Added shift version of XOR checksum

XOR:      sum = sum ^ value
XOR-shift sum = etl::rotate_left(sum) ^ value

src/checksum.h

@@ -110,6 +110,30 @@ namespace etl
     }
   };
 
+  //***************************************************************************
+  /// XOR-shift checksum policy.
+  //***************************************************************************
+  template <typename T>
+  struct checksum_policy_xor_shift
+  {
+    typedef T value_type;
+
+    inline T initial() const
+    {
+      return 0;
+    }
+
+    inline T add(T sum, uint8_t value) const
+    {
+      return etl::rotate_left(sum) ^ value;
+    }
+
+    inline T final(T sum) const
+    {
+      return sum;
+    }
+  };
+
   //*************************************************************************
   /// Standard Checksum.
   //*************************************************************************
@@ -196,6 +220,35 @@ namespace etl
       this->add(begin, end);
     }
   };
+
+  //*************************************************************************
+  /// XOR-shift Checksum.
+  //*************************************************************************
+  template <typename T>
+  class xor_shift_checksum : public etl::frame_check_sequence<etl::checksum_policy_xor_shift<T> >
+  {
+  public:
+
+    //*************************************************************************
+    /// Default constructor.
+    //*************************************************************************
+    xor_shift_checksum()
+    {
+      this->reset();
+    }
+
+    //*************************************************************************
+    /// Constructor from range.
+    /// \param begin Start of the range.
+    /// \param end   End of the range.
+    //*************************************************************************
+    template<typename TIterator>
+    xor_shift_checksum(TIterator begin, const TIterator end)
+    {
+      this->reset();
+      this->add(begin, end);
+    }
+  };
 }
 
 #endif

test/test_xor_shift_checksum.cpp

@@ -0,0 +1,149 @@
+/******************************************************************************
+The MIT License(MIT)
+
+Embedded Template Library.
+https://github.com/ETLCPP/etl
+http://www.etlcpp.com
+
+Copyright(c) 2017 jwellbelove
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files(the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions :
+
+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.
+******************************************************************************/
+
+#include "UnitTest++.h"
+
+#include <iterator>
+#include <string>
+#include <vector>
+#include <stdint.h>
+
+#include "checksum.h"
+
+namespace
+{
+  template <typename TSum, typename TIterator>
+  TSum reference_checksum(TIterator begin, TIterator end)
+  {
+    typedef typename std::iterator_traits<TIterator>::value_type value_type;
+    TSum checksum = 0;
+
+    while (begin != end)
+    {
+      value_type value = *begin++;
+      checksum = etl::rotate_left(checksum) ^ value;
+    }
+
+    return checksum;
+  }
+
+  SUITE(test_checksum)
+  {
+    //*************************************************************************
+    TEST(test_checksum_constructor)
+    {
+      std::string data("123456789");
+
+      uint8_t sum     = etl::xor_shift_checksum<uint8_t>(data.begin(), data.end());
+      uint8_t compare = reference_checksum<uint8_t>(data.begin(), data.end());
+
+      CHECK_EQUAL(int(compare), int(sum));
+    }
+
+    //*************************************************************************
+    TEST(test_checksum_add_values8_add)
+    {
+      std::string data("123456789");
+
+      etl::xor_shift_checksum<uint8_t> checksum_calculator;
+
+      for (size_t i = 0; i < data.size(); ++i)
+      {
+        checksum_calculator.add(data[i]);
+      }
+      
+      uint8_t sum     = checksum_calculator;
+      uint8_t compare = reference_checksum<uint8_t>(data.begin(), data.end());
+
+      CHECK_EQUAL(int(compare), int(sum));
+    }
+
+    //*************************************************************************
+    TEST(test_checksum_add_values8_operator_plus_equals)
+    {
+      std::string data("123456789");
+
+      etl::xor_shift_checksum<uint8_t> checksum_calculator;
+
+      for (size_t i = 0; i < data.size(); ++i)
+      {
+        checksum_calculator.add(data[i]);
+      }
+
+      uint8_t sum     = checksum_calculator;
+      uint8_t compare = reference_checksum<uint8_t>(data.begin(), data.end());
+
+      CHECK_EQUAL(int(compare), int(sum));
+    }
+
+    //*************************************************************************
+    TEST(test_checksum_add_range)
+    {
+      std::string data("123456789");
+
+      etl::xor_shift_checksum<uint8_t> checksum_calculator;
+
+      checksum_calculator.add(data.begin(), data.end());
+
+      uint8_t sum     = checksum_calculator.value();
+      uint8_t compare = reference_checksum<uint8_t>(data.begin(), data.end());
+
+      CHECK_EQUAL(int(compare), int(sum));
+    }
+
+    //*************************************************************************
+    TEST(test_checksum_add_range_sum32)
+    {
+      std::string data("1");
+
+      etl::xor_shift_checksum<uint32_t> checksum_calculator;
+
+      checksum_calculator.add(data.begin(), data.end());
+
+      uint32_t sum     = checksum_calculator.value();
+      uint32_t compare = reference_checksum<uint32_t>(data.begin(), data.end());
+
+      CHECK_EQUAL(compare, sum);
+    }
+
+    //*************************************************************************
+    TEST(test_checksum_add_range_endian)
+    {
+      std::vector<uint8_t>  data1 = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 };
+      std::vector<uint32_t> data2 = { 0x04030201, 0x08070605 };
+      std::vector<uint8_t>  data3 = { 0x08, 0x07, 0x06, 0x05, 0x04, 0x03, 0x02, 0x01 };
+
+      uint64_t hash1 = etl::xor_shift_checksum<uint8_t>(data1.begin(), data1.end());
+      uint64_t hash2 = etl::xor_shift_checksum<uint8_t>((uint8_t*)&data2[0], (uint8_t*)&data2[0] + (data2.size() * sizeof(uint32_t)));
+      uint64_t hash3 = etl::xor_shift_checksum<uint8_t>(data3.rbegin(), data3.rend());
+      CHECK_EQUAL(hash1, hash2);
+      CHECK_EQUAL(hash1, hash3);
+    }
+  };
+}
+

test/vs2017/etl.vcxproj

@@ -467,6 +467,7 @@
     <ClCompile Include="..\test_vector_pointer.cpp" />
     <ClCompile Include="..\test_visitor.cpp" />
     <ClCompile Include="..\test_xor_checksum.cpp" />
+    <ClCompile Include="..\test_xor_shift_checksum.cpp" />
   </ItemGroup>
   <ItemGroup>
     <None Include="..\..\Doxyfile" />

test/vs2017/etl.vcxproj.filters

@@ -953,6 +953,9 @@
     <ClCompile Include="..\test_array_wrapper.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="..\test_xor_shift_checksum.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <None Include="..\..\Doxyfile">