flush OS write buffers before saving control file

This ensures that pieces are physically written to disk before
marking them as finished in the control file.

This should prevent data loss and corruption when resuming downloads
after a system crash.

Signed-off-by: Ali MJ Al-Nasrawy <alimjalnasrawy@gmail.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/AbstractDiskWriter.cc b/src/AbstractDiskWriter.cc
index ff4f8856..f21c5261 100644
--- a/src/AbstractDiskWriter.cc
+++ b/src/AbstractDiskWriter.cc
@@ -590,4 +590,16 @@ void AbstractDiskWriter::dropCache(int64_t len, int64_t offset)
 #endif // HAVE_POSIX_FADVISE
 }
 
+void AbstractDiskWriter::flushOSBuffers()
+{
+  if (fd_ == A2_BAD_FD) {
+    return;
+  }
+#ifdef __MINGW32__
+  FlushFileBuffers(fd_);
+#else // !__MINGW32__
+  fsync(fd_);
+#endif // __MINGW32__
+}
+
 } // namespace aria2