perf util: Support no index time percent slice

Previously, the time percent slice needs an index to specify which one
the user wants.

It may be easier to use if the index can be omitted. So with this
patch, for example,

perf report --stdio --time 10%/1 should be equivalent to
perf report --stdio --time 10%

Signed-off-by: Jin Yao <[e-mail]>
Suggested-by: Arnaldo Carvalho de Melo <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Reviewed-by: Jiri Olsa <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/time-utils.c

···
 	return i;
 }
 
+static int one_percent_convert(struct perf_time_interval *ptime_buf,
+			       const char *ostr, u64 start, u64 end, char *c)
+{
+	char *str;
+	int len = strlen(ostr), ret;
+
+	/*
+	 * c points to '%'.
+	 * '%' should be the last character
+	 */
+	if (ostr + len - 1 != c)
+		return -1;
+
+	/*
+	 * Construct a string like "xx%/1"
+	 */
+	str = malloc(len + 3);
+	if (str == NULL)
+		return -ENOMEM;
+
+	memcpy(str, ostr, len);
+	strcpy(str + len, "/1");
+
+	ret = percent_slash_split(str, ptime_buf, start, end);
+	if (ret == 0)
+		ret = 1;
+
+	free(str);
+	return ret;
+}
+
 int perf_time__percent_parse_str(struct perf_time_interval *ptime_buf, int num,
 				 const char *ostr, u64 start, u64 end)
 {
···
 	 * ostr example:
 	 * 10%/2,10%/3: select the second 10% slice and the third 10% slice
 	 * 0%-10%,30%-40%: multiple time range
+	 * 50%: just one percent
 	 */
 
 	memset(ptime_buf, 0, sizeof(*ptime_buf) * num);
···
 		return percent_comma_split(ptime_buf, num, ostr, start,
 					   end, percent_dash_split);
 	}
+
+	c = strchr(ostr, '%');
+	if (c)
+		return one_percent_convert(ptime_buf, ostr, start, end, c);
 
 	return -1;
 }