Fix file_base::append on windows

qicosmos · Dec 6, 2024 · 7032352 · 7032352
1 parent 9957d37
commit 7032352
Showing 1 changed file with 20 additions and 1 deletion.
diff --git a/include/asio/detail/impl/win_iocp_file_service.ipp b/include/asio/detail/impl/win_iocp_file_service.ipp
@@ -67,6 +67,8 @@ asio::error_code win_iocp_file_service::open(
     access = GENERIC_WRITE;
   else if ((open_flags & file_base::read_write) != 0)
     access = GENERIC_READ | GENERIC_WRITE;
+  else if ((open_flags & file_base::append) != 0)
+    access = GENERIC_WRITE;
 
   DWORD share = FILE_SHARE_READ | FILE_SHARE_WRITE;
 
@@ -82,6 +84,8 @@ asio::error_code win_iocp_file_service::open(
   {
     if ((open_flags & file_base::truncate) != 0)
       disposition = TRUNCATE_EXISTING;
+    else if ((open_flags & file_base::append) != 0)
+      disposition = OPEN_ALWAYS;
     else
       disposition = OPEN_EXISTING;
   }
@@ -94,6 +98,7 @@ asio::error_code win_iocp_file_service::open(
   if ((open_flags & file_base::sync_all_on_write) != 0)
     flags |= FILE_FLAG_WRITE_THROUGH;
 
+  impl.offset_ = 0;
   HANDLE handle = ::CreateFileA(path, access, share, 0, disposition, flags, 0);
   if (handle != INVALID_HANDLE_VALUE)
   {
@@ -109,10 +114,24 @@ asio::error_code win_iocp_file_service::open(
       }
     }
 
+    if (disposition == OPEN_ALWAYS || (open_flags & file_base::append) != 0) {
+      LARGE_INTEGER distance, new_offset;
+      distance.QuadPart = 0;
+      if (::SetFilePointerEx(handle, distance, &new_offset, FILE_END))
+        impl.offset_ = static_cast<uint64_t>(new_offset.QuadPart);
+      else
+      {
+        DWORD last_error = ::GetLastError();
+        ::CloseHandle(handle);
+        ec.assign(last_error, asio::error::get_system_category());
+        ASIO_ERROR_LOCATION(ec);
+        return ec;
+      }
+    }
+
     handle_service_.assign(impl, handle, ec);
     if (ec)
       ::CloseHandle(handle);
-    impl.offset_ = 0;
     ASIO_ERROR_LOCATION(ec);
     return ec;
   }