CheckSumGenerator.h

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/*--------------------------------------------------------------------------------------------
Copyright (c) 2019, NDEVR LLC
tyler.parke@ndevr.org
  __    __   ____     _____ __     __  _______
 |  \  |  | |  __ \  |  ___|\ \   / / |   __  \
 |   \ |  | | |  \ \ | |___  \ \ / /  |  |__)  |
 |  . \|  | | |__/ / | |___   \ V /   |   _   /
 |  |\    |_|_____/__|_____|___\_/____|  | \  \
 |__| \__________________________________|  \__\
 
Subject to the terms of the Enterprise+ Agreement, NDEVR hereby grants 
Licensee a limited, non-exclusive, non-transferable, royalty-free license 
(without the right to sublicense) to use the API solely for the purpose of 
Licensee's internal development efforts to develop applications for which 
the API was provided.
 
The above copyright notice and this permission notice shall be included in all 
copies or substantial portions of the Software.
 
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.
 
Library: Base
File: CheckSumGenerator
Included in API: True
Author(s): Tyler Parke
 *-----------------------------------------------------------------------------------------**/
#pragma once
#include <NDEVR/Buffer.h>
 
namespace NDEVR
{
    /**----------------------------------------------------------------------------
    \brief Logic for generating checksums based on initial value and a type.
    ----------------------------------------------------------------------------*/
    template<class t_hash_type>
    class CheckSumGenerator
    {
    public:
        CheckSumGenerator()
            : type_buffer(0)
            , m_checksum(5381)
        {};
        template <class t_type, class t_allocator, class t_memory_manager>
        void update(const Buffer<t_type, t_allocator, t_memory_manager>& buffer)
        {
            if (buffer.size() == 0)
            {
                m_checksum = ((m_checksum << 5) + m_checksum) + 5381;
            }
            for (uint04 ii = 0; ii < buffer.size(); ii++)
            {
                update<t_type>(buffer[ii]);
            }
        }
        template <class t_type, class t_allocator, class t_memory_manager>
        void update(const Buffer<t_type, t_allocator, t_memory_manager>& buffer, uint04 max_size)
        {
            const uint04 size = getMin(max_size, buffer.size());
            for (uint04 ii = 0; ii < size; ii++)
            {
                update<t_type>(buffer[ii]);
            }
        }
        template<class t_type>
        void update(const t_type& object)
        {
            if (sizeof(t_type) == sizeof(t_hash_type))
            {
                memcpy(&type_buffer, &object, sizeof(t_type));
            }
            else if ((sizeof(t_type) > sizeof(t_hash_type)))
            {
                static const uint04 remainder = sizeof(t_type) % sizeof(t_hash_type);
                static const uint04 num_to_copy = sizeof(t_type) / sizeof(t_hash_type);
                for (uint04 ii = 0; ii < num_to_copy; ii++)
                {
                    memcpy(&type_buffer, ((uint01*)(&object)) + sizeof(t_hash_type) * ii, sizeof(t_hash_type));
                    update(type_buffer);
                }
                if (remainder != 0)
                {
                    memcpy(&type_buffer, ((uint01*)(&object)) + sizeof(t_hash_type) * num_to_copy, sizeof(remainder));
                    update(type_buffer);
                }
            }
            else
            {
                memcpy(&type_buffer, &object, sizeof(t_type));
                update(type_buffer);
            }
        }
        template<>
        void update(const t_hash_type& hash_value)
        {
            m_checksum = ((m_checksum << 5) + m_checksum) + hash_value;
        }
        t_hash_type getCheckSum() { return m_checksum; }
        t_hash_type type_buffer;
        t_hash_type m_checksum;
    };
}