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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package poll
import "syscall"
// maxSendfileSize is the largest chunk size we ask the kernel to copy
// at a time.
const maxSendfileSize int = 4 << 20
// SendFile wraps the sendfile system call.
func SendFile(dstFD *FD, src int, remain int64) (written int64, err error, handled bool) {
if err := dstFD.writeLock(); err != nil {
return 0, err, false
}
defer dstFD.writeUnlock()
if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil {
return 0, err, false
}
dst := dstFD.Sysfd
for remain > 0 {
n := maxSendfileSize
if int64(n) > remain {
n = int(remain)
}
n, err = syscall.Sendfile(dst, src, nil, n)
if n > 0 {
written += int64(n)
remain -= int64(n)
continue
} else if err != syscall.EAGAIN && err != syscall.EINTR {
// This includes syscall.ENOSYS (no kernel
// support) and syscall.EINVAL (fd types which
// don't implement sendfile), and other errors.
// We should end the loop when there is no error
// returned from sendfile(2) or it is not a retryable error.
break
}
if err == syscall.EINTR {
continue
}
if err = dstFD.pd.waitWrite(dstFD.isFile); err != nil {
break
}
}
handled = written != 0 || (err != syscall.ENOSYS && err != syscall.EINVAL)
return
}
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