threads: introduce `git_thread_exit`

Introduce `git_thread_exit`, which will allow threads to terminate at an
arbitrary time, returning a `void *`.  On Windows, this means that we
need to store the current `git_thread` in TLS, so that we can set its
`return` value when terminating.

We cannot simply use `ExitThread`, since Win32 returns `DWORD`s from
threads; we return `void *`.

1 files changed, 18 insertions, 0 deletions

diff --git a/src/win32/thread.c b/src/win32/thread.c
index 80d56ce5d..87318c9d3 100644
--- a/src/win32/thread.c
+++ b/src/win32/thread.c
@@ -26,6 +26,9 @@ static DWORD WINAPI git_win32__threadproc(LPVOID lpParameter)
 {
 	git_thread *thread = lpParameter;
 
+	/* Set the current thread for `git_thread_exit` */
+	GIT_GLOBAL->current_thread = thread;
+
 	thread->result = thread->proc(thread->param);
 
 	git__free_tls_data();
@@ -95,6 +98,21 @@ int git_thread_join(
 	return 0;
 }
 
+void git_thread_exit(void *value)
+{
+	assert(GIT_GLOBAL->current_thread);
+	GIT_GLOBAL->current_thread->result = value;
+
+	git__free_tls_data();
+
+	ExitThread(CLEAN_THREAD_EXIT);
+}
+
+size_t git_thread_currentid(void)
+{
+	return GetCurrentThreadId();
+}
+
 int git_mutex_init(git_mutex *GIT_RESTRICT mutex)
 {
 	InitializeCriticalSection(mutex);