yacy_search_server/source/net/yacy/document/AbstractParser.java

/**
 *  Parser
 *  Copyright 2010 by Michael Peter Christen, mc@yacy.net, Frankfurt am Main, Germany
 *  First released 29.6.2010 at http://yacy.net
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program in the file lgpl21.txt
 *  If not, see <http://www.gnu.org/licenses/>.
 */

// this is a new implementation of the parser interface using multiple documents as result set
// and a much simpler method structure with only one single parser method to implement

package net.yacy.document;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

import net.yacy.cora.document.id.DigestURL;
import net.yacy.cora.util.ConcurrentLog;
import net.yacy.document.parser.html.TagValency;

public abstract class AbstractParser implements Parser {

    public final static ConcurrentLog log = new ConcurrentLog("PARSER");
    // use LinkedHashSet to maintain order, as in TextParser.initParser() supported_Extensions are mapped to 1. mime-type
    // means also, add the most common mime first, which is mapped to all extension
    protected final Set<String> SUPPORTED_MIME_TYPES = new LinkedHashSet<String>(); 
    protected final Set<String> SUPPORTED_EXTENSIONS = new HashSet<String>();
    private   final String name;

    /**
     * initialize a parser with a name
     * @param name
     */
    public AbstractParser(final String name) {
        this.name = name;
    }

    /*
     *  The following abstract implementations create a circular call which would cause an endless loop when called.
     *  They are both here because one of them must be overridden by the implementing class.
     */

    @Override
    public Document[] parse(
            DigestURL url,
            String mimeType,
            String charset,
            VocabularyScraper scraper,
            int timezoneOffset,
            InputStream source
            ) throws Parser.Failure, InterruptedException {
        return parse(url, mimeType, charset, TagValency.EVAL, new HashSet<String>(), scraper, timezoneOffset, source);
    }

    @Override
    public Document[] parse(
            DigestURL url,
            String mimeType,
            String charset,
            final TagValency defaultValency,
            final Set<String> valencySwitchTagNames,
            VocabularyScraper scraper,
            int timezoneOffset,
            InputStream source
            ) throws Parser.Failure, InterruptedException {
        return parse(url, mimeType, charset, scraper, timezoneOffset, source);
    }

    /*
     *  The following abstract implementations create a circular call which would cause an endless loop when called.
     *  They are both here because one of them must be overridden by the implementing class.
     */

    @Override
    public Document[] parseWithLimits(
            final DigestURL location,
            final String mimeType,
            final String charset,
            final VocabularyScraper scraper,
            final int timezoneOffset,
            final InputStream source,
            final int maxLinks,
            final long maxBytes) throws UnsupportedOperationException, Failure, InterruptedException {
        return parseWithLimits(location, mimeType, charset, TagValency.EVAL, new HashSet<String>(), scraper, timezoneOffset, source, maxLinks, maxBytes);
    }

    @Override
    public Document[] parseWithLimits(
            DigestURL location,
            String mimeType,
            String charset,
            final TagValency defaultValency,
            final Set<String> valencySwitchTagNames,
            VocabularyScraper scraper,
            int timezoneOffset,
            InputStream source,
            int maxLinks,
            long maxBytes)
            throws Failure, InterruptedException, UnsupportedOperationException {
        return parseWithLimits(location, mimeType, charset, scraper, timezoneOffset, source, maxLinks, maxBytes);
    }

    /**
     * return the name of the parser
     */
    @Override
    public String getName() {
        return this.name;
    }

    /**
     * each parser must define a set of supported mime types
     * @return a set of mime type strings that are supported
     */
    @Override
    public Set<String> supportedMimeTypes() {
        return this.SUPPORTED_MIME_TYPES;
    }

    /**
     * each parser must define a set of supported file extensions
     * @return a set of file name extensions that are supported
     */
    @Override
    public Set<String> supportedExtensions() {
        return this.SUPPORTED_EXTENSIONS;
    }

    /**
     * check equivalence of parsers; this simply tests equality of parser names
     * @param o the object to check. Must be a {@link Parser} implementation.
     * @return true when this parser is equivalent to o
     */
    @Override
    public boolean equals(final Object o) {
        return getName().equals(((Parser) o).getName());
    }

    /**
     * the hash code of a parser
     * @return the hash code of the parser name string
     */
    @Override
    public int hashCode() {
        return getName().hashCode();
    }

    public static List<String> singleList(String t) {
        List<String> c = new ArrayList<String>(1);
        if (t != null) c.add(t);
        return c;
    }

    @Override
    public boolean isParseWithLimitsSupported() {
        /* Please override on subclasses when parseWithLimits is supported */
        return false;
    }

}