...
Run Format

Source file src/net/sendfile_linux.go

  // 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.
  
  package net
  
  import (
  	"io"
  	"os"
  	"syscall"
  )
  
  // maxSendfileSize is the largest chunk size we ask the kernel to copy
  // at a time.
  const maxSendfileSize int = 4 << 20
  
  // sendFile copies the contents of r to c using the sendfile
  // system call to minimize copies.
  //
  // if handled == true, sendFile returns the number of bytes copied and any
  // non-EOF error.
  //
  // if handled == false, sendFile performed no work.
  func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
  	var remain int64 = 1 << 62 // by default, copy until EOF
  
  	lr, ok := r.(*io.LimitedReader)
  	if ok {
  		remain, r = lr.N, lr.R
  		if remain <= 0 {
  			return 0, nil, true
  		}
  	}
  	f, ok := r.(*os.File)
  	if !ok {
  		return 0, nil, false
  	}
  
  	if err := c.writeLock(); err != nil {
  		return 0, err, true
  	}
  	defer c.writeUnlock()
  
  	dst := c.sysfd
  	src := int(f.Fd())
  	for remain > 0 {
  		n := maxSendfileSize
  		if int64(n) > remain {
  			n = int(remain)
  		}
  		n, err1 := syscall.Sendfile(dst, src, nil, n)
  		if n > 0 {
  			written += int64(n)
  			remain -= int64(n)
  		}
  		if n == 0 && err1 == nil {
  			break
  		}
  		if err1 == syscall.EAGAIN {
  			if err1 = c.pd.waitWrite(); 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
  		}
  	}
  	if lr != nil {
  		lr.N = remain
  	}
  	if err != nil {
  		err = os.NewSyscallError("sendfile", err)
  	}
  	return written, err, written > 0
  }
  

View as plain text