github.com/SandwichDev/go-internals@v0.0.0-20210605002614-12311ac6b2c5/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  	if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil {
    24  		return 0, err
    25  	}
    26  
    27  	dst := int(dstFD.Sysfd)
    28  	var written int64
    29  	var err error
    30  	for remain > 0 {
    31  		n := maxSendfileSize
    32  		if int64(n) > remain {
    33  			n = int(remain)
    34  		}
    35  		pos1 := pos
    36  		n, err1 := syscall.Sendfile(dst, src, &pos1, n)
    37  		if err1 == syscall.EAGAIN || err1 == syscall.EINTR {
    38  			// partial write may have occurred
    39  			n = int(pos1 - pos)
    40  		}
    41  		if n > 0 {
    42  			pos += int64(n)
    43  			written += int64(n)
    44  			remain -= int64(n)
    45  		} else if n == 0 && err1 == nil {
    46  			break
    47  		}
    48  		if err1 == syscall.EAGAIN {
    49  			if err1 = dstFD.pd.waitWrite(dstFD.isFile); err1 == nil {
    50  				continue
    51  			}
    52  		}
    53  		if err1 == syscall.EINTR {
    54  			continue
    55  		}
    56  		if err1 != nil {
    57  			// This includes syscall.ENOSYS (no kernel
    58  			// support) and syscall.EINVAL (fd types which
    59  			// don't implement sendfile)
    60  			err = err1
    61  			break
    62  		}
    63  	}
    64  	return written, err
    65  }