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// Copyright 2015 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
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package cors provides CORS support for http.Handlers.
package cors
import (
"net/http"
)
// Handler is an http.Handler that wraps other http.Handlers and provides CORS
// support.
type Handler struct {
handler http.Handler
origin string
allowCredentials bool
}
// NewHandler wraps an existing http.Handler allowing it to be requested via CORS.
func NewHandler(h http.Handler) *Handler {
return &Handler{
handler: h,
origin: "*",
}
}
// SetOrigin sets the origin(s) to allow when requested with CORS.
func (h *Handler) SetOrigin(origin string) {
h.origin = origin
}
// AllowCredentials allows cookies to be read by the CORS request.
func (h *Handler) AllowCredentials(allow bool) {
h.allowCredentials = allow
}
// ServeHTTP determines if a request is a CORS request (normal or preflight)
// and sets the appropriate Access-Control-Allow-* headers. It will send the
// request to the underlying handler in all cases, except for a preflight
// (OPTIONS) request.
func (h *Handler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
// Definitely not a CORS request, send it directly to handler.
if req.Header.Get("Origin") == "" {
h.handler.ServeHTTP(rw, req)
return
}
rw.Header().Set("Access-Control-Allow-Origin", h.origin)
if h.allowCredentials {
rw.Header().Set("Access-Control-Allow-Credentials", "true")
}
acrm := req.Header.Get("Access-Control-Request-Method")
rw.Header().Set("Access-Control-Allow-Methods", acrm)
if acrh := req.Header.Get("Access-Control-Request-Headers"); acrh != "" {
rw.Header().Set("Access-Control-Allow-Headers", acrh)
}
// Preflight request, don't bother sending it to the handler.
if req.Method == "OPTIONS" {
return
}
h.handler.ServeHTTP(rw, req)
}
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