gvisor.dev/gvisor@v0.0.0-20240520182842-f9d4d51c7e0f/pkg/eventfd/eventfd_unsafe.go (about)

     1  // Copyright 2021 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package eventfd
    16  
    17  import (
    18  	"unsafe"
    19  
    20  	"golang.org/x/sys/unix"
    21  )
    22  
    23  // nonBlockingWrite writes the given buffer to a file descriptor. It fails if
    24  // partial data is written.
    25  func nonBlockingWrite(fd int, buf []byte) (int, error) {
    26  	var ptr unsafe.Pointer
    27  	if len(buf) > 0 {
    28  		ptr = unsafe.Pointer(&buf[0])
    29  	}
    30  
    31  	nwritten, _, errno := unix.RawSyscall(unix.SYS_WRITE, uintptr(fd), uintptr(ptr), uintptr(len(buf)))
    32  	if errno != 0 {
    33  		return int(nwritten), errno
    34  	}
    35  	return int(nwritten), nil
    36  }