SafeBrowsing: Implement cache eviction for API full hash results.

components/safe_browsing_db/database_manager.cc

 // Copyright 2015 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 "components/safe_browsing_db/database_manager.h"
 
 #include "components/safe_browsing_db/v4_get_hash_protocol_manager.h"
 #include "content/public/browser/browser_thread.h"
 #include "net/url_request/url_request_context_getter.h"
 #include "url/gurl.h"
@@ skipping 149 matching lines @@
   //     Case 2: The prefix is not in the cache.
   //             We need to send a request for full hashes.
   //
   // Eviction:
   //   SBCachedFullHashResult entries can be removed from the cache only when
   //   the negative cache expire time and the cache expire time of all full
   //   hash results for that prefix have expired.
   //   Individual full hash results can be removed from the prefix's
   //   cache entry if they expire AND their expire time is after the negative
   //   cache expire time.
-  //
-  // TODO(kcarattini): Implement cache eviction.
   for (const SBFullHash& full_hash : full_hashes) {
     auto entry = v4_full_hash_cache_[threat_type].find(full_hash.prefix);
     if (entry != v4_full_hash_cache_[threat_type].end()) {
       // Case 1.
-      const SBCachedFullHashResult& cache_result = entry->second;
+      SBCachedFullHashResult& cache_result = entry->second;
 
       const SBFullHashResult* found_full_hash = nullptr;
+      size_t matched_idx = 0;
       for (const SBFullHashResult& hash_result : cache_result.full_hashes) {
         if (SBFullHashEqual(full_hash, hash_result.hash)) {
           found_full_hash = &hash_result;
           break;
         }
+        ++matched_idx;
       }
 
       if (found_full_hash) {
         // Case a.
         if (found_full_hash->cache_expire_after > now) {
           // Case i.
           cached_results->push_back(*found_full_hash);
         } else {
           // Case ii.
           prefixes_needing_reqs->push_back(full_hash.prefix);
+          // If the negative cache expire time has passed, evict this full hash
+          // result from the cache.
+          if (cache_result.expire_after <= now) {
+            cache_result.full_hashes.erase(
+                cache_result.full_hashes.begin() + matched_idx);
+            // If there are no more full hashes, we can evict the entire entry.
+            if (cache_result.full_hashes.empty()) {
+              v4_full_hash_cache_[threat_type].erase(entry);
+            }
+          }
         }
       } else {
         // Case b.
         if (cache_result.expire_after > now) {
           // Case i.
         } else {
           // Case ii.
           prefixes_needing_reqs->push_back(full_hash.prefix);
         }
       }
     } else {
       // Case 2.
       prefixes_needing_reqs->push_back(full_hash.prefix);
     }
   }
 
   // Multiple full hashes could share a prefix, remove duplicates.
+  // TODO(kcarattini): Make |prefixes_needing_reqs| a set.
   std::sort(prefixes_needing_reqs->begin(), prefixes_needing_reqs->end());
   prefixes_needing_reqs->erase(std::unique(prefixes_needing_reqs->begin(),
       prefixes_needing_reqs->end()), prefixes_needing_reqs->end());
 }
 
 void SafeBrowsingDatabaseManager::HandleGetHashesWithApisResults(
     SafeBrowsingApiCheck* check,
     const std::vector<SBFullHashResult>& full_hash_results,
     const base::Time& negative_cache_expire) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
@@ skipping 61 matching lines @@
     const std::vector<SBFullHashResult>& cached_results,
     Client* client)
     : url_(url), prefixes_(prefixes), full_hashes_(full_hashes),
       cached_results_(cached_results), client_(client) {
 }
 
 SafeBrowsingDatabaseManager::SafeBrowsingApiCheck::~SafeBrowsingApiCheck() {
 }
 
 }  // namespace safe_browsing