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Source file src/internal/poll/sendfile_bsd.go

Documentation: internal/poll

  // Copyright 2011 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  // +build dragonfly freebsd
  
  package poll
  
  import "syscall"
  
  // maxSendfileSize is the largest chunk size we ask the kernel to copy
  // at a time.
  const maxSendfileSize int = 4 << 20
  
  // SendFile wraps the sendfile system call.
  func SendFile(dstFD *FD, src int, pos, remain int64) (int64, error) {
  	if err := dstFD.writeLock(); err != nil {
  		return 0, err
  	}
  	defer dstFD.writeUnlock()
  	dst := int(dstFD.Sysfd)
  	var written int64
  	var err error
  	for remain > 0 {
  		n := maxSendfileSize
  		if int64(n) > remain {
  			n = int(remain)
  		}
  		pos1 := pos
  		n, err1 := syscall.Sendfile(dst, src, &pos1, n)
  		if n > 0 {
  			pos += int64(n)
  			written += int64(n)
  			remain -= int64(n)
  		}
  		if n == 0 && err1 == nil {
  			break
  		}
  		if err1 == syscall.EAGAIN {
  			if err1 = dstFD.pd.waitWrite(dstFD.isFile); err1 == nil {
  				continue
  			}
  		}
  		if err1 != nil {
  			// This includes syscall.ENOSYS (no kernel
  			// support) and syscall.EINVAL (fd types which
  			// don't implement sendfile)
  			err = err1
  			break
  		}
  	}
  	return written, err
  }
  

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