Commit b3e45327 authored by Jiri Olsa's avatar Jiri Olsa Committed by Arnaldo Carvalho de Melo
Browse files

tools lib: Adopt memchr_inv() from kernel 



We'll use it to check for undefined/zero data.

Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Suggested-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: default avatarNamhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20201126170026.2619053-6-jolsa@kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 05e91e7f

tools/include/linux/string.h

+1 −0
Original line number Diff line number Diff line
@@ -46,4 +46,5 @@ extern char * __must_check skip_spaces(const char *); 


extern char *strim(char *);



extern void *memchr_inv(const void *start, int c, size_t bytes);

#endif /* _TOOLS_LINUX_STRING_H_ */

tools/lib/string.c

+58 −0
Original line number Diff line number Diff line
@@ -168,3 +168,61 @@ char *strreplace(char *s, char old, char new) 
			*s = new;

	return s;

}



static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)

{

	while (bytes) {

		if (*start != value)

			return (void *)start;

		start++;

		bytes--;

	}

	return NULL;

}



/**

 * memchr_inv - Find an unmatching character in an area of memory.

 * @start: The memory area

 * @c: Find a character other than c

 * @bytes: The size of the area.

 *

 * returns the address of the first character other than @c, or %NULL

 * if the whole buffer contains just @c.

 */

void *memchr_inv(const void *start, int c, size_t bytes)

{

	u8 value = c;

	u64 value64;

	unsigned int words, prefix;



	if (bytes <= 16)

		return check_bytes8(start, value, bytes);



	value64 = value;

	value64 |= value64 << 8;

	value64 |= value64 << 16;

	value64 |= value64 << 32;



	prefix = (unsigned long)start % 8;

	if (prefix) {

		u8 *r;



		prefix = 8 - prefix;

		r = check_bytes8(start, value, prefix);

		if (r)

			return r;

		start += prefix;

		bytes -= prefix;

	}



	words = bytes / 8;



	while (words) {

		if (*(u64 *)start != value64)

			return check_bytes8(start, value, 8);

		start += 8;

		words--;

	}



	return check_bytes8(start, value, bytes % 8);

}