Add `etcpak` library for faster ETC/ETC2/S3TC imports.

- `etc` module was renamed to `etcpak` and modified to use the new library.
- PKM importer is removed in the process, it's obsolete.
- Old library `etc2comp` is removed.
- S3TC compression no longer done via `squish` (but decompression still is).
- Slight modifications to etcpak sources for MinGW compatibility,
  to fix LLVM `-Wc++11-narrowing` errors, and to allow using vendored or
  system libpng.

Co-authored-by: Rémi Verschelde <rverschelde@gmail.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/thirdparty/etcpak/TaskDispatch.hpp b/thirdparty/etcpak/TaskDispatch.hpp
new file mode 100644
index 0000000000..b513de4c0c
--- /dev/null
+++ b/thirdparty/etcpak/TaskDispatch.hpp
@@ -0,0 +1,34 @@
+#ifndef __DARKRL__TASKDISPATCH_HPP__
+#define __DARKRL__TASKDISPATCH_HPP__
+
+#include <atomic>
+#include <condition_variable>
+#include <functional>
+#include <mutex>
+#include <thread>
+#include <vector>
+
+class TaskDispatch
+{
+public:
+    TaskDispatch( size_t workers );
+    ~TaskDispatch();
+
+    static void Queue( const std::function<void(void)>& f );
+    static void Queue( std::function<void(void)>&& f );
+
+    static void Sync();
+
+private:
+    void Worker();
+
+    std::vector<std::function<void(void)>> m_queue;
+    std::mutex m_queueLock;
+    std::condition_variable m_cvWork, m_cvJobs;
+    std::atomic<bool> m_exit;
+    size_t m_jobs;
+
+    std::vector<std::thread> m_workers;
+};
+
+#endif