Hello Digitalis Samples

ARM64-only sample apps for testing Digitalis ARM64→x86_64 binary translation. Every module builds a single-ABI (arm64-v8a) APK; on the Digitalis x86_64 emulator all of its native code runs through NativeBridge translation (libberberis_arm64.so). The samples are the spec: when one fails, the bug is in the translator, not the sample.

Credits

The NDK-port modules are ported from Google's Android NDK Samples, licensed under the Apache License 2.0, modified to build as ARM64-only modules. renderscript-toolkit vendors AOSP's RenderScript intrinsics replacement toolkit source (Apache 2.0). The third-party-library samples pull each library's published arm64-v8a artifact from Maven (or a public mirror); those libraries remain under their own licenses. Everything else was written for the Digitalis project.

Module catalog (139 samples)

133 modules build inside this Gradle project; hello-qt and hello-realm build standalone (see Standalone builds). Build any suite module with ./gradlew :<module>:assembleDebug.

hello-shadowhook (ByteDance's native inline/PLT hooking engine, bytedance/android-inline-hook) is a gated sample. Its ShadowHook.init() used to fail with SHADOWHOOK_ERRNO_INIT_LINKER (12): the guest ARM64 linker advertises its name as /system/bin/linker64, which on the x86_64 host image symlinks to the host x86_64 linker, so ShadowHook's xDL read a wrong-architecture ELF when resolving the linker's internal symbols. A shipped guest-loader open() redirect (kernel_api/open_emulation.cc) fixes init, and with it ShadowHook's UNIQUE-mode inline hooking works end to end under translation — this probe installs a hook, the proxy fires, the chained original returns correctly, and unhook restores the bytes ("SHADOWHOOK OK"). The redirect was verified not to regress the apps that bundle libshadowhook (an earlier "NetEase Cloud Music regresses" observation was an emulator-memory-degradation flake, clean on a fresh emulator). (An earlier "trampoline-execution SIGSEGV" was a bug in this sample — it used the MULTI/ SHARED-mode SHADOWHOOK_CALL_PREV/POP_STACK hub macros for a UNIQUE-mode hook, which would fault on a real device too — now fixed to call the saved orig directly.)

NDK-samples ports (21)

Module	Exercises
hello-jni	Basic JNI — calls C code from a Kotlin Activity
hello-jniCallback	JNI callbacks — native code calls Java methods
exceptions	C++ exception handling across the JNI boundary
bitmap-plasma	Plasma effect rendered into an Android Bitmap via JNI
hello-gl2	OpenGL ES 2.0 triangle via JNI
gles3jni	OpenGL ES 3.0 instanced rendering
native-activity	Pure C++ NativeActivity with EGL/GLES
native-audio	OpenSL ES playback and recording
native-codec	Video playback through the NDK media codec API
native-midi	Android native MIDI API
sensor-graph	Accelerometer visualization with OpenGL
camera-basic	Camera2 NDK preview and JPEG capture
camera-texture-view	Camera preview into a TextureView
teapots-classic	Utah teapot, GLES 2.0 + touch gestures
teapots-more	GLES 3.0 instanced teapots
teapots-textured	Textured teapot with ImageDecoder
endless-tunnel	3D tunnel game (scene management, GLES 2.0)
sanitizers	HWASan/ASan/UBSan demo
unit-test	Native GoogleTest via Prefab
vectorization	SIMD vectorization benchmarks
orderfile	Linker order-file optimization

Graphics & proxy-library smoke tests (10)

Module	Exercises
hello-vulkan	Vulkan triangle renderer (the original Digitalis sample)
hello-gles1	GLES 1.x calls through libberberis_proxy_libGLESv1_CM
hello-gles3	OpenGL ES 3.2 EGL context (granted as host-max ES 3.1), deterministic pattern
hello-msaa	1x/2x/4x/8x multisample FBO grid, resolved into one frame
hello-aaudio	AAudio stream builder through libberberis_proxy_libaaudio
hello-binder-ndk	NDK binder define/new + host-thread callback round-trip
hello-jnihelp	Drives + self-checks the 12 covered libnativehelper jni* trampolines (throw-family, jniCreateString, jniGetNioBuffer*, jniLogException, jniRegisterNativeMethods)
hello-nnapi	NNAPI device enumeration through libberberis_proxy_libneuralnetworks
hello-vktexture	Vulkan R8 OPTIMAL-tiled image upload/readback round-trip (gfxstream linear<->tiled conversion integrity, the Chromium glyph-atlas path)
hello-webview-functor	libwebviewchromium_plat_support WebView hardware-accel draw-functor registration (RegisterDrawFunctor/RegisterDrawGLFunctor/RegisterGraphicsUtils)

ARM extension & ABI probes (24)

Module	Exercises
hello-neon	NEON intrinsics battery: arithmetic, permutes (EXT, REV32, DUP), CRC32/CRC32C, URECPE/URSQRTE
hello-fp-vector	Vector FP three-same: FMUL/FADD/FSUB/FMLA/FMLS on .4S and .2D
hello-fp16	Armv8.2-FP16 half-precision ops, scalar FCVTAS/FCVTAU
hello-bf16	Armv8.6-BF16
hello-dotprod	Armv8.4-DotProd (SDOT/UDOT)
hello-jscvt	Armv8.3-JSCVT (FJCVTZS)
hello-complex	Armv8.3-FCMA (FCMLA/FCADD)
hello-lse	Armv8.1-LSE atomics (CAS/SWP/LDADD family)
hello-lrcpc	Armv8.3-LRCPC and Armv8.1-LOR (LDAPR/LDLAR family)
hello-ldxp	Exclusive pairs: LDXP/LDAXP/STXP/STLXP
hello-barriers	Memory/synchronization barriers (DMB/DSB/ISB)
hello-aes	AES crypto extension (AESE/AESD/AESMC/AESIMC)
hello-sha-crypto	SHA-1/SHA-2 and SM3 crypto extensions
hello-widemul	Widening multiplies (SMULL/UMULL/PMULL/PMULL2, high halves)
hello-cntvct	Generic-timer system registers via MRS (CNTFRQ/CNTVCT/CNTPCT_EL0)
hello-bti	Armv8.5-BTI branch-target identification
hello-pac-ret	Pointer-authentication return-address signing
hello-ld-interleave	NEON multi-structure LD1/ST1 and interleaved LD2/ST2
hello-superpack-regress	Regression probes for JIT bugs once hit by Facebook/WhatsApp (LDP base aliasing and friends)
hello-libc-libm	Digitalis extra libc/libm fast-path trampolines
hello-sigaction	sigaction install/readback, SIGSEGV delivery + siglongjmp recovery
hello-seccomp	guest seccomp-bpf filter install (SECCOMP_SET_MODE_FILTER) — AArch64-ABI filters must not be forwarded verbatim to the x86_64 host
hello-glyphblit	Skia NEON A8 glyph mask blit (blit_mask_d32_a8_neon) self-checked against a scalar reference
hello-fdsweep	process-spawn fd hygiene: fork + pre-exec fd sweep (close/close_range) + post-sweep translation, posix_spawn of a host binary

UI engines (3)

Module	Exercises
hello-reactnative	React Native + Hermes, prebuilt bytecode bundle
hello-lynx	Lynx (ReactLynx + PrimJS), prebuilt .lynx.bundle
hello-qt	Qt 6 widgets (standalone build)

Third-party native libraries (73)

Media:

Module	Exercises
hello-ijkplayer	bilibili ijkplayer (FFmpeg) playback
hello-libvlc	libVLC playback
hello-ffmpeg-kit	FFmpegKit — FFprobe media information over a bundled WAV
hello-oboe	Oboe — open/start/write/stop an audio stream
hello-opus	Opus audio codec — PCM encode→decode round-trip (SILK/CELT fixed-point), via techery/opus_android (libopustool.so)

Imaging:

Module	Exercises
hello-fresco	Fresco native image pipeline decode
hello-gpuimage	GPUImage native filter
hello-libpag	Tencent libpag PAG render
hello-gif	android-gif-drawable native GIF decode
hello-pdfium	PDFium page render
hello-renderscript-toolkit	RenderScript replacement Toolkit intrinsics (blur, histogram, …) via the vendored renderscript-toolkit module
hello-avif	AOMedia libavif AV1 still-image decode (SIMD inverse-transform / loop-filter)
hello-rive	Rive native vector-animation runtime — parses a .riv document and inspects its artboard/animations (librive-android.so)
hello-libyuv	Google libyuv ARGB↔I420 (YUV 4:2:0) NEON color conversion round-trip (libyuv_android.so)
hello-leptonica	Leptonica native image processing (PIX create / pixel round-trip / pixScale), via JavaCPP
hello-maplibre	MapLibre Native map renderer init (was a documented gap; now passing after the free-quarantine fix)
hello-filament	Google Filament native engine + GPU-resource allocation, headless (libfilament-jni.so)
hello-filament-render	Google Filament on-screen Vulkan render of a glTF cube model loaded via gltfio (screenshot test); enabled by the guest libgui.so stub
hello-gltfio	Filament gltfio native glTF 2.0 parse of an embedded triangle (libgltfio-jni.so)
hello-mupdf	Artifex MuPDF (fitz) native PDF page rasterization — alternate render engine to PDFium (libmupdf_java.so)
hello-libwebp	Google libwebp WebP lossless encode→decode round-trip (VP8L Huffman / color transforms), via aureusapps webp-android

Vision & ML:

Module	Exercises
hello-opencv	OpenCV NEON computer vision
hello-tflite	TensorFlow Lite inference
hello-litert-llm	LiteRT-LM on-device LLM runtime
hello-pytorch	PyTorch Mobile inference
hello-ncnn	Tencent ncnn CPU inference (fp32 pinned)
hello-zxing	zxing-cpp native C++ barcode decode (libzxingcpp_android.so; Java ZXing used only to synthesize the test QR)
hello-tesseract	Tesseract OCR
hello-onnxruntime	ONNX Runtime native tensor allocation + provider query
hello-mediapipe	MediaPipe Tasks Vision (FaceDetector) native TFLite inference
hello-vosk	Vosk / Kaldi speech native-load smoke (model-free)

Crypto, storage & runtimes:

Module	Exercises
hello-sqlcipher	SQLCipher encrypted SQLite
hello-conscrypt	Conscrypt TLS/crypto provider
hello-libsignal	Signal Protocol session encrypt/decrypt
hello-realm	Realm Kotlin native store (standalone build)
hello-objectbox	ObjectBox store round-trip
hello-mmkv	Tencent MMKV mmap-backed key-value store
hello-zstd	zstd compression round-trip
hello-snappy	Google Snappy native compression round-trip (snappy-java; arm64 native + libc++_shared delivered via jniLibs)
hello-secp256k1	libsecp256k1 EC crypto — pubkey derive, ECDSA sign/verify, tamper-reject, ECDH agree (ACINQ arm64 native)
hello-quickjs	QuickJS JavaScript engine eval
hello-cronet	Cronet TLS handshake
hello-libsodium	libsodium crypto round-trip (XSalsa20-Poly1305 secretbox + Blake2b), via JNA
hello-themis	Themis SecureCell passphrase encrypt/decrypt (BoringSSL)
hello-wcdb	Tencent WCDB encrypted (SQLCipher-style) SQLite
hello-argon2	Argon2id memory-hard password hash + verify
hello-couchbase	Couchbase Lite (native LiteCore) document round-trip
hello-j2v8	J2V8 — Google V8 JS engine; hot loop drives V8's optimizing JIT (IC IVAU)
hello-duktape	Duktape embedded JavaScript interpreter eval
hello-javet	Javet — Google V8 JS engine; 5000-run hot loop drives V8's optimizing JIT (IC IVAU) + string marshalling
hello-lua	Native Lua 5.4 VM — runs a Lua script and reads results back via luajava (liblua54.so)
hello-leveldb	Google LevelDB LSM-tree key-value store — put/get/delete round-trip (libleveldb.so)
hello-libarchive	libarchive multi-format archive read (ustar) — format detection + entry decode (libarchive-jni.so)
hello-pcre2	PCRE2 regex — pcre2_jit_compile (sljit) + JIT/interpreted match; the JIT path exercises IC IVAU self-modified-code invalidation
hello-libxml2	libxml2 XML parser — xmlReadMemory + DOM tree walk (recursive-descent, byte-at-a-time, no SIMD)
hello-sentry-ndk	Sentry NDK native crash backend init + signal-handler stack-unwinder install (libsentry.so)

Math, science & physics:

Module	Exercises
hello-openblas	OpenBLAS cblas_sgemm / sdot — dense FP matrix kernels (NEON FMA), via JavaCPP
hello-fftw	FFTW forward complex 1D DFT, peak-bin verification — complex-FP butterflies, via JavaCPP
hello-gsl	GNU Scientific Library special functions (bessel/gamma/erf), double-precision, via JavaCPP
hello-box2d	libGDX Box2D native physics — gravity drop + collision/constraint solver (libgdx-box2d.so)
hello-bullet	libGDX Bullet 3D rigid-body physics — gravity drop + collision broadphase/constraint solver (libgdx-bullet.so)

FFI & native interop:

Module	Exercises
hello-jna	Java Native Access — libffi dynamic calls into bionic libc
hello-fbjni	Facebook fbjni JNI runtime init (JNI_OnLoad + native registration)
hello-yoga	Facebook Yoga flexbox layout engine (libyoga.so) — native solver via YogaNode JNI, self-checks flexGrow width/offset math
hello-firebase-crashlytics	Firebase Crashlytics NDK Breakpad natives (libcrashlytics + -common/-handler/-trampoline) load + JNI_OnLoad — the most common native crash SDK across real apps
hello-xcrash	iQIYI xCrash native crash-capture (libxcrash + libxcrash_dumper) init + signal/ANR handler install
hello-hiddenapibypass	LSPosed HiddenApiBypass — grants a hidden-API exemption then reflectively reaches a @hide framework API enforcement would deny (pure-Java lib, no .so; runs on host ART)
hello-tinker	Tencent Tinker runtime patch primitives (bsdiff-util) — BSDiff delta + BSPatch reconstruct round-trip (pure-Java lib, no .so; native bsdiff/dexdiff is build-time only)
hello-msaoaid	MSA (移动安全联盟) OAID SDK security lib (libmsaoaidsec.so) — its ELF-constructor anti-tamper soinfo-list walk resolves the linker via /proc/self/maps canonical paths; regression fixture for the guest/host linker-view fix
hello-javacpp	JavaCPP off-heap native pointer alloc / read / write

Networking:

Module	Exercises
hello-webrtc	WebRTC native init + headless SDP offer (DataChannel)
hello-libtorrent4j	libtorrent4j (libtorrent + Boost) session lifecycle + SHA-1
hello-wireguard	wireguard-go GoBackend.wgVersion() — exercises the embedded Go runtime under translation (libwg-go.so; tunnel classes vendored minus an unused record, see vendor-tunnel.sh)

AndroidX native:

Module	Exercises
hello-sqlite-bundled	androidx.sqlite bundled SQLite
hello-graphics-path	androidx.graphics.path iteration
hello-camera-core	CameraX native image-util
hello-tracing-perfetto	Perfetto SDK tracing
hello-appsearch	AppSearch/Icing (schema-less GenericDocument probe)
hello-ink	androidx.ink stroke geometry

Helper modules (not samples)

• status-test-lib / screenshot-test-lib — the instrumentation harnesses the samples share (see Testing).
• renderscript-toolkit — vendored library consumed by hello-renderscript-toolkit.

Standalone builds

Two samples need toolchains the suite's AGP version cannot host, so they are self-contained Gradle projects with their own settings.gradle.kts, pinned wrapper, and build-apk.sh; they are intentionally absent from the suite's settings.gradle.kts:

• hello-qt — Qt 6 widgets; verified by launch.
• hello-realm — Realm Kotlin's compiler plugin requires Kotlin ≤ 2.0.x, so it pins Gradle 8.9 / AGP 8.7.3 / Kotlin 2.0.20; verified by launch (REALM OK in logcat). See hello-realm/NOTES.md.

Two more module directories exist but are excluded from the build entirely: hello-media3-ffmpeg and hello-media3-av1. Google publishes no prebuilt AAR for the Media3 FFmpeg/AV1 decoder extensions (source-only artifacts), so there is nothing to build against; each module's NOTES.md documents the gap and the unblock step.

Prerequisites

• JDK 21
• Android SDK with NDK and CMake 3.22.1+
• glslangValidator for GLSL-to-SPIR-V shader compilation (in the NDK's shader-tools/, or via the Vulkan SDK, or apt install glslang-tools)

Build

./gradlew assembleDebug                       # all suite modules
./gradlew assembleDebug assembleAndroidTest   # what CI builds on every push
(cd hello-qt && ./build-apk.sh)               # standalone
(cd hello-realm && ./build-apk.sh)            # standalone

Testing

Every suite module carries a deterministic instrumented test: a StatusTest that runs the module's core native op and asserts a known result, or — for rendering modules — a ScreenshotTest that compares the rendered frame against a committed reference image. On a running Digitalis emulator:

./gradlew :hello-jni:connectedDebugAndroidTest

In the Digitalis AOSP tree the whole suite is driven by .claude/scripts/test-samples.sh, which installs each APK, runs its instrumentation, and watches logcat for Fatal signal / Undefined arm64 instruction / FATAL EXCEPTION. The standalone modules are verified by launch + logcat instead (their pinned toolchains can't consume status-test-lib).

Digitalis compatibility

As of 2026-07-03, all 130 suite-tested modules PASS liveness on the Digitalis emulator (sdk_phone64_x86_64_digitalis, ANGLE GLES + gfxstream Vulkan) and all 14 rendering modules pass their ScreenshotTest pixel-compares — no crashes, every rendered frame matches its reference. The newly registered hello-fdsweep and hello-vktexture also pass their StatusTest assertions (the last full StatusTest sweep, 2026-06-15, was 70/70 on the modules registered then). The standalone module hello-realm passes its launch verification (REALM OK); hello-qt is launch-verified by the script.

Samples are written against the full ARM64 API surface without regard to what the translator implements yet. A sample that crashes with Undefined arm64 instruction is a translator gap: the fix goes into frameworks/libs/binary_translation/ (decoder + interpreter, plus JIT when applicable) — never into the sample.