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Copyright 2010-2011, D. E. Shaw Research.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions, and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions, and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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* Neither the name of D. E. Shaw Research nor the names of its
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contributors may be used to endorse or promote products derived from
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this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#ifndef __ReinterpretCtr_dot_hpp__
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#define __ReinterpretCtr_dot_hpp__
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#include "features/compilerfeatures.h"
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ReinterpretCtr uses memcpy to map back and forth
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between a CBRNG's ctr_type and the specified ToType. For example,
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typedef ReinterpretCtr<r123array4x32, Philox2x64> G;
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G is a bona fide CBRNG with ctr_type r123array4x32.
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WARNING: ReinterpretCtr is endian dependent. The
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values returned by G, declared as above,
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will depend on the endianness of the machine on which it runs.
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template <typename ToType, typename CBRNG>
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struct ReinterpretCtr{
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typedef ToType ctr_type;
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typedef typename CBRNG::key_type key_type;
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typedef typename CBRNG::ctr_type bctype;
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typedef typename CBRNG::ukey_type ukey_type;
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R123_STATIC_ASSERT(sizeof(ToType) == sizeof(bctype) && sizeof(typename bctype::value_type) != 16,
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"ReinterpretCtr: sizeof(ToType) is not the same as sizeof(CBRNG::ctr_type) or CBRNG::ctr_type::value_type looks like it might be __m128i");
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// It's amazingly difficult to safely do conversions with __m128i.
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// If we use the operator() implementation below with a CBRNG
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// whose ctr_type is r123array1xm128i, gcc4.6 optimizes away the
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// memcpys, inlines the operator()(c,k), and produces assembly
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// language that ends with an aesenclast instruction with a
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// destination operand pointing to an unaligned memory address ...
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// Segfault! See: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50444
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// MSVC also produces code that crashes. We suspect a
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// similar mechanism but haven't done the debugging necessary to
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// be sure. We were able to 'fix' gcc4.6 by making bc a mutable
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// data member rather than declaring it in the scope of
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// operator(). That didn't fix the MSVC problems, though.
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// Conclusion - don't touch __m128i, at least for now. The
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// easiest (but highly imprecise) way to do that is the static
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// assertion above that rejects bctype::value_types of size 16. -
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ctr_type operator()(ctr_type c, key_type k){
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std::memcpy(&bc, &c, sizeof(c));
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std::memcpy(&c, &bc, sizeof(bc));