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Add __constant_flsl(), because it's useful for finding out the next

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power-of-two up from a given constant via
  ( 1 << fls ( constant - 1 ) )

fls(), flsl(), ffs() and ffsl() appear in strings.h according to
POSIX.
This commit is contained in:
Michael Brown 2006-04-24 23:00:32 +00:00
parent a81f96998b
commit 2f0d412210
1 changed files with 54 additions and 0 deletions
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54
src/include/strings.h Normal file
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#ifndef _STRINGS_H
#define _STRINGS_H
#include <limits.h>
static inline __attribute__ (( always_inline )) int
__constant_flsl ( unsigned long x ) {
int r = 0;
#if ULONG_MAX > 0xffffffff
if ( x & 0xffffffff00000000UL ) {
x >>= 32;
r += 32;
}
#endif
if ( x & 0xffff0000UL ) {
x >>= 16;
r += 16;
}
if ( x & 0xff00 ) {
x >>= 8;
r += 8;
}
if ( x & 0xf0 ) {
x >>= 4;
r += 4;
}
if ( x & 0xc ) {
x >>= 2;
r += 2;
}
if ( x & 0x2 ) {
x >>= 1;
r += 1;
}
if ( x & 0x1 ) {
r += 1;
}
return r;
}
#define __constant_fls(x) __constant_flsl(x)
/* We don't actually have these functions yet */
extern int __fls ( int x );
extern int __flsl ( long x );
#define flsl( x ) \
( __builtin_constant_p ( x ) ? __constant_flsl ( x ) : __flsl ( x ) )
#define fls( x ) \
( __builtin_constant_p ( x ) ? __constant_fls ( x ) : __fls ( x ) )
#endif /* _STRINGS_H */