niki/vendor/golang.org/x/net/http2/headermap.go

// Copyright 2014 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 http2

import (
	"net/http"
	"sync"
)

var (
	commonBuildOnce sync.Once

	commonLowerHeader map[string]string // Go-Canonical-Case -> lower-case

	commonCanonHeader map[string]string // lower-case -> Go-Canonical-Case

)

func buildCommonHeaderMapsOnce() {

	commonBuildOnce.Do(buildCommonHeaderMaps)

}

func buildCommonHeaderMaps() {

	common := []string{

		"accept",

		"accept-charset",

		"accept-encoding",

		"accept-language",

		"accept-ranges",

		"age",

		"access-control-allow-credentials",

		"access-control-allow-headers",

		"access-control-allow-methods",

		"access-control-allow-origin",

		"access-control-expose-headers",

		"access-control-max-age",

		"access-control-request-headers",

		"access-control-request-method",

		"allow",

		"authorization",

		"cache-control",

		"content-disposition",

		"content-encoding",

		"content-language",

		"content-length",

		"content-location",

		"content-range",

		"content-type",

		"cookie",

		"date",

		"etag",

		"expect",

		"expires",

		"from",

		"host",

		"if-match",

		"if-modified-since",

		"if-none-match",

		"if-unmodified-since",

		"last-modified",

		"link",

		"location",

		"max-forwards",

		"origin",

		"proxy-authenticate",

		"proxy-authorization",

		"range",

		"referer",

		"refresh",

		"retry-after",

		"server",

		"set-cookie",

		"strict-transport-security",

		"trailer",

		"transfer-encoding",

		"user-agent",

		"vary",

		"via",

		"www-authenticate",

		"x-forwarded-for",

		"x-forwarded-proto",
	}

	commonLowerHeader = make(map[string]string, len(common))

	commonCanonHeader = make(map[string]string, len(common))

	for _, v := range common {

		chk := http.CanonicalHeaderKey(v)

		commonLowerHeader[chk] = v

		commonCanonHeader[v] = chk

	}

}

func lowerHeader(v string) (lower string, ascii bool) {

	buildCommonHeaderMapsOnce()

	if s, ok := commonLowerHeader[v]; ok {

		return s, true

	}

	return asciiToLower(v)

}

func canonicalHeader(v string) string {

	buildCommonHeaderMapsOnce()

	if s, ok := commonCanonHeader[v]; ok {

		return s

	}

	return http.CanonicalHeaderKey(v)

}