http: add DumpRequest, DumpResponse, for debugging

R=rsc
CC=golang-dev
https://golang.org/cl/206050

src/pkg/http/Makefile

@@ -8,6 +8,7 @@ TARG=http
 GOFILES=\
 	chunked.go\
 	client.go\
+	dump.go\
 	fs.go\
 	lex.go\
 	persist.go\

src/pkg/http/dump.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 http
+
+import (
+	"bytes"
+	"io"
+	"os"
+)
+
+
+// One of the copies, say from b to r2, could be avoided by using a more
+// elaborate trick where the other copy is made during Request/Response.Write.
+// This would complicate things too much, given that these functions are for
+// debugging only.
+func drainBody(b io.ReadCloser) (r1, r2 io.ReadCloser, err os.Error) {
+	var buf bytes.Buffer
+	if _, err = buf.ReadFrom(b); err != nil {
+		return nil, nil, err
+	}
+	if err = b.Close(); err != nil {
+		return nil, nil, err
+	}
+	return nopCloser{&buf}, nopCloser{bytes.NewBuffer(buf.Bytes())}, nil
+}
+
+// DumpRequest returns the wire representation of req,
+// optionally including the request body, for debugging.
+// DumpRequest is semantically a no-op, but in order to
+// dump the body, it reads the body data into memory and
+// changes req.Body to refer to the in-memory copy.
+func DumpRequest(req *Request, body bool) (dump []byte, err os.Error) {
+	var b bytes.Buffer
+	save := req.Body
+	if !body || req.Body == nil {
+		req.Body = nil
+	} else {
+		save, req.Body, err = drainBody(req.Body)
+		if err != nil {
+			return
+		}
+	}
+	err = req.Write(&b)
+	req.Body = save
+	if err != nil {
+		return
+	}
+	dump = b.Bytes()
+	return
+}
+
+// DumpResponse is like DumpRequest but dumps a response.
+func DumpResponse(resp *Response, body bool) (dump []byte, err os.Error) {
+	var b bytes.Buffer
+	save := resp.Body
+	savecl := resp.ContentLength
+	if !body || resp.Body == nil {
+		resp.Body = nil
+		resp.ContentLength = 0
+	} else {
+		save, resp.Body, err = drainBody(resp.Body)
+		if err != nil {
+			return
+		}
+	}
+	err = resp.Write(&b)
+	resp.Body = save
+	resp.ContentLength = savecl
+	if err != nil {
+		return
+	}
+	dump = b.Bytes()
+	return
+}