sendfile_bsd.go

Documentation: internal/poll

     1  // Copyright 2011 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  //go:build dragonfly || freebsd
     6  // +build dragonfly freebsd
     7  
     8  package poll
     9  
    10  import "syscall"
    11  
    12  // maxSendfileSize is the largest chunk size we ask the kernel to copy
    13  // at a time.
    14  const maxSendfileSize int = 4 << 20
    15  
    16  // SendFile wraps the sendfile system call.
    17  func SendFile(dstFD *FD, src int, pos, remain int64) (int64, error) {
    18  	if err := dstFD.writeLock(); err != nil {
    19  		return 0, err
    20  	}
    21  	defer dstFD.writeUnlock()
    22  	if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil {
    23  		return 0, err
    24  	}
    25  
    26  	dst := dstFD.Sysfd
    27  	var written int64
    28  	var err error
    29  	for remain > 0 {
    30  		n := maxSendfileSize
    31  		if int64(n) > remain {
    32  			n = int(remain)
    33  		}
    34  		pos1 := pos
    35  		n, err1 := syscall.Sendfile(dst, src, &pos1, n)
    36  		if n > 0 {
    37  			pos += int64(n)
    38  			written += int64(n)
    39  			remain -= int64(n)
    40  		} else if n == 0 && err1 == nil {
    41  			break
    42  		}
    43  		if err1 == syscall.EINTR {
    44  			continue
    45  		}
    46  		if err1 == syscall.EAGAIN {
    47  			if err1 = dstFD.pd.waitWrite(dstFD.isFile); err1 == nil {
    48  				continue
    49  			}
    50  		}
    51  		if err1 != nil {
    52  			// This includes syscall.ENOSYS (no kernel
    53  			// support) and syscall.EINVAL (fd types which
    54  			// don't implement sendfile)
    55  			err = err1
    56  			break
    57  		}
    58  	}
    59  	return written, err
    60  }
    61
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