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[libc] Add ffs(), ffsl(), and ffsll()

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Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2015-03-15 19:28:05 +00:00
parent 57bab4e1d3
commit 79697c75ee
4 changed files with 233 additions and 6 deletions
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81
src/include/strings.h
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@@ -12,6 +12,54 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#include <string.h>
#include <bits/strings.h>
/**
* Find first (i.e. least significant) set bit
*
* @v x Value
* @ret lsb Least significant bit set in value (LSB=1), or zero
*/
static inline __attribute__ (( always_inline )) int
__constant_ffsll ( unsigned long long x ) {
int r = 0;
if ( ! ( x & 0x00000000ffffffffULL ) ) {
x >>= 32;
r += 32;
}
if ( ! ( x & 0x0000ffffUL ) ) {
x >>= 16;
r += 16;
}
if ( ! ( x & 0x00ff ) ) {
x >>= 8;
r += 8;
}
if ( ! ( x & 0x0f ) ) {
x >>= 4;
r += 4;
}
if ( ! ( x & 0x3 ) ) {
x >>= 2;
r += 2;
}
if ( ! ( x & 0x1 ) ) {
x >>= 1;
r += 1;
}
return ( x ? ( r + 1 ) : 0 );
}
/**
* Find first (i.e. least significant) set bit
*
* @v x Value
* @ret lsb Least significant bit set in value (LSB=1), or zero
*/
static inline __attribute__ (( always_inline )) int
__constant_ffsl ( unsigned long x ) {
return __constant_ffsll ( x );
}
/**
* Find last (i.e. most significant) set bit
*
@@ -46,10 +94,7 @@ __constant_flsll ( unsigned long long x ) {
x >>= 1;
r += 1;
}
if ( x & 0x1 ) {
r += 1;
}
return r;
return ( x ? ( r + 1 ) : 0 );
}
/**
@@ -63,9 +108,37 @@ __constant_flsl ( unsigned long x ) {
return __constant_flsll ( x );
}
int __ffsll ( long long x );
int __ffsl ( long x );
int __flsll ( long long x );
int __flsl ( long x );
/**
* Find first (i.e. least significant) set bit
*
* @v x Value
* @ret lsb Least significant bit set in value (LSB=1), or zero
*/
#define ffsll( x ) \
( __builtin_constant_p ( x ) ? __constant_ffsll ( x ) : __ffsll ( x ) )
/**
* Find first (i.e. least significant) set bit
*
* @v x Value
* @ret lsb Least significant bit set in value (LSB=1), or zero
*/
#define ffsl( x ) \
( __builtin_constant_p ( x ) ? __constant_ffsl ( x ) : __ffsl ( x ) )
/**
* Find first (i.e. least significant) set bit
*
* @v x Value
* @ret lsb Least significant bit set in value (LSB=1), or zero
*/
#define ffs( x ) ffsl ( x )
/**
* Find last (i.e. most significant) set bit
*