github.com/tidwall/go@v0.0.0-20170415222209-6694a6888b7d/src/internal/poll/sendfile_solaris.go (about)

     1  // Copyright 2015 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  package poll
     6  
     7  import "syscall"
     8  
     9  // Not strictly needed, but very helpful for debugging, see issue #10221.
    10  //go:cgo_import_dynamic _ _ "libsendfile.so"
    11  //go:cgo_import_dynamic _ _ "libsocket.so"
    12  
    13  // maxSendfileSize is the largest chunk size we ask the kernel to copy
    14  // at a time.
    15  const maxSendfileSize int = 4 << 20
    16  
    17  // SendFile wraps the sendfile system call.
    18  func SendFile(dstFD *FD, src int, pos, remain int64) (int64, error) {
    19  	if err := dstFD.writeLock(); err != nil {
    20  		return 0, err
    21  	}
    22  	defer dstFD.writeUnlock()
    23  
    24  	dst := int(dstFD.Sysfd)
    25  	var written int64
    26  	var err error
    27  	for remain > 0 {
    28  		n := maxSendfileSize
    29  		if int64(n) > remain {
    30  			n = int(remain)
    31  		}
    32  		pos1 := pos
    33  		n, err1 := syscall.Sendfile(dst, src, &pos1, n)
    34  		if err1 == syscall.EAGAIN || err1 == syscall.EINTR {
    35  			// partial write may have occurred
    36  			if n = int(pos1 - pos); n == 0 {
    37  				// nothing more to write
    38  				err1 = nil
    39  			}
    40  		}
    41  		if n > 0 {
    42  			pos += int64(n)
    43  			written += int64(n)
    44  			remain -= int64(n)
    45  		}
    46  		if n == 0 && err1 == nil {
    47  			break
    48  		}
    49  		if err1 == syscall.EAGAIN {
    50  			if err1 = dstFD.pd.waitWrite(); err1 == nil {
    51  				continue
    52  			}
    53  		}
    54  		if err1 == syscall.EINTR {
    55  			continue
    56  		}
    57  		if err1 != nil {
    58  			// This includes syscall.ENOSYS (no kernel
    59  			// support) and syscall.EINVAL (fd types which
    60  			// don't implement sendfile)
    61  			err = err1
    62  			break
    63  		}
    64  	}
    65  	return written, err
    66  }