Eric Seidel
8649c75206
* perf: mmap libapp.so out of the APK instead of buffering in RAM `open_base_lib` previously read the entire decompressed libapp.so into a Vec<u8> via `read_to_end` and handed bipatch a Cursor over that buffer. For large apps libapp.so can be tens of megabytes, and that allocation happens immediately after the patch download is buffered to disk — a plausible OOM trigger on memory-constrained devices (we have at least one customer report on OnePlus where the patch install appears to halt silently right after the download completes). Modern AGP (3.6+) defaults to extractNativeLibs=false, which keeps libapp.so STORED uncompressed inside the APK so the dynamic linker can mmap it directly. When that's the case, do the same: find the entry's data offset via the zip crate, drop the archive, reopen the APK, and mmap the entry's slice. Cursor<Mmap> implements Read + Seek, which is what bipatch's `Reader::new(patch, base)` requires. When the entry isn't stored uncompressed (older builds, or builds that explicitly compress native libs), fall back to the previous buffered read so we always succeed. Mmap doesn't change the peak working set when bipatch traverses the whole base linearly, but file-backed mappings are clean and reclaimable under memory pressure where an anonymous Vec is not, and we avoid the ~2x transient allocation peak from `read_to_end` growing the buffer. Tests cover both paths (stored → mmap, deflated → buffered) on the host. * ci: add mmap, memmap, SIGBUS to cspell dictionary
Updater library
This is the Rust side of the Shorebird code push system. This is built
in Rust with a C API for easy calling from other languages, most notably
for linking into libflutter.so.
The primary modification Shorebird makes to the stock Flutter engine is adding support for the updater library (this repo). The updater library is written in Rust and is used to update the code running in the Flutter app. The updater library is built as a static library and is linked into the Flutter engine during build time.
Parts
library: Runtime library linked into Flutter Engine to unpack and apply updates. Build into libupdater.a and linked into libflutter.so.patch: Developer tooling to package Shorebird updates ("patches"). Built intopatch.exeand downloaded and run byshorebirdcommand line tool: https://github.com/shorebirdtech/shorebird/tree/main/packages/shorebird_cli.shorebird_code_push: The Dart bindings for communicating with the updater library from within a Flutter app. Published to pub.dev, usage is optional by developers.
Most interesting code is in the library directory. There is also
a README.md in that directory explaining the design.
Developing
It's best to edit this repository from within an engine checkout. See BUILDING_ENGINE.md for instructions on how to set up an engine checkout.
The workflow I use involves 2 to 3 VSC windows:
- Opening the engine
src.
In that terminal I:
cd third_party/updater
- To build the updater as part of the engine:
cargo ndk --target aarch64-linux-android build --release && \
ninja -C ../../out/android_release_arm64 && say "done"
The cargo part should not be needed, but I haven't yet done the work to integrate the Rust code into the gn files for the Flutter engine yet.
I add say "done" to the end as linking can take several minutes for release
Android builds.
-
In a second window, I open
code third_party/updater. I do this because otherwise therust_analyzercan't seem to find the rust code. We could fix this by adding the directory to the VSC workspace, but I'm not sure where we would put the workspace file in the first place.srcis actuallyshorebirdtech/buildrootand is controlled viagclientbyshorebirdtech/engine/DEPS. -
In a third window I open my test app. e.g.:
flutter create test_app
cd test_app
shorebird init
shorebird release
code .
- To run the test app with my local engine I use:
shorebird run --local-engine-src-path $HOME/Documents/GitHub/engine/src \
--local-engine android_release_arm64
You may also need to build out/host_release once as flutter build looks for
some Dart .dill files in host_release.
Coverage
We'd like to get to 100% coverage but aren't there yet.
https://github.com/taiki-e/cargo-llvm-cov is the best tool I've found for generating coverage reports.
Install: https://github.com/taiki-e/cargo-llvm-cov#installation
cargo llvm-cov will then generate the report.