include/asm-generic/bitops/ffs.h

Source file repositories/reference/linux-study-clean/include/asm-generic/bitops/ffs.h

File Facts

System
Linux kernel
Corpus path
include/asm-generic/bitops/ffs.h
Extension
.h
Size
742 bytes
Lines
47
Domain
Repository Root And Misc
Bucket
include
Inferred role
Repository Root And Misc: implementation source
Status
source implementation candidate

Why This File Exists

Top-level or miscellaneous repository surface. Use this as map coverage unless a later manual pass promotes the file into a deeper subsystem dossier.

Dependency Surface

Detected Declarations

Annotated Snippet

#ifndef _ASM_GENERIC_BITOPS_FFS_H_
#define _ASM_GENERIC_BITOPS_FFS_H_

/**
 * generic_ffs - find first bit set
 * @x: the word to search
 *
 * This is defined the same way as
 * the libc and compiler builtin ffs routines, therefore
 * differs in spirit from ffz (man ffs).
 */
static inline __attribute_const__ int generic_ffs(int x)
{
	int r = 1;

	if (!x)
		return 0;
	if (!(x & 0xffff)) {
		x >>= 16;
		r += 16;
	}
	if (!(x & 0xff)) {
		x >>= 8;
		r += 8;
	}
	if (!(x & 0xf)) {
		x >>= 4;
		r += 4;
	}
	if (!(x & 3)) {
		x >>= 2;
		r += 2;
	}
	if (!(x & 1)) {
		x >>= 1;
		r += 1;
	}
	return r;
}

#ifndef __HAVE_ARCH_FFS
#define ffs(x) generic_ffs(x)
#endif

#endif /* _ASM_GENERIC_BITOPS_FFS_H_ */

Annotation

Implementation Notes