File: [Development] / xfs-linux-nodel / xfs_bit.c (download)
Revision 1.5, Sat Dec 20 00:22:42 1997 UTC (19 years, 10 months ago) by doucette
Branch: MAIN
Changes since 1.4: +31 -24
lines
Rewrite so there are fewer return points. The compiler had
a hard time generating compact code for the earlier form.
pv: 546137
rv: mostek@cray.com
|
#ident "$Revision: 1.4 $"
/*
* XFS bit manipulation routines, used in non-realtime code.
*/
#include <sys/types.h>
#include "xfs_bit.h"
/*
* Index of low bit number in byte, -1 for none set, 0..7 otherwise.
*/
const char xfs_lowbit[256] = {
-1, 0, 1, 0, 2, 0, 1, 0, /* 00 .. 07 */
3, 0, 1, 0, 2, 0, 1, 0, /* 08 .. 0f */
4, 0, 1, 0, 2, 0, 1, 0, /* 10 .. 17 */
3, 0, 1, 0, 2, 0, 1, 0, /* 18 .. 1f */
5, 0, 1, 0, 2, 0, 1, 0, /* 20 .. 27 */
3, 0, 1, 0, 2, 0, 1, 0, /* 28 .. 2f */
4, 0, 1, 0, 2, 0, 1, 0, /* 30 .. 37 */
3, 0, 1, 0, 2, 0, 1, 0, /* 38 .. 3f */
6, 0, 1, 0, 2, 0, 1, 0, /* 40 .. 47 */
3, 0, 1, 0, 2, 0, 1, 0, /* 48 .. 4f */
4, 0, 1, 0, 2, 0, 1, 0, /* 50 .. 57 */
3, 0, 1, 0, 2, 0, 1, 0, /* 58 .. 5f */
5, 0, 1, 0, 2, 0, 1, 0, /* 60 .. 67 */
3, 0, 1, 0, 2, 0, 1, 0, /* 68 .. 6f */
4, 0, 1, 0, 2, 0, 1, 0, /* 70 .. 77 */
3, 0, 1, 0, 2, 0, 1, 0, /* 78 .. 7f */
7, 0, 1, 0, 2, 0, 1, 0, /* 80 .. 87 */
3, 0, 1, 0, 2, 0, 1, 0, /* 88 .. 8f */
4, 0, 1, 0, 2, 0, 1, 0, /* 90 .. 97 */
3, 0, 1, 0, 2, 0, 1, 0, /* 98 .. 9f */
5, 0, 1, 0, 2, 0, 1, 0, /* a0 .. a7 */
3, 0, 1, 0, 2, 0, 1, 0, /* a8 .. af */
4, 0, 1, 0, 2, 0, 1, 0, /* b0 .. b7 */
3, 0, 1, 0, 2, 0, 1, 0, /* b8 .. bf */
6, 0, 1, 0, 2, 0, 1, 0, /* c0 .. c7 */
3, 0, 1, 0, 2, 0, 1, 0, /* c8 .. cf */
4, 0, 1, 0, 2, 0, 1, 0, /* d0 .. d7 */
3, 0, 1, 0, 2, 0, 1, 0, /* d8 .. df */
5, 0, 1, 0, 2, 0, 1, 0, /* e0 .. e7 */
3, 0, 1, 0, 2, 0, 1, 0, /* e8 .. ef */
4, 0, 1, 0, 2, 0, 1, 0, /* f0 .. f7 */
3, 0, 1, 0, 2, 0, 1, 0, /* f8 .. ff */
};
/*
* Index of high bit number in byte, -1 for none set, 0..7 otherwise.
*/
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 */
};
/*
* Count of bits set in byte, 0..8.
*/
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.
*/
int
xfs_highbit32(
__uint32_t v)
{
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];
}
/*
* xfs_lowbit64: get low bit set out of 64-bit argument, -1 if none set.
*/
int
xfs_lowbit64(
__uint64_t v)
{
int i;
#if (_MIPS_SIM == _ABIN32 || _MIPS_SIM == _ABI64)
if (v & 0x00000000ffffffff)
if (v & 0x000000000000ffff)
if (v & 0x00000000000000ff)
i = 0;
else
i = 8;
else
if (v & 0x0000000000ff0000)
i = 16;
else
i = 24;
else if (v & 0xffffffff00000000)
if (v & 0x0000ffff00000000)
if (v & 0x000000ff00000000)
i = 32;
else
i = 40;
else
if (v & 0x00ff000000000000)
i = 48;
else
i = 56;
else
return -1;
return i + xfs_lowbit[(v >> i) & 0xff];
#else
__uint32_t vw;
if (vw = v) {
if (vw & 0x0000ffff)
if (vw & 0x000000ff)
i = 0;
else
i = 8;
else
if (vw & 0x00ff0000)
i = 16;
else
i = 24;
return i + xfs_lowbit[(vw >> i) & 0xff];
} else if (vw = v >> 32) {
if (vw & 0x0000ffff)
if (vw & 0x000000ff)
i = 32;
else
i = 40;
else
if (vw & 0x00ff0000)
i = 48;
else
i = 56;
return i + xfs_lowbit[(vw >> (i - 32)) & 0xff];
} else
return -1;
#endif
}
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