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/*
* Hash Function Base Class
* (C) 1999-2008 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#ifndef BOTAN_HASH_FUNCTION_BASE_CLASS_H_
#define BOTAN_HASH_FUNCTION_BASE_CLASS_H_
#include <botan/buf_comp.h>
#include <string>
#include <memory>
namespace Botan {
/**
* This class represents hash function (message digest) objects
*/
class BOTAN_PUBLIC_API(2,0) HashFunction : public Buffered_Computation
{
public:
/**
* Create an instance based on a name, or return null if the
* algo/provider combination cannot be found. If provider is
* empty then best available is chosen.
*/
static std::unique_ptr<HashFunction>
create(const std::string& algo_spec,
const std::string& provider = "");
/**
* Create an instance based on a name
* If provider is empty then best available is chosen.
* @param algo_spec algorithm name
* @param provider provider implementation to use
* Throws Lookup_Error if not found.
*/
static std::unique_ptr<HashFunction>
create_or_throw(const std::string& algo_spec,
const std::string& provider = "");
/**
* @return list of available providers for this algorithm, empty if not available
* @param algo_spec algorithm name
*/
static std::vector<std::string> providers(const std::string& algo_spec);
/**
* @return new object representing the same algorithm as *this
*/
virtual HashFunction* clone() const = 0;
/**
* @return provider information about this implementation. Default is "base",
* might also return "sse2", "avx2", "openssl", or some other arbitrary string.
*/
virtual std::string provider() const { return "base"; }
virtual ~HashFunction() = default;
/**
* Reset the state.
*/
virtual void clear() = 0;
/**
* @return the hash function name
*/
virtual std::string name() const = 0;
/**
* @return hash block size as defined for this algorithm
*/
virtual size_t hash_block_size() const { return 0; }
/**
* Return a new hash object with the same state as *this. This
* allows computing the hash of several messages with a common
* prefix more efficiently than would otherwise be possible.
*
* This function should be called `clone` but that was already
* used for the case of returning an uninitialized object.
* @return new hash object
*/
virtual std::unique_ptr<HashFunction> copy_state() const = 0;
};
}
#endif
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