msokolov commented on a change in pull request #177: URL: https://github.com/apache/lucene/pull/177#discussion_r648221346
########## File path: lucene/core/src/java/org/apache/lucene/store/MemorySegmentIndexInput.java ########## @@ -0,0 +1,614 @@ +/* + * 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.EOFException; +import java.io.IOException; +import java.lang.invoke.VarHandle; +import java.nio.ByteOrder; +import java.util.Arrays; +import java.util.Objects; +import jdk.incubator.foreign.MemoryHandles; +import jdk.incubator.foreign.MemorySegment; +import jdk.incubator.foreign.ResourceScope; + +/** + * Base IndexInput implementation that uses an array of MemorySegments to represent a file. + * + * <p>For efficiency, this class requires that the segment size are a power-of-two (<code> + * chunkSizePower</code>). + */ +public abstract class MemorySegmentIndexInput extends IndexInput implements RandomAccessInput { + // We pass 1L as alignment, because currently Lucene file formats are heavy unaligned: :( + static final VarHandle VH_getByte = + MemoryHandles.varHandle(byte.class, 1L, ByteOrder.LITTLE_ENDIAN).withInvokeExactBehavior(); + static final VarHandle VH_getShort = + MemoryHandles.varHandle(short.class, 1L, ByteOrder.LITTLE_ENDIAN).withInvokeExactBehavior(); + static final VarHandle VH_getInt = + MemoryHandles.varHandle(int.class, 1L, ByteOrder.LITTLE_ENDIAN).withInvokeExactBehavior(); + static final VarHandle VH_getLong = + MemoryHandles.varHandle(long.class, 1L, ByteOrder.LITTLE_ENDIAN).withInvokeExactBehavior(); + + static final boolean IS_LITTLE_ENDIAN = (ByteOrder.nativeOrder() == ByteOrder.LITTLE_ENDIAN); + + final boolean isClone; + final long length; + final long chunkSizeMask; + final int chunkSizePower; + final ResourceScope scope; + final MemorySegment[] segments; + + int curSegmentIndex = -1; + MemorySegment + curSegment; // redundant for speed: segments[curSegmentIndex], also marker if closed! + long curPosition; // relative to curSegment, not globally + + public static MemorySegmentIndexInput newInstance( + String resourceDescription, + ResourceScope scope, + MemorySegment[] segments, + long length, + int chunkSizePower) { + if (segments.length == 1) { + return new SingleSegmentImpl( + resourceDescription, scope, segments[0], length, chunkSizePower, false); + } else { + return new MultiSegmentImpl( + resourceDescription, scope, segments, 0, length, chunkSizePower, false); + } + } + + private MemorySegmentIndexInput( + String resourceDescription, + ResourceScope scope, + MemorySegment[] segments, + long length, + int chunkSizePower, + boolean isClone) { + super(resourceDescription); + this.scope = scope; + this.segments = segments; + assert Arrays.stream(segments).map(MemorySegment::scope).allMatch(scope::equals); + this.length = length; + this.chunkSizePower = chunkSizePower; + this.chunkSizeMask = (1L << chunkSizePower) - 1L; + this.isClone = isClone; + this.curSegment = segments[0]; + } + + void ensureOpen() { + if (curSegment == null) { + throw alreadyClosed(); + } + } + + RuntimeException wrapAlreadyClosedException(RuntimeException e) { + if (e instanceof NullPointerException) { + return alreadyClosed(); + } + // TODO: maybe open a JDK issue to have a separate, more + // meaningful exception for unmapped segments: + if (e.getMessage() != null && e.getMessage().contains("closed")) { + return alreadyClosed(); + } + return e; + } + + RuntimeException handlePositionalIOOBE(String action, long pos) throws IOException { + if (pos < 0L) { + return new IllegalArgumentException(action + " negative position: " + this); + } else { + throw new EOFException(action + " past EOF: " + this); + } + } + + private AlreadyClosedException alreadyClosed() { + return new AlreadyClosedException("Already closed: " + this); + } + + @Override + public final byte readByte() throws IOException { + try { + final byte v = (byte) VH_getByte.get(curSegment, curPosition); + curPosition++; + return v; + } catch ( + @SuppressWarnings("unused") + IndexOutOfBoundsException e) { + do { + curSegmentIndex++; + if (curSegmentIndex >= segments.length) { + throw new EOFException("read past EOF: " + this); + } + curSegment = segments[curSegmentIndex]; + curPosition = 0L; + } while (curSegment.byteSize() == 0L); + final byte v = (byte) VH_getByte.get(curSegment, curPosition); + curPosition++; + return v; + } catch (NullPointerException | IllegalStateException e) { + throw wrapAlreadyClosedException(e); + } + } + + @Override + public final void readBytes(byte[] b, int offset, int len) throws IOException { + final MemorySegment arraySegment = MemorySegment.ofArray(b); + try { + arraySegment.asSlice(offset).copyFrom(curSegment.asSlice(curPosition, len)); + curPosition += len; + } catch ( + @SuppressWarnings("unused") + IndexOutOfBoundsException e) { + readBytesBoundary(arraySegment, offset, len); + } catch (NullPointerException | IllegalStateException e) { + throw wrapAlreadyClosedException(e); + } + } + + private void readBytesBoundary(final MemorySegment arraySegment, int offset, int len) + throws IOException { + try { + long curAvail = curSegment.byteSize() - curPosition; + while (len > curAvail) { + arraySegment.asSlice(offset).copyFrom(curSegment.asSlice(curPosition, curAvail)); + len -= curAvail; + offset += curAvail; + curSegmentIndex++; + if (curSegmentIndex >= segments.length) { + throw new EOFException("read past EOF: " + this); + } + curSegment = segments[curSegmentIndex]; + curPosition = 0L; + curAvail = curSegment.byteSize(); + } + arraySegment.asSlice(offset).copyFrom(curSegment.asSlice(curPosition, len)); + curPosition += len; + } catch (NullPointerException | IllegalStateException e) { + throw wrapAlreadyClosedException(e); + } + } + + @Override + public void readLongs(long[] dst, int offset, int length) throws IOException { + if (IS_LITTLE_ENDIAN) { + final MemorySegment targetSlice = + MemorySegment.ofArray(dst).asSlice((long) offset << 3, (long) length << 3); + try { + targetSlice.copyFrom(curSegment.asSlice(curPosition, targetSlice.byteSize())); + curPosition += targetSlice.byteSize(); + } catch ( + @SuppressWarnings("unused") + IndexOutOfBoundsException iobe) { + super.readLongs(dst, offset, length); Review comment: thanks for the explanations -- This is an automated message from the Apache Git Service. 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