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/**
* An algorithm cache (used by Algorithm_Factory)
*/

#ifndef BOTAN_ALGORITHM_CACHE_TEMPLATE_H__
#define BOTAN_ALGORITHM_CACHE_TEMPLATE_H__

#include <botan/scan_name.h>
#include <botan/mutex.h>
#include <stdexcept>
#include <map>
#include <string>

namespace Botan {

template<typename T>
class Algorithm_Cache
   {
   public:
      const T* get(const SCAN_Name& request);
      void add(T* algo, const std::string& provider);

      Algorithm_Cache(Mutex* m) : mutex(m) {}
      ~Algorithm_Cache();
   private:
      Mutex* mutex;
      std::map<std::string, std::map<std::string, T*> > algorithms;
      typedef typename std::map<std::string, std::map<std::string, T*> >::iterator algorithms_iterator;
      typedef typename std::map<std::string, T*>::iterator provider_iterator;
   };

/**
* Look for an algorithm implementation in the cache
*/
template<typename T>
const T* Algorithm_Cache<T>::get(const SCAN_Name& request)
   {
   Mutex_Holder lock(mutex);

   algorithms_iterator algo = algorithms.find(request.as_string());

   if(algo == algorithms.end())
      return 0;

   const std::string requested_provider = request.providers_string();

   if(requested_provider != "")
      {
      provider_iterator provider = algo->second.find(requested_provider);

      if(provider != algo->second.end())
         return provider->second;
      }
   else // no specific provider requested: pick one
      {
      provider_iterator provider = algo->second.begin();

      while(provider != algo->second.end())
         ++provider;

      provider = algo->second.begin();
      // @fixme: Just picks the lexicographically first one
      if(provider != algo->second.end())
         return provider->second;
      }

   return 0; // cache miss
   }

/**
* Add an implementation to the cache
*/
template<typename T>
void Algorithm_Cache<T>::add(T* algo, const std::string& provider)
   {
   if(!algo)
      return;

   Mutex_Holder lock(mutex);

   delete algorithms[algo->name()][provider];
   algorithms[algo->name()][provider] = algo;
   }

/**
* Algorithm_Cache<T> Destructor
*/
template<typename T>
Algorithm_Cache<T>::~Algorithm_Cache()
   {
   algorithms_iterator algo = algorithms.begin();

   while(algo != algorithms.end())
      {
      provider_iterator provider = algo->second.begin();

      while(provider != algo->second.end())
         {
         delete provider->second;
         ++provider;
         }

      ++algo;
      }

   delete mutex;
   }

}

#endif