http: sniffing placeholder

R=dsymonds
CC=golang-dev
https://golang.org/cl/4746041

diff --git a/src/pkg/http/Makefile b/src/pkg/http/Makefile
index 2a2a2a3beb8a5152c3507e9c0344199bb3bfe629..b8bc093d49c714b9dec2c6dd8358171658511ffa 100644 (file)
--- a/src/pkg/http/Makefile
+++ b/src/pkg/http/Makefile
@@ -18,6 +18,7 @@ GOFILES=\
        response.go\
        reverseproxy.go\
        server.go\
+       sniff.go\
        status.go\
        transfer.go\
        transport.go\

diff --git a/src/pkg/http/server.go b/src/pkg/http/server.go
index ab960f4f0a8e12a08301a1481ef85e50ed8143a4..d71a24959a57de5dd917383f8b58bb20f0e2be5d 100644 (file)
--- a/src/pkg/http/server.go
+++ b/src/pkg/http/server.go
@@ -98,7 +98,8 @@ type conn struct {
        rwc        net.Conn             // i/o connection
        buf        *bufio.ReadWriter    // buffered rwc
        hijacked   bool                 // connection has been hijacked by handler
-       tlsState   *tls.ConnectionState // or nil when not using TLS        
+       tlsState   *tls.ConnectionState // or nil when not using TLS
+       body       []byte
 }
 
 // A response represents the server side of an HTTP response.
@@ -112,6 +113,7 @@ type response struct {
        written       int64    // number of bytes written in body
        contentLength int64    // explicitly-declared Content-Length; or -1
        status        int      // status code passed to WriteHeader
+       needSniff     bool     // need to sniff to find Content-Type
 
        // close connection after this reply.  set on request and
        // updated after response from handler if there's a
@@ -147,6 +149,7 @@ func newConn(rwc net.Conn, handler Handler) (c *conn, err os.Error) {
        c.remoteAddr = rwc.RemoteAddr().String()
        c.handler = handler
        c.rwc = rwc
+       c.body = make([]byte, sniffLen)
        br := bufio.NewReader(rwc)
        bw := bufio.NewWriter(rwc)
        c.buf = bufio.NewReadWriter(br, bw)
@@ -209,6 +212,7 @@ func (c *conn) readRequest() (w *response, err os.Error) {
        w.req = req
        w.header = make(Header)
        w.contentLength = -1
+       c.body = c.body[:0]
        return w, nil
 }
 
@@ -249,9 +253,9 @@ func (w *response) WriteHeader(code int) {
                        }
                }
        } else {
-               // Default output is HTML encoded in UTF-8.
+               // If no content type, apply sniffing algorithm to body.
                if w.header.Get("Content-Type") == "" {
-                       w.header.Set("Content-Type", "text/html; charset=utf-8")
+                       w.needSniff = true
                }
        }
 
@@ -337,7 +341,34 @@ func (w *response) WriteHeader(code int) {
        }
        io.WriteString(w.conn.buf, proto+" "+codestring+" "+text+"\r\n")
        w.header.Write(w.conn.buf)
+
+       // If we need to sniff the body, leave the header open.
+       // Otherwise, end it here.
+       if !w.needSniff {
+               io.WriteString(w.conn.buf, "\r\n")
+       }
+}
+
+// sniff uses the first block of written data,
+// stored in w.conn.body, to decide the Content-Type
+// for the HTTP body.
+func (w *response) sniff() {
+       if !w.needSniff {
+               return
+       }
+       w.needSniff = false
+
+       data := w.conn.body
+       ctype := detectContentType(data)
+       if ctype != "" {
+               fmt.Fprintf(w.conn.buf, "Content-Type: %s\r\n", ctype)
+       }
        io.WriteString(w.conn.buf, "\r\n")
+
+       if w.chunking && len(data) > 0 {
+               fmt.Fprintf(w.conn.buf, "%x\r\n", len(data))
+               w.conn.buf.Write(data)
+       }
 }
 
 // bodyAllowed returns true if a Write is allowed for this response type.
@@ -369,6 +400,18 @@ func (w *response) Write(data []byte) (n int, err os.Error) {
                return 0, ErrContentLength
        }
 
+       var m int
+       if w.needSniff {
+               body := w.conn.body
+               m = copy(body[len(body):], data)
+               w.conn.body = body[:len(body)+m]
+               if m == len(data) {
+                       return m, nil
+               }
+               w.sniff()
+               data = data[m:]
+       }
+
        // TODO(rsc): if chunking happened after the buffering,
        // then there would be fewer chunk headers.
        // On the other hand, it would make hijacking more difficult.
@@ -385,7 +428,7 @@ func (w *response) Write(data []byte) (n int, err os.Error) {
                }
        }
 
-       return n, err
+       return m + n, err
 }
 
 // If this is an error reply (4xx or 5xx)
@@ -449,6 +492,9 @@ func (w *response) finishRequest() {
        if !w.wroteHeader {
                w.WriteHeader(StatusOK)
        }
+       if w.needSniff {
+               w.sniff()
+       }
        errorKludge(w)
        if w.chunking {
                io.WriteString(w.conn.buf, "0\r\n")
@@ -471,6 +517,7 @@ func (w *response) Flush() {
        if !w.wroteHeader {
                w.WriteHeader(StatusOK)
        }
+       w.sniff()
        w.conn.buf.Flush()
 }
 
@@ -517,6 +564,7 @@ func (c *conn) serve() {
                        if req.ContentLength == 0 {
                                w.Header().Set("Connection", "close")
                                w.WriteHeader(StatusBadRequest)
+                               w.finishRequest()
                                break
                        }
                        req.Header.Del("Expect")
@@ -535,6 +583,7 @@ func (c *conn) serve() {
                        // respond with a 417 (Expectation Failed) status."
                        w.Header().Set("Connection", "close")
                        w.WriteHeader(StatusExpectationFailed)
+                       w.finishRequest()
                        break
                }
 

diff --git a/src/pkg/http/sniff.go b/src/pkg/http/sniff.go
new file mode 100644 (file)
index 0000000..9fd6fee
--- /dev/null
+++ b/src/pkg/http/sniff.go
@@ -0,0 +1,18 @@
+// 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
+
+// Content-type sniffing algorithm.
+// http://tools.ietf.org/html/draft-ietf-websec-mime-sniff-03
+
+// The algorithm prefers to use sniffLen bytes to make its decision.
+const sniffLen = 1024
+
+// detectContentType returns the sniffed Content-Type string
+// for the given data.
+func detectContentType(data []byte) string {
+       // TODO(dsymonds,rsc): Implement algorithm from draft.
+       return "text/html; charset=utf-8"
+}