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// Copyright 2018 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 net
import (
"internal/poll"
"io"
)
// splice transfers data from r to c using the splice system call to minimize
// copies from and to userspace. c must be a TCP connection. Currently, splice
// is only enabled if r is a TCP or a stream-oriented Unix connection.
//
// If splice returns handled == false, it has performed no work.
func splice(c *netFD, r io.Reader) (written int64, err error, handled bool) {
var remain int64 = 1<<63 - 1 // by default, copy until EOF
lr, ok := r.(*io.LimitedReader)
if ok {
remain, r = lr.N, lr.R
if remain <= 0 {
return 0, nil, true
}
}
var s *netFD
if tc, ok := r.(*TCPConn); ok {
s = tc.fd
} else if uc, ok := r.(*UnixConn); ok {
if uc.fd.net != "unix" {
return 0, nil, false
}
s = uc.fd
} else {
return 0, nil, false
}
written, handled, sc, err := poll.Splice(&c.pfd, &s.pfd, remain)
if lr != nil {
lr.N -= written
}
return written, wrapSyscallError(sc, err), handled
}
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