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/* bithelp.h - Some bit manipulation helpers
* Copyright (C) 1999, 2002 Free Software Foundation, Inc.
*
* This file is part of Libgcrypt.
*
* Libgcrypt is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* Libgcrypt is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
#ifndef GCRYPT_BITHELP_H
#define GCRYPT_BITHELP_H
#include "types.h"
/****************
* Rotate the 32 bit unsigned integer X by N bits left/right
*/
static inline u32 rol(u32 x, int n)
{
return ( (x << (n&(32-1))) | (x >> ((32-n)&(32-1))) );
}
static inline u32 ror(u32 x, int n)
{
return ( (x >> (n&(32-1))) | (x << ((32-n)&(32-1))) );
}
/* Byte swap for 32-bit and 64-bit integers. If available, use compiler
provided helpers. */
#ifdef HAVE_BUILTIN_BSWAP32
# define _gcry_bswap32 __builtin_bswap32
#else
static inline u32
_gcry_bswap32(u32 x)
{
return ((rol(x, 8) & 0x00ff00ffL) | (ror(x, 8) & 0xff00ff00L));
}
#endif
#ifdef HAVE_BUILTIN_BSWAP64
# define _gcry_bswap64 __builtin_bswap64
#else
static inline u64
_gcry_bswap64(u64 x)
{
return ((u64)_gcry_bswap32(x) << 32) | (_gcry_bswap32(x >> 32));
}
#endif
/* Endian dependent byte swap operations. */
#ifdef WORDS_BIGENDIAN
# define le_bswap32(x) _gcry_bswap32(x)
# define be_bswap32(x) ((u32)(x))
# define le_bswap64(x) _gcry_bswap64(x)
# define be_bswap64(x) ((u64)(x))
#else
# define le_bswap32(x) ((u32)(x))
# define be_bswap32(x) _gcry_bswap32(x)
# define le_bswap64(x) ((u64)(x))
# define be_bswap64(x) _gcry_bswap64(x)
#endif
/* Count trailing zero bits in an unsigend int. We return an int
because that is what gcc's builtin does. Returns the number of
bits in X if X is 0. */
static inline int
_gcry_ctz (unsigned int x)
{
#if defined (HAVE_BUILTIN_CTZ)
return x? __builtin_ctz (x) : 8 * sizeof (x);
#else
/* See
* http://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightModLookup
*/
static const unsigned char mod37[] =
{
sizeof (unsigned int)*8,
0, 1, 26, 2, 23, 27, 0, 3, 16, 24, 30, 28, 11, 0, 13,
4, 7, 17, 0, 25, 22, 31, 15, 29, 10, 12, 6, 0, 21, 14, 9,
5, 20, 8, 19, 18
};
return (int)mod37[(-x & x) % 37];
#endif
}
/* Count trailing zero bits in an u64. We return an int because that
is what gcc's builtin does. Returns the number of bits in X if X
is 0. */
static inline int
_gcry_ctz64(u64 x)
{
#if defined (HAVE_BUILTIN_CTZ) && SIZEOF_UNSIGNED_INT >= 8
#warning hello
return x? __builtin_ctz (x) : 8 * sizeof (x);
#else
if ((x & 0xffffffff))
return _gcry_ctz (x);
else
return 32 + _gcry_ctz (x >> 32);
#endif
}
#endif /*GCRYPT_BITHELP_H*/
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