rmuir commented on a change in pull request #177: URL: https://github.com/apache/lucene/pull/177#discussion_r647598763
########## 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: you can go through the history of why it looks this way. It happens because it is a rare event (exceptional case) and speeds up the optimized case. it may only make e.g. one PFOR block crossing boundaries slightly slower, and won't slow entire query. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@lucene.apache.org For additional commands, e-mail: issues-h...@lucene.apache.org
