http: add file protocol transport
Off by default (security risk), but users can
wire it up if desired.
Fixes #2113
R=rsc, bradfitz
CC=golang-dev
https://golang.org/cl/4959049
diff --git a/src/pkg/http/filetransport.go b/src/pkg/http/filetransport.go
new file mode 100644
index 0000000..78f3aa2
--- /dev/null
+++ b/src/pkg/http/filetransport.go
@@ -0,0 +1,124 @@
+// 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 http
+
+import (
+ "fmt"
+ "io"
+ "os"
+)
+
+// fileTransport implements RoundTripper for the 'file' protocol.
+type fileTransport struct {
+ fh fileHandler
+}
+
+// NewFileTransport returns a new RoundTripper, serving the provided
+// FileSystem. The returned RoundTripper ignores the URL host in its
+// incoming requests, as well as most other properties of the
+// request.
+//
+// The typical use case for NewFileTransport is to register the "file"
+// protocol with a Transport, as in:
+//
+// t := &http.Transport{}
+// t.RegisterProtocol("file", http.NewFileTransport(http.Dir("/")))
+// c := &http.Client{Transport: t}
+// res, err := c.Get("file:///etc/passwd")
+// ...
+func NewFileTransport(fs FileSystem) RoundTripper {
+ return fileTransport{fileHandler{fs}}
+}
+
+func (t fileTransport) RoundTrip(req *Request) (resp *Response, err os.Error) {
+ // We start ServeHTTP in a goroutine, which may take a long
+ // time if the file is large. The newPopulateResponseWriter
+ // call returns a channel which either ServeHTTP or finish()
+ // sends our *Response on, once the *Response itself has been
+ // populated (even if the body itself is still being
+ // written to the res.Body, a pipe)
+ rw, resc := newPopulateResponseWriter()
+ go func() {
+ t.fh.ServeHTTP(rw, req)
+ rw.finish()
+ }()
+ return <-resc, nil
+}
+
+func newPopulateResponseWriter() (*populateResponse, <-chan *Response) {
+ pr, pw := io.Pipe()
+ rw := &populateResponse{
+ ch: make(chan *Response),
+ pw: pw,
+ res: &Response{
+ Proto: "HTTP/1.0",
+ ProtoMajor: 1,
+ Header: make(Header),
+ Close: true,
+ Body: pr,
+ },
+ }
+ return rw, rw.ch
+}
+
+// populateResponse is a ResponseWriter that populates the *Response
+// in res, and writes its body to a pipe connected to the response
+// body. Once writes begin or finish() is called, the response is sent
+// on ch.
+type populateResponse struct {
+ res *Response
+ ch chan *Response
+ wroteHeader bool
+ hasContent bool
+ sentResponse bool
+ pw *io.PipeWriter
+}
+
+func (pr *populateResponse) finish() {
+ if !pr.wroteHeader {
+ pr.WriteHeader(500)
+ }
+ if !pr.sentResponse {
+ pr.sendResponse()
+ }
+ pr.pw.Close()
+}
+
+func (pr *populateResponse) sendResponse() {
+ if pr.sentResponse {
+ return
+ }
+ pr.sentResponse = true
+
+ if pr.hasContent {
+ pr.res.ContentLength = -1
+ }
+ pr.ch <- pr.res
+}
+
+func (pr *populateResponse) Header() Header {
+ return pr.res.Header
+}
+
+func (pr *populateResponse) WriteHeader(code int) {
+ if pr.wroteHeader {
+ return
+ }
+ pr.wroteHeader = true
+
+ pr.res.StatusCode = code
+ pr.res.Status = fmt.Sprintf("%d %s", code, StatusText(code))
+}
+
+func (pr *populateResponse) Write(p []byte) (n int, err os.Error) {
+ if !pr.wroteHeader {
+ pr.WriteHeader(StatusOK)
+ }
+ pr.hasContent = true
+ if !pr.sentResponse {
+ pr.sendResponse()
+ }
+ return pr.pw.Write(p)
+}
