tools lib: Adopt memchr_inv() from kernel

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

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Suggested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Namhyung 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: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/include/linux/string.h b/tools/include/linux/string.h
index 5e9e781..db5c993 100644 (file)
--- a/tools/include/linux/string.h
+++ b/tools/include/linux/string.h
@@ -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_ */

diff --git a/tools/lib/string.c b/tools/lib/string.c
index f645343..8b6892f 100644 (file)
--- a/tools/lib/string.c
+++ b/tools/lib/string.c
@@ -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);
+}