github.com/ice-blockchain/go/src@v0.0.0-20240403114104-1564d284e521/internal/poll/sendfile_bsd.go (about)

     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  	if err := dstFD.writeLock(); err != nil {
    18  		return 0, err, false
    19  	}
    20  	defer dstFD.writeUnlock()
    21  
    22  	if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil {
    23  		return 0, err, false
    24  	}
    25  
    26  	dst := dstFD.Sysfd
    27  	for remain > 0 {
    28  		n := maxSendfileSize
    29  		if int64(n) > remain {
    30  			n = int(remain)
    31  		}
    32  		pos1 := pos
    33  		n, err = syscall.Sendfile(dst, src, &pos1, n)
    34  		if n > 0 {
    35  			pos += int64(n)
    36  			written += int64(n)
    37  			remain -= int64(n)
    38  		}
    39  		if err == syscall.EINTR {
    40  			continue
    41  		}
    42  		// This includes syscall.ENOSYS (no kernel
    43  		// support) and syscall.EINVAL (fd types which
    44  		// don't implement sendfile), and other errors.
    45  		// We should end the loop when there is no error
    46  		// returned from sendfile(2) or it is not a retryable error.
    47  		if err != syscall.EAGAIN {
    48  			break
    49  		}
    50  		if err = dstFD.pd.waitWrite(dstFD.isFile); err != nil {
    51  			break
    52  		}
    53  	}
    54  	handled = written != 0 || (err != syscall.ENOSYS && err != syscall.EINVAL)
    55  	return
    56  }