mirror of
https://github.com/UberGames/RPG-X2.git
synced 2024-11-27 22:52:33 +00:00
109 lines
2.9 KiB
C
109 lines
2.9 KiB
C
/*
|
|
Some useful bit functions
|
|
*/
|
|
|
|
C_MODE_START
|
|
#ifdef HAVE_INLINE
|
|
|
|
extern const char _my_bits_nbits[256];
|
|
extern const uchar _my_bits_reverse_table[256];
|
|
|
|
/*
|
|
Find smallest X in 2^X >= value
|
|
This can be used to divide a number with value by doing a shift instead
|
|
*/
|
|
|
|
STATIC_INLINE uint my_bit_log2(ulong value)
|
|
{
|
|
uint bit;
|
|
for (bit=0 ; value > 1 ; value>>=1, bit++) ;
|
|
return bit;
|
|
}
|
|
|
|
STATIC_INLINE uint my_count_bits(ulonglong v)
|
|
{
|
|
#if SIZEOF_LONG_LONG > 4
|
|
/* The following code is a bit faster on 16 bit machines than if we would
|
|
only shift v */
|
|
ulong v2=(ulong) (v >> 32);
|
|
return (uint) (uchar) (_my_bits_nbits[(uchar) v] +
|
|
_my_bits_nbits[(uchar) (v >> 8)] +
|
|
_my_bits_nbits[(uchar) (v >> 16)] +
|
|
_my_bits_nbits[(uchar) (v >> 24)] +
|
|
_my_bits_nbits[(uchar) (v2)] +
|
|
_my_bits_nbits[(uchar) (v2 >> 8)] +
|
|
_my_bits_nbits[(uchar) (v2 >> 16)] +
|
|
_my_bits_nbits[(uchar) (v2 >> 24)]);
|
|
#else
|
|
return (uint) (uchar) (_my_bits_nbits[(uchar) v] +
|
|
_my_bits_nbits[(uchar) (v >> 8)] +
|
|
_my_bits_nbits[(uchar) (v >> 16)] +
|
|
_my_bits_nbits[(uchar) (v >> 24)]);
|
|
#endif
|
|
}
|
|
|
|
STATIC_INLINE uint my_count_bits_ushort(ushort v)
|
|
{
|
|
return _my_bits_nbits[v];
|
|
}
|
|
|
|
|
|
/*
|
|
Next highest power of two
|
|
|
|
SYNOPSIS
|
|
my_round_up_to_next_power()
|
|
v Value to check
|
|
|
|
RETURN
|
|
Next or equal power of 2
|
|
Note: 0 will return 0
|
|
|
|
NOTES
|
|
Algorithm by Sean Anderson, according to:
|
|
http://graphics.stanford.edu/~seander/bithacks.html
|
|
(Orignal code public domain)
|
|
|
|
Comments shows how this works with 01100000000000000000000000001011
|
|
*/
|
|
|
|
STATIC_INLINE uint32 my_round_up_to_next_power(uint32 v)
|
|
{
|
|
v--; /* 01100000000000000000000000001010 */
|
|
v|= v >> 1; /* 01110000000000000000000000001111 */
|
|
v|= v >> 2; /* 01111100000000000000000000001111 */
|
|
v|= v >> 4; /* 01111111110000000000000000001111 */
|
|
v|= v >> 8; /* 01111111111111111100000000001111 */
|
|
v|= v >> 16; /* 01111111111111111111111111111111 */
|
|
return v+1; /* 10000000000000000000000000000000 */
|
|
}
|
|
|
|
STATIC_INLINE uint32 my_clear_highest_bit(uint32 v)
|
|
{
|
|
uint32 w=v >> 1;
|
|
w|= w >> 1;
|
|
w|= w >> 2;
|
|
w|= w >> 4;
|
|
w|= w >> 8;
|
|
w|= w >> 16;
|
|
return v & w;
|
|
}
|
|
|
|
STATIC_INLINE uint32 my_reverse_bits(uint32 key)
|
|
{
|
|
return
|
|
(_my_bits_reverse_table[ key & 255] << 24) |
|
|
(_my_bits_reverse_table[(key>> 8) & 255] << 16) |
|
|
(_my_bits_reverse_table[(key>>16) & 255] << 8) |
|
|
_my_bits_reverse_table[(key>>24) ];
|
|
}
|
|
|
|
#else /* HAVE_INLINE */
|
|
extern uint my_bit_log2(ulong value);
|
|
extern uint32 my_round_up_to_next_power(uint32 v);
|
|
uint32 my_clear_highest_bit(uint32 v);
|
|
uint32 my_reverse_bits(uint32 key);
|
|
extern uint my_count_bits(ulonglong v);
|
|
extern uint my_count_bits_ushort(ushort v);
|
|
#endif /* HAVE_INLINE */
|
|
C_MODE_END
|