ServiceWorker: Support longest-prefix-match for registration scope

content/browser/service_worker/service_worker_utils.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/service_worker/service_worker_utils.h"
 
+#include <string>
+
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "content/public/common/content_switches.h"
 #include "url/url_canon.h"
 
 namespace content {
 
+namespace {
+
+bool ContainsWildcard(const GURL& scope) {
+  DCHECK(!scope.is_empty());
+  const std::string& scope_spec = scope.spec();
+  return scope_spec[scope_spec.size() - 1] == '*';
+}
+
+}  // namespace
+
 // static
 bool ServiceWorkerUtils::IsFeatureEnabled() {
   static bool enabled = CommandLine::ForCurrentProcess()->HasSwitch(
       switches::kEnableServiceWorker);
   return enabled;
 }
 
 // static
-bool ServiceWorkerUtils::ScopeMatches(const GURL& scope, const GURL& url) {
+ServiceWorkerUtils::MatchResult ServiceWorkerUtils::ScopeMatches(
+    const GURL& scope, const GURL& url) {
   DCHECK(!scope.has_ref());
   DCHECK(!url.has_ref());
   const std::string& scope_spec = scope.spec();
-  const std::string& url_spec = url.spec();
+  if (scope_spec == url.spec())
+    return SCOPE_EXACT_MATCH;
+  size_t len = scope_spec.size();
+  if (len > 0 && ContainsWildcard(scope) &&
+      scope_spec.compare(0, len - 1, url.spec(), 0, len - 1) == 0) {
+    return SCOPE_WILDCARD_MATCH;
+  }
+  return SCOPE_NO_MATCH;
+}
 
-  size_t len = scope_spec.size();
-  if (len > 0 && scope_spec[len - 1] == '*') {
-    return scope_spec.compare(0, len - 1, url_spec, 0, len - 1) == 0;
-  }
-  return scope_spec == url_spec;
+// static
+int ServiceWorkerUtils::CompareScopePriorities(
+    const GURL& scope1, const GURL& scope2) {
+  DCHECK(!scope1.is_empty() && !scope2.is_empty());
+  DCHECK_EQ(scope1.GetOrigin(), scope2.GetOrigin());
+  if (scope1 == scope2)
+    return 0;
+
+  // Prioritize a scope which doesn't contain a wildcard (i.e. exact match).

[jsbell, 2014/05/21 19:20:03]

Again, not clear that prioritizing exact match over wildcard match is desired
behavior per spec.

+  if (!ContainsWildcard(scope1) && ContainsWildcard(scope2))
+    return 1;
+  if (ContainsWildcard(scope1) && !ContainsWildcard(scope2))
+    return -1;
+  DCHECK(ContainsWildcard(scope1) && ContainsWildcard(scope2));
+
+  // If |scope1| and |scope2| have the same length, both or one of them should
+  // be the exact match and handled above.
+  DCHECK_NE(scope1.spec().size(), scope2.spec().size());
+  return scope1.spec().size() - scope2.spec().size();

[jsbell, 2014/05/21 19:20:03]

unsigned - unsigned = unsigned; this only works because the (typically large)
unsigned result is being cast to an int and truncates to negative - ISTR this is
implementation dependent.

Maybe cast before subtracting?

 }
 
 }  // namespace content