246 lines
11 KiB
Java
246 lines
11 KiB
Java
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package dev.kreuzberg;
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import java.lang.foreign.Arena;
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import java.lang.foreign.FunctionDescriptor;
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import java.lang.foreign.Linker;
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import java.lang.foreign.MemoryLayout;
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import java.lang.foreign.MemorySegment;
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import java.lang.foreign.ValueLayout;
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import java.lang.invoke.MethodHandles;
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import java.lang.invoke.MethodType;
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import java.util.concurrent.ConcurrentHashMap;
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import com.fasterxml.jackson.databind.ObjectMapper;
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/**
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* Allocates Panama FFM upcall stubs for an IRenderer implementation,
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* assembles the C vtable in native memory, and provides static
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* registerRenderer/unregisterRenderer helpers.
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*/
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public final class RendererBridge implements AutoCloseable {
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private static final Linker LINKER = Linker.nativeLinker();
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private static final MethodHandles.Lookup LOOKUP = MethodHandles.lookup();
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private static final ObjectMapper JSON = new ObjectMapper();
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/** Live registry — keeps Arenas and upcall stubs alive past the register call. */
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private static final ConcurrentHashMap<String, RendererBridge>
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RENDERER_BRIDGES = new ConcurrentHashMap<>();
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// C vtable: 7 fields (4 plugin methods + 1 trait methods + free_string + free_user_data)
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private static final MemoryLayout VTABLE_LAYOUT = MemoryLayout.structLayout(ValueLayout.ADDRESS, ValueLayout.ADDRESS, ValueLayout.ADDRESS, ValueLayout.ADDRESS, ValueLayout.ADDRESS, ValueLayout.ADDRESS, ValueLayout.ADDRESS);
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private static final long VTABLE_SIZE = VTABLE_LAYOUT.byteSize();
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private final Arena arena;
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private final MemorySegment vtable;
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private final IRenderer impl;
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RendererBridge(final IRenderer impl) {
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this.impl = impl;
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this.arena = Arena.ofShared();
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this.vtable = arena.allocate(VTABLE_SIZE);
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try {
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long offset = 0L;
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var stubName = LINKER.upcallStub(LOOKUP.bind(this, "handleName",
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MethodType.methodType(int.class, MemorySegment.class, MemorySegment.class, MemorySegment.class)),
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FunctionDescriptor.of(ValueLayout.JAVA_INT, ValueLayout.ADDRESS, ValueLayout.ADDRESS, ValueLayout.ADDRESS),
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arena);
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vtable.set(ValueLayout.ADDRESS, offset, stubName);
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offset += ValueLayout.ADDRESS.byteSize();
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var stubVersion = LINKER.upcallStub(LOOKUP.bind(this, "handleVersion",
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MethodType.methodType(int.class, MemorySegment.class, MemorySegment.class, MemorySegment.class)),
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FunctionDescriptor.of(ValueLayout.JAVA_INT, ValueLayout.ADDRESS, ValueLayout.ADDRESS, ValueLayout.ADDRESS),
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arena);
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vtable.set(ValueLayout.ADDRESS, offset, stubVersion);
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offset += ValueLayout.ADDRESS.byteSize();
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var stubInitialize = LINKER.upcallStub(LOOKUP.bind(this, "handleInitialize",
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MethodType.methodType(int.class, MemorySegment.class, MemorySegment.class)),
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FunctionDescriptor.of(ValueLayout.JAVA_INT, ValueLayout.ADDRESS, ValueLayout.ADDRESS),
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arena);
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vtable.set(ValueLayout.ADDRESS, offset, stubInitialize);
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offset += ValueLayout.ADDRESS.byteSize();
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var stubShutdown = LINKER.upcallStub(LOOKUP.bind(this, "handleShutdown",
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MethodType.methodType(int.class, MemorySegment.class, MemorySegment.class)),
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FunctionDescriptor.of(ValueLayout.JAVA_INT, ValueLayout.ADDRESS, ValueLayout.ADDRESS),
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arena);
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vtable.set(ValueLayout.ADDRESS, offset, stubShutdown);
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offset += ValueLayout.ADDRESS.byteSize();
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var stubRender = LINKER.upcallStub(LOOKUP.bind(this, "handleRender",
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MethodType.methodType(int.class, MemorySegment.class, MemorySegment.class, MemorySegment.class, MemorySegment.class)),
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FunctionDescriptor.of(
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ValueLayout.JAVA_INT,
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ValueLayout.ADDRESS,
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ValueLayout.ADDRESS,
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ValueLayout.ADDRESS,
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ValueLayout.ADDRESS
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),
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arena);
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vtable.set(ValueLayout.ADDRESS, offset, stubRender);
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offset += ValueLayout.ADDRESS.byteSize();
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var stubFreeString = LINKER.upcallStub(LOOKUP.bind(this, "freeString",
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MethodType.methodType(void.class, MemorySegment.class)),
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FunctionDescriptor.ofVoid(ValueLayout.ADDRESS),
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arena);
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vtable.set(ValueLayout.ADDRESS, offset, stubFreeString);
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offset += ValueLayout.ADDRESS.byteSize();
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var stubFreeUserData = LINKER.upcallStub(LOOKUP.bind(this, "freeUserData",
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MethodType.methodType(void.class, MemorySegment.class)),
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FunctionDescriptor.ofVoid(ValueLayout.ADDRESS),
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arena);
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vtable.set(ValueLayout.ADDRESS, offset, stubFreeUserData);
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offset += ValueLayout.ADDRESS.byteSize();
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} catch (ReflectiveOperationException e) {
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arena.close();
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throw new RuntimeException("Failed to create trait bridge stubs", e);
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}
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}
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MemorySegment vtableSegment() { return vtable; }
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private int handleName(MemorySegment userData, MemorySegment outName, MemorySegment outError) {
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try {
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outName.set(ValueLayout.ADDRESS, 0, arena.allocateFrom(impl.name()));
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return 0;
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} catch (Throwable e) { return 1; }
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}
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private int handleVersion(MemorySegment userData, MemorySegment outVersion, MemorySegment outError) {
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try {
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outVersion.set(ValueLayout.ADDRESS, 0, arena.allocateFrom(impl.version()));
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return 0;
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} catch (Throwable e) { return 1; }
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}
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private int handleInitialize(MemorySegment userData, MemorySegment outError) {
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try {
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impl.initialize();
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return 0;
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} catch (Throwable e) { return 1; }
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}
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private int handleShutdown(MemorySegment userData, MemorySegment outError) {
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try {
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impl.shutdown();
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return 0;
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} catch (Throwable e) { return 1; }
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}
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private int handleRender(MemorySegment userData, MemorySegment doc_in, MemorySegment outResult, MemorySegment outError) {
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try {
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String doc = doc_in.reinterpret(Long.MAX_VALUE).getString(0);
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String result = impl.render(doc);
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MemorySegment jsonCs = arena.allocateFrom(result);
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outResult.set(ValueLayout.ADDRESS, 0, jsonCs);
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return 0;
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} catch (Throwable e) {
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writeError(outError, e);
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return 1;
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}
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}
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private void writeError(MemorySegment outError, Throwable e) {
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try { outError.set(ValueLayout.ADDRESS, 0, arena.allocateFrom(e.getClass().getSimpleName() + ": " + e.getMessage())); }
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catch (Throwable ignored) { /* swallow */ }
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}
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private void freeString(MemorySegment ptr) {
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// Strings returned by Java callbacks are arena-owned and released when this bridge closes.
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}
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private void freeUserData(MemorySegment userData) {
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// User data is Java-side state (the impl object), not freed by Rust on drop.
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}
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/** Read a NUL-terminated native C string safely without unbounded reinterpret. */
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private static String readNativeString(MemorySegment ptr) {
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return ptr.reinterpret(4096).getString(0);
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}
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@Override
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public void close() { arena.close(); }
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/** Register a Renderer implementation via Panama FFM upcall stubs. */
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public static void registerRenderer(final IRenderer impl) throws Exception {
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var bridge = new RendererBridge(impl);
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try {
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try (var nameArena = Arena.ofShared()) {
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var nameCs = nameArena.allocateFrom(impl.name());
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MemorySegment outErr = nameArena.allocate(ValueLayout.ADDRESS);
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int rc = (int) NativeLib.KREUZBERG_REGISTER_RENDERER.invoke(nameCs, bridge.vtableSegment(), MemorySegment.NULL, outErr);
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if (rc != 0) {
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MemorySegment errPtr = outErr.get(ValueLayout.ADDRESS, 0);
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String msg = errPtr.equals(MemorySegment.NULL) ? "registration failed (rc=" + rc + ")" : readNativeString(errPtr);
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throw new RuntimeException("registerRenderer: " + msg);
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}
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}
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} catch (Throwable t) {
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bridge.close();
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if (t instanceof Exception e) {
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throw e;
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} else {
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throw new RuntimeException("Unexpected error during registration", t);
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}
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}
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RENDERER_BRIDGES.put(impl.name(), bridge);
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}
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/** Unregister a Renderer implementation by name. */
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public static void unregisterRenderer(String name) throws Exception {
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try {
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try (var nameArena = Arena.ofShared()) {
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var nameCs = nameArena.allocateFrom(name);
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MemorySegment outErr = nameArena.allocate(ValueLayout.ADDRESS);
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int rc = (int) NativeLib.KREUZBERG_UNREGISTER_RENDERER.invoke(nameCs, outErr);
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if (rc != 0) {
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MemorySegment errPtr = outErr.get(ValueLayout.ADDRESS, 0);
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String msg = errPtr.equals(MemorySegment.NULL)
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? "unregistration failed (rc=" + rc + ")"
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: errPtr.reinterpret(Long.MAX_VALUE).getString(0);
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throw new RuntimeException("unregisterRenderer: " + msg);
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}
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}
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} catch (Throwable t) {
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if (t instanceof Exception e) {
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throw e;
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} else {
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throw new RuntimeException("Unexpected error during unregistration", t);
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}
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}
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RendererBridge old = RENDERER_BRIDGES.remove(name);
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if (old != null) { old.close(); }
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}
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/** Clear all registered Renderer implementations. */
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public static void clearRenderers() throws Exception {
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try {
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try (var arena = Arena.ofShared()) {
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MemorySegment outErr = arena.allocate(ValueLayout.ADDRESS);
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int rc = (int) NativeLib.KREUZBERG_CLEAR_RENDERER.invoke(outErr);
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if (rc != 0) {
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MemorySegment errPtr = outErr.get(ValueLayout.ADDRESS, 0);
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String msg = errPtr.equals(MemorySegment.NULL)
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? "clear failed (rc=" + rc + ")"
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: errPtr.reinterpret(Long.MAX_VALUE).getString(0);
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throw new RuntimeException("clearRenderers: " + msg);
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}
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}
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} catch (Throwable t) {
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if (t instanceof Exception e) {
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throw e;
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} else {
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throw new RuntimeException("Unexpected error during clear", t);
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}
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}
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RENDERER_BRIDGES.values().forEach(RendererBridge::close);
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RENDERER_BRIDGES.clear();
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}
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}
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