From 6cea1f239d01fc065bc6f4b22d765d89b6db0152 Mon Sep 17 00:00:00 2001
From: Matt Holt <mholt@users.noreply.github.com>
Date: Mon, 20 Jul 2020 12:28:40 -0600
Subject: push: Implement HTTP/2 server push (#3573)

* push: Implement HTTP/2 server push (close #3551)

* push: Abstract header ops by embedding into new struct type

This will allow us to add more fields to customize headers in
push-specific ways in the future.

* push: Ensure Link resources are pushed before response is written

* Change header name from X-Caddy-Push to Caddy-Push
---
 modules/caddyhttp/push/link.go | 78 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)
 create mode 100644 modules/caddyhttp/push/link.go

(limited to 'modules/caddyhttp/push/link.go')

diff --git a/modules/caddyhttp/push/link.go b/modules/caddyhttp/push/link.go
new file mode 100644
index 0000000..16b0e7d
--- /dev/null
+++ b/modules/caddyhttp/push/link.go
@@ -0,0 +1,78 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// 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 push
+
+import (
+	"strings"
+)
+
+// linkResource contains the results of a parsed Link header.
+type linkResource struct {
+	uri    string
+	params map[string]string
+}
+
+// parseLinkHeader is responsible for parsing Link header
+// and returning list of found resources.
+//
+// Accepted formats are:
+//
+//     Link: <resource>; as=script
+//     Link: <resource>; as=script,<resource>; as=style
+//     Link: <resource>;<resource2>
+//
+// where <resource> begins with a forward slash (/).
+func parseLinkHeader(header string) []linkResource {
+	resources := []linkResource{}
+
+	if header == "" {
+		return resources
+	}
+
+	for _, link := range strings.Split(header, comma) {
+		l := linkResource{params: make(map[string]string)}
+
+		li, ri := strings.Index(link, "<"), strings.Index(link, ">")
+		if li == -1 || ri == -1 {
+			continue
+		}
+
+		l.uri = strings.TrimSpace(link[li+1 : ri])
+
+		for _, param := range strings.Split(strings.TrimSpace(link[ri+1:]), semicolon) {
+			parts := strings.SplitN(strings.TrimSpace(param), equal, 2)
+			key := strings.TrimSpace(parts[0])
+			if key == "" {
+				continue
+			}
+			if len(parts) == 1 {
+				l.params[key] = key
+			}
+			if len(parts) == 2 {
+				l.params[key] = strings.TrimSpace(parts[1])
+			}
+		}
+
+		resources = append(resources, l)
+	}
+
+	return resources
+}
+
+const (
+	comma     = ","
+	semicolon = ";"
+	equal     = "="
+)
-- 
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