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/*
* 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.util;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Objects;
/**
* A simple append only random-access {@link BytesRef} array that stores full copies of the appended
* bytes in a {@link ByteBlockPool}.
*
* Note: This class is not Thread-Safe!
*
* @lucene.internal
* @lucene.experimental
*/
public final class BytesRefArray implements SortableBytesRefArray {
private final ByteBlockPool pool;
private int[] offsets = new int[1];
private int lastElement = 0;
private int currentOffset = 0;
private final Counter bytesUsed;
/** Creates a new {@link BytesRefArray} with a counter to track allocated bytes */
public BytesRefArray(Counter bytesUsed) {
this.pool = new ByteBlockPool(new ByteBlockPool.DirectTrackingAllocator(bytesUsed));
pool.nextBuffer();
bytesUsed.addAndGet(RamUsageEstimator.NUM_BYTES_ARRAY_HEADER * (long) Integer.BYTES);
this.bytesUsed = bytesUsed;
}
/** Clears this {@link BytesRefArray} */
@Override
public void clear() {
lastElement = 0;
currentOffset = 0;
// TODO: it's trappy that this does not return storage held by int[] offsets array!
Arrays.fill(offsets, 0);
pool.reset(false, true); // no need to 0 fill the buffers we control the allocator
}
/**
* Appends a copy of the given {@link BytesRef} to this {@link BytesRefArray}.
*
* @param bytes the bytes to append
* @return the index of the appended bytes
*/
@Override
public int append(BytesRef bytes) {
if (lastElement >= offsets.length) {
int oldLen = offsets.length;
offsets = ArrayUtil.grow(offsets, offsets.length + 1);
bytesUsed.addAndGet((offsets.length - oldLen) * (long) Integer.BYTES);
}
pool.append(bytes);
offsets[lastElement++] = currentOffset;
currentOffset += bytes.length;
return lastElement - 1;
}
/**
* Returns the current size of this {@link BytesRefArray}
*
* @return the current size of this {@link BytesRefArray}
*/
@Override
public int size() {
return lastElement;
}
/**
* Returns the n'th element of this {@link BytesRefArray}
*
* @param spare a spare {@link BytesRef} instance
* @param index the elements index to retrieve
* @return the n'th element of this {@link BytesRefArray}
*/
public BytesRef get(BytesRefBuilder spare, int index) {
Objects.checkIndex(index, lastElement);
int offset = offsets[index];
int length = index == lastElement - 1 ? currentOffset - offset : offsets[index + 1] - offset;
spare.growNoCopy(length);
spare.setLength(length);
pool.readBytes(offset, spare.bytes(), 0, spare.length());
return spare.get();
}
/**
* Used only by sort below, to set a {@link BytesRef} with the specified slice, avoiding copying
* bytes in the common case when the slice is contained in a single block in the byte block pool.
*/
private void setBytesRef(BytesRefBuilder spare, BytesRef result, int index) {
Objects.checkIndex(index, lastElement);
int offset = offsets[index];
int length;
if (index == lastElement - 1) {
length = currentOffset - offset;
} else {
length = offsets[index + 1] - offset;
}
pool.setBytesRef(spare, result, offset, length);
}
/**
* Returns a {@link SortState} representing the order of elements in this array. This is a
* non-destructive operation.
*
* @param comp The comparator to compare {@link BytesRef}s. A radix sort optimization is available
* if the comparator implements {@link BytesRefComparator}
* @param stable If the sort needs to be stable
* @return A {@link SortState} that could be used in {@link BytesRefArray#iterator(SortState)}
*/
public SortState sort(final Comparator comp, boolean stable) {
final int[] orderedEntries = new int[size()];
for (int i = 0; i < orderedEntries.length; i++) {
orderedEntries[i] = i;
}
StringSorter sorter;
if (stable) {
sorter =
new StableStringSorter(comp) {
private final int[] tmp = new int[size()];
@Override
protected void get(BytesRefBuilder builder, BytesRef result, int i) {
BytesRefArray.this.setBytesRef(builder, result, orderedEntries[i]);
}
@Override
protected void save(int i, int j) {
tmp[j] = orderedEntries[i];
}
@Override
protected void restore(int i, int j) {
System.arraycopy(tmp, i, orderedEntries, i, j - i);
}
@Override
protected void swap(int i, int j) {
int o = orderedEntries[i];
orderedEntries[i] = orderedEntries[j];
orderedEntries[j] = o;
}
};
} else {
sorter =
new StringSorter(comp) {
@Override
protected void get(BytesRefBuilder builder, BytesRef result, int i) {
BytesRefArray.this.setBytesRef(builder, result, orderedEntries[i]);
}
@Override
protected void swap(int i, int j) {
int o = orderedEntries[i];
orderedEntries[i] = orderedEntries[j];
orderedEntries[j] = o;
}
};
}
sorter.sort(0, size());
return new SortState(orderedEntries);
}
/** sugar for {@link #iterator(Comparator)} with a null comparator */
public BytesRefIterator iterator() {
return iterator((SortState) null);
}
/**
* Returns a {@link BytesRefIterator} with point in time semantics. The iterator provides access
* to all so far appended {@link BytesRef} instances.
*
* If a non null {@link Comparator} is provided the iterator will iterate the byte
* values in the order specified by the comparator. Otherwise the order is the same as the values
* were appended.
*
*
This is a non-destructive operation.
*/
@Override
public BytesRefIterator iterator(final Comparator comp) {
return iterator(sort(comp, false));
}
/**
* Returns an {@link IndexedBytesRefIterator} with point in time semantics. The iterator provides
* access to all so far appended {@link BytesRef} instances. If a non-null sortState is specified
* then the iterator will iterate the byte values in the order of the sortState; otherwise, the
* order is the same as the values were appended.
*/
public IndexedBytesRefIterator iterator(final SortState sortState) {
final int size = size();
final int[] indices = sortState == null ? null : sortState.indices;
assert indices == null || indices.length == size : indices.length + " != " + size;
final BytesRefBuilder spare = new BytesRefBuilder();
final BytesRef result = new BytesRef();
return new IndexedBytesRefIterator() {
int pos = -1;
int ord = 0;
@Override
public BytesRef next() {
++pos;
if (pos < size) {
ord = indices == null ? pos : indices[pos];
setBytesRef(spare, result, ord);
return result;
}
return null;
}
@Override
public int ord() {
return ord;
}
};
}
/** Used to iterate the elements of an array in a given order. */
public static final class SortState implements Accountable {
private final int[] indices;
private SortState(int[] indices) {
this.indices = indices;
}
@Override
public long ramBytesUsed() {
return RamUsageEstimator.NUM_BYTES_ARRAY_HEADER + indices.length * Integer.BYTES;
}
}
/**
* An extension of {@link BytesRefIterator} that allows retrieving the index of the current
* element
*/
public interface IndexedBytesRefIterator extends BytesRefIterator {
/**
* Returns the ordinal position of the element that was returned in the latest call of {@link
* #next()}. Do not call this method if {@link #next()} is not called yet or the last call
* returned a null value.
*/
int ord();
}
}