Bug 1491151 - Part 2: Use MruCache for eTLD table. r=smaug

--HG--
extra : rebase_source : 5c588e2b2615549e5a5cc2fb6aa7dc9922d05c99

netwerk/dns/nsEffectiveTLDService.cpp

@@ -10,6 +10,7 @@
 
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/HashFunctions.h"
+#include "mozilla/Maybe.h"
 #include "mozilla/MemoryReporting.h"
 
 #include "MainThreadUtils.h"
@@ -214,17 +215,20 @@ nsEffectiveTLDService::GetBaseDomainInternal(nsCString  &aHostname,
 
   // Lookup in the cache if this is a normal query. This is restricted to
   // main thread-only as the cache is not thread-safe.
-  TLDCacheEntry* entry = nullptr;
+  Maybe<TldCache::Entry> entry;
   if (aAdditionalParts == 1 && NS_IsMainThread()) {
-    if (LookupForAdd(aHostname, &entry)) {
+    auto p = mMruTable.Lookup(aHostname);
+    if (p) {
       // There was a match, just return the cached value.
-      aBaseDomain = entry->mBaseDomain;
+      aBaseDomain = p.Data().mBaseDomain;
       if (trailingDot) {
         aBaseDomain.Append('.');
       }
 
       return NS_OK;
     }
+
+    entry = Some(p);
   }
 
   // Walk up the domain tree, most specific to least specific,
@@ -310,8 +314,7 @@ nsEffectiveTLDService::GetBaseDomainInternal(nsCString  &aHostname,
 
   // Update the MRU table if in use.
   if (entry) {
-    entry->mHost = aHostname;
-    entry->mBaseDomain = aBaseDomain;
+    entry->Set(TLDCacheEntry{aHostname, nsCString(aBaseDomain)});
   }
 
   // add on the trailing dot, if applicable
@@ -337,16 +340,6 @@ nsEffectiveTLDService::NormalizeHostname(nsCString &aHostname)
   return NS_OK;
 }
 
-bool
-nsEffectiveTLDService::LookupForAdd(const nsACString& aHost, TLDCacheEntry** aEntry)
-{
-  MOZ_ASSERT(NS_IsMainThread());
-
-  const uint32_t hash = HashString(aHost.BeginReading(), aHost.Length());
-  *aEntry = &mMruTable[hash % kTableSize];
-  return (*aEntry)->mHost == aHost;
-}
-
 NS_IMETHODIMP
 nsEffectiveTLDService::HasRootDomain(const nsACString& aInput,
                                      const nsACString& aHost,

netwerk/dns/nsEffectiveTLDService.h

@@ -8,12 +8,14 @@
 
 #include "nsIEffectiveTLDService.h"
 
+#include "nsHashKeys.h"
 #include "nsIMemoryReporter.h"
 #include "nsString.h"
 #include "nsCOMPtr.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/Dafsa.h"
 #include "mozilla/MemoryReporting.h"
+#include "mozilla/MruCache.h"
 
 class nsIIDNService;
 
@@ -55,22 +57,20 @@ private:
   // cache the result. During standard browsing the same domains are repeatedly
   // fed into |GetBaseDomainInternal| so this ends up being an effective
   // mitigation getting about a 99% hit rate with four tabs open.
-  //
-  // A size of 31 is used rather than a more logical power-of-two such as 32
-  // since it is a prime number and provides fewer collisions when when used
-  // with our hash algorithms.
-  static const uint32_t kTableSize = 31;
-  TLDCacheEntry mMruTable[kTableSize];
+  struct TldCache :
+    public mozilla::MruCache<nsACString, TLDCacheEntry, TldCache>
+  {
+    static mozilla::HashNumber Hash(const nsACString& aKey)
+    {
+      return mozilla::HashString(aKey);
+    }
+    static bool Match(const nsACString& aKey, const TLDCacheEntry& aVal)
+    {
+      return aKey == aVal.mHost;
+    }
+  };
 
-  /**
-   * Performs a lookup on the MRU table and provides a pointer to the hash
-   * entry that matched or should be used for adding this host.
-   *
-   * @param aHost The host to lookup.
-   * @param aEntry Out param, the entry in the MRU table to use.
-   * @return True if a match was found, false if there was a miss.
-   */
-  inline bool LookupForAdd(const nsACString& aHost, TLDCacheEntry** aEntry);
+  TldCache mMruTable;
 };
 
 #endif // EffectiveTLDService_h