ChrisHegarty commented on code in PR #13196: URL: https://github.com/apache/lucene/pull/13196#discussion_r1534254114
########## lucene/core/src/java21/org/apache/lucene/store/NativeAccess.java: ########## @@ -0,0 +1,65 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.lucene.store; + +import java.io.IOException; +import java.lang.foreign.MemorySegment; +import java.util.logging.Logger; +import org.apache.lucene.util.Constants; + +@SuppressWarnings("preview") +abstract class NativeAccess { + private static final Logger LOG = Logger.getLogger(NativeAccess.class.getName()); + + // these constants were extracted form glibc and macos header files - luckily they are the same: + + /** No further special treatment. */ + public static final int POSIX_MADV_NORMAL = 0; + + /** Expect random page references. */ + public static final int POSIX_MADV_RANDOM = 1; + + /** Expect sequential page references. */ + public static final int POSIX_MADV_SEQUENTIAL = 2; + + /** Will need these pages. */ + public static final int POSIX_MADV_WILLNEED = 3; + + /** Don't need these pages. */ + public static final int POSIX_MADV_DONTNEED = 4; + + /** Invoke the {@code madvise} call for the given {@link MemorySegment}. */ + public abstract void madvise(MemorySegment segment, int advise) throws IOException; + + /** + * Return the NativeAccess instance for this platform. At moment we only support Linux and MacOS + */ + public static NativeAccess getImplementation() { + if (Constants.LINUX || Constants.MAC_OS_X) { Review Comment: For me, this is the right level of abstraction. Support can be added for other platforms if and when desired - no need to block anything on Windows! ;-) ########## lucene/core/src/java21/org/apache/lucene/store/PosixNativeAccess.java: ########## @@ -0,0 +1,80 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.lucene.store; + +import java.io.IOException; +import java.lang.foreign.FunctionDescriptor; +import java.lang.foreign.Linker; +import java.lang.foreign.MemorySegment; +import java.lang.foreign.SymbolLookup; +import java.lang.foreign.ValueLayout; +import java.lang.invoke.MethodHandle; +import java.util.Locale; + +@SuppressWarnings("preview") +final class PosixNativeAccess extends NativeAccess { + + private final MethodHandle mh$posix_madvise; + + PosixNativeAccess() { + final Linker linker = Linker.nativeLinker(); + final SymbolLookup stdlib = linker.defaultLookup(); + this.mh$posix_madvise = + findFunction( + linker, + stdlib, + "posix_madvise", + FunctionDescriptor.of( + ValueLayout.JAVA_INT, + ValueLayout.ADDRESS, + ValueLayout.JAVA_LONG, + ValueLayout.JAVA_INT)); + } + + private static MethodHandle findFunction( + Linker linker, SymbolLookup lookup, String name, FunctionDescriptor desc) { + final MemorySegment symbol = + lookup + .find(name) + .orElseThrow( + () -> + new UnsupportedOperationException( + "Platform has no symbol for '" + name + "' in libc.")); + return linker.downcallHandle(symbol, desc); Review Comment: we can use captureCallState to capture the errno if this fails. https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/foreign/Linker.Option.html#captureCallState(java.lang.String...) -- This is an automated message from the Apache Git Service. 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