From 2f271fe46646971c66beb6f0ea906a2c771b6a1c Mon Sep 17 00:00:00 2001
From: Yurii Zubrytskyi <zyy@google.com>
Date: Thu, 19 Dec 2024 17:53:13 -0800
Subject: [res] Don't create extra asset provider when not needed

MultiAssetsProvider is useful to combine a ResourcesLoader with
a file-based provider, but most of the time it's used without
any loaders, and ends up with an EmptyAssetsProvider object that
just wastes cycles and RAM.

This CL optimizes that out, only creating the extra layer when
we have a real loader, and falling back to the only remaining
provider otherwise

Bug: 319137634
Test: build + boot + manual + atest libandroidfw_tests
Flag: EXEMPT optimization
Change-Id: Ibc5ac60adc5e008b70a62481a747758c89083ff9
---
 libs/androidfw/AssetsProvider.cpp | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

(limited to 'libs/androidfw/AssetsProvider.cpp')

diff --git a/libs/androidfw/AssetsProvider.cpp b/libs/androidfw/AssetsProvider.cpp
index 59c6aba7b8b0..11b12eb030a6 100644
--- a/libs/androidfw/AssetsProvider.cpp
+++ b/libs/androidfw/AssetsProvider.cpp
@@ -24,9 +24,8 @@
 #include <ziparchive/zip_archive.h>
 
 namespace android {
-namespace {
-constexpr const char* kEmptyDebugString = "<empty>";
-} // namespace
+
+static constexpr std::string_view kEmptyDebugString = "<empty>";
 
 std::unique_ptr<Asset> AssetsProvider::Open(const std::string& path, Asset::AccessMode mode,
                                             bool* file_exists) const {
@@ -356,8 +355,14 @@ MultiAssetsProvider::MultiAssetsProvider(std::unique_ptr<AssetsProvider>&& prima
 
 std::unique_ptr<AssetsProvider> MultiAssetsProvider::Create(
     std::unique_ptr<AssetsProvider>&& primary, std::unique_ptr<AssetsProvider>&& secondary) {
-  if (primary == nullptr || secondary == nullptr) {
-    return nullptr;
+  if (primary == nullptr && secondary == nullptr) {
+    return EmptyAssetsProvider::Create();
+  }
+  if (!primary) {
+    return secondary;
+  }
+  if (!secondary) {
+    return primary;
   }
   return std::unique_ptr<MultiAssetsProvider>(new MultiAssetsProvider(std::move(primary),
                                                                       std::move(secondary)));
@@ -425,7 +430,7 @@ const std::string& EmptyAssetsProvider::GetDebugName() const {
   if (path_.has_value()) {
     return *path_;
   }
-  const static std::string kEmpty = kEmptyDebugString;
+  constexpr static std::string kEmpty{kEmptyDebugString};
   return kEmpty;
 }
 
-- 
cgit v1.2.3-59-g8ed1b