From: Olivier Dion <odion@efficios.com>
Date: Mon, 6 Feb 2023 20:55:39 +0000 (-0500)
Subject: lttng: Add list_sessions utility
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=ca938aa52e0d841fc638ecffb4261a80d846831f;p=lttng-tools.git

lttng: Add list_sessions utility

Get a list of sessions given a session specification.

The `NAME' specification returns the session that has the given
name. The `GLOB_PATTERN' specification returns all sessions that match a
pattern. The `ALL' specification returns all sessions.

Change-Id: If69698d6dd59d54ba16669571ef49ed5bb9b8997
Signed-off-by: Olivier Dion <odion@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/src/bin/lttng/utils.cpp b/src/bin/lttng/utils.cpp
index 90ca90fde..5b0c461d9 100644
--- a/src/bin/lttng/utils.cpp
+++ b/src/bin/lttng/utils.cpp
@@ -12,10 +12,13 @@
 
 #include <common/defaults.hpp>
 #include <common/error.hpp>
+#include <common/exception.hpp>
+#include <common/make-unique-wrapper.hpp>
 #include <common/utils.hpp>
 
 #include <arpa/inet.h>
 #include <ctype.h>
+#include <fnmatch.h>
 #include <inttypes.h>
 #include <limits.h>
 #include <netinet/in.h>
@@ -659,3 +662,81 @@ end:
 	}
 	return ret;
 }
+
+namespace {
+template <typename FilterFunctionType>
+session_list get_sessions(const FilterFunctionType& filter, bool return_first_match_only = false)
+{
+	session_list list;
+
+	{
+		int list_ret;
+		struct lttng_session *psessions;
+
+		list_ret = lttng_list_sessions(&psessions);
+
+		if (list_ret < 0) {
+			LTTNG_THROW_CTL("Failed to list sessions",
+					static_cast<lttng_error_code>(list_ret));
+		}
+
+		list = session_list(psessions, list_ret);
+	}
+
+	std::size_t write_to = 0;
+	for (std::size_t read_from = 0; read_from < list.size(); ++read_from) {
+		if (!filter(list[read_from])) {
+			continue;
+		}
+
+		if (read_from != write_to) {
+			list[write_to] = list[read_from];
+		}
+
+		++write_to;
+
+		if (return_first_match_only) {
+			return session_list(std::move(list), 1);
+		}
+	}
+
+	list.resize(write_to);
+
+	return list;
+}
+} /* namespace */
+
+session_list list_sessions(const struct session_spec& spec)
+{
+	switch (spec.type) {
+	case session_spec::NAME:
+		if (spec.value == nullptr) {
+			const auto configured_name =
+				lttng::make_unique_wrapper<char, lttng::free>(get_session_name());
+
+			if (configured_name) {
+				const struct session_spec new_spec = {
+					.type = session_spec::NAME, .value = configured_name.get()
+				};
+
+				return list_sessions(new_spec);
+			}
+
+			return session_list();
+		}
+
+		return get_sessions(
+			[&spec](const lttng_session& session) {
+				return strcmp(session.name, spec.value) == 0;
+			},
+			true);
+	case session_spec::GLOB_PATTERN:
+		return get_sessions([&spec](const lttng_session& session) {
+			return fnmatch(spec.value, session.name, 0) == 0;
+		});
+	case session_spec::ALL:
+		return get_sessions([](const lttng_session&) { return true; });
+	}
+
+	return session_list();
+}
diff --git a/src/bin/lttng/utils.hpp b/src/bin/lttng/utils.hpp
index 64605575e..c3b442056 100644
--- a/src/bin/lttng/utils.hpp
+++ b/src/bin/lttng/utils.hpp
@@ -10,9 +10,12 @@
 
 #include <common/argpar/argpar.h>
 #include <common/dynamic-array.hpp>
+#include <common/make-unique-wrapper.hpp>
 
 #include <lttng/lttng.h>
 
+#include <iterator>
+#include <memory>
 #include <popt.h>
 
 extern char *opt_relayd_path;
@@ -22,6 +25,127 @@ extern pid_t sessiond_pid;
 
 struct cmd_struct;
 
+struct session_spec {
+	enum type {
+		NAME,
+		GLOB_PATTERN,
+		ALL,
+	};
+
+	type type;
+	const char *value;
+};
+
+/*
+ * We don't use a std::vector here because it would make a copy of the C array.
+ */
+class session_list {
+	class iterator : public std::iterator<std::random_access_iterator_tag, std::size_t> {
+	public:
+		explicit iterator(session_list& list, std::size_t k) : _list(list), _index(k)
+		{
+		}
+
+		iterator& operator++() noexcept
+		{
+			++_index;
+			return *this;
+		}
+
+		iterator& operator--() noexcept
+		{
+			--_index;
+			return *this;
+		}
+
+		iterator& operator++(int) noexcept
+		{
+			_index++;
+			return *this;
+		}
+
+		iterator& operator--(int) noexcept
+		{
+			_index--;
+			return *this;
+		}
+
+		bool operator==(iterator other) const noexcept
+		{
+			return _index == other._index;
+		}
+
+		bool operator!=(iterator other) const noexcept
+		{
+			return !(*this == other);
+		}
+
+		lttng_session& operator*() const noexcept
+		{
+			return _list[_index];
+		}
+
+	private:
+		session_list& _list;
+		std::size_t _index;
+	};
+
+public:
+	session_list() : _sessions_count(0), _sessions(nullptr)
+	{
+	}
+
+	session_list(session_list&& original, std::size_t new_count)
+	{
+		_sessions_count = new_count;
+		_sessions = std::move(original._sessions);
+	}
+
+	session_list(struct lttng_session *raw_sessions, std::size_t raw_sessions_count)
+	{
+		_sessions_count = raw_sessions_count;
+		_sessions.reset(raw_sessions);
+	}
+
+	iterator begin() noexcept
+	{
+		return iterator(*this, 0);
+	}
+
+	iterator end() noexcept
+	{
+		return iterator(*this, _sessions_count);
+	}
+
+	std::size_t size() const noexcept
+	{
+		return _sessions_count;
+	}
+
+	void resize(std::size_t new_size) noexcept
+	{
+		_sessions_count = new_size;
+	}
+
+	lttng_session& operator[](std::size_t index)
+	{
+		LTTNG_ASSERT(index < _sessions_count);
+		return _sessions.get()[index];
+	}
+
+	const lttng_session& operator[](std::size_t index) const
+	{
+		LTTNG_ASSERT(index < _sessions_count);
+		return _sessions.get()[index];
+	}
+
+private:
+	std::size_t _sessions_count;
+	std::unique_ptr<lttng_session,
+			lttng::details::create_unique_class<lttng_session, lttng::free>>
+		_sessions;
+};
+
 char *get_session_name(void);
 char *get_session_name_quiet(void);
 void list_commands(struct cmd_struct *commands, FILE *ofp);
@@ -62,4 +186,6 @@ int print_trace_archive_location(const struct lttng_trace_archive_location *loca
 int validate_exclusion_list(const char *event_name,
 			    const struct lttng_dynamic_pointer_array *exclusions);
 
+session_list list_sessions(const struct session_spec& spec);
+
 #endif /* _LTTNG_UTILS_H */