70 lines
2.2 KiB
C++
70 lines
2.2 KiB
C++
/*
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* Copyright (c) 2003 The Regents of The University of Michigan
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* All rights reserved.
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*
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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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* met: 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 the copyright holders 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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*
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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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*/
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#ifndef __BITFIELD_HH
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#define __BITFIELD_HH
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#include <inttypes.h>
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/**
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* Generate a 64-bit mask of 'nbits' 1s, right justified.
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*/
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inline uint64_t
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mask(int nbits)
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{
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return (nbits == 64) ? (uint64_t)-1LL : (1ULL << nbits) - 1;
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}
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/**
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* Extract the bitfield from position 'first' to 'last' (inclusive)
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* from 'val' and right justify it. MSB is numbered 63, LSB is 0.
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*/
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template <class T>
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inline
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T
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bits(T val, int first, int last)
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{
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int nbits = first - last + 1;
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return (val >> last) & mask(nbits);
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}
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/**
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* Sign-extend an N-bit value to 64 bits.
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*/
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template <int N>
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inline
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int64_t
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sext(uint64_t val)
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{
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int sign_bit = bits(val, N-1, N-1);
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return sign_bit ? (val | ~mask(N)) : val;
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}
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#endif
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