1 files changed, 162 insertions, 0 deletions
diff --git a/src/util/runtime.c b/src/util/runtime.c
new file mode 100644
index 000000000..a7711ffc4
--- /dev/null
+++ b/src/util/runtime.c
@@ -0,0 +1,162 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "git2_util.h"
+#include "runtime.h"
+
+static git_runtime_shutdown_fn shutdown_callback[32];
+static git_atomic32 shutdown_callback_count;
+
+static git_atomic32 init_count;
+
+static int init_common(git_runtime_init_fn init_fns[], size_t cnt)
+{
+	size_t i;
+	int ret;
+
+	/* Initialize subsystems that have global state */
+	for (i = 0; i < cnt; i++) {
+		if ((ret = init_fns[i]()) != 0)
+			break;
+	}
+
+	GIT_MEMORY_BARRIER;
+
+	return ret;
+}
+
+static void shutdown_common(void)
+{
+	git_runtime_shutdown_fn cb;
+	int pos;
+
+	for (pos = git_atomic32_get(&shutdown_callback_count);
+	     pos > 0;
+	     pos = git_atomic32_dec(&shutdown_callback_count)) {
+		cb = git_atomic_swap(shutdown_callback[pos - 1], NULL);
+
+		if (cb != NULL)
+			cb();
+	}
+}
+
+int git_runtime_shutdown_register(git_runtime_shutdown_fn callback)
+{
+	int count = git_atomic32_inc(&shutdown_callback_count);
+
+	if (count > (int)ARRAY_SIZE(shutdown_callback) || count == 0) {
+		git_error_set(GIT_ERROR_INVALID,
+		              "too many shutdown callbacks registered");
+		git_atomic32_dec(&shutdown_callback_count);
+		return -1;
+	}
+
+	shutdown_callback[count - 1] = callback;
+
+	return 0;
+}
+
+#if defined(GIT_THREADS) && defined(GIT_WIN32)
+
+/*
+ * On Win32, we use a spinlock to provide locking semantics.  This is
+ * lighter-weight than a proper critical section.
+ */
+static volatile LONG init_spinlock = 0;
+
+GIT_INLINE(int) init_lock(void)
+{
+	while (InterlockedCompareExchange(&init_spinlock, 1, 0)) { Sleep(0); }
+	return 0;
+}
+
+GIT_INLINE(int) init_unlock(void)
+{
+	InterlockedExchange(&init_spinlock, 0);
+	return 0;
+}
+
+#elif defined(GIT_THREADS) && defined(_POSIX_THREADS)
+
+/*
+ * On POSIX, we need to use a proper mutex for locking.  We might prefer
+ * a spinlock here, too, but there's no static initializer for a
+ * pthread_spinlock_t.
+ */
+static pthread_mutex_t init_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+GIT_INLINE(int) init_lock(void)
+{
+	return pthread_mutex_lock(&init_mutex) == 0 ? 0 : -1;
+}
+
+GIT_INLINE(int) init_unlock(void)
+{
+	return pthread_mutex_unlock(&init_mutex) == 0 ? 0 : -1;
+}
+
+#elif defined(GIT_THREADS)
+# error unknown threading model
+#else
+
+# define init_lock() git__noop()
+# define init_unlock() git__noop()
+
+#endif
+
+int git_runtime_init(git_runtime_init_fn init_fns[], size_t cnt)
+{
+	int ret;
+
+	if (init_lock() < 0)
+		return -1;
+
+	/* Only do work on a 0 -> 1 transition of the refcount */
+	if ((ret = git_atomic32_inc(&init_count)) == 1) {
+		if (init_common(init_fns, cnt) < 0)
+			ret = -1;
+	}
+
+	if (init_unlock() < 0)
+		return -1;
+
+	return ret;
+}
+
+int git_runtime_init_count(void)
+{
+	int ret;
+
+	if (init_lock() < 0)
+		return -1;
+
+	ret = git_atomic32_get(&init_count);
+
+	if (init_unlock() < 0)
+		return -1;
+
+	return ret;
+}
+
+int git_runtime_shutdown(void)
+{
+	int ret;
+
+	/* Enter the lock */
+	if (init_lock() < 0)
+		return -1;
+
+	/* Only do work on a 1 -> 0 transition of the refcount */
+	if ((ret = git_atomic32_dec(&init_count)) == 0)
+		shutdown_common();
+
+	/* Exit the lock */
+	if (init_unlock() < 0)
+		return -1;
+
+	return ret;
+}