/http/chunked.go

 1// Copyright 2009 The Go Authors. All rights reserved.
 2// Use of this source code is governed by a BSD-style
 3// license that can be found in the LICENSE file.
 4
 5package http
 6
 7import (
 8	"bufio"
 9	"io"
10	"log"
11	"os"
12	"strconv"
13)
14
15// NewChunkedWriter returns a new writer that translates writes into HTTP
16// "chunked" format before writing them to w. Closing the returned writer
17// sends the final 0-length chunk that marks the end of the stream.
18//
19// NewChunkedWriter is not needed by normal applications. The http
20// package adds chunking automatically if handlers don't set a
21// Content-Length header. Using NewChunkedWriter inside a handler
22// would result in double chunking or chunking with a Content-Length
23// length, both of which are wrong.
24func NewChunkedWriter(w io.Writer) io.WriteCloser {
25	if _, bad := w.(*response); bad {
26		log.Printf("warning: using NewChunkedWriter in an http.Handler; expect corrupt output")
27	}
28	return &chunkedWriter{w}
29}
30
31// Writing to ChunkedWriter translates to writing in HTTP chunked Transfer
32// Encoding wire format to the underlying Wire writer.
33type chunkedWriter struct {
34	Wire io.Writer
35}
36
37// Write the contents of data as one chunk to Wire.
38// NOTE: Note that the corresponding chunk-writing procedure in Conn.Write has
39// a bug since it does not check for success of io.WriteString
40func (cw *chunkedWriter) Write(data []byte) (n int, err os.Error) {
41
42	// Don't send 0-length data. It looks like EOF for chunked encoding.
43	if len(data) == 0 {
44		return 0, nil
45	}
46
47	head := strconv.Itob(len(data), 16) + "\r\n"
48
49	if _, err = io.WriteString(cw.Wire, head); err != nil {
50		return 0, err
51	}
52	if n, err = cw.Wire.Write(data); err != nil {
53		return
54	}
55	if n != len(data) {
56		err = io.ErrShortWrite
57		return
58	}
59	_, err = io.WriteString(cw.Wire, "\r\n")
60
61	return
62}
63
64func (cw *chunkedWriter) Close() os.Error {
65	_, err := io.WriteString(cw.Wire, "0\r\n")
66	return err
67}
68
69// NewChunkedReader returns a new reader that translates the data read from r
70// out of HTTP "chunked" format before returning it. 
71// The reader returns os.EOF when the final 0-length chunk is read.
72//
73// NewChunkedReader is not needed by normal applications. The http package
74// automatically decodes chunking when reading response bodies.
75func NewChunkedReader(r *bufio.Reader) io.Reader {
76	return &chunkedReader{r: r}
77}