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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"
)
// spliceFrom 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, spliceFrom is only enabled if r is a TCP or a stream-oriented Unix connection.
//
// If spliceFrom returns handled == false, it has performed no work.
func spliceFrom(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
switch v := r.(type) {
case *TCPConn:
s = v.fd
case tcpConnWithoutWriteTo:
s = v.fd
case *UnixConn:
if v.fd.net != "unix" {
return 0, nil, false
}
s = v.fd
default:
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
}
// spliceTo transfers data from c to w using the splice system call to minimize
// copies from and to userspace. c must be a TCP connection.
// Currently, spliceTo is only enabled if w is a stream-oriented Unix connection.
//
// If spliceTo returns handled == false, it has performed no work.
func spliceTo(w io.Writer, c *netFD) (written int64, err error, handled bool) {
uc, ok := w.(*UnixConn)
if !ok || uc.fd.net != "unix" {
return
}
written, handled, sc, err := poll.Splice(&uc.fd.pfd, &c.pfd, 1<<63-1)
return written, wrapSyscallError(sc, err), handled
}
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