src/java.base/share/classes/sun/net/www/MimeTable.java

/*
 * Copyright (c) 1994, 2024, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.net.www;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.io.IOException;
import java.net.FileNameMap;
import java.util.Enumeration;
import java.util.Locale;
import java.util.Hashtable;
import java.util.Properties;
import java.util.StringTokenizer;

public final class MimeTable implements FileNameMap {

    /** Hash mark introducing a URI fragment */
    private static final int HASH_MARK = '#';

    /** Keyed by file extension (with the .), returns MimeEntries */
    private final Hashtable<String, MimeEntry> extensionMap = new Hashtable<>();

    private MimeTable() {
        load();
    }

    private static final class DefaultInstanceHolder {
        private static final MimeTable defaultInstance = getDefaultInstance();

        private static MimeTable getDefaultInstance() {
            final MimeTable instance = new MimeTable();
            URLConnection.setFileNameMap(instance);
            return instance;
        }
    }

    /**
     * Get the single instance of this class.  First use will load the
     * table from a data file.
     */
    public static MimeTable getDefaultTable() {
        return DefaultInstanceHolder.defaultInstance;
    }

    public synchronized String getContentTypeFor(String fileName) {
        MimeEntry entry = findByFileName(fileName);
        if (entry != null) {
            return entry.getType();
        } else {
            return null;
        }
    }

    private void add(MimeEntry m) {
        String[] exts = m.getExtensions();
        if (exts == null) {
            return;
        }

        for (String ext : exts) {
            extensionMap.put(ext, m);
        }
    }

    /**
     * Extracts the file extension and uses it to look up the entry.
     */
    private MimeEntry findByFileExtension(String fname) {
        int i = fname.lastIndexOf('.');
        // REMIND: OS specific delimiters appear here
        i = Math.max(i, fname.lastIndexOf('/'));
        i = Math.max(i, fname.lastIndexOf('?'));

        String ext = "";
        if (i != -1 && fname.charAt(i) == '.') {
            ext = fname.substring(i).toLowerCase(Locale.ROOT);
        }

        return extensionMap.get(ext);

    }

    /**
     * Locate a MimeEntry by its associated file extension.
     * Parses general file names, and URLs.
     *
     * @param fname the file name
     *
     * @return the MIME entry associated with the file name or {@code null}
     */
    private MimeEntry findByFileName(String fname) {

        // If an optional fragment introduced by a hash mark is
        // present, then strip it and use the prefix
        int hashIndex = fname.lastIndexOf(HASH_MARK);
        if (hashIndex > 0) {
            MimeEntry entry = findByFileExtension(fname.substring(0, hashIndex));
            if (entry != null) {
                return entry;
            }
        }

        // If either no optional fragment was present, or the entry was not
        // found with the fragment stripped, then try again with the full name
        return findByFileExtension(fname);

    }

    private synchronized void load() {
        Properties entries = new Properties();
        File file;
        InputStream in;

        // First try to load the user-specific table, if it exists
        String userTablePath = System.getProperty("content.types.user.table");
        if (userTablePath != null && (file = new File(userTablePath)).exists()) {
            try {
                in = new FileInputStream(file);
            } catch (FileNotFoundException e) {
                System.err.println("Warning: " + file.getPath()
                                   + " mime table not found.");
                return;
            }
        } else {
            in = MimeTable.class.getResourceAsStream("content-types.properties");
            if (in == null)
                throw new InternalError("default mime table not found");
        }

        try (in) {
            entries.load(in);
        } catch (IOException e) {
            System.err.println("Warning: " + e.getMessage());
        }
        parse(entries);
    }

    private void parse(Properties entries) {
        // first, strip out the platform-specific temp file template
        String tempFileTemplate = (String)entries.get("temp.file.template");
        if (tempFileTemplate != null) {
            entries.remove("temp.file.template");
        }

        // now, parse the mime-type spec's
        Enumeration<?> types = entries.propertyNames();
        while (types.hasMoreElements()) {
            String type = (String)types.nextElement();
            String attrs = entries.getProperty(type);
            parse(type, attrs);
        }
    }

    //
    // Table format:
    //
    // <entry> ::= <table_tag> | <type_entry>
    //
    // <table_tag> ::= <table_format_version> | <temp_file_template>
    //
    // <type_entry> ::= <type_subtype_pair> '=' <type_attrs_list>
    //
    // <type_subtype_pair> ::= <type> '/' <subtype>
    //
    // <type_attrs_list> ::= <attr_value_pair> [ ';' <attr_value_pair> ]*
    //                       | [ <attr_value_pair> ]+
    //
    // <attr_value_pair> ::= <attr_name> '=' <attr_value>
    //
    // <attr_name> ::= 'description' | 'action' | 'application'
    //                 | 'file_extensions' | 'icon'
    //
    // <attr_value> ::= <legal_char>*
    //
    // Embedded ';' in an <attr_value> are quoted with leading '\' .
    //
    // Interpretation of <attr_value> depends on the <attr_name> it is
    // associated with.
    //

    private void parse(String type, String attrs) {
        MimeEntry newEntry = new MimeEntry(type);

        // REMIND handle embedded ';' and '|' and literal '"'
        StringTokenizer tokenizer = new StringTokenizer(attrs, ";");
        while (tokenizer.hasMoreTokens()) {
            String pair = tokenizer.nextToken();
            parse(pair, newEntry);
        }

        add(newEntry);
    }

    private static void parse(String pair, MimeEntry entry) {
        // REMIND add exception handling...
        String name = null;
        String value = null;

        boolean gotName = false;
        StringTokenizer tokenizer = new StringTokenizer(pair, "=");
        while (tokenizer.hasMoreTokens()) {
            if (gotName) {
                value = tokenizer.nextToken().trim();
            }
            else {
                name = tokenizer.nextToken().trim();
                gotName = true;
            }
        }

        fill(entry, name, value);
    }

    private static void fill(MimeEntry entry, String name, String value) {
        if ("description".equalsIgnoreCase(name)) {
            entry.setDescription(value);
        }
        else if ("action".equalsIgnoreCase(name)) {
            entry.setAction(getActionCode(value));
        }
        else if ("application".equalsIgnoreCase(name)) {
            entry.setCommand(value);
        }
        else if ("icon".equalsIgnoreCase(name)) {
            entry.setImageFileName(value);
        }
        else if ("file_extensions".equalsIgnoreCase(name)) {
            entry.setExtensions(value);
        }

        // else illegal name exception
    }

    private static int getActionCode(String action) {
        for (int i = 0; i < MimeEntry.actionKeywords.length; i++) {
            if (action.equalsIgnoreCase(MimeEntry.actionKeywords[i])) {
                return i;
            }
        }

        return MimeEntry.UNKNOWN;
    }

}