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linux-sg2042/fs/xfs/xfs_bit.c

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/*
* Copyright (c) 2000-2004 Silicon Graphics, Inc. All Rights Reserved.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of version 2 of the GNU General Public License as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it would be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
*
* Further, this software is distributed without any warranty that it is
* free of the rightful claim of any third person regarding infringement
* or the like. Any license provided herein, whether implied or
* otherwise, applies only to this software file. Patent licenses, if
* any, provided herein do not apply to combinations of this program with
* other software, or any other product whatsoever.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write the Free Software Foundation, Inc., 59
* Temple Place - Suite 330, Boston MA 02111-1307, USA.
*
* Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
* Mountain View, CA 94043, or:
*
* http://www.sgi.com
*
* For further information regarding this notice, see:
*
* http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/
*/
/*
* XFS bit manipulation routines, used in non-realtime code.
*/
#include "xfs.h"
#include "xfs_bit.h"
#include "xfs_log.h"
#include "xfs_trans.h"
#include "xfs_buf_item.h"
#ifndef HAVE_ARCH_HIGHBIT
/*
* Index of high bit number in byte, -1 for none set, 0..7 otherwise.
*/
STATIC const char xfs_highbit[256] = {
-1, 0, 1, 1, 2, 2, 2, 2, /* 00 .. 07 */
3, 3, 3, 3, 3, 3, 3, 3, /* 08 .. 0f */
4, 4, 4, 4, 4, 4, 4, 4, /* 10 .. 17 */
4, 4, 4, 4, 4, 4, 4, 4, /* 18 .. 1f */
5, 5, 5, 5, 5, 5, 5, 5, /* 20 .. 27 */
5, 5, 5, 5, 5, 5, 5, 5, /* 28 .. 2f */
5, 5, 5, 5, 5, 5, 5, 5, /* 30 .. 37 */
5, 5, 5, 5, 5, 5, 5, 5, /* 38 .. 3f */
6, 6, 6, 6, 6, 6, 6, 6, /* 40 .. 47 */
6, 6, 6, 6, 6, 6, 6, 6, /* 48 .. 4f */
6, 6, 6, 6, 6, 6, 6, 6, /* 50 .. 57 */
6, 6, 6, 6, 6, 6, 6, 6, /* 58 .. 5f */
6, 6, 6, 6, 6, 6, 6, 6, /* 60 .. 67 */
6, 6, 6, 6, 6, 6, 6, 6, /* 68 .. 6f */
6, 6, 6, 6, 6, 6, 6, 6, /* 70 .. 77 */
6, 6, 6, 6, 6, 6, 6, 6, /* 78 .. 7f */
7, 7, 7, 7, 7, 7, 7, 7, /* 80 .. 87 */
7, 7, 7, 7, 7, 7, 7, 7, /* 88 .. 8f */
7, 7, 7, 7, 7, 7, 7, 7, /* 90 .. 97 */
7, 7, 7, 7, 7, 7, 7, 7, /* 98 .. 9f */
7, 7, 7, 7, 7, 7, 7, 7, /* a0 .. a7 */
7, 7, 7, 7, 7, 7, 7, 7, /* a8 .. af */
7, 7, 7, 7, 7, 7, 7, 7, /* b0 .. b7 */
7, 7, 7, 7, 7, 7, 7, 7, /* b8 .. bf */
7, 7, 7, 7, 7, 7, 7, 7, /* c0 .. c7 */
7, 7, 7, 7, 7, 7, 7, 7, /* c8 .. cf */
7, 7, 7, 7, 7, 7, 7, 7, /* d0 .. d7 */
7, 7, 7, 7, 7, 7, 7, 7, /* d8 .. df */
7, 7, 7, 7, 7, 7, 7, 7, /* e0 .. e7 */
7, 7, 7, 7, 7, 7, 7, 7, /* e8 .. ef */
7, 7, 7, 7, 7, 7, 7, 7, /* f0 .. f7 */
7, 7, 7, 7, 7, 7, 7, 7, /* f8 .. ff */
};
#endif
/*
* Count of bits set in byte, 0..8.
*/
static const char xfs_countbit[256] = {
0, 1, 1, 2, 1, 2, 2, 3, /* 00 .. 07 */
1, 2, 2, 3, 2, 3, 3, 4, /* 08 .. 0f */
1, 2, 2, 3, 2, 3, 3, 4, /* 10 .. 17 */
2, 3, 3, 4, 3, 4, 4, 5, /* 18 .. 1f */
1, 2, 2, 3, 2, 3, 3, 4, /* 20 .. 27 */
2, 3, 3, 4, 3, 4, 4, 5, /* 28 .. 2f */
2, 3, 3, 4, 3, 4, 4, 5, /* 30 .. 37 */
3, 4, 4, 5, 4, 5, 5, 6, /* 38 .. 3f */
1, 2, 2, 3, 2, 3, 3, 4, /* 40 .. 47 */
2, 3, 3, 4, 3, 4, 4, 5, /* 48 .. 4f */
2, 3, 3, 4, 3, 4, 4, 5, /* 50 .. 57 */
3, 4, 4, 5, 4, 5, 5, 6, /* 58 .. 5f */
2, 3, 3, 4, 3, 4, 4, 5, /* 60 .. 67 */
3, 4, 4, 5, 4, 5, 5, 6, /* 68 .. 6f */
3, 4, 4, 5, 4, 5, 5, 6, /* 70 .. 77 */
4, 5, 5, 6, 5, 6, 6, 7, /* 78 .. 7f */
1, 2, 2, 3, 2, 3, 3, 4, /* 80 .. 87 */
2, 3, 3, 4, 3, 4, 4, 5, /* 88 .. 8f */
2, 3, 3, 4, 3, 4, 4, 5, /* 90 .. 97 */
3, 4, 4, 5, 4, 5, 5, 6, /* 98 .. 9f */
2, 3, 3, 4, 3, 4, 4, 5, /* a0 .. a7 */
3, 4, 4, 5, 4, 5, 5, 6, /* a8 .. af */
3, 4, 4, 5, 4, 5, 5, 6, /* b0 .. b7 */
4, 5, 5, 6, 5, 6, 6, 7, /* b8 .. bf */
2, 3, 3, 4, 3, 4, 4, 5, /* c0 .. c7 */
3, 4, 4, 5, 4, 5, 5, 6, /* c8 .. cf */
3, 4, 4, 5, 4, 5, 5, 6, /* d0 .. d7 */
4, 5, 5, 6, 5, 6, 6, 7, /* d8 .. df */
3, 4, 4, 5, 4, 5, 5, 6, /* e0 .. e7 */
4, 5, 5, 6, 5, 6, 6, 7, /* e8 .. ef */
4, 5, 5, 6, 5, 6, 6, 7, /* f0 .. f7 */
5, 6, 6, 7, 6, 7, 7, 8, /* f8 .. ff */
};
/*
* xfs_highbit32: get high bit set out of 32-bit argument, -1 if none set.
*/
inline int
xfs_highbit32(
__uint32_t v)
{
#ifdef HAVE_ARCH_HIGHBIT
return highbit32(v);
#else
int i;
if (v & 0xffff0000)
if (v & 0xff000000)
i = 24;
else
i = 16;
else if (v & 0x0000ffff)
if (v & 0x0000ff00)
i = 8;
else
i = 0;
else
return -1;
return i + xfs_highbit[(v >> i) & 0xff];
#endif
}
/*
* xfs_lowbit64: get low bit set out of 64-bit argument, -1 if none set.
*/
int
xfs_lowbit64(
__uint64_t v)
{
__uint32_t w = (__uint32_t)v;
int n = 0;
if (w) { /* lower bits */
n = ffs(w);
} else { /* upper bits */
w = (__uint32_t)(v >> 32);
if (w && (n = ffs(w)))
n += 32;
}
return n - 1;
}
/*
* xfs_highbit64: get high bit set out of 64-bit argument, -1 if none set.
*/
int
xfs_highbit64(
__uint64_t v)
{
__uint32_t h = (__uint32_t)(v >> 32);
if (h)
return xfs_highbit32(h) + 32;
return xfs_highbit32((__uint32_t)v);
}
/*
* Count the number of bits set in the bitmap starting with bit
* start_bit. Size is the size of the bitmap in words.
*
* Do the counting by mapping a byte value to the number of set
* bits for that value using the xfs_countbit array, i.e.
* xfs_countbit[0] == 0, xfs_countbit[1] == 1, xfs_countbit[2] == 1,
* xfs_countbit[3] == 2, etc.
*/
int
xfs_count_bits(uint *map, uint size, uint start_bit)
{
register int bits;
register unsigned char *bytep;
register unsigned char *end_map;
int byte_bit;
bits = 0;
end_map = (char*)(map + size);
bytep = (char*)(map + (start_bit & ~0x7));
byte_bit = start_bit & 0x7;
/*
* If the caller fell off the end of the map, return 0.
*/
if (bytep >= end_map) {
return (0);
}
/*
* If start_bit is not byte aligned, then process the
* first byte separately.
*/
if (byte_bit != 0) {
/*
* Shift off the bits we don't want to look at,
* before indexing into xfs_countbit.
*/
bits += xfs_countbit[(*bytep >> byte_bit)];
bytep++;
}
/*
* Count the bits in each byte until the end of the bitmap.
*/
while (bytep < end_map) {
bits += xfs_countbit[*bytep];
bytep++;
}
return (bits);
}
/*
* Count the number of contiguous bits set in the bitmap starting with bit
* start_bit. Size is the size of the bitmap in words.
*/
int
xfs_contig_bits(uint *map, uint size, uint start_bit)
{
uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
uint result = 0;
uint tmp;
size <<= BIT_TO_WORD_SHIFT;
ASSERT(start_bit < size);
size -= start_bit & ~(NBWORD - 1);
start_bit &= (NBWORD - 1);
if (start_bit) {
tmp = *p++;
/* set to one first offset bits prior to start */
tmp |= (~0U >> (NBWORD-start_bit));
if (tmp != ~0U)
goto found;
result += NBWORD;
size -= NBWORD;
}
while (size) {
if ((tmp = *p++) != ~0U)
goto found;
result += NBWORD;
size -= NBWORD;
}
return result - start_bit;
found:
return result + ffz(tmp) - start_bit;
}
/*
* This takes the bit number to start looking from and
* returns the next set bit from there. It returns -1
* if there are no more bits set or the start bit is
* beyond the end of the bitmap.
*
* Size is the number of words, not bytes, in the bitmap.
*/
int xfs_next_bit(uint *map, uint size, uint start_bit)
{
uint * p = ((unsigned int *) map) + (start_bit >> BIT_TO_WORD_SHIFT);
uint result = start_bit & ~(NBWORD - 1);
uint tmp;
size <<= BIT_TO_WORD_SHIFT;
if (start_bit >= size)
return -1;
size -= result;
start_bit &= (NBWORD - 1);
if (start_bit) {
tmp = *p++;
/* set to zero first offset bits prior to start */
tmp &= (~0U << start_bit);
if (tmp != 0U)
goto found;
result += NBWORD;
size -= NBWORD;
}
while (size) {
if ((tmp = *p++) != 0U)
goto found;
result += NBWORD;
size -= NBWORD;
}
return -1;
found:
return result + ffs(tmp) - 1;
}
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