code review 4536076: net: Sendfile for win32.

src/pkg/net/sendfile_windows.go

+// 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 net
+
+import (
+        "io"
+        "os"
+        "syscall"
+)
+
+type sendfileOp struct {
+        anOp
+        src int32 // source
+        n   uint32
+}
+
+func (o *sendfileOp) Submit() (errno int) {
+        return syscall.TransmitFile(int32(o.fd.sysfd), o.src, o.n, 0, &o.o, nil, syscall.TF_WRITE_BEHIND)
+}
+
+func (o *sendfileOp) Name() string {
+        return "TransmitFile"
+}
+
+// sendFile copies the contents of r to c using the TransmitFile
+// system call to minimize copies.
+//
+// if handled == true, sendFile returns the number of bytes copied and any
+// non-EOF error.
+//
+// if handled == false, sendFile performed no work.
+//
+// Note that sendfile for windows does not suppport >2GB file.
+func sendFile(c *netFD, r io.Reader) (written int64, err os.Error, handled bool) {
+        var n int64 = 0 // by default, copy until EOF
+
+        lr, ok := r.(*io.LimitedReader)
+        if ok {
+                n, r = lr.N, lr.R
+                if n <= 0 {
+                        return 0, nil, true
+                }
+        }
+        f, ok := r.(*os.File)
+        if !ok {
+                return 0, nil, false
+        }
+
+        c.wio.Lock()
+        defer c.wio.Unlock()
+        c.incref()
+        defer c.decref()
+
+        var o sendfileOp
+        o.Init(c)
+        o.n = uint32(n)
+        o.src = int32(f.Fd())
+        done, err := iosrv.ExecIO(&o, 0)
+        if err != nil {
+                return 0, err, false
+        }
+        if lr != nil {
+                lr.N -= int64(done)
+        }
+        return int64(done), nil, true
+}