org.apache.lucene.index.PostingsEnum.java Source code

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Here is the source code for org.apache.lucene.index.PostingsEnum.java

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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.index;

import java.io.IOException;

import org.apache.lucene.search.DocIdSetIterator;
import org.apache.lucene.util.BytesRef;

/** Iterates through the postings.
 *  NOTE: you must first call {@link #nextDoc} before using
 *  any of the per-doc methods. */
public abstract class PostingsEnum extends DocIdSetIterator {

    /**
     * Flag to pass to {@link TermsEnum#postings(PostingsEnum, int)} if you don't
     * require per-document postings in the returned enum.
     */
    public static final short NONE = 0;

    /** Flag to pass to {@link TermsEnum#postings(PostingsEnum, int)}
     *  if you require term frequencies in the returned enum. */
    public static final short FREQS = 1 << 3;

    /** Flag to pass to {@link TermsEnum#postings(PostingsEnum, int)}
     * if you require term positions in the returned enum. */
    public static final short POSITIONS = FREQS | 1 << 4;

    /** Flag to pass to {@link TermsEnum#postings(PostingsEnum, int)}
     *  if you require offsets in the returned enum. */
    public static final short OFFSETS = POSITIONS | 1 << 5;

    /** Flag to pass to  {@link TermsEnum#postings(PostingsEnum, int)}
     *  if you require payloads in the returned enum. */
    public static final short PAYLOADS = POSITIONS | 1 << 6;

    /**
     * Flag to pass to {@link TermsEnum#postings(PostingsEnum, int)}
     * to get positions, payloads and offsets in the returned enum
     */
    public static final short ALL = OFFSETS | PAYLOADS;

    /**
     * Returns true if the given feature is requested in the flags, false otherwise.
     */
    public static boolean featureRequested(int flags, short feature) {
        return (flags & feature) == feature;
    }

    /** Sole constructor. (For invocation by subclass 
     *  constructors, typically implicit.) */
    protected PostingsEnum() {
    }

    /**
     * Returns term frequency in the current document, or 1 if the field was
     * indexed with {@link IndexOptions#DOCS}. Do not call this before
     * {@link #nextDoc} is first called, nor after {@link #nextDoc} returns
     * {@link DocIdSetIterator#NO_MORE_DOCS}.
     * 
     * <p>
     * <b>NOTE:</b> if the {@link PostingsEnum} was obtain with {@link #NONE},
     * the result of this method is undefined.
     */
    public abstract int freq() throws IOException;

    /**
     * Returns the next position, or -1 if positions were not indexed.
     * Calling this more than {@link #freq()} times is undefined.
     */
    public abstract int nextPosition() throws IOException;

    /** Returns start offset for the current position, or -1
     *  if offsets were not indexed. */
    public abstract int startOffset() throws IOException;

    /** Returns end offset for the current position, or -1 if
     *  offsets were not indexed. */
    public abstract int endOffset() throws IOException;

    /** Returns the payload at this position, or null if no
     *  payload was indexed. You should not modify anything 
     *  (neither members of the returned BytesRef nor bytes 
     *  in the byte[]). */
    public abstract BytesRef getPayload() throws IOException;

}