[res] Reuse memory in RebuildFilterList()

Original code deleted all allocated arrays to new' them back
right away. Now, with new methods in ByteBucketArray the code
only clears the vectors without releasing the capacity, and then
proceeds to free the vectors that ended up not being used.

This speeds up theme changes (accents / dark theme etc) by
about 20%

+ small other improvements in ByteBucketArray

Bug: 237583012
Test: build + UTs + boot
Change-Id: I158af793e5476b4f3215dbe602daa872136d633f

1 files changed, 6 insertions, 5 deletions

diff --git a/libs/androidfw/AssetManager2.cpp b/libs/androidfw/AssetManager2.cpp
index 27b121b0cccc..2864c6843633 100644
--- a/libs/androidfw/AssetManager2.cpp
+++ b/libs/androidfw/AssetManager2.cpp
@@ -1356,21 +1356,22 @@ base::expected<uint32_t, NullOrIOError> AssetManager2::GetResourceId(
 
 void AssetManager2::RebuildFilterList() {
   for (PackageGroup& group : package_groups_) {
-    for (ConfiguredPackage& impl : group.packages_) {
-      impl.filtered_configs_.clear();
-
+    for (ConfiguredPackage& package : group.packages_) {
+      package.filtered_configs_.forEachItem([](auto, auto& fcg) { fcg.type_entries.clear(); });
       // Create the filters here.
-      impl.loaded_package_->ForEachTypeSpec([&](const TypeSpec& type_spec, uint8_t type_id) {
+      package.loaded_package_->ForEachTypeSpec([&](const TypeSpec& type_spec, uint8_t type_id) {
         FilteredConfigGroup* group = nullptr;
         for (const auto& type_entry : type_spec.type_entries) {
           if (type_entry.config.match(configuration_)) {
             if (!group) {
-              group = &impl.filtered_configs_.editItemAt(type_id - 1);
+              group = &package.filtered_configs_.editItemAt(type_id - 1);
             }
             group->type_entries.push_back(&type_entry);
           }
         }
       });
+      package.filtered_configs_.trimBuckets(
+          [](const auto& fcg) { return fcg.type_entries.empty(); });
     }
   }
 }