// 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 }