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lib/file_read_operation.cpp

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+///////////////////////////////////////////////////////////////////////////////
+// Copyright (c) Lewis Baker
+// Licenced under MIT license. See LICENSE.txt for details.
+///////////////////////////////////////////////////////////////////////////////
+
+#include <cppcoro/file_read_operation.hpp>
+
+#if CPPCORO_OS_WINNT
+# ifndef WIN32_LEAN_AND_MEAN
+#  define WIN32_LEAN_AND_MEAN
+# endif
+# include <Windows.h>
+
+bool cppcoro::file_read_operation_impl::try_start(
+	cppcoro::detail::win32_overlapped_operation_base& operation) noexcept
+{
+	const DWORD numberOfBytesToRead =
+		m_byteCount <= 0xFFFFFFFF ?
+		static_cast<DWORD>(m_byteCount) : DWORD(0xFFFFFFFF);
+
+	DWORD numberOfBytesRead = 0;
+	BOOL ok = ::ReadFile(
+		m_fileHandle,
+		m_buffer,
+		numberOfBytesToRead,
+		&numberOfBytesRead,
+		operation.get_overlapped());
+	const DWORD errorCode = ok ? ERROR_SUCCESS : ::GetLastError();
+	if (errorCode != ERROR_IO_PENDING)
+	{
+		// Completed synchronously.
+		//
+		// We are assuming that the file-handle has been set to the
+		// mode where synchronous completions do not post a completion
+		// event to the I/O completion port and thus can return without
+		// suspending here.
+
+		operation.m_errorCode = errorCode;
+		operation.m_numberOfBytesTransferred = numberOfBytesRead;
+
+		return false;
+	}
+
+	return true;
+}
+
+void cppcoro::file_read_operation_impl::cancel(
+	cppcoro::detail::win32_overlapped_operation_base& operation) noexcept
+{
+	(void)::CancelIoEx(m_fileHandle, operation.get_overlapped());
+}
+
+#endif // CPPCORO_OS_WINNT