Bug 1353956 - P6. Load the old prefixset(.pset) when there is no .vlpset. r=gcp

To avoid forcing a redownload of SafeBrowsing v4 list.

Differential Revision: https://phabricator.services.mozilla.com/D21876

toolkit/components/url-classifier/LookupCacheV4.cpp

@@ -344,6 +344,68 @@ nsresult LookupCacheV4::CleanOldPrefixSet() {
   return NS_OK;
 }
 
+nsresult LookupCacheV4::LoadLegacyFile() {
+  nsCOMPtr<nsIFile> file;
+  nsresult rv = mStoreDirectory->Clone(getter_AddRefs(file));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  rv = file->AppendNative(mTableName + NS_LITERAL_CSTRING(".pset"));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  bool exists;
+  rv = file->Exists(&exists);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (!exists) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsIInputStream> localInFile;
+  rv = NS_NewLocalFileInputStream(getter_AddRefs(localInFile), file,
+                                  PR_RDONLY | nsIFile::OS_READAHEAD);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  // Calculate how big the file is, make sure our read buffer isn't bigger
+  // than the file itself which is just wasting memory.
+  int64_t fileSize;
+  rv = file->GetFileSize(&fileSize);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  if (fileSize < 0 || fileSize > UINT32_MAX) {
+    return NS_ERROR_FAILURE;
+  }
+
+  uint32_t bufferSize =
+      std::min<uint32_t>(static_cast<uint32_t>(fileSize), MAX_BUFFER_SIZE);
+
+  // Convert to buffered stream
+  nsCOMPtr<nsIInputStream> in;
+  rv = NS_NewBufferedInputStream(getter_AddRefs(in), localInFile.forget(),
+                                 bufferSize);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  // Load data
+  rv = mVLPrefixSet->LoadPrefixes(in);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  mPrimed = true;
+
+  LOG(("[%s] Loading Legacy PrefixSet successful", mTableName.get()));
+  return NS_OK;
+}
+
 nsresult LookupCacheV4::LoadFromFile(nsCOMPtr<nsIFile>& aFile) {
   NS_ENSURE_ARG_POINTER(aFile);