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Source file src/net/http/filetransport.go

Documentation: net/http

  // 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"
  )
  
  // 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 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 error) {
  	if !pr.wroteHeader {
  		pr.WriteHeader(StatusOK)
  	}
  	pr.hasContent = true
  	if !pr.sentResponse {
  		pr.sendResponse()
  	}
  	return pr.pw.Write(p)
  }
  

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