[PATCH v3 05/23] trace-cmd: Add new local function to check if a trace clock is supported

["Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com>]

A new local function is added to check if a given trace clock is
supported by the ftrace:
 clock_is_supported()
This function is used by the other patches from the set.
The logic should be part of the tracefs library, when a tracefs API is
implemeneted, this local funciton will be removed.

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 tracecmd/trace-record.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c
index 635897e1..5f7f5b3d 100644
--- a/tracecmd/trace-record.c
+++ b/tracecmd/trace-record.c
@@ -5683,6 +5683,33 @@ check_instance_die(struct buffer_instance *instance, char *param)
 		    tracefs_instance_get_name(instance->tracefs), param);
 }
 
+static bool clock_is_supported(struct tracefs_instance *instance, char *clock)
+{
+	char *all_clocks = NULL;
+	char *ret = NULL;
+
+	all_clocks  = tracefs_instance_file_read(instance, "trace_clock", NULL);
+	if (!all_clocks)
+		return false;
+
+	ret = strstr(all_clocks, clock);
+	if (ret && (ret == all_clocks || ret[-1] == ' ' || ret[-1] == '[')) {
+		switch (ret[strlen(clock)]) {
+		case ' ':
+		case '\0':
+		case ']':
+			break;
+		default:
+			ret = NULL;
+		}
+	} else {
+		ret = NULL;
+	}
+	free(all_clocks);
+
+	return ret != NULL;
+}
+
 static void parse_record_options(int argc,
 				 char **argv,
 				 enum trace_cmd curr_cmd,
-- 
2.30.2