commit e7c1f00739c0f2747acb353ccef2b41f2a92a01e
author Yurii Zubrytskyi <zyy@google.com> Tue Jan 30 13:50:57 2024 -0800
committer Yurii Zubrytskyi <zyy@google.com> Thu Feb 29 17:43:06 2024 +0000
tree 2f75c7f3cdd227fa0ff41ba1731cf31f99771018
parent 43ff4a403fb4abad851d387a341e1184c015463e

[res] Use fstat() for idmap::IsUpToDate()

The most common operation when getting a new Resources object
is checking if all apks and overlays are still up to date to
reuse the cached object. It makes sense to optimize it by
excluding the file by path lookups and instead keeping an open
FD to the file in the cache

+ Make IsFabricatedOverlay() more efficient via a name check
  and string_view where possible

Bug: 282215580
Test: build + boot + presubmit
Change-Id: Ib1ab20cba359c2195a72dd2e10096883d95b4453

libs/androidfw/Idmap.cpp

diff --git a/libs/androidfw/Idmap.cpp b/libs/androidfw/Idmap.cpp
index 5f98b8f..9824190 100644
--- a/libs/androidfw/Idmap.cpp
+++ b/libs/androidfw/Idmap.cpp
@@ -18,8 +18,10 @@
 
 #include "androidfw/Idmap.h"
 
+#include "android-base/file.h"
 #include "android-base/logging.h"
 #include "android-base/stringprintf.h"
+#include "android-base/utf8.h"
 #include "androidfw/misc.h"
 #include "androidfw/ResourceTypes.h"
 #include "androidfw/Util.h"
@@ -250,7 +252,12 @@
 }
 } // namespace
 
-LoadedIdmap::LoadedIdmap(std::string&& idmap_path, const Idmap_header* header,
+// O_PATH is a lightweight way of creating an FD, only exists on Linux
+#ifndef O_PATH
+#define O_PATH (0)
+#endif
+
+LoadedIdmap::LoadedIdmap(const std::string& idmap_path, const Idmap_header* header,
                          const Idmap_data_header* data_header,
                          const Idmap_target_entry* target_entries,
                          const Idmap_target_entry_inline* target_inline_entries,
@@ -267,10 +274,10 @@
       configurations_(configs),
       overlay_entries_(overlay_entries),
       string_pool_(std::move(string_pool)),
-      idmap_path_(std::move(idmap_path)),
+      idmap_fd_(android::base::utf8::open(idmap_path.c_str(), O_RDONLY|O_CLOEXEC|O_BINARY|O_PATH)),
       overlay_apk_path_(overlay_apk_path),
       target_apk_path_(target_apk_path),
-      idmap_last_mod_time_(getFileModDate(idmap_path_.data())) {}
+      idmap_last_mod_time_(getFileModDate(idmap_fd_.get())) {}
 
 std::unique_ptr<LoadedIdmap> LoadedIdmap::Load(StringPiece idmap_path, StringPiece idmap_data) {
   ATRACE_CALL();
@@ -368,7 +375,7 @@
 }
 
 bool LoadedIdmap::IsUpToDate() const {
-  return idmap_last_mod_time_ == getFileModDate(idmap_path_.c_str());
+  return idmap_last_mod_time_ == getFileModDate(idmap_fd_.get());
 }
 
 }  // namespace android