package org.apache.lucene.index;
/**
* 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.
*/
import java.io.IOException;
import java.util.Iterator;
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.BytesRef;
import org.apache.lucene.util.StringHelper;
/**
* Prefix codes term instances (prefixes are shared)
* @lucene.experimental
*/
class PrefixCodedTerms implements Iterable<Term> {
final RAMFile buffer;
private PrefixCodedTerms(RAMFile buffer) {
this.buffer = buffer;
}
/** @return size in bytes */
public long getSizeInBytes() {
return buffer.getSizeInBytes();
}
/** @return iterator over the bytes */
public Iterator<Term> iterator() {
return new PrefixCodedTermsIterator();
}
class PrefixCodedTermsIterator implements Iterator<Term> {
final IndexInput input;
String field = "";
BytesRef bytes = new BytesRef();
Term term = new Term(field, "");
PrefixCodedTermsIterator() {
try {
input = new RAMInputStream("PrefixCodedTermsIterator", buffer);
} catch (IOException e) {
throw new RuntimeException(e);
}
}
public boolean hasNext() {
return input.getFilePointer() < input.length();
}
public Term next() {
assert hasNext();
try {
int code = input.readVInt();
if ((code & 1) != 0) {
// new field
field = StringHelper.intern(input.readString());
}
int prefix = code >>> 1;
int suffix = input.readVInt();
bytes.grow(prefix + suffix);
input.readBytes(bytes.bytes, prefix, suffix);
bytes.length = prefix + suffix;
term.set(field, bytes.utf8ToString());
return term;
} catch (IOException e) {
throw new RuntimeException(e);
}
}
public void remove() {
throw new UnsupportedOperationException();
}
}
/** Builds a PrefixCodedTerms: call add repeatedly, then finish. */
public static class Builder {
private RAMFile buffer = new RAMFile();
private RAMOutputStream output = new RAMOutputStream(buffer);
private Term lastTerm = new Term("");
private BytesRef lastBytes = new BytesRef();
private BytesRef scratch = new BytesRef();
/** add a term */
public void add(Term term) {
assert lastTerm.equals(new Term("")) || term.compareTo(lastTerm) > 0;
scratch.copy(term.text);
try {
int prefix = sharedPrefix(lastBytes, scratch);
int suffix = scratch.length - prefix;
if (term.field.equals(lastTerm.field)) {
output.writeVInt(prefix << 1);
} else {
output.writeVInt(prefix << 1 | 1);
output.writeString(term.field);
}
output.writeVInt(suffix);
output.writeBytes(scratch.bytes, scratch.offset + prefix, suffix);
lastBytes.copy(scratch);
lastTerm.text = term.text;
lastTerm.field = term.field;
} catch (IOException e) {
throw new RuntimeException(e);
}
}
/** return finalized form */
public PrefixCodedTerms finish() {
try {
output.close();
return new PrefixCodedTerms(buffer);
} 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;
}
}
}