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

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