nonblocking_windows.go

     1  // Copyright 2025 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package windows
     6  
     7  import (
     8  	"syscall"
     9  	"unsafe"
    10  )
    11  
    12  // IsNonblock returns whether the file descriptor fd is opened
    13  // in non-blocking mode, that is, the [syscall.FILE_FLAG_OVERLAPPED] flag
    14  // was set when the file was opened.
    15  func IsNonblock(fd syscall.Handle) (nonblocking bool, err error) {
    16  	var info FILE_MODE_INFORMATION
    17  	if err := NtQueryInformationFile(syscall.Handle(fd), &IO_STATUS_BLOCK{}, unsafe.Pointer(&info), uint32(unsafe.Sizeof(info)), FileModeInformation); err != nil {
    18  		return false, err
    19  	}
    20  	return info.Mode&(FILE_SYNCHRONOUS_IO_ALERT|FILE_SYNCHRONOUS_IO_NONALERT) == 0, nil
    21  }
    22
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