sendfile_bsd.go

     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 darwin || dragonfly || freebsd
     6  
     7  package poll
     8  
     9  import "syscall"
    10  
    11  // maxSendfileSize is the largest chunk size we ask the kernel to copy
    12  // at a time.
    13  const maxSendfileSize int = 4 << 20
    14  
    15  // SendFile wraps the sendfile system call.
    16  func SendFile(dstFD *FD, src int, pos, remain int64) (written int64, err error, handled bool) {
    17  	defer func() {
    18  		TestHookDidSendFile(dstFD, src, written, err, handled)
    19  	}()
    20  	if err := dstFD.writeLock(); err != nil {
    21  		return 0, err, false
    22  	}
    23  	defer dstFD.writeUnlock()
    24  
    25  	if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil {
    26  		return 0, err, false
    27  	}
    28  
    29  	dst := dstFD.Sysfd
    30  	for remain > 0 {
    31  		n := maxSendfileSize
    32  		if int64(n) > remain {
    33  			n = int(remain)
    34  		}
    35  		pos1 := pos
    36  		n, err = syscall.Sendfile(dst, src, &pos1, n)
    37  		if n > 0 {
    38  			pos += int64(n)
    39  			written += int64(n)
    40  			remain -= int64(n)
    41  		}
    42  		if err == syscall.EINTR {
    43  			continue
    44  		}
    45  		// This includes syscall.ENOSYS (no kernel
    46  		// support) and syscall.EINVAL (fd types which
    47  		// don't implement sendfile), and other errors.
    48  		// We should end the loop when there is no error
    49  		// returned from sendfile(2) or it is not a retryable error.
    50  		if err != syscall.EAGAIN {
    51  			break
    52  		}
    53  		if err = dstFD.pd.waitWrite(dstFD.isFile); err != nil {
    54  			break
    55  		}
    56  	}
    57  	handled = written != 0 || (err != syscall.ENOSYS && err != syscall.EINVAL)
    58  	return
    59  }
    60
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