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/*=========================================================================
Program: Insight Segmentation & Registration Toolkit
Module: $RCSfile: itkStructHashFunction.h,v $
Language: C++
Date: $Date: 2007-12-21 16:50:20 $
Version: $Revision: 1.5 $
Copyright (c) Insight Software Consortium. All rights reserved.
See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details.
This software is distributed WITHOUT ANY WARRANTY; without even
the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE. See the above copyright notices for more information.
=========================================================================*/
#ifndef itkStructHashFunction_h
#define itkStructHashFunction_h
namespace itk
{
/** \class StructHashFunction
*
* \brief Generic hash function for an arbitrary struct (or class).
*
* This regards the input key as a string of bytes, and applies a
* hash function similar to one that has been used in perl. If the
* data in the input key has pointers to other classes, then the
* function will be hashing on the value of the pointer itself, not
* on the data it points to. It is imagined that this function will
* be used more for structs (with fully exposed data) than for
* general classes.
*/
template< class TInput >
class StructHashFunction
{
public:
/** Standard class typedefs. */
typedef StructHashFunction Self;
/** Input type */
typedef TInput InputType;
unsigned int operator()( const InputType& key ) const;
};
template< class TInput >
inline unsigned int
StructHashFunction< TInput >
::operator()( const InputType& key ) const
{
::size_t len = sizeof( InputType );
const char* p = reinterpret_cast< const char* >( &key );
unsigned int hash = 0;
while( len-- )
{
hash = hash * 65 + *p++;
}
hash += (hash >> 5);
return hash;
}
}
#endif // ndef itkStructHashFunction_h
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