code review 4528084: syscall,io,net,os,http: sendfile support

src/pkg/os/file.go

 // Copyright 2009 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 os provides a platform-independent interface to operating system
 // functionality.  The design is Unix-like.
 package os
 
 import (
         "runtime"
         "sync"
         "syscall"
 )
 
 // File represents an open file descriptor.
 type File struct {
         fd      int
         name    string
         dirinfo *dirInfo   // nil unless directory being read
         nepipe  int        // number of consecutive EPIPE in Write
         l       sync.Mutex // used to implement windows pread/pwrite
 }
 
 // Fd returns the integer Unix file descriptor referencing the open file.
 func (file *File) Fd() int { return file.fd }
 
+// SendfileSourceFd implements the io package's SendfileSource
+// interface for faster disk to network copies, staying inside
+// userspace. It returns the fd or an error if this fd cannot be used
+// as a sendfile source.
+func (file *File) SendfileSourceFd() (int, Error) {
+        return file.fd, nil
+}
+
 // Name returns the name of the file as presented to Open.
 func (file *File) Name() string { return file.name }
 
 // NewFile returns a new File with the given file descriptor and name.
 func NewFile(fd int, name string) *File {
         if fd < 0 {
                 return nil
         }
         f := &File{fd: fd, name: name}
         runtime.SetFinalizer(f, (*File).Close)
@@ skipping 189 matching lines @@
 }
 
 // Create creates the named file mode 0666 (before umask), truncating
 // it if it already exists.  If successful, methods on the returned
 // File can be used for I/O; the associated file descriptor has mode
 // O_RDWR.
 // It returns the File and an Error, if any.
 func Create(name string) (file *File, err Error) {
         return OpenFile(name, O_RDWR|O_CREATE|O_TRUNC, 0666)
 }