Support for statically compressed gzip content-encoding

1 files changed, 80 insertions, 0 deletions

diff --git a/internal/httputil/negotiate.go b/internal/httputil/negotiate.go
new file mode 100644
index 00000000..a25e3ed1
--- /dev/null
+++ b/internal/httputil/negotiate.go
@@ -0,0 +1,80 @@
+// Copyright 2013 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 or at
+// https://developers.google.com/open-source/licenses/bsd.
+
+package httputil
+
+import (
+	"net/http"
+	"strings"
+
+	"gitlab.com/gitlab-org/gitlab-pages/internal/httputil/header"
+)
+
+// NegotiateContentEncoding returns the best offered content encoding for the
+// request's Accept-Encoding header. If two offers match with equal weight and
+// then the offer earlier in the list is preferred. If no offers are
+// acceptable, then "" is returned.
+func NegotiateContentEncoding(r *http.Request, offers []string) string {
+	bestOffer := "identity"
+	bestQ := -1.0
+	specs := header.ParseAccept(r.Header, "Accept-Encoding")
+	for _, offer := range offers {
+		for _, spec := range specs {
+			if spec.Q > bestQ &&
+				(spec.Value == "*" || spec.Value == offer) {
+				bestQ = spec.Q
+				bestOffer = offer
+			}
+		}
+	}
+	if bestQ == 0 {
+		bestOffer = ""
+	}
+	return bestOffer
+}
+
+// NegotiateContentType returns the best offered content type for the request's
+// Accept header. If two offers match with equal weight, then the more specific
+// offer is preferred.  For example, text/* trumps */*. If two offers match
+// with equal weight and specificity, then the offer earlier in the list is
+// preferred. If no offers match, then defaultOffer is returned.
+func NegotiateContentType(r *http.Request, offers []string, defaultOffer string) string {
+	bestOffer := defaultOffer
+	bestQ := -1.0
+	bestWild := 3
+	specs := header.ParseAccept(r.Header, "Accept")
+	for _, offer := range offers {
+		for _, spec := range specs {
+			switch {
+			case spec.Q == 0.0:
+				// ignore
+			case spec.Q < bestQ:
+				// better match found
+			case spec.Value == "*/*":
+				if spec.Q > bestQ || bestWild > 2 {
+					bestQ = spec.Q
+					bestWild = 2
+					bestOffer = offer
+				}
+			case strings.HasSuffix(spec.Value, "/*"):
+				if strings.HasPrefix(offer, spec.Value[:len(spec.Value)-1]) &&
+					(spec.Q > bestQ || bestWild > 1) {
+					bestQ = spec.Q
+					bestWild = 1
+					bestOffer = offer
+				}
+			default:
+				if spec.Value == offer &&
+					(spec.Q > bestQ || bestWild > 0) {
+					bestQ = spec.Q
+					bestWild = 0
+					bestOffer = offer
+				}
+			}
+		}
+	}
+	return bestOffer
+}