflag; } void invalidate_whole_cache() const; public: lazymanager(); void copylazymanager(const lazymanager &); void set_whole_cache_validity(const bool newflag) const { validflag = newflag; } }; //-------------------------------------------------------------------------// // Body of lazy member functions (put here as cannot simply separate // templated definitions into seperate source files if building a library) template const T& lazy::value() const { if ( (iptr == 0) || (tag==0) ) { cerr << "Error: uninitialized lazy evaluation class" << endl; exit(-1); } if (! iptr->is_whole_cache_valid() ) { iptr->invalidate_whole_cache(); iptr->set_whole_cache_validity(true); } if (! iptr->is_cache_entry_valid(tag)) { //cerr << "Calculating value" << endl; storedval = calculate_val(); iptr->set_cache_entry_validity(tag,true); } return storedval; } template const T& lazy::force_recalculation() const { if ( (iptr == 0) || (tag==0) ) { cerr << "Error: uninitialized lazy evaluation class" << endl; exit(-1); } // still process the whole cache vailidity so that this calculation // can get cached correctly if (! iptr->is_whole_cache_valid() ) { iptr->invalidate_whole_cache(); iptr->set_whole_cache_validity(true); } storedval = calculate_val(); iptr->set_cache_entry_validity(tag,true); return storedval; } template void lazy::init(const S *ip, T (*fnptr)(const S &)) { iptr = ip; calc_fn = fnptr; tag = iptr->getnewtag(); iptr->set_cache_entry_validity(tag,false); } template void lazy::copy(const lazy &source, const S *ip) { storedval = source.storedval; tag = source.tag; calc_fn = source.calc_fn; // Do NOT copy the same parent class pointer // (allows parent class to be copied correctly) iptr = ip; } #ifndef NO_NAMESPACE } #endif #endif