Retry commits of file writes for up to a second to work around AV scanning

Poorly-written antivirus software briefly lock newly written files to
scan them for viruses, which makes the rename from the temp file to
actual file fail. Work around this by retrying the rename up to ten
times.

Closes #1620.

aegisub/libaegisub/common/io.cpp

@@ -64,7 +64,18 @@ Save::Save(fs::path const& file, bool binary)
 
 Save::~Save() {
 	fp->close(); // Need to close before rename on Windows to unlock the file
-	fs::Rename(tmp_name, file_name);
+	for (int i = 0; i < 10; ++i) {
+		try {
+			fs::Rename(tmp_name, file_name);
+			return;
+		}
+		catch (agi::fs::FileSystemError const&) {
+			// Retry up to ten times in case it's just locked by a poorly-written antivirus scanner
+			if (i == 9)
+				throw;
+			util::sleep_for(100);
+		}
+	}
 }
 
 	} // namespace io

aegisub/libaegisub/include/libaegisub/util.h

@@ -70,5 +70,10 @@ namespace agi {
 	}
 #endif
 
+	/// A thin wrapper around this_thread::sleep_for that uses std::thread on
+	/// Windows (to avoid having to compile boost.thread) and boost::thread
+	/// elsewhere (because libstcc++ 4.7 is missing it).
+	void sleep_for(int ms);
+
 	} // namespace util
 } // namespace agi

aegisub/libaegisub/unix/util.cpp

@@ -20,6 +20,8 @@
 
 #include "libaegisub/util.h"
 
+#include <boost/thread.hpp>
+
 namespace agi { namespace util {
 
 timeval time_log() {
@@ -30,4 +32,8 @@ timeval time_log() {
 
 void SetThreadName(const char *) { }
 
+void sleep_for(int ms) {
+	boost::this_thread::sleep_for(boost::chrono::milliseconds(ms));
+}
+
 } }

aegisub/libaegisub/windows/util_win.cpp

@@ -23,6 +23,8 @@
 
 #include "libaegisub/charset_conv_win.h"
 
+#include <thread>
+
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
 
@@ -99,5 +101,9 @@ void SetThreadName(LPCSTR szThreadName) {
 	__except (EXCEPTION_CONTINUE_EXECUTION) {}
 }
 
+void sleep_for(int ms) {
+	std::this_thread::sleep_for(std::chrono::milliseconds(ms));
+}
+
 	} // namespace io
 } // namespace agi

aegisub/src/subtitles_provider_libass.cpp

@@ -50,13 +50,12 @@
 
 #include <libaegisub/dispatch.h>
 #include <libaegisub/log.h>
+#include <libaegisub/util.h>
 
 #include <boost/gil/gil_all.hpp>
 #include <boost/range/algorithm_ext/push_back.hpp>
-#include <boost/thread.hpp>
 #include <memory>
 #include <mutex>
-#include <thread>
 
 namespace {
 std::unique_ptr<agi::dispatch::Queue> cache_queue;
@@ -104,11 +103,7 @@ LibassSubtitlesProvider::LibassSubtitlesProvider(std::string)
 	progress.Run([=](agi::ProgressSink *ps) {
 		ps->SetIndeterminate();
 		while (!*done && !ps->IsCancelled())
-#ifdef _MSC_VER
-			std::this_thread::sleep_for(std::chrono::milliseconds(250));
-#else
-			boost::this_thread::sleep_for(boost::chrono::milliseconds(250));
-#endif
+			agi::util::sleep_for(250);
 	});
 
 	ass_renderer = *renderer;