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2f0d412210
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.
55 lines
887 B
C
55 lines
887 B
C
#ifndef _STRINGS_H
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#define _STRINGS_H
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#include <limits.h>
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static inline __attribute__ (( always_inline )) int
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__constant_flsl ( unsigned long x ) {
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int r = 0;
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#if ULONG_MAX > 0xffffffff
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if ( x & 0xffffffff00000000UL ) {
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x >>= 32;
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r += 32;
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}
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#endif
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if ( x & 0xffff0000UL ) {
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x >>= 16;
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r += 16;
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}
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if ( x & 0xff00 ) {
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x >>= 8;
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r += 8;
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}
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if ( x & 0xf0 ) {
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x >>= 4;
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r += 4;
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}
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if ( x & 0xc ) {
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x >>= 2;
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r += 2;
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}
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if ( x & 0x2 ) {
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x >>= 1;
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r += 1;
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}
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if ( x & 0x1 ) {
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r += 1;
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}
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return r;
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}
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#define __constant_fls(x) __constant_flsl(x)
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/* We don't actually have these functions yet */
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extern int __fls ( int x );
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extern int __flsl ( long x );
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#define flsl( x ) \
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( __builtin_constant_p ( x ) ? __constant_flsl ( x ) : __flsl ( x ) )
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#define fls( x ) \
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( __builtin_constant_p ( x ) ? __constant_fls ( x ) : __fls ( x ) )
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#endif /* _STRINGS_H */
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