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// 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-origin",
"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",
"proxy-authenticate",
"proxy-authorization",
"range",
"referer",
"refresh",
"retry-after",
"server",
"set-cookie",
"strict-transport-security",
"trailer",
"transfer-encoding",
"user-agent",
"vary",
"via",
"www-authenticate",
}
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)
}
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