content: package org.apache.lucene.index;
  
  import java.util.regex.Pattern;
  
  /**
   * 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.
   */
  
  /**
   * This class contains useful constants representing filenames and extensions
   * used by lucene, as well as convenience methods for querying whether a file
   * name matches an extension ({@link #matchesExtension(String, String)
   * matchesExtension}), as well as generating file names from a segment name,
   * generation and extension (
   * {@link #fileNameFromGeneration(String, String, long) fileNameFromGeneration},
   * {@link #segmentFileName(String, String) segmentFileName}).
   * 
   * @lucene.internal
   */
  public final class IndexFileNames {
  
    /** Name of the index segment file */
    public static final String SEGMENTS = "segments";
    
    public static final String SEGMENTS_CHECKSUM = "yn_segments_crc";
  
    /** Name of the generation reference file name */
    public static final String SEGMENTS_GEN = "segments.gen";
    
    /** Name of the index deletable file (only used in
     * pre-lockless indices) */
    public static final String DELETABLE = "deletable";
     
    /** Extension of norms file */
    public static final String NORMS_EXTENSION = "nrm";
  
    /** Extension of freq postings file */
    public static final String FREQ_EXTENSION = "frq";
  
    /** Extension of prox postings file */
    public static final String PROX_EXTENSION = "prx";
  
    /** Extension of terms file */
    public static final String TERMS_EXTENSION = "tis";
  
    /** Extension of terms index file */
    public static final String TERMS_INDEX_EXTENSION = "tii";
    
    
    /** Extension of terms file */
    public static final String TERMS_EXTENSION_SIZE = "yntis";
  
    /** Extension of terms index file */
    public static final String TERMS_INDEX_EXTENSION_SIZE = "yntii";
    
    public static final String TERMS_INDEX_EXTENSION_QUICK = "quicktii";
    public static final String TERMS_EXTENSION_QUICK_OLD = "quicktis";
    public static final String TERMS_EXTENSION_QUICK = "doctotm";
    public static final String TERMS_EXTENSION_QUICK_TXT = "tmtorealval";
    public static final String TERMS_EXTENSION_QUICK_VAL = "tmtonumval";
  
  
    /** Extension of stored fields index file */
    public static final String FIELDS_INDEX_EXTENSION = "fdx";
  
    /** Extension of stored fields file */
    public static final String FIELDS_EXTENSION = "fdt";
  
    /** Extension of vectors fields file */
    public static final String VECTORS_FIELDS_EXTENSION = "tvf";
  
    /** Extension of vectors documents file */
    public static final String VECTORS_DOCUMENTS_EXTENSION = "tvd";
  
    /** Extension of vectors index file */
    public static final String VECTORS_INDEX_EXTENSION = "tvx";
  
    /** Extension of compound file */
    public static final String COMPOUND_FILE_EXTENSION = "cfs";
    
    public static final String COMPOUND_FILE_EXTENSION_POS = "yncfs";
  
    /** Extension of compound file for doc store files*/
    public static final String COMPOUND_FILE_STORE_EXTENSION = "cfx";
    
    public static final String COMPOUND_FILE_STORE_EXTENSION_POS = "yncfx";
  
  
    /** Extension of deletes */
    public static final String DELETES_EXTENSION = "del";
  
    /** Extension of field infos */
    public static final String FIELD_INFOS_EXTENSION = "fnm";
  
    /** Extension of plain norms */
    public static final String PLAIN_NORMS_EXTENSION = "f";
  
    /** Extension of separate norms */
    public static final String SEPARATE_NORMS_EXTENSION = "s";
  
    /** Extension of gen file */
    public static final String GEN_EXTENSION = "gen";
  
    /**
     * This array contains all filename extensions used by
     * Lucene's index files, with two exceptions, namely the
     * extension made up from <code>.f</code> + a number and
     * from <code>.s</code> + a number.  Also note that
     * Lucene's <code>segments_N</code> files do not have any
     * filename extension.
     */
    public static final String INDEX_EXTENSIONS[] = new String[] {
      COMPOUND_FILE_EXTENSION,
      COMPOUND_FILE_EXTENSION_POS,
      FIELD_INFOS_EXTENSION,
      FIELDS_INDEX_EXTENSION,
      FIELDS_EXTENSION,
      TERMS_INDEX_EXTENSION,
      TERMS_INDEX_EXTENSION_QUICK,
      TERMS_INDEX_EXTENSION_SIZE,
      TERMS_EXTENSION,
      TERMS_EXTENSION_QUICK_OLD,
      TERMS_EXTENSION_QUICK,
      TERMS_EXTENSION_QUICK_TXT,
      TERMS_EXTENSION_QUICK_VAL,
      TERMS_EXTENSION_SIZE,
      FREQ_EXTENSION,
      PROX_EXTENSION,
      DELETES_EXTENSION,
      VECTORS_INDEX_EXTENSION,
      VECTORS_DOCUMENTS_EXTENSION,
      VECTORS_FIELDS_EXTENSION,
      GEN_EXTENSION,
      NORMS_EXTENSION,
      COMPOUND_FILE_STORE_EXTENSION,
      COMPOUND_FILE_STORE_EXTENSION_POS
    };
  
    /** File extensions that are added to a compound file
     * (same as above, minus "del", "gen", "cfs"). */
    public static final String[] INDEX_EXTENSIONS_IN_COMPOUND_FILE = new String[] {
      FIELD_INFOS_EXTENSION,
      FIELDS_INDEX_EXTENSION,
      FIELDS_EXTENSION,
      TERMS_INDEX_EXTENSION,
      TERMS_INDEX_EXTENSION_QUICK,
      TERMS_INDEX_EXTENSION_SIZE,
      TERMS_EXTENSION,
      TERMS_INDEX_EXTENSION_QUICK,
      TERMS_EXTENSION_QUICK_OLD,
      TERMS_EXTENSION_QUICK,
      TERMS_EXTENSION_QUICK_TXT,
      TERMS_EXTENSION_QUICK_VAL,
      TERMS_EXTENSION_SIZE,
      FREQ_EXTENSION,
      PROX_EXTENSION,
      VECTORS_INDEX_EXTENSION,
      VECTORS_DOCUMENTS_EXTENSION,
      VECTORS_FIELDS_EXTENSION,
      NORMS_EXTENSION
    };
  
    public static final String[] STORE_INDEX_EXTENSIONS = new String[] {
      VECTORS_INDEX_EXTENSION,
      VECTORS_FIELDS_EXTENSION,
      VECTORS_DOCUMENTS_EXTENSION,
      FIELDS_INDEX_EXTENSION,
      FIELDS_EXTENSION
    };
  
    public static final String[] NON_STORE_INDEX_EXTENSIONS = new String[] {
      FIELD_INFOS_EXTENSION,
      FREQ_EXTENSION,
      PROX_EXTENSION,
      TERMS_EXTENSION,
      TERMS_EXTENSION_QUICK_OLD,
      TERMS_EXTENSION_QUICK,
      TERMS_EXTENSION_QUICK_TXT,
      TERMS_EXTENSION_QUICK_VAL,
      TERMS_EXTENSION_SIZE,
      TERMS_INDEX_EXTENSION,
      TERMS_INDEX_EXTENSION_QUICK,
      TERMS_INDEX_EXTENSION_SIZE,
      NORMS_EXTENSION
    };
    
    /** File extensions of old-style index files */
    public static final String COMPOUND_EXTENSIONS[] = new String[] {
      FIELD_INFOS_EXTENSION,
      FREQ_EXTENSION,
      PROX_EXTENSION,
      FIELDS_INDEX_EXTENSION,
      FIELDS_EXTENSION,
      TERMS_INDEX_EXTENSION,
      TERMS_INDEX_EXTENSION_QUICK,
      TERMS_INDEX_EXTENSION_SIZE,
      TERMS_EXTENSION,
      TERMS_EXTENSION_SIZE
    };
    
    /** File extensions for term vector support */
    public static final String VECTOR_EXTENSIONS[] = new String[] {
      VECTORS_INDEX_EXTENSION,
      VECTORS_DOCUMENTS_EXTENSION,
      VECTORS_FIELDS_EXTENSION
    };
  
    /**
     * Computes the full file name from base, extension and generation. If the
     * generation is -1, the file name is null. If it's 0, the file name is
     * &lt;base&gt;.&lt;ext&gt;. If it's > 0, the file name is
     * &lt;base&gt;_&lt;gen&gt;.&lt;ext&gt;.<br>
     * <b>NOTE:</b> .&lt;ext&gt; is added to the name only if <code>ext</code> is
     * not an empty string.
     * 
     * @param base main part of the file name
     * @param ext extension of the filename
     * @param gen generation
     */
    public static final String fileNameFromGeneration(String base, String ext, long gen) {
      if (gen == SegmentInfo.NO) {
        return null;
      } else if (gen == SegmentInfo.WITHOUT_GEN) {
        return segmentFileName(base, ext);
      } else {
        // The '6' part in the length is: 1 for '.', 1 for '_' and 4 as estimate
        // to the gen length as string (hopefully an upper limit so SB won't
        // expand in the middle.
        StringBuilder res = new StringBuilder(base.length() + 6 + ext.length())
            .append(base).append('_').append(Long.toString(gen, Character.MAX_RADIX));
        if (ext.length() > 0) {
          res.append('.').append(ext);
        }
        return res.toString();
      }
    }
  
    /**
     * Returns true if the provided filename is one of the doc store files (ends
     * with an extension in {@link #STORE_INDEX_EXTENSIONS}).
     */
    public static final boolean isDocStoreFile(String fileName) {
      if (fileName.endsWith(COMPOUND_FILE_STORE_EXTENSION))
        return true;
      for (String ext : STORE_INDEX_EXTENSIONS) {
        if (fileName.endsWith(ext))
          return true;
      }
      return false;
    }
  
    /**
     * Returns the file name that matches the given segment name and extension.
     * This method takes care to return the full file name in the form
     * &lt;segmentName&gt;.&lt;ext&gt;, therefore you don't need to prefix the
     * extension with a '.'.<br>
     * <b>NOTE:</b> .&lt;ext&gt; is added to the result file name only if
     * <code>ext</code> is not empty.
     */
    public static final String segmentFileName(String segmentName, String ext) {
      if (ext.length() > 0) {
        return new StringBuilder(segmentName.length() + 1 + ext.length()).append(
            segmentName).append('.').append(ext).toString();
      } else {
        return segmentName;
      }
    }
    
    /**
     * Returns true if the given filename ends with the given extension. One
     * should provide a <i>pure</i> extension, without '.'.
     */
    public static final boolean matchesExtension(String filename, String ext) {
      // It doesn't make a difference whether we allocate a StringBuilder ourself
      // or not, since there's only 1 '+' operator.
      return filename.endsWith("." + ext);
    }
  
    /**
     * Strips the segment file name out of the given one. If you used
     * {@link #segmentFileName} or {@link #fileNameFromGeneration} to create your
     * files, then this method simply removes whatever comes before the first '.',
     * or the second '_' (excluding both), in case of deleted docs.
     * 
     * @return the filename with the segment name removed, or the given filename
     *         if it does not contain a '.' and '_'.
     */
    public static final String stripSegmentName(String filename) {
      // If it is a .del file, there's an '_' after the first character
      int idx = filename.indexOf('_', 1);
      if (idx == -1) {
        // If it's not, strip everything that's before the '.'
        idx = filename.indexOf('.');
      }
      if (idx != -1) {
        filename = filename.substring(idx);
      }
      return filename;
    }
  
    /**
     * Returns true if the given filename ends with the separate norms file
     * pattern: {@code SEPARATE_NORMS_EXTENSION + "[0-9]+"}.
     */
    public static boolean isSeparateNormsFile(String filename) {
      int idx = filename.lastIndexOf('.');
      if (idx == -1) return false;
      String ext = filename.substring(idx + 1);
      return Pattern.matches(SEPARATE_NORMS_EXTENSION + "[0-9]+", ext);
    }
  
  }
  