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// Copyright 2014 Google Inc. All Rights Reserved.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
// Package internal provides support for the cloud packages.
// Users should not import this package directly.
package internal
import (
const userAgent = "gcloud-golang/0.1"
// Transport is an http.RoundTripper that appends Google Cloud client's
// user-agent to the original request's user-agent header.
type Transport struct {
// TODO(bradfitz): delete internal.Transport. It's too wrappy for what it does.
// Do User-Agent some other way.
// Base is the actual http.RoundTripper
// requests will use. It must not be nil.
Base http.RoundTripper
// RoundTrip appends a user-agent to the existing user-agent
// header and delegates the request to the base http.RoundTripper.
func (t *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
req = cloneRequest(req)
ua := req.Header.Get("User-Agent")
if ua == "" {
ua = userAgent
} else {
ua = fmt.Sprintf("%s %s", ua, userAgent)
req.Header.Set("User-Agent", ua)
return t.Base.RoundTrip(req)
// cloneRequest returns a clone of the provided *http.Request.
// The clone is a shallow copy of the struct and its Header map.
func cloneRequest(r *http.Request) *http.Request {
// shallow copy of the struct
r2 := new(http.Request)
*r2 = *r
// deep copy of the Header
r2.Header = make(http.Header)
for k, s := range r.Header {
r2.Header[k] = s
return r2