content: package org.apache.lucene.index;
  
  /**
   * 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.
   */
  
  import org.apache.lucene.store.Directory;
  import org.apache.lucene.store.IndexOutput;
  import org.apache.lucene.store.IndexInput;
  import org.apache.lucene.util.BitVector;
  import org.apache.lucene.util.Constants;
  
  import java.io.IOException;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.HashMap;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Set;
  
  /**
   * Information about a segment such as it's name, directory, and files related
   * to the segment.
   * 
   * @lucene.experimental
   */
  public final class SegmentInfo implements Cloneable {
  
    static final int NO = -1;          // e.g. no norms; no deletes;
    static final int YES = 1;          // e.g. have norms; have deletes;
    static final int CHECK_DIR = 0;    // e.g. must check dir to see if there are norms/deletions
    static final int WITHOUT_GEN = 0;  // a file name that has no GEN in it. 
  
    public String name;				  // unique name in dir
    public int docCount;				  // number of docs in seg
    public Directory dir;				  // where segment resides
  
    private boolean preLockless;                    // true if this is a segments file written before
                                                    // lock-less commits (2.1)
  
    private long delGen;                            // current generation of del file; NO if there
                                                    // are no deletes; CHECK_DIR if it's a pre-2.1 segment
                                                    // (and we must check filesystem); YES or higher if
                                                    // there are deletes at generation N
     
    private long[] normGen;                         // current generation of each field's norm file.
                                                    // If this array is null, for lockLess this means no 
                                                    // separate norms.  For preLockLess this means we must 
                                                    // check filesystem. If this array is not null, its 
                                                    // values mean: NO says this field has no separate  
                                                    // norms; CHECK_DIR says it is a preLockLess segment and    
                                                    // filesystem must be checked; >= YES says this field  
                                                    // has separate norms with the specified generation
  
    private byte isCompoundFile;                    // NO if it is not; YES if it is; CHECK_DIR if it's
                                                    // pre-2.1 (ie, must check file system to see
                                                    // if <name>.cfs and <name>.nrm exist)         
  
    private boolean hasSingleNormFile;              // true if this segment maintains norms in a single file; 
                                                    // false otherwise
                                                    // this is currently false for segments populated by DocumentWriter
                                                    // and true for newly created merged segments (both
                                                    // compound and non compound).
    
    private volatile List<String> files;            // cached list of files that this segment uses
                                                    // in the Directory
  
    private volatile long sizeInBytesNoStore = -1;           // total byte size of all but the store files (computed on demand)
    private volatile long sizeInBytesWithStore = -1;         // total byte size of all of our files (computed on demand)
  
    private int docStoreOffset;                     // if this segment shares stored fields & vectors, this
                                                    // offset is where in that file this segment's docs begin
    private String docStoreSegment;                 // name used to derive fields/vectors file we share with
                                                    // other segments
    private boolean docStoreIsCompoundFile;         // whether doc store files are stored in compound file (*.cfx)
  
    private int delCount;                           // How many deleted docs in this segment, or -1 if not yet known
                                                    // (if it's an older index)
  
    private boolean hasProx;                        // True if this segment has any fields with omitTermFreqAndPositions==false
  
    private boolean hasVectors;                     // True if this segment wrote term vectors
  
    private Map<String,String> diagnostics;
  
    // Tracks the Lucene version this segment was created with, since 3.1. The
    // format expected is "x.y" - "2.x" for pre-3.0 indexes, and specific versions
    // afterwards ("3.0", "3.1" etc.).
    // see Constants.LUCENE_MAIN_VERSION.
    private String version;
  
    // NOTE: only used in-RAM by IW to track buffered deletes;
    // this is never written to/read from the Directory
    private long bufferedDeletesGen;
    
    public SegmentInfo(String name, int docCount, Directory dir, boolean isCompoundFile, boolean hasSingleNormFile,
                       boolean hasProx, boolean hasVectors) { 
      this.name = name;
      this.docCount = docCount;
      this.dir = dir;
      delGen = NO;
      this.isCompoundFile = (byte) (isCompoundFile ? YES : NO);
      preLockless = false;
      this.hasSingleNormFile = hasSingleNormFile;
      this.docStoreOffset = -1;
      delCount = 0;
      this.hasProx = hasProx;
      this.hasVectors = hasVectors;
      this.version = Constants.LUCENE_MAIN_VERSION;
    }
  
    /**
     * Copy everything from src SegmentInfo into our instance.
     */
    void reset(SegmentInfo src) {
      clearFiles();
      version = src.version;
      name = src.name;
      docCount = src.docCount;
      dir = src.dir;
      preLockless = src.preLockless;
      delGen = src.delGen;
      docStoreOffset = src.docStoreOffset;
      docStoreIsCompoundFile = src.docStoreIsCompoundFile;
      hasVectors = src.hasVectors;
      hasProx = src.hasProx;
      if (src.normGen == null) {
        normGen = null;
      } else {
        normGen = new long[src.normGen.length];
        System.arraycopy(src.normGen, 0, normGen, 0, src.normGen.length);
      }
      isCompoundFile = src.isCompoundFile;
      hasSingleNormFile = src.hasSingleNormFile;
      delCount = src.delCount;
    }
  
    void setDiagnostics(Map<String, String> diagnostics) {
      this.diagnostics = diagnostics;
    }
  
    public Map<String, String> getDiagnostics() {
      return diagnostics;
    }
  
    /**
     * Construct a new SegmentInfo instance by reading a
     * previously saved SegmentInfo from input.
     *
     * @param dir directory to load from
     * @param format format of the segments info file
     * @param input input handle to read segment info from
     */
    SegmentInfo(Directory dir, int format, IndexInput input) throws IOException {
      this.dir = dir;
      if (format <= SegmentInfos.FORMAT_3_1) {
        version = input.readString();
      }
      name = input.readString();
      docCount = input.readInt();
      if (format <= SegmentInfos.FORMAT_LOCKLESS) {
        delGen = input.readLong();
        if (format <= SegmentInfos.FORMAT_SHARED_DOC_STORE) {
          docStoreOffset = input.readInt();
          if (docStoreOffset != -1) {
            docStoreSegment = input.readString();
            docStoreIsCompoundFile = (1 == input.readByte());
          } else {
            docStoreSegment = name;
            docStoreIsCompoundFile = false;
          }
        } else {
          docStoreOffset = -1;
          docStoreSegment = name;
          docStoreIsCompoundFile = false;
        }
        if (format <= SegmentInfos.FORMAT_SINGLE_NORM_FILE) {
          hasSingleNormFile = (1 == input.readByte());
        } else {
          hasSingleNormFile = false;
        }
        int numNormGen = input.readInt();
        if (numNormGen == NO) {
          normGen = null;
        } else {
          normGen = new long[numNormGen];
          for(int j=0;j<numNormGen;j++) {
            normGen[j] = input.readLong();
          }
        }
        isCompoundFile = input.readByte();
        preLockless = (isCompoundFile == CHECK_DIR);
        if (format <= SegmentInfos.FORMAT_DEL_COUNT) {
          delCount = input.readInt();
          assert delCount <= docCount;
        } else
          delCount = -1;
        if (format <= SegmentInfos.FORMAT_HAS_PROX)
          hasProx = input.readByte() == 1;
        else
          hasProx = true;
  
        if (format <= SegmentInfos.FORMAT_DIAGNOSTICS) {
          diagnostics = input.readStringStringMap();
        } else {
          diagnostics = Collections.<String,String>emptyMap();
        }
  
        if (format <= SegmentInfos.FORMAT_HAS_VECTORS) {
          hasVectors = input.readByte() == 1;
        } else {
          final String storesSegment;
          final String ext;
          final String extpos;
          final boolean isCompoundFile;
          if (docStoreOffset != -1) {
            storesSegment = docStoreSegment;
            isCompoundFile = docStoreIsCompoundFile;
            ext = IndexFileNames.COMPOUND_FILE_STORE_EXTENSION;
            extpos=IndexFileNames.COMPOUND_FILE_STORE_EXTENSION_POS;
          } else {
            storesSegment = name;
            isCompoundFile = getUseCompoundFile();
            ext = IndexFileNames.COMPOUND_FILE_EXTENSION;
            extpos=IndexFileNames.COMPOUND_FILE_EXTENSION_POS;
          }
          final Directory dirToTest;
          if (isCompoundFile) {
            dirToTest = new CompoundFileReader(dir, IndexFileNames.segmentFileName(storesSegment, ext), IndexFileNames.segmentFileName(storesSegment, extpos));
          } else {
            dirToTest = dir;
          }
          try {
            hasVectors = dirToTest.fileExists(IndexFileNames.segmentFileName(storesSegment, IndexFileNames.VECTORS_INDEX_EXTENSION));
          } finally {
            if (isCompoundFile) {
              dirToTest.close();
            }
          }
        }
      } else {
        delGen = CHECK_DIR;
        normGen = null;
        isCompoundFile = CHECK_DIR;
        preLockless = true;
        hasSingleNormFile = false;
        docStoreOffset = -1;
        docStoreIsCompoundFile = false;
        docStoreSegment = null;
        delCount = -1;
        hasProx = true;
        diagnostics = Collections.<String,String>emptyMap();
      }
    }
    
    void setNumFields(int numFields) {
      if (normGen == null) {
        // normGen is null if we loaded a pre-2.1 segment
        // file, or, if this segments file hasn't had any
        // norms set against it yet:
        normGen = new long[numFields];
  
        if (preLockless) {
          // Do nothing: thus leaving normGen[k]==CHECK_DIR (==0), so that later we know  
          // we have to check filesystem for norm files, because this is prelockless.
          
        } else {
          // This is a FORMAT_LOCKLESS segment, which means
          // there are no separate norms:
          for(int i=0;i<numFields;i++) {
            normGen[i] = NO;
          }
        }
      }
    }
  
    /**
     * Returns total size in bytes of all of files used by this segment (if
     * {@code includeDocStores} is true), or the size of all files except the store
     * files otherwise.
     */
    public long sizeInBytes(boolean includeDocStores) throws IOException {
      if (includeDocStores) {
        if (sizeInBytesWithStore != -1) {
          return sizeInBytesWithStore;
        }
        long sum = 0;
        for (final String fileName : files()) {
          // We don't count bytes used by a shared doc store
          // against this segment
          if (docStoreOffset == -1 || !IndexFileNames.isDocStoreFile(fileName)) {
            sum += dir.fileLength(fileName);
          }
        }
        sizeInBytesWithStore = sum;
        return sizeInBytesWithStore;
      } else {
        if (sizeInBytesNoStore != -1) {
          return sizeInBytesNoStore;
        }
        long sum = 0;
        for (final String fileName : files()) {
          if (IndexFileNames.isDocStoreFile(fileName)) {
            continue;
          }
          sum += dir.fileLength(fileName);
        }
        sizeInBytesNoStore = sum;
        return sizeInBytesNoStore;
      }
    }
  
    public boolean getHasVectors() throws IOException {
      return hasVectors;
    }
  
    public void setHasVectors(boolean v) {
      hasVectors = v;
      clearFiles();
    }
  
    public boolean hasDeletions()
      throws IOException {
      // Cases:
      //
      //   delGen == NO: this means this segment was written
      //     by the LOCKLESS code and for certain does not have
      //     deletions yet
      //
      //   delGen == CHECK_DIR: this means this segment was written by
      //     pre-LOCKLESS code which means we must check
      //     directory to see if .del file exists
      //
      //   delGen >= YES: this means this segment was written by
      //     the LOCKLESS code and for certain has
      //     deletions
      //
      if (delGen == NO) {
        return false;
      } else if (delGen >= YES) {
        return true;
      } else {
        return dir.fileExists(getDelFileName());
      }
    }
  
    void advanceDelGen() {
      // delGen 0 is reserved for pre-LOCKLESS format
      if (delGen == NO) {
        delGen = YES;
      } else {
        delGen++;
      }
      clearFiles();
    }
  
    void clearDelGen() {
      delGen = NO;
      clearFiles();
    }
  
    @Override
    public Object clone() {
      SegmentInfo si = new SegmentInfo(name, docCount, dir, false, hasSingleNormFile,
                                       hasProx, hasVectors);
      si.docStoreOffset = docStoreOffset;
      si.docStoreSegment = docStoreSegment;
      si.docStoreIsCompoundFile = docStoreIsCompoundFile;
      si.delGen = delGen;
      si.delCount = delCount;
      si.preLockless = preLockless;
      si.isCompoundFile = isCompoundFile;
      si.diagnostics = new HashMap<String, String>(diagnostics);
      if (normGen != null) {
        si.normGen = normGen.clone();
      }
      si.version = version;
      return si;
    }
  
    public String getDelFileName() {
      if (delGen == NO) {
        // In this case we know there is no deletion filename
        // against this segment
        return null;
      } else {
        // If delGen is CHECK_DIR, it's the pre-lockless-commit file format
        return IndexFileNames.fileNameFromGeneration(name, IndexFileNames.DELETES_EXTENSION, delGen); 
      }
    }
  
    /**
     * Returns true if this field for this segment has saved a separate norms file (_<segment>_N.sX).
     *
     * @param fieldNumber the field index to check
     */
    public boolean hasSeparateNorms(int fieldNumber)
      throws IOException {
      if ((normGen == null && preLockless) || (normGen != null && normGen[fieldNumber] == CHECK_DIR)) {
        // Must fallback to directory file exists check:
        String fileName = name + ".s" + fieldNumber;
        return dir.fileExists(fileName);
      } else if (normGen == null || normGen[fieldNumber] == NO) {
        return false;
      } else {
        return true;
      }
    }
  
    /**
     * Returns true if any fields in this segment have separate norms.
     */
    public boolean hasSeparateNorms()
      throws IOException {
      if (normGen == null) {
        if (!preLockless) {
          // This means we were created w/ LOCKLESS code and no
          // norms are written yet:
          return false;
        } else {
          // This means this segment was saved with pre-LOCKLESS
          // code.  So we must fallback to the original
          // directory list check:
          String[] result = dir.listAll();
          if (result == null)
            throw new IOException("cannot read directory " + dir + ": listAll() returned null");
  
          final IndexFileNameFilter filter = IndexFileNameFilter.getFilter();
          String pattern;
          pattern = name + ".s";
          int patternLength = pattern.length();
          for(int i = 0; i < result.length; i++){
            String fileName = result[i];
            if (filter.accept(null, fileName) && fileName.startsWith(pattern) && Character.isDigit(fileName.charAt(patternLength)))
                return true;
          }
          return false;
        }
      } else {
        // This means this segment was saved with LOCKLESS
        // code so we first check whether any normGen's are >= 1
        // (meaning they definitely have separate norms):
        for(int i=0;i<normGen.length;i++) {
          if (normGen[i] >= YES) {
            return true;
          }
        }
        // Next we look for any == 0.  These cases were
        // pre-LOCKLESS and must be checked in directory:
        for(int i=0;i<normGen.length;i++) {
          if (normGen[i] == CHECK_DIR) {
            if (hasSeparateNorms(i)) {
              return true;
            }
          }
        }
      }
  
      return false;
    }
  
    /**
     * Increment the generation count for the norms file for
     * this field.
     *
     * @param fieldIndex field whose norm file will be rewritten
     */
    void advanceNormGen(int fieldIndex) {
      if (normGen[fieldIndex] == NO) {
        normGen[fieldIndex] = YES;
      } else {
        normGen[fieldIndex]++;
      }
      clearFiles();
    }
  
    /**
     * Get the file name for the norms file for this field.
     *
     * @param number field index
     */
    public String getNormFileName(int number) throws IOException {
      long gen;
      if (normGen == null) {
        gen = CHECK_DIR;
      } else {
        gen = normGen[number];
      }
      
      if (hasSeparateNorms(number)) {
        // case 1: separate norm
        return IndexFileNames.fileNameFromGeneration(name, "s" + number, gen);
      }
  
      if (hasSingleNormFile) {
        // case 2: lockless (or nrm file exists) - single file for all norms 
        return IndexFileNames.fileNameFromGeneration(name, IndexFileNames.NORMS_EXTENSION, WITHOUT_GEN);
      }
        
      // case 3: norm file for each field
      return IndexFileNames.fileNameFromGeneration(name, "f" + number, WITHOUT_GEN);
    }
  
    /**
     * Mark whether this segment is stored as a compound file.
     *
     * @param isCompoundFile true if this is a compound file;
     * else, false
     */
    void setUseCompoundFile(boolean isCompoundFile) {
      if (isCompoundFile) {
        this.isCompoundFile = YES;
      } else {
        this.isCompoundFile = NO;
      }
      clearFiles();
    }
  
    /**
     * Returns true if this segment is stored as a compound
     * file; else, false.
     */
    public boolean getUseCompoundFile() throws IOException {
      if (isCompoundFile == NO) {
        return false;
      } else if (isCompoundFile == YES) {
        return true;
      } else {
        return dir.fileExists(IndexFileNames.segmentFileName(name, IndexFileNames.COMPOUND_FILE_EXTENSION));
      }
    }
  
    public int getDelCount() throws IOException {
      if (delCount == -1) {
        if (hasDeletions()) {
          final String delFileName = getDelFileName();
          delCount = new BitVector(dir, delFileName).count();
        } else
          delCount = 0;
      }
      assert delCount <= docCount;
      return delCount;
    }
  
    void setDelCount(int delCount) {
      this.delCount = delCount;
      assert delCount <= docCount;
    }
  
    public int getDocStoreOffset() {
      return docStoreOffset;
    }
    
    public boolean getDocStoreIsCompoundFile() {
      return docStoreIsCompoundFile;
    }
    
    void setDocStoreIsCompoundFile(boolean v) {
      docStoreIsCompoundFile = v;
      clearFiles();
    }
    
    public String getDocStoreSegment() {
      return docStoreSegment;
    }
    
    public void setDocStoreSegment(String segment) {
      docStoreSegment = segment;
    }
    
    void setDocStoreOffset(int offset) {
      docStoreOffset = offset;
      clearFiles();
    }
  
    void setDocStore(int offset, String segment, boolean isCompoundFile) {        
      docStoreOffset = offset;
      docStoreSegment = segment;
      docStoreIsCompoundFile = isCompoundFile;
      clearFiles();
    }
    
    /**
     * Save this segment's info.
     */
    void write(IndexOutput output)
      throws IOException {
      assert delCount <= docCount: "delCount=" + delCount + " docCount=" + docCount + " segment=" + name;
      // Write the Lucene version that created this segment, since 3.1
      output.writeString(version); 
      output.writeString(name);
      output.writeInt(docCount);
      output.writeLong(delGen);
      output.writeInt(docStoreOffset);
      if (docStoreOffset != -1) {
        output.writeString(docStoreSegment);
        output.writeByte((byte) (docStoreIsCompoundFile ? 1:0));
      }
  
      output.writeByte((byte) (hasSingleNormFile ? 1:0));
      if (normGen == null) {
        output.writeInt(NO);
      } else {
        output.writeInt(normGen.length);
        for(int j = 0; j < normGen.length; j++) {
          output.writeLong(normGen[j]);
        }
      }
      output.writeByte(isCompoundFile);
      output.writeInt(delCount);
      output.writeByte((byte) (hasProx ? 1:0));
      output.writeStringStringMap(diagnostics);
      output.writeByte((byte) (hasVectors ? 1 : 0));
    }
  
    void setHasProx(boolean hasProx) {
      this.hasProx = hasProx;
      clearFiles();
    }
  
    public boolean getHasProx() {
      return hasProx;
    }
  
    private void addIfExists(Set<String> files, String fileName) throws IOException {
      if (dir.fileExists(fileName))
        files.add(fileName);
    }
  
    /*
     * Return all files referenced by this SegmentInfo.  The
     * returns List is a locally cached List so you should not
     * modify it.
     */
  
    public List<String> files() throws IOException {
  
      if (files != null) {
        // Already cached:
        return files;
      }
      
      HashSet<String> filesSet = new HashSet<String>();
      
      boolean useCompoundFile = getUseCompoundFile();
  
      if (useCompoundFile) {
        filesSet.add(IndexFileNames.segmentFileName(name, IndexFileNames.COMPOUND_FILE_EXTENSION));
        filesSet.add(IndexFileNames.segmentFileName(name, IndexFileNames.COMPOUND_FILE_EXTENSION_POS));
  
      } else {
        for (String ext : IndexFileNames.NON_STORE_INDEX_EXTENSIONS)
          addIfExists(filesSet, IndexFileNames.segmentFileName(name, ext));
      }
  
      if (docStoreOffset != -1) {
        // We are sharing doc stores (stored fields, term
        // vectors) with other segments
        assert docStoreSegment != null;
        if (docStoreIsCompoundFile) {
          filesSet.add(IndexFileNames.segmentFileName(docStoreSegment, IndexFileNames.COMPOUND_FILE_STORE_EXTENSION));
          filesSet.add(IndexFileNames.segmentFileName(docStoreSegment, IndexFileNames.COMPOUND_FILE_STORE_EXTENSION_POS));
  
        } else {
          filesSet.add(IndexFileNames.segmentFileName(docStoreSegment, IndexFileNames.FIELDS_INDEX_EXTENSION));
          filesSet.add(IndexFileNames.segmentFileName(docStoreSegment, IndexFileNames.FIELDS_EXTENSION));
          if (hasVectors) {
            filesSet.add(IndexFileNames.segmentFileName(docStoreSegment, IndexFileNames.VECTORS_INDEX_EXTENSION));
            filesSet.add(IndexFileNames.segmentFileName(docStoreSegment, IndexFileNames.VECTORS_DOCUMENTS_EXTENSION));
            filesSet.add(IndexFileNames.segmentFileName(docStoreSegment, IndexFileNames.VECTORS_FIELDS_EXTENSION));
          }
        }
      } else if (!useCompoundFile) {
        filesSet.add(IndexFileNames.segmentFileName(name, IndexFileNames.FIELDS_INDEX_EXTENSION));
        filesSet.add(IndexFileNames.segmentFileName(name, IndexFileNames.FIELDS_EXTENSION));
        if (hasVectors) {
          filesSet.add(IndexFileNames.segmentFileName(name, IndexFileNames.VECTORS_INDEX_EXTENSION));
          filesSet.add(IndexFileNames.segmentFileName(name, IndexFileNames.VECTORS_DOCUMENTS_EXTENSION));
          filesSet.add(IndexFileNames.segmentFileName(name, IndexFileNames.VECTORS_FIELDS_EXTENSION));
        }      
      }
  
      String delFileName = IndexFileNames.fileNameFromGeneration(name, IndexFileNames.DELETES_EXTENSION, delGen);
      if (delFileName != null && (delGen >= YES || dir.fileExists(delFileName))) {
        filesSet.add(delFileName);
      }
  
      // Careful logic for norms files    
      if (normGen != null) {
        for(int i=0;i<normGen.length;i++) {
          long gen = normGen[i];
          if (gen >= YES) {
            // Definitely a separate norm file, with generation:
            filesSet.add(IndexFileNames.fileNameFromGeneration(name, IndexFileNames.SEPARATE_NORMS_EXTENSION + i, gen));
          } else if (NO == gen) {
            // No separate norms but maybe plain norms
            // in the non compound file case:
            if (!hasSingleNormFile && !useCompoundFile) {
              String fileName = IndexFileNames.segmentFileName(name, IndexFileNames.PLAIN_NORMS_EXTENSION + i);
              if (dir.fileExists(fileName)) {
                filesSet.add(fileName);
              }
            }
          } else if (CHECK_DIR == gen) {
            // Pre-2.1: we have to check file existence
            String fileName = null;
            if (useCompoundFile) {
              fileName = IndexFileNames.segmentFileName(name, IndexFileNames.SEPARATE_NORMS_EXTENSION + i);
            } else if (!hasSingleNormFile) {
              fileName = IndexFileNames.segmentFileName(name, IndexFileNames.PLAIN_NORMS_EXTENSION + i);
            }
            if (fileName != null && dir.fileExists(fileName)) {
              filesSet.add(fileName);
            }
          }
        }
      } else if (preLockless || (!hasSingleNormFile && !useCompoundFile)) {
        // Pre-2.1: we have to scan the dir to find all
        // matching _X.sN/_X.fN files for our segment:
        String prefix;
        if (useCompoundFile)
          prefix = IndexFileNames.segmentFileName(name, IndexFileNames.SEPARATE_NORMS_EXTENSION);
        else
          prefix = IndexFileNames.segmentFileName(name, IndexFileNames.PLAIN_NORMS_EXTENSION);
        int prefixLength = prefix.length();
        String[] allFiles = dir.listAll();
        final IndexFileNameFilter filter = IndexFileNameFilter.getFilter();
        for(int i=0;i<allFiles.length;i++) {
          String fileName = allFiles[i];
          if (filter.accept(null, fileName) && fileName.length() > prefixLength && Character.isDigit(fileName.charAt(prefixLength)) && fileName.startsWith(prefix)) {
            filesSet.add(fileName);
          }
        }
      }
      return files = new ArrayList<String>(filesSet);
    }
  
    /* Called whenever any change is made that affects which
     * files this segment has. */
    private void clearFiles() {
      files = null;
      sizeInBytesNoStore = -1;
      sizeInBytesWithStore = -1;
    }
  
    /** {@inheritDoc} */
    @Override
    public String toString() {
      return toString(dir, 0);
    }
  
    /** Used for debugging.  Format may suddenly change.
     * 
     *  <p>Current format looks like
     *  <code>_a(3.1):c45/4->_1</code>, which means the segment's
     *  name is <code>_a</code>; it was created with Lucene 3.1 (or
     *  '?' if it's unkown); it's using compound file
     *  format (would be <code>C</code> if not compound); it
     *  has 45 documents; it has 4 deletions (this part is
     *  left off when there are no deletions); it's using the
     *  shared doc stores named <code>_1</code> (this part is
     *  left off if doc stores are private).</p>
     */
    public String toString(Directory dir, int pendingDelCount) {
  
      StringBuilder s = new StringBuilder();
      s.append(name).append('(').append(version == null ? "?" : version).append(')').append(':');
  
      char cfs;
      try {
        if (getUseCompoundFile()) {
          cfs = 'c';
        } else {
          cfs = 'C';
        }
      } catch (IOException ioe) {
        cfs = '?';
      }
      s.append(cfs);
  
      if (this.dir != dir) {
        s.append('x');
      }
      if (hasVectors) {
        s.append('v');
      }
      s.append(docCount);
  
      int delCount;
      try {
        delCount = getDelCount();
      } catch (IOException ioe) {
        delCount = -1;
      }
      if (delCount != -1) {
        delCount += pendingDelCount;
      }
      if (delCount != 0) {
        s.append('/');
        if (delCount == -1) {
          s.append('?');
        } else {
          s.append(delCount);
        }
      }
      
      if (docStoreOffset != -1) {
        s.append("->").append(docStoreSegment);
        if (docStoreIsCompoundFile) {
          s.append('c');
        } else {
          s.append('C');
        }
        s.append('+').append(docStoreOffset);
      }
  
      return s.toString();
    }
  
    /** We consider another SegmentInfo instance equal if it
     *  has the same dir and same name. */
    @Override
    public boolean equals(Object obj) {
      if (this == obj) return true;
      if (obj instanceof SegmentInfo) {
        final SegmentInfo other = (SegmentInfo) obj;
        return other.dir == dir && other.name.equals(name);
      } else {
        return false;
      }
    }
  
    @Override
    public int hashCode() {
      return dir.hashCode() + name.hashCode();
    }
  
    /**
     * Used by SegmentInfos to upgrade segments that do not record their code
     * version (either "2.x" or "3.0").
     * <p>
     * <b>NOTE:</b> this method is used for internal purposes only - you should
     * not modify the version of a SegmentInfo, or it may result in unexpected
     * exceptions thrown when you attempt to open the index.
     * 
     * @lucene.internal
     */
    void setVersion(String version) {
      this.version = version;
    }
    
    /** Returns the version of the code which wrote the segment. */
    public String getVersion() {
      return version;
    }
  
    long getBufferedDeletesGen() {
      return bufferedDeletesGen;
    }
  
    void setBufferedDeletesGen(long v) {
      bufferedDeletesGen = v;
    }
  }
  