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/* bits.h - Bit manipulation functions.
Copyright (C) 2007, 2009 Free Software Foundation, Inc.
Written by Neal H. Walfield <neal@gnu.org>.
This file is part of the GNU Hurd.
The GNU Hurd is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 3 of the
License, or (at your option) any later version.
The GNU Hurd 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
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see
<http://www.gnu.org/licenses/>. */
#ifndef RM_BITS_H
#define RM_BITS_H
#include <stdint.h>
#include <assert.h>
/* Return the C bits of word W starting a bit S. (The LSB is 0 and
the MSB is WORDSIZE.) */
static inline unsigned int
extract_bits (uintptr_t w, int s, int c)
{
assert (0 <= s && s < (sizeof (uintptr_t) * 8));
assert (0 <= c && s + c <= (sizeof (uintptr_t) * 8));
if (c == (sizeof (unsigned int) * 8))
/* 1U << (sizeof (uintptr_t) * 8) is problematic: "If the value of
the right operand is negative or is greater than or equal to
the width of the promoted left operand, the behavior is
undefined." */
{
assert (s == 0);
return w;
}
else
return (w >> s) & ((1ULL << c) - 1);
}
static inline uint64_t
extract_bits64 (uint64_t w, int s, int c)
{
assert (0 <= s && s < (sizeof (uint64_t) * 8));
assert (0 <= c && s + c <= (sizeof (uint64_t) * 8));
if (c == (sizeof (uint64_t) * 8))
{
assert (s == 0);
return w;
}
else
return (w >> s) & ((1ULL << c) - 1);
}
/* Return the C bits of word W ending at bit E. (The LSB is 0 and the
MSB is (sizeof (unsigned int) * 8).) */
static inline uintptr_t
extract_bits_inv (uintptr_t w, int e, int c)
{
/* We special case this check here to allow extract_bits_inv (w, 31,
0). */
if (c == 0)
return 0;
return extract_bits (w, e - c + 1, c);
}
static inline uint64_t
extract_bits64_inv (uint64_t w, int e, int c)
{
/* We special case this check here to allow extract_bits64_inv (w, 63,
0). */
if (c == 0)
return 0;
return extract_bits64 (w, e - c + 1, c);
}
#endif
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