onexit: add an on exit callback utility

Adds a class that executes registered callbacks in its destructor. Since
static duration objects have their destructors called when returning
from main or calling exit then this can be used as a replacement for
on_exit.

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/src/include/on_exit.h b/src/include/on_exit.h
new file mode 100644
index 00000000000..4bb8f2c0687
--- /dev/null
+++ b/src/include/on_exit.h
@@ -0,0 +1,48 @@
+#ifndef CEPH_ON_EXIT_H
+#define CEPH_ON_EXIT_H
+
+#include <pthread.h>
+#include <assert.h>
+#include <vector>
+
+/*
+ * Create a static instance at the file level to get callbacks called when the
+ * process exits via main() or exit().
+ */
+
+class OnExitManager {
+  public:
+    typedef void (*callback_t)(void *arg);
+
+    OnExitManager() {
+      assert(pthread_mutex_init(&lock_, NULL) == 0);
+    }
+
+    ~OnExitManager() {
+      pthread_mutex_lock(&lock_);
+      std::vector<struct cb>::iterator it;
+      for (it = funcs_.begin(); it != funcs_.end(); it++) {
+        it->func(it->arg);
+      }
+      funcs_.clear();
+      pthread_mutex_unlock(&lock_);
+    }
+
+    void add_callback(callback_t func, void *arg) {
+      pthread_mutex_lock(&lock_);
+      struct cb callback = { func, arg };
+      funcs_.push_back(callback);
+      pthread_mutex_unlock(&lock_);
+    }
+
+  private:
+    struct cb {
+      callback_t func;
+      void *arg;
+    };
+
+    std::vector<struct cb> funcs_;
+    pthread_mutex_t lock_;
+};
+
+#endif