Subject: [Boost-commit] svn:boost r62938 - in sandbox/SOC/2010/bit_masks: boost/integer lib/integer/test lib/integer/test/bft_testing
From: bbartmanboost_at_[hidden]
Date: 2010-06-14 13:59:40
Author: bbartman
Date: 2010-06-14 13:59:40 EDT (Mon, 14 Jun 2010)
New Revision: 62938
URL: http://svn.boost.org/trac/boost/changeset/62938
Log:
completed basic work for twos complement encoding of a type inside a bitfield
Text files modified:
sandbox/SOC/2010/bit_masks/boost/integer/bits_mask.hpp | 2
sandbox/SOC/2010/bit_masks/lib/integer/test/Jamfile.v2 | 2
sandbox/SOC/2010/bit_masks/lib/integer/test/bft_testing/twos_complement_testing.cpp | 262 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 264 insertions(+), 2 deletions(-)
Modified: sandbox/SOC/2010/bit_masks/boost/integer/bits_mask.hpp
==============================================================================
--- sandbox/SOC/2010/bit_masks/boost/integer/bits_mask.hpp (original)
+++ sandbox/SOC/2010/bit_masks/boost/integer/bits_mask.hpp 2010-06-14 13:59:40 EDT (Mon, 14 Jun 2010)
@@ -35,7 +35,7 @@
:integral_mask<T, (low_bits_mask<T,Width>::value << Offset) >
{
// precondition 1.
- BOOST_STATIC_ASSERT(( (Offset + Width) < ( bit_width<T>::value - 1) ));
+ BOOST_STATIC_ASSERT(( (Offset + Width) <= ( bit_width<T>::value ) ));
// precondition 2.
BOOST_STATIC_ASSERT(( Width > 0 ));
Modified: sandbox/SOC/2010/bit_masks/lib/integer/test/Jamfile.v2
==============================================================================
--- sandbox/SOC/2010/bit_masks/lib/integer/test/Jamfile.v2 (original)
+++ sandbox/SOC/2010/bit_masks/lib/integer/test/Jamfile.v2 2010-06-14 13:59:40 EDT (Mon, 14 Jun 2010)
@@ -37,6 +37,6 @@
[ run bft_testing/ref_type_testing.cpp ]
[ run bft_testing/name_accessor_test.cpp ]
[ run bft_testing/get_interface_test.cpp ]
- [ run bft_testing/two_complement_testing.cpp ]
+ [ run bft_testing/twos_complement_testing.cpp ]
;
Modified: sandbox/SOC/2010/bit_masks/lib/integer/test/bft_testing/twos_complement_testing.cpp
==============================================================================
--- sandbox/SOC/2010/bit_masks/lib/integer/test/bft_testing/twos_complement_testing.cpp (original)
+++ sandbox/SOC/2010/bit_masks/lib/integer/test/bft_testing/twos_complement_testing.cpp 2010-06-14 13:59:40 EDT (Mon, 14 Jun 2010)
@@ -0,0 +1,262 @@
+// Copyright 2010 Brian Bartman.
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+
+
+// boost includes.
+#include <boost/assert.hpp>
+#include <boost/static_assert.hpp>
+#include <boost/integer/bits_mask.hpp>
+#include <boost/cstdint.hpp>
+#include <boost/type_traits.hpp>
+
+// std includes.
+#include <cstddef>
+#include <stdexcept>
+#include <iostream>
+
+using namespace std;
+namespace boost { namespace details {
+
+
+template < typename Encoded_Type,
+ std::size_t Width,
+ typename Return_Type,
+ bool Is_Signed
+>
+struct twos_complement_decoding_impl;
+
+
+template <typename Decoding_From_Type, std::size_t Width, typename Return_Type>
+struct twos_complement_decoding_impl<Decoding_From_Type,Width,Return_Type,true> {
+ Return_Type operator() (Decoding_From_Type const& encoded_value) {
+ // sign bit
+ Return_Type sign_bit = static_cast<Return_Type>(
+ encoded_value
+ &
+ bits_mask<
+ Decoding_From_Type,
+ Width - 1
+ >::value
+ );
+ // Value Bits.
+ Return_Type value_bits =
+ encoded_value
+ &
+ low_bits_mask<Decoding_From_Type,Width-1>::value;
+
+ return value_bits + (Return_Type(0) - sign_bit);
+ }
+};
+
+template <typename Decoding_Type, std::size_t Width, typename Return_Type >
+struct twos_complement_decoding_impl<Decoding_Type,Width,Return_Type,false> {
+ Return_Type operator() (Decoding_Type const& non_encoded_value) {
+ return non_encoded_value;
+ }
+};
+
+
+
+template < typename Encoding_Type,
+ std::size_t Width,
+ typename Return_Type,
+ bool Is_Signed
+>
+struct twos_complement_encoding_impl;
+
+
+template <typename Encoding_Type, std::size_t Width, typename Return_Type>
+struct twos_complement_encoding_impl<Encoding_Type, Width, Return_Type, true> {
+ Return_Type operator() (Encoding_Type const& value_to_encode) {
+ return static_cast<
+ typename make_unsigned<Encoding_Type>::type
+ >(
+ value_to_encode & low_bits_mask<Return_Type, Width - 1>::value
+ )
+ ^
+ (static_cast<
+ typename make_unsigned<Encoding_Type>::type
+ >(
+ value_to_encode & bits_mask<
+ Encoding_Type,
+ bit_width<Encoding_Type>::value - 1
+ >::value
+ ) >> (bit_width<Encoding_Type>::value - Width));
+ }
+};
+
+template <typename Encoding_Type, std::size_t Width, typename Return_Type>
+struct twos_complement_encoding_impl<Encoding_Type, Width, Return_Type, false> {
+ Return_Type operator() (Encoding_Type const& value_to_encode) {
+ return Return_Type(value_to_encode);
+ }
+};
+
+
+
+} // end details.
+
+template <typename Encoded_Type, std::size_t Width, typename Return_Type>
+Return_Type twos_complement_encoding(Encoded_Type x) {
+ BOOST_STATIC_ASSERT( Width != 0 );
+ return details::twos_complement_encoding_impl<
+ Encoded_Type,
+ Width,
+ Return_Type,
+ is_signed<Encoded_Type>::value
+ >()(x);
+}
+
+template <typename Decoding_Type, std::size_t Width, typename Return_Type>
+Return_Type twos_complement_decoding(Decoding_Type x) {
+ BOOST_STATIC_ASSERT( Width != 0 );
+ return details::twos_complement_decoding_impl<
+ Decoding_Type,
+ Width,
+ Return_Type,
+ is_signed<Return_Type>::value
+ >()( x );
+}
+
+}
+
+
+
+
+using namespace boost;
+using namespace std;
+int main() {
+ {
+ char encoded_value = -2;
+
+ cout << bool( (encoded_value & bits_mask<char,7>::value) >> bits_mask<char,7>::offset );
+ cout << bool( (encoded_value & bits_mask<char,6>::value) >> bits_mask<char,6>::offset );
+ cout << bool( (encoded_value & bits_mask<char,5>::value) >> bits_mask<char,5>::offset );
+ cout << bool( (encoded_value & bits_mask<char,4>::value) >> bits_mask<char,4>::offset );
+ cout << bool( (encoded_value & bits_mask<char,3>::value) >> bits_mask<char,3>::offset );
+ cout << bool( (encoded_value & bits_mask<char,2>::value) >> bits_mask<char,2>::offset );
+ cout << bool( (encoded_value & bits_mask<char,1>::value) >> bits_mask<char,1>::offset );
+ cout << bool( (encoded_value & bits_mask<char,0>::value) >> bits_mask<char,0>::offset );
+ cout << endl;
+
+
+
+ // BOOST_ASSERT((storage == 0xc));
+
+ // 1111 1110 == -2 in a char.
+ // Return_Type(encoded_value & low_bits_mask<Return_Type, Width - 1>::value)
+ // - Return_Type(encoded_value & bits_mask<Decoding_Type, Width>::value);
+ const unsigned int Width = 4;
+ typedef std::size_t Return_Type;
+ typedef char Encoding_Type;
+ Return_Type eval_1(encoded_value & low_bits_mask<Return_Type, Width - 1>::value );
+ BOOST_ASSERT(( encoded_value == static_cast<char>(0xfe)));
+ BOOST_ASSERT(( eval_1 == bits_mask<Return_Type, 1,2>::value ));
+
+ // get the sign bit
+ Return_Type eval_2(
+ static_cast<
+ make_unsigned<Encoding_Type>::type
+ >(
+ encoded_value & bits_mask<
+ Encoding_Type,
+ bit_width<Encoding_Type>::value - 1
+ >::value
+ ) >> (bit_width<Encoding_Type>::value - Width)
+ );
+ BOOST_ASSERT(( eval_2 == 0x8));
+
+ // this is how to encode a type with two's complement.
+ Return_Type eval_3 = static_cast<
+ make_unsigned<Encoding_Type>::type
+ >(
+ encoded_value & low_bits_mask<Return_Type, Width - 1>::value
+ )
+ ^
+ (static_cast<
+ make_unsigned<Encoding_Type>::type
+ >(
+ encoded_value & bits_mask<
+ Encoding_Type,
+ bit_width<Encoding_Type>::value - 1
+ >::value
+ ) >> (bit_width<Encoding_Type>::value - Width));
+
+ BOOST_ASSERT(( eval_3 == 0xe));
+ }
+
+ // decoding a type inside of a Return_Type
+ {
+ typedef char Return_Type;
+ typedef std::size_t Decoding_From_Type;
+ const std::size_t Width = 4;
+
+ std::size_t storage = 0xe;
+
+
+ // get sign bit.
+ Return_Type eval_4 = static_cast<Return_Type>(storage & bits_mask<Decoding_From_Type,Width - 1>::value);
+ BOOST_ASSERT(( eval_4 == 0x8 ));
+
+ Return_Type eval_5 = static_cast<Return_Type>(storage & bits_mask<Decoding_From_Type,Width - 1>::value) << (bit_width<Return_Type>::value - Width);
+ BOOST_ASSERT(( eval_5 == static_cast<Return_Type>(0x80)));
+
+ // getting value bits
+ Return_Type eval_6 = static_cast<Return_Type>(storage & low_bits_mask<Decoding_From_Type,Width-1>::value );
+ BOOST_ASSERT(( eval_6 == bits_mask<Return_Type,1,2>::value));
+
+
+
+ /*
+ // Attempting to reconstruct the value
+ // Return_Type eval_7 =
+ // sign bit.
+ Return_Type sign_bit = static_cast<Return_Type>(
+ high_bits_mask<
+ Return_Type,
+ bit_width<
+ Return_Type
+ >::value - Width
+ >::value
+ );
+
+ // Value Bits.
+ Return_Type value_bits =
+ static_cast<Return_Type>(
+ storage
+ &
+ bits_mask<
+ Decoding_From_Type,
+ Width - 1
+ >::value
+ )
+ <<
+ (bit_width<Return_Type>::value - Width);
+
+ // if(
+ */
+
+ }
+ {
+ std::size_t storage = 0;
+ char temp = -2;
+ storage = twos_complement_encoding< char, 4, unsigned int >( temp );
+ BOOST_ASSERT((storage == 0xe));
+
+ temp = twos_complement_decoding< unsigned int, 4, char >( storage );
+ cout << "Value of Temp == "<< (int)temp <<endl;
+ BOOST_ASSERT((temp == -2));
+
+ cout << static_cast<int>(temp) << endl;
+ cout << bits_mask<int,1,2>::value << endl;
+ int temp_2 (0);
+ temp_2 = ~temp_2;
+ temp_2 << 1;
+ cout << temp_2 << endl;
+ }
+ return 0;
+}
+