perf util: Add parse_nsec_time() function

The parse_nsec_time() function is for parsing a string of time into
64-bit nsec value.  It's a preparation of time filtering in some of perf
commands.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: David Ahern <dsahern@gmail.com>
Acked-by: David Ahern <dsahern@gmail.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1370310629-9642-1-git-send-email-namhyung@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/util.c

@@ -328,3 +328,36 @@ void put_tracing_file(char *file)
 {
 	free(file);
 }
+
+int parse_nsec_time(const char *str, u64 *ptime)
+{
+	u64 time_sec, time_nsec;
+	char *end;
+
+	time_sec = strtoul(str, &end, 10);
+	if (*end != '.' && *end != '\0')
+		return -1;
+
+	if (*end == '.') {
+		int i;
+		char nsec_buf[10];
+
+		if (strlen(++end) > 9)
+			return -1;
+
+		strncpy(nsec_buf, end, 9);
+		nsec_buf[9] = '\0';
+
+		/* make it nsec precision */
+		for (i = strlen(nsec_buf); i < 9; i++)
+			nsec_buf[i] = '0';
+
+		time_nsec = strtoul(nsec_buf, &end, 10);
+		if (*end != '\0')
+			return -1;
+	} else
+		time_nsec = 0;
+
+	*ptime = time_sec * NSEC_PER_SEC + time_nsec;
+	return 0;
+}

tools/perf/util/util.h

@@ -208,6 +208,8 @@ static inline int has_extension(const char *filename, const char *ext)
 #define NSEC_PER_MSEC	1000000L
 #endif
 
+int parse_nsec_time(const char *str, u64 *ptime);
+
 extern unsigned char sane_ctype[256];
 #define GIT_SPACE		0x01
 #define GIT_DIGIT		0x02