[PATCH v2 1/4] libtracefs: Implement tracefs_instances()

[Steven Rostedt <rostedt@xxxxxxxxxxx>]

From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>

Implement tracefs_instances() that will take a regex (or NULL for all) and
return a list of instances in the system.

Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
 include/tracefs.h      |  1 +
 src/tracefs-instance.c | 78 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 79 insertions(+)

diff --git a/include/tracefs.h b/include/tracefs.h
index da8ad4189d4d..a21d2d2f22a6 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -44,6 +44,7 @@ int tracefs_instance_file_read_number(struct tracefs_instance *instance,
 int tracefs_instance_file_open(struct tracefs_instance *instance,
 			       const char *file, int mode);
 int tracefs_instances_walk(int (*callback)(const char *, void *), void *context);
+char **tracefs_instances(const char *regex);
 
 bool tracefs_instance_exists(const char *name);
 bool tracefs_file_exists(struct tracefs_instance *instance, const char *name);
diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
index 2aeb529903bd..d833fae0fb0c 100644
--- a/src/tracefs-instance.c
+++ b/src/tracefs-instance.c
@@ -14,6 +14,7 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <dirent.h>
+#include <regex.h>
 #include <limits.h>
 #include <pthread.h>
 #include "tracefs.h"
@@ -630,6 +631,83 @@ out:
 	return fret;
 }
 
+static inline bool match(const char *str, regex_t *re)
+{
+	if (!re)
+		return true;
+	return regexec(re, str, 0, NULL, 0) == 0;
+}
+
+struct instance_list {
+	regex_t		*re;
+	char		**list;
+	int		size;
+	int		failed;
+};
+
+static int build_list(const char *name, void *data)
+{
+	struct instance_list *list = data;
+	char **instances;
+	int ret = -1;
+
+	if (!match(name, list->re))
+		return 0;
+
+	instances = realloc(list->list, list->size + 2);
+	if (!instances)
+		goto out;
+
+	list->list = instances;
+	list->list[list->size] = strdup(name);
+	if (!list->list[list->size])
+		goto out;
+
+	list->size++;
+	ret = 0;
+
+ out:
+	list->failed = ret;
+	return ret;
+}
+
+/**
+ * tracefs_instances - return a list of instance names
+ * @regex: A regex of instances to filter on (NULL to match all)
+ *
+ * Returns a list of names of existing instances, that must be
+ * freed with tracefs_list_free(). Note, if there are no matches
+ * then an empty list will be returned (not NULL).
+ * NULL on error.
+ */
+char **tracefs_instances(const char *regex)
+{
+	struct instance_list list = { .re = NULL, .list = NULL };
+	regex_t re;
+	int ret;
+
+	if (regex) {
+		ret = regcomp(&re, regex, REG_ICASE|REG_NOSUB);
+		if (ret < 0)
+			return NULL;
+		list.re = &re;
+	}
+
+	ret = tracefs_instances_walk(build_list, &list);
+	if (ret < 0 || list.failed) {
+		tracefs_list_free(list.list);
+		list.list = NULL;
+	} else {
+		if (!list.list) {
+			/* No matches should produce an empty list */
+			list.list = malloc(sizeof(*list.list));
+			if (list.list)
+				list.list[0] = NULL;
+		}
+	}
+	return list.list;
+}
+
 /**
  * tracefs_get_clock - Get the current trace clock
  * @instance: ftrace instance, can be NULL for the top instance
-- 
2.30.2