android: pure-sx EGL+GLES3 clear-color demo on NativeActivity
Verified on Pixel 7 Pro: solid purple frame, 'rendered 60 frames'
logcat line every second. End-to-end exercise of the new
sx-build → libsxhello.so → APK toolchain shipped today: NDK clang
link + native_app_glue bundling + aapt2/zipalign/apksigner pipeline +
isExportedEntryName so android_main lands in .dynsym.
Notes the source captures so future Android work doesn't repeat the
debugging:
- android_app field offsets for arm64 NDK 29 (window @ 72,
destroyRequested @ 100, source process fn-ptr @ 16).
- ALooper_pollOnce(-1, ...) blows the stack inside Looper::pollOnce
on this device/OS combo; ALooper_pollOnce(0, ...) is fine. We
drive the event loop non-blocking and sleep 16ms.
Outside the regression set on purpose (no tests/expected/99-*.txt) —
same convention as 63-metal-clear.sx. Build instructions live in the
file's leading comment.
This commit is contained in:
agra
197
examples/99-android-egl-clear.sx
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197
examples/99-android-egl-clear.sx
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// Android-only: pure-sx NativeActivity that brings up EGL on the
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// ANativeWindow delivered by native_app_glue and clears the screen
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// every frame via GLES3. Equivalent of `examples/63-metal-clear.sx`
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// for the Android target.
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//
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// What this exercises end-to-end (Session 70's Android port):
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// - `sx build --target android` toolchain (NDK clang, native_app_glue
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// compile + link, -shared .so).
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// - `--apk` APK assembly (manifest + aapt2 + zipalign + apksigner).
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// - `android_main` and `ANativeActivity_onCreate` keep external LLVM
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// linkage so the loader can call them (isExportedEntryName allowlist
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// in lower.zig).
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// - Foreign declarations of EGL / GLES3 / ALooper / __android_log_print.
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//
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// Build + install on a connected device:
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//
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// /Users/agra/projects/sx/zig-out/bin/sx build --target android \
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// --apk /tmp/sxhello.apk --bundle-id co.swipelab.sxhello \
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// -o /tmp/libsxhello.so examples/99-android-egl-clear.sx
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// adb install -r /tmp/sxhello.apk
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// adb shell am start -n co.swipelab.sxhello/android.app.NativeActivity
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// adb logcat -d --pid=$(adb shell pidof co.swipelab.sxhello)
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//
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// Expected: solid purple frame on the device. `egl: setup ok` + periodic
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// `rendered 60 frames` lines in logcat.
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//
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// Known quirk: `ALooper_pollOnce(-1, ...)` (blocking variant) crashes
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// inside Looper::pollOnce on Pixel 7 Pro + Android 16 with what looks
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// like a stack-guard overflow. `ALooper_pollOnce(0, ...)` is fine, so
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// we drive the event loop non-blocking and sleep 16ms per tick instead
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// of relying on the blocking timeout. Worth revisiting later.
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#import "modules/std.sx";
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// ── Foreign declarations ────────────────────────────────────────────────
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__android_log_print :: (prio: s32, tag: *u8, fmt: *u8) -> s32 #foreign;
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usleep :: (us: u32) -> s32 #foreign;
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ALooper_pollOnce :: (ms: s32, outFd: *s32, outEvents: *s32, outData: **void) -> s32 #foreign;
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// EGL — display/surface/context/config are opaque pointers from our side.
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eglGetDisplay :: (display_id: *void) -> *void #foreign;
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eglInitialize :: (display: *void, major: *s32, minor: *s32) -> u32 #foreign;
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eglChooseConfig :: (display: *void, attrib_list: *s32, configs: **void, config_size: s32, num_config: *s32) -> u32 #foreign;
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eglCreateContext :: (display: *void, config: *void, share: *void, attrib_list: *s32) -> *void #foreign;
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eglCreateWindowSurface:: (display: *void, config: *void, window: *void, attrib_list: *s32) -> *void #foreign;
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eglMakeCurrent :: (display: *void, draw: *void, read: *void, ctx: *void) -> u32 #foreign;
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eglSwapBuffers :: (display: *void, surface: *void) -> u32 #foreign;
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// GLES3 (linked via -lGLESv3)
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glClearColor :: (r: f32, g: f32, b: f32, a: f32) #foreign;
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glClear :: (mask: u32) #foreign;
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// ── EGL/GL constants ───────────────────────────────────────────────────
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EGL_NONE :s32: 0x3038;
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EGL_SURFACE_TYPE :s32: 0x3033;
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EGL_WINDOW_BIT :s32: 0x0004;
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EGL_RENDERABLE_TYPE :s32: 0x3040;
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EGL_OPENGL_ES2_BIT :s32: 0x0004;
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EGL_BLUE_SIZE :s32: 0x3022;
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EGL_GREEN_SIZE :s32: 0x3023;
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EGL_RED_SIZE :s32: 0x3024;
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EGL_DEPTH_SIZE :s32: 0x3025;
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EGL_CONTEXT_CLIENT_VERSION :s32: 0x3098;
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GL_COLOR_BUFFER_BIT :u32: 0x4000;
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// ── android_app + android_poll_source layout (NDK 29, arm64) ───────────
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// Offsets measured against the NDK header on this host with offsetof().
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APP_OFF_window :s64: 72;
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APP_OFF_destroyRequested :s64: 100;
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SRC_OFF_process :s64: 16; // id(4) + pad(4) + app*(8) = process fn-ptr
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// ── Helpers ────────────────────────────────────────────────────────────
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log :: (msg: *u8) {
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__android_log_print(4, "sxhello".ptr, msg);
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}
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read_ptr :: (base: s64, off: s64) -> *void {
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p : **void = xx (base + off);
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p.*;
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}
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read_s32 :: (base: s64, off: s64) -> s32 {
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p : *s32 = xx (base + off);
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p.*;
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}
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// ── EGL setup ──────────────────────────────────────────────────────────
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EGLContext :: struct {
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display: *void = null;
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surface: *void = null;
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context: *void = null;
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config: *void = null;
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}
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egl_setup :: (egl: *EGLContext, window: *void) -> bool {
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egl.display = eglGetDisplay(null);
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if egl.display == null { log("egl: getDisplay failed\n".ptr); return false; }
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major : s32 = 0;
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minor : s32 = 0;
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if eglInitialize(egl.display, @major, @minor) == 0 {
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log("egl: initialize failed\n".ptr); return false;
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}
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attribs : [13]s32 = .{
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EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
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EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
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EGL_BLUE_SIZE, 8,
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EGL_GREEN_SIZE, 8,
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EGL_RED_SIZE, 8,
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EGL_DEPTH_SIZE, 0,
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EGL_NONE,
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};
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num_config : s32 = 0;
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if eglChooseConfig(egl.display, @attribs[0], @egl.config, 1, @num_config) == 0 or num_config < 1 {
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log("egl: chooseConfig failed\n".ptr); return false;
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}
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ctx_attribs : [3]s32 = .{ EGL_CONTEXT_CLIENT_VERSION, 2, EGL_NONE };
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egl.context = eglCreateContext(egl.display, egl.config, null, @ctx_attribs[0]);
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if egl.context == null { log("egl: createContext failed\n".ptr); return false; }
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egl.surface = eglCreateWindowSurface(egl.display, egl.config, window, null);
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if egl.surface == null { log("egl: createWindowSurface failed\n".ptr); return false; }
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if eglMakeCurrent(egl.display, egl.surface, egl.surface, egl.context) == 0 {
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log("egl: makeCurrent failed\n".ptr); return false;
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}
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log("egl: setup ok\n".ptr);
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true;
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}
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// ── android_main ───────────────────────────────────────────────────────
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// native_app_glue invokes us on a worker thread once the activity is
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// up. We poll the looper non-blocking, drain any pending sources (their
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// `process` callbacks are what populate app->window for us), then
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// either wait for the window or render a frame.
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android_main :: (app: *void) {
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log("android_main: enter\n".ptr);
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base : s64 = xx app;
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egl : EGLContext = .{};
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out_fd : s32 = 0;
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out_events : s32 = 0;
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out_data : *void = null;
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frame : s32 = 0;
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while true {
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ret := ALooper_pollOnce(0, @out_fd, @out_events, @out_data);
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if ret >= 0 {
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if out_data != null {
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src_base : s64 = xx out_data;
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process_addr := read_ptr(src_base, SRC_OFF_process);
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if process_addr != null {
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process_fn : (*void, *void) -> void = xx process_addr;
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process_fn(app, out_data);
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}
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}
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}
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if read_s32(base, APP_OFF_destroyRequested) != 0 {
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log("android_main: destroy requested\n".ptr);
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break;
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}
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window := read_ptr(base, APP_OFF_window);
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if window != null and egl.surface == null {
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if egl_setup(@egl, window) == false {
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log("android_main: egl setup failed\n".ptr);
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break;
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}
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}
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if egl.surface != null {
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// Steady purple — same role as 63-metal-clear's blue: prove
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// the GPU touched the framebuffer.
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glClearColor(0.5, 0.2, 0.8, 1.0);
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glClear(GL_COLOR_BUFFER_BIT);
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eglSwapBuffers(egl.display, egl.surface);
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frame += 1;
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if (frame % 60) == 0 {
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log("android_main: rendered 60 frames\n".ptr);
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}
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}
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usleep(16000);
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}
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}
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