/*
* 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.index;
import java.io.IOException;
import java.util.Objects;
import org.apache.lucene.store.IndexInput;
import org.apache.lucene.store.RAMFile;
import org.apache.lucene.store.RAMInputStream;
import org.apache.lucene.store.RAMOutputStream;
import org.apache.lucene.util.Accountable;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.BytesRefBuilder;
/**
* Prefix codes term instances (prefixes are shared). This is expected to be
* faster to build than a FST and might also be more compact if there are no
* common suffixes.
* @lucene.internal
*/
public class PrefixCodedTerms implements Accountable {
final RAMFile buffer;
private final long size;
private long delGen;
private PrefixCodedTerms(RAMFile buffer, long size) {
this.buffer = Objects.requireNonNull(buffer);
this.size = size;
}
@Override
public long ramBytesUsed() {
return buffer.ramBytesUsed() + 2 * Long.BYTES;
}
/** Records del gen for this packet. */
public void setDelGen(long delGen) {
this.delGen = delGen;
}
/** Builds a PrefixCodedTerms: call add repeatedly, then finish. */
public static class Builder {
private RAMFile buffer = new RAMFile();
private RAMOutputStream output = new RAMOutputStream(buffer, false);
private Term lastTerm = new Term("");
private BytesRefBuilder lastTermBytes = new BytesRefBuilder();
private long size;
/** Sole constructor. */
public Builder() {}
/** add a term */
public void add(Term term) {
add(term.field(), term.bytes());
}
/** add a term. This fully consumes in the incoming {@link BytesRef}. */
public void add(String field, BytesRef bytes) {
assert lastTerm.equals(new Term("")) || new Term(field, bytes).compareTo(lastTerm) > 0;
try {
int prefix = sharedPrefix(lastTerm.bytes, bytes);
int suffix = bytes.length - prefix;
if (field.equals(lastTerm.field)) {
output.writeVInt(prefix << 1);
} else {
output.writeVInt(prefix << 1 | 1);
output.writeString(field);
}
output.writeVInt(suffix);
output.writeBytes(bytes.bytes, bytes.offset + prefix, suffix);
lastTermBytes.copyBytes(bytes);
lastTerm.bytes = lastTermBytes.get();
lastTerm.field = field;
size += 1;
} catch (IOException e) {
throw new RuntimeException(e);
}
}
/** return finalized form */
public PrefixCodedTerms finish() {
try {
output.close();
return new PrefixCodedTerms(buffer, size);
} catch (IOException e) {
throw new RuntimeException(e);
}
}
private int sharedPrefix(BytesRef term1, BytesRef term2) {
int pos1 = 0;
int pos1End = pos1 + Math.min(term1.length, term2.length);
int pos2 = 0;
while(pos1 < pos1End) {
if (term1.bytes[term1.offset + pos1] != term2.bytes[term2.offset + pos2]) {
return pos1;
}
pos1++;
pos2++;
}
return pos1;
}
}
/** An iterator over the list of terms stored in a {@link PrefixCodedTerms}. */
public static class TermIterator extends FieldTermIterator {
final IndexInput input;
final BytesRefBuilder builder = new BytesRefBuilder();
final BytesRef bytes = builder.get();
final long end;
final long delGen;
String field = "";
private TermIterator(long delGen, RAMFile buffer) {
try {
input = new RAMInputStream("MergedPrefixCodedTermsIterator", buffer);
} catch (IOException e) {
throw new RuntimeException(e);
}
end = input.length();
this.delGen = delGen;
}
@Override
public BytesRef next() {
if (input.getFilePointer() < end) {
try {
int code = input.readVInt();
boolean newField = (code & 1) != 0;
if (newField) {
field = input.readString();
}
int prefix = code >>> 1;
int suffix = input.readVInt();
readTermBytes(prefix, suffix);
return bytes;
} catch (IOException e) {
throw new RuntimeException(e);
}
} else {
field = null;
return null;
}
}
// TODO: maybe we should freeze to FST or automaton instead?
private void readTermBytes(int prefix, int suffix) throws IOException {
builder.grow(prefix + suffix);
input.readBytes(builder.bytes(), prefix, suffix);
builder.setLength(prefix + suffix);
}
@Override
public String field() {
return field;
}
@Override
public long delGen() {
return delGen;
}
}
/** Return an iterator over the terms stored in this {@link PrefixCodedTerms}. */
public TermIterator iterator() {
return new TermIterator(delGen, buffer);
}
/** Return the number of terms stored in this {@link PrefixCodedTerms}. */
public long size() {
return size;
}
@Override
public int hashCode() {
int h = buffer.hashCode();
h = 31 * h + (int) (delGen ^ (delGen >>> 32));
return h;
}
@Override
public boolean equals(Object obj) {
if (this == obj) return true;
if (obj == null) return false;
if (getClass() != obj.getClass()) return false;
PrefixCodedTerms other = (PrefixCodedTerms) obj;
return buffer.equals(other.buffer) && delGen == other.delGen;
}
}