fixcrlffilter.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.tools.ant.filters;

import java.io.IOException;
import java.io.Reader;
import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.taskdefs.condition.Os;
import org.apache.tools.ant.types.EnumeratedAttribute;

/**
 * Converts text to local OS formatting conventions, as well as repair text
 * damaged by misconfigured or misguided editors or file transfer programs.
 * <p>
 * This filter can take the following arguments:
 * <ul>
 * <li>eof
 * <li>eol
 * <li>fixlast
 * <li>javafiles
 * <li>tab
 * <li>tablength
 * </ul>
 * None of which are required.
 * <p>
 * This version generalises the handling of EOL characters, and allows for
 * CR-only line endings (the standard on Mac systems prior to OS X). Tab
 * handling has also been generalised to accommodate any tabwidth from 2 to 80,
 * inclusive. Importantly, it can leave untouched any literal TAB characters
 * embedded within Java string or character constants.
 * <p>
 * <em>Caution:</em> run with care on carefully formatted files. This may
 * sound obvious, but if you don't specify asis, presume that your files are
 * going to be modified. If "tabs" is "add" or "remove", whitespace characters
 * may be added or removed as necessary. Similarly, for EOLs, eol="asis"
 * actually means convert to your native O/S EOL convention while eol="crlf" or
 * cr="add" can result in CR characters being removed in one special case
 * accommodated, i.e., CRCRLF is regarded as a single EOL to handle cases where
 * other programs have converted CRLF into CRCRLF.
 *
 * <P>
 * Example:
 *
 * <pre>
 * &lt;&lt;fixcrlf tab=&quot;add&quot; eol=&quot;crlf&quot; eof=&quot;asis&quot;/&gt;
 * </pre>
 *
 * Or:
 *
 * <pre>
 * &lt;filterreader classname=&quot;org.apache.tools.ant.filters.FixCrLfFilter&quot;&gt;
 *   &lt;param eol=&quot;crlf&quot; tab=&quot;asis&quot;/&gt;
 *  &lt;/filterreader&gt;
 * </pre>
 *
 */
public final class FixCrLfFilter extends BaseParamFilterReader implements ChainableReader {
    private static final int DEFAULT_TAB_LENGTH = 8;
    private static final int MIN_TAB_LENGTH = 2;
    private static final int MAX_TAB_LENGTH = 80;
    private static final char CTRLZ = '\u001A';

    private int tabLength = DEFAULT_TAB_LENGTH;

    private CrLf eol;

    private AddAsisRemove ctrlz;

    private AddAsisRemove tabs;

    private boolean javafiles = false;

    private boolean fixlast = true;

    private boolean initialized = false;

    /**
     * Constructor for "dummy" instances.
     *
     * @see BaseFilterReader#BaseFilterReader()
     */
    public FixCrLfFilter() {
        super();
    }

    /**
     * Create a new filtered reader.
     *
     * @param in
     *            A Reader object providing the underlying stream. Must not be
     *            <code>null</code>.
     * @throws IOException on error.
     */
    public FixCrLfFilter(final Reader in) throws IOException {
        super(in);
    }

    // Instance initializer: Executes just after the super() call in this
    // class's constructor.
    {
        tabs = AddAsisRemove.ASIS;
        if (Os.isFamily("mac") && !Os.isFamily("unix")) {
            ctrlz = AddAsisRemove.REMOVE;
            setEol(CrLf.MAC);
        } else if (Os.isFamily("dos")) {
            ctrlz = AddAsisRemove.ASIS;
            setEol(CrLf.DOS);
        } else {
            ctrlz = AddAsisRemove.REMOVE;
            setEol(CrLf.UNIX);
        }
    }

    /**
     * Create a new FixCrLfFilter using the passed in Reader for instantiation.
     *
     * @param rdr
     *            A Reader object providing the underlying stream. Must not be
     *            <code>null</code>.
     *
     * @return a new filter based on this configuration, but filtering the
     *         specified reader.
     */
    public Reader chain(final Reader rdr) {
        try {
            FixCrLfFilter newFilter = new FixCrLfFilter(rdr);

            newFilter.setJavafiles(getJavafiles());
            newFilter.setEol(getEol());
            newFilter.setTab(getTab());
            newFilter.setTablength(getTablength());
            newFilter.setEof(getEof());
            newFilter.setFixlast(getFixlast());
            newFilter.initInternalFilters();

            return newFilter;
        } catch (IOException e) {
            throw new BuildException(e);
        }
    }

    /**
     * Get how DOS EOF (control-z) characters are being handled.
     *
     * @return values:
     *         <ul>
     *         <li>add: ensure that there is an eof at the end of the file
     *         <li>asis: leave eof characters alone
     *         <li>remove: remove any eof character found at the end
     *         </ul>
     */
    public AddAsisRemove getEof() {
        // Return copy so that the call must call setEof() to change the state
        // of fixCRLF
        return ctrlz.newInstance();
    }

    /**
     * Get how EndOfLine characters are being handled.
     *
     * @return values:
     *         <ul>
     *         <li>asis: convert line endings to your O/S convention
     *         <li>cr: convert line endings to CR
     *         <li>lf: convert line endings to LF
     *         <li>crlf: convert line endings to CRLF
     *         </ul>
     */
    public CrLf getEol() {
        // Return copy so that the call must call setEol() to change the state
        // of fixCRLF
        return eol.newInstance();
    }

    /**
     * Get whether a missing EOL be added to the final line of the stream.
     *
     * @return true if a filtered file will always end with an EOL
     */
    public boolean getFixlast() {
        return fixlast;
    }

    /**
     * Get whether the stream is to be treated as though it contains Java
     * source.
     * <P>
     * This attribute is only used in assocation with the &quot;<i><b>tab</b></i>&quot;
     * attribute. Tabs found in Java literals are protected from changes by this
     * filter.
     *
     * @return true if whitespace in Java character and string literals is
     *         ignored.
     */
    public boolean getJavafiles() {
        return javafiles;
    }

    /**
     * Return how tab characters are being handled.
     *
     * @return values:
     *         <ul>
     *         <li>add: convert sequences of spaces which span a tab stop to
     *         tabs
     *         <li>asis: leave tab and space characters alone
     *         <li>remove: convert tabs to spaces
     *         </ul>
     */
    public AddAsisRemove getTab() {
        // Return copy so that the caller must call setTab() to change the state
        // of fixCRLF.
        return tabs.newInstance();
    }

    /**
     * Get the tab length to use.
     *
     * @return the length of tab in spaces
     */
    public int getTablength() {
        return tabLength;
    }

    private static String calculateEolString(CrLf eol) {
        // Calculate the EOL string per the current config
        if (eol == CrLf.ASIS) {
            return System.getProperty("line.separator");
        }
        if (eol == CrLf.CR || eol == CrLf.MAC) {
            return "\r";
        }
        if (eol == CrLf.CRLF || eol == CrLf.DOS) {
            return "\r\n";
        }
        // assume (eol == CrLf.LF || eol == CrLf.UNIX)
        return "\n";
    }

    /**
     * Wrap the input stream with the internal filters necessary to perform the
     * configuration settings.
     */
    private void initInternalFilters() {

        // If I'm removing an EOF character, do so first so that the other
        // filters don't see that character.
        in = (ctrlz == AddAsisRemove.REMOVE) ? new RemoveEofFilter(in) : in;

        // Change all EOL characters to match the calculated EOL string. If
        // configured to do so, append a trailing EOL so that the file ends on
        // a EOL.
        in = new NormalizeEolFilter(in, calculateEolString(eol), getFixlast());

        if (tabs != AddAsisRemove.ASIS) {
            // If filtering Java source, prevent changes to whitespace in
            // character and string literals.
            if (getJavafiles()) {
                in = new MaskJavaTabLiteralsFilter(in);
            }
            // Add/Remove tabs
            in = (tabs == AddAsisRemove.ADD) ? (Reader) new AddTabFilter(in, getTablength())
                    : (Reader) new RemoveTabFilter(in, getTablength());
        }
        // Add missing EOF character
        in = (ctrlz == AddAsisRemove.ADD) ? new AddEofFilter(in) : in;
        initialized = true;
    }

    /**
     * Return the next character in the filtered stream.
     *
     * @return the next character in the resulting stream, or -1 if the end of
     *         the resulting stream has been reached.
     *
     * @exception IOException
     *                if the underlying stream throws an IOException during
     *                reading.
     */
    public synchronized int read() throws IOException {
        if (!initialized) {
            initInternalFilters();
        }
        return in.read();
    }

    /**
     * Specify how DOS EOF (control-z) characters are to be handled.
     *
     * @param attr
     *            valid values:
     *            <ul>
     *            <li>add: ensure that there is an eof at the end of the file
     *            <li>asis: leave eof characters alone
     *            <li>remove: remove any eof character found at the end
     *            </ul>
     */
    public void setEof(AddAsisRemove attr) {
        ctrlz = attr.resolve();
    }

    /**
     * Specify how end of line (EOL) characters are to be handled.
     *
     * @param attr
     *            valid values:
     *            <ul>
     *            <li>asis: convert line endings to your O/S convention
     *            <li>cr: convert line endings to CR
     *            <li>lf: convert line endings to LF
     *            <li>crlf: convert line endings to CRLF
     *            </ul>
     */
    public void setEol(CrLf attr) {
        eol = attr.resolve();
    }

    /**
     * Specify whether a missing EOL will be added to the final line of input.
     *
     * @param fixlast
     *            if true a missing EOL will be appended.