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/*
* An algorithm cache (used by Algorithm_Factory)
* (C) 2008-2009,2011 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#ifndef BOTAN_ALGORITHM_CACHE_TEMPLATE_H__
#define BOTAN_ALGORITHM_CACHE_TEMPLATE_H__
#include <botan/types.h>
#include <botan/internal/stl_util.h>
#include <mutex>
#include <string>
#include <vector>
#include <map>
namespace Botan {
/**
* @param prov_name a provider name
* @return weight for this provider
*/
size_t static_provider_weight(const std::string& prov_name);
/**
* Algorithm_Cache (used by Algorithm_Factory)
*/
template<typename T>
class Algorithm_Cache
{
public:
/**
* @param algo_spec names the requested algorithm
* @param pref_provider suggests a preferred provider
* @return prototype object, or NULL
*/
const T* get(const std::string& algo_spec,
const std::string& pref_provider);
/**
* Add a new algorithm implementation to the cache
* @param algo the algorithm prototype object
* @param requested_name how this name will be requested
* @param provider_name is the name of the provider of this prototype
*/
void add(T* algo,
const std::string& requested_name,
const std::string& provider_name);
/**
* Set the preferred provider
* @param algo_spec names the algorithm
* @param provider names the preferred provider
*/
void set_preferred_provider(const std::string& algo_spec,
const std::string& provider);
/**
* Return the list of providers of this algorithm
* @param algo_name names the algorithm
* @return list of providers of this algorithm
*/
std::vector<std::string> providers_of(const std::string& algo_name);
/**
* Clear the cache
*/
void clear_cache();
~Algorithm_Cache() { clear_cache(); }
private:
typename std::map<std::string, std::map<std::string, T*> >::const_iterator
find_algorithm(const std::string& algo_spec);
std::mutex mutex;
std::map<std::string, std::string> aliases;
std::map<std::string, std::string> pref_providers;
std::map<std::string, std::map<std::string, T*> > algorithms;
};
/*
* Look for an algorithm implementation in the cache, also checking aliases
* Assumes object lock is held
*/
template<typename T>
typename std::map<std::string, std::map<std::string, T*> >::const_iterator
Algorithm_Cache<T>::find_algorithm(const std::string& algo_spec)
{
auto algo = algorithms.find(algo_spec);
// Not found? Check if a known alias
if(algo == algorithms.end())
{
auto alias = aliases.find(algo_spec);
if(alias != aliases.end())
algo = algorithms.find(alias->second);
}
return algo;
}
/*
* Look for an algorithm implementation by a particular provider
*/
template<typename T>
const T* Algorithm_Cache<T>::get(const std::string& algo_spec,
const std::string& requested_provider)
{
std::lock_guard<std::mutex> lock(mutex);
auto algo = find_algorithm(algo_spec);
if(algo == algorithms.end()) // algo not found at all (no providers)
return nullptr;
// If a provider is requested specifically, return it or fail entirely
if(requested_provider != "")
{
auto prov = algo->second.find(requested_provider);
if(prov != algo->second.end())
return prov->second;
return nullptr;
}
const T* prototype = nullptr;
std::string prototype_provider;
size_t prototype_prov_weight = 0;
const std::string pref_provider = search_map(pref_providers, algo_spec);
for(auto i = algo->second.begin(); i != algo->second.end(); ++i)
{
const std::string prov_name = i->first;
const size_t prov_weight = static_provider_weight(prov_name);
// preferred prov exists, return immediately
if(prov_name == pref_provider)
return i->second;
if(prototype == nullptr || prov_weight > prototype_prov_weight)
{
prototype = i->second;
prototype_provider = i->first;
prototype_prov_weight = prov_weight;
}
}
return prototype;
}
/*
* Add an implementation to the cache
*/
template<typename T>
void Algorithm_Cache<T>::add(T* algo,
const std::string& requested_name,
const std::string& provider)
{
if(!algo)
return;
std::lock_guard<std::mutex> lock(mutex);
if(algo->name() != requested_name &&
aliases.find(requested_name) == aliases.end())
{
aliases[requested_name] = algo->name();
}
if(!algorithms[algo->name()][provider])
algorithms[algo->name()][provider] = algo;
else
delete algo;
}
/*
* Find the providers of this algo (if any)
*/
template<typename T> std::vector<std::string>
Algorithm_Cache<T>::providers_of(const std::string& algo_name)
{
std::lock_guard<std::mutex> lock(mutex);
std::vector<std::string> providers;
auto algo = find_algorithm(algo_name);
if(algo != algorithms.end())
{
auto provider = algo->second.begin();
while(provider != algo->second.end())
{
providers.push_back(provider->first);
++provider;
}
}
return providers;
}
/*
* Set the preferred provider for an algorithm
*/
template<typename T>
void Algorithm_Cache<T>::set_preferred_provider(const std::string& algo_spec,
const std::string& provider)
{
std::lock_guard<std::mutex> lock(mutex);
pref_providers[algo_spec] = provider;
}
/*
* Clear out the cache
*/
template<typename T>
void Algorithm_Cache<T>::clear_cache()
{
auto algo = algorithms.begin();
while(algo != algorithms.end())
{
auto provider = algo->second.begin();
while(provider != algo->second.end())
{
delete provider->second;
++provider;
}
++algo;
}
algorithms.clear();
}
}
#endif
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