framework/src/main/java/org/apache/felix/framework/FindEntriesEnumeration.java

/* 
 * 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.felix.framework;

import java.util.*;

class FindEntriesEnumeration implements Enumeration
{
    private FelixBundle m_bundle = null;
    private Enumeration m_enumeration = null;
    private String m_path = null;
    private String[] m_filePattern = null;
    private boolean m_recurse = false;
    private Object m_next = null;

    public FindEntriesEnumeration(
        FelixBundle bundle, String path, String filePattern, boolean recurse)
    {
        m_bundle = bundle;
        m_path = path;
        m_enumeration = (m_bundle.getInfo().getCurrentModule().getContentLoader().getContent() == null)
            ? null : m_bundle.getInfo().getCurrentModule().getContentLoader().getContent().getEntries();
        m_recurse = recurse;

        // Sanity check the parameters.
        if (m_path == null)
        {
            throw new IllegalArgumentException("The path for findEntries() cannot be null.");
        }
        // Strip leading '/' if present.
        if ((m_path.length() > 0) && (m_path.charAt(0) == '/'))
        {
            m_path = m_path.substring(1);
        }
        // Add a '/' to the end if not present.
        if ((m_path.length() > 0) && (m_path.charAt(m_path.length() - 1) != '/'))
        {
            m_path = m_path + "/";
        }

        // File pattern defaults to "*" if not specified.
        filePattern = (filePattern == null) ? "*" : filePattern;

        m_filePattern = parseSubstring(filePattern);

        m_next = findNext();
    }

    public boolean hasMoreElements()
    {
        return (m_next != null);
    }

    public Object nextElement()
    {
        if (m_next == null)
        {
            throw new NoSuchElementException("No more entry paths.");
        }
        Object last = m_next;
        m_next = findNext();
        return last;
    }

    private Object findNext()
    {
        // This method filters the content entry enumeration, such that
        // it only displays the contents of the directory specified by
        // the path argument either recursively or not; much like using
        // "ls -R" or "ls" to list the contents of a directory, respectively.
        while ((m_enumeration != null) && m_enumeration.hasMoreElements())
        {
            // Get the next entry name.
            String entryName = (String) m_enumeration.nextElement();
            // Check to see if it is a descendent of the specified path.
            if (!entryName.equals(m_path) && entryName.startsWith(m_path))
            {
                // If this is recursive search, then try to match any
                // entry path that starts with the specified path;
                // otherwise, only try to match children of the specified
                // path and not any grandchild. This code uses the knowledge
                // that content entries corresponding to directories end in '/'.
                int idx = entryName.indexOf('/', m_path.length());
                if (m_recurse || (idx < 0) || (idx == (entryName.length() - 1)))
                {
                    // Get the last element of the entry path, not including
                    // the '/' if it is a directory.
                    int endIdx = (entryName.charAt(entryName.length() - 1) == '/')
                        ? entryName.length() - 1
                        : entryName.length();
                    int startIdx = (entryName.charAt(entryName.length() - 1) == '/')
                        ? entryName.lastIndexOf('/', endIdx - 1) + 1
                        : entryName.lastIndexOf('/', endIdx) + 1;
                    String lastElement = entryName.substring(startIdx, endIdx);
                    
                    // See if the file pattern matches the last element of the path.
                    if (checkSubstring(m_filePattern, lastElement))
                    {
                        // Convert entry name into an entry URL.
                        return m_bundle.getInfo().getCurrentModule()
                            .getContentLoader().getResourceFromContent(entryName);
                    }
                }
            }
        }

        return null;
    }

    //
    // The following substring-related code was lifted and modified
    // from the LDAP parser code.
    //

    private static String[] parseSubstring(String target)
    {
        List pieces = new ArrayList();
        StringBuffer ss = new StringBuffer();
        // int kind = SIMPLE; // assume until proven otherwise
        boolean wasStar = false; // indicates last piece was a star
        boolean leftstar = false; // track if the initial piece is a star
        boolean rightstar = false; // track if the final piece is a star

        int idx = 0;

        // We assume (sub)strings can contain leading and trailing blanks
        for (;;)
        {
            if (idx >= target.length())
            {
                if (wasStar)
                {
                    // insert last piece as "" to handle trailing star
                    rightstar = true;
                }
                else
                {
                    pieces.add(ss.toString());
                    // accumulate the last piece
                    // note that in the case of
                    // (cn=); this might be
                    // the string "" (!=null)
                }
                ss.setLength(0);
                break;
            }
    
            char c = target.charAt(idx++);
            if (c == '*')
            {
                if (wasStar)
                {
                    // encountered two successive stars;
                    // I assume this is illegal
                    throw new IllegalArgumentException("Invalid filter string: " + target);
                }
                if (ss.length() > 0)
                {
                    pieces.add(ss.toString()); // accumulate the pieces
                    // between '*' occurrences
                }
                ss.setLength(0);
                // if this is a leading star, then track it
                if (pieces.size() == 0)
                {
                    leftstar = true;
                }
                ss.setLength(0);
                wasStar = true;
            }
            else
            {
                wasStar = false;
                ss.append(c);
            }
        }
        if (leftstar || rightstar || pieces.size() > 1)
        {
            // insert leading and/or trailing "" to anchor ends
            if (rightstar)
            {
                pieces.add("");
            }
            if (leftstar)
            {
                pieces.add(0, "");
            }
        }

        return (String[]) pieces.toArray(new String[pieces.size()]);
    }

    private static boolean checkSubstring(String[] pieces, String s)
    {
        // Walk the pieces to match the string
        // There are implicit stars between each piece,
        // and the first and last pieces might be "" to anchor the match.
        // assert (pieces.length > 1)
        // minimal case is <string>*<string>

        boolean result = false;
        int len = pieces.length;
        int index = 0;

        for (int i = 0; i < len; i++)
        {
            String piece = (String) pieces[i];
            if (i == len - 1)
            {
                // this is the last piece
                if (s.endsWith(piece))
                {
                    result = true;
                }
                else
                {
                    result = false;
                }
                break;
            }
            // initial non-star; assert index == 0
            else if (i == 0)
            {
                if (!s.startsWith(piece))
                {
                    result = false;
                    break;
                }
            }
            // assert i > 0 && i < len-1
            else
            {
                // Sure wish stringbuffer supported e.g. indexOf
                index = s.indexOf(piece, index);
                if (index < 0)
                {
                    result = false;
                    break;
                }
            }
            // start beyond the matching piece
            index += piece.length();
        }

        return result;
    }
}