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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.naming.resources;
 
Implements a special purpose cache.

Author(s):
Remy Maucherat
Version:
$Revision: 1914 $
 
 public class ResourceCache {
     
     
     // ----------------------------------------------------------- Constructors
     
     
     public ResourceCache() {
     }
     
     
     // ----------------------------------------------------- Instance Variables
 

    
Random generator used to determine elements to free.
 
     protected Random random = new Random();


    
Cache. Path -> Cache entry.
 
     protected CacheEntry[] cache = new CacheEntry[0];


    
Not found cache.
 
     protected HashMap notFoundCache = new HashMap();


    
Max size of resources which will have their content cached.
 
     protected int cacheMaxSize = 10240; // 10 MB
 

    
Max amount of removals during a make space.
 
     protected int maxAllocateIterations = 20;


    
Entry hit ratio at which an entry will never be removed from the cache. Compared with entry.access / hitsCount
 
     protected long desiredEntryAccessRatio = 3;


    
Spare amount of not found entries.
 
     protected int spareNotFoundEntries = 500;


    
Current cache size in KB.
 
     protected int cacheSize = 0;


    
Number of accesses to the cache.
 
     protected long accessCount = 0;


    
Number of cache hits.
    protected long hitsCount = 0;
    // ------------------------------------------------------------- Properties


    
Return the access count. Note: Update is not synced, so the number may not be completely accurate.
    public long getAccessCount() {
        return ;
    }


    
Return the maximum size of the cache in KB.
    public int getCacheMaxSize() {
        return ;
    }


    
Set the maximum size of the cache in KB.
    public void setCacheMaxSize(int cacheMaxSize) {
        this. = cacheMaxSize;
    }


    
Return the current cache size in KB.
    public int getCacheSize() {
        return ;
    }


    
Return desired entry access ratio.
    public long getDesiredEntryAccessRatio() {
        return ;
    }


    
Set the desired entry access ratio.
    public void setDesiredEntryAccessRatio(long desiredEntryAccessRatio) {
        this. = desiredEntryAccessRatio;
    }


    
Return the number of cache hits. Note: Update is not synced, so the number may not be completely accurate.
    public long getHitsCount() {
        return ;
    }


    
Return the maximum amount of iterations during a space allocation.
    public int getMaxAllocateIterations() {
        return ;
    }


    
Set the maximum amount of iterations during a space allocation.
    public void setMaxAllocateIterations(int maxAllocateIterations) {
        this. = maxAllocateIterations;
    }


    
Return the amount of spare not found entries.
    public int getSpareNotFoundEntries() {
        return ;
    }


    
Set the amount of spare not found entries.
    public void setSpareNotFoundEntries(int spareNotFoundEntries) {
        this. = spareNotFoundEntries;
    }
    // --------------------------------------------------------- Public Methods
    public boolean allocate(int space) {
        int toFree = space - ( - );
        if (toFree <= 0) {
            return true;
        }
        // Increase the amount to free so that allocate won't have to run right
        // away again
        toFree += ( / 16);
        int size = .size();
        if (size > ) {
            .clear();
             -= size;
            toFree -= size;
        }
        if (toFree <= 0) {
            return true;
        }
        int attempts = 0;
        int entriesFound = 0;
        long totalSpace = 0;
        int[] toRemove = new int[];
        while (toFree > 0) {
            if (attempts == ) {
                // Give up, no changes are made to the current cache
                return false;
            }
            if (toFree > 0) {
                // Randomly select an entry in the array
                int entryPos = -1;
                boolean unique = false;
                while (!unique) {
                    unique = true;
                    entryPos = .nextInt(.) ;
                    // Guarantee uniqueness
                    for (int i = 0; i < entriesFoundi++) {
                        if (toRemove[i] == entryPos) {
                            unique = false;
                        }
                    }
                }
                long entryAccessRatio = 
                    (([entryPos]. * 100) / );
                if (entryAccessRatio < ) {
                    toRemove[entriesFound] = entryPos;
                    totalSpace += [entryPos].;
                    toFree -= [entryPos].;
                    entriesFound++;
                }
            }
            attempts++;
        }
        // Now remove the selected entries
        java.util.Arrays.sort(toRemove, 0, entriesFound);
        CacheEntry[] newCache = new CacheEntry[. - entriesFound];
        int pos = 0;
        int n = -1;
        if (entriesFound > 0) {
            n = toRemove[0];
            for (int i = 0; i < .i++) {
                if (i == n) {
                    if ((pos + 1) < entriesFound) {
                        n = toRemove[pos + 1];
                        pos++;
                    } else {
                        pos++;
                        n = -1;
                    }
                } else {
                    newCache[i - pos] = [i];
                }
            }
        }
         = newCache;
         -= totalSpace;
        return true;
    }
    public CacheEntry lookup(String name) {
        CacheEntry cacheEntry = null;
        CacheEntry[] currentCache = ;
        ++;
        int pos = find(currentCachename);
        if ((pos != -1) && (name.equals(currentCache[pos].))) {
            cacheEntry = currentCache[pos];
        }
        if (cacheEntry == null) {
            try {
                cacheEntry = (CacheEntry.get(name);
            } catch (Exception e) {
                // Ignore: the reliability of this lookup is not critical
            }
        }
        if (cacheEntry != null) {
            ++;
        }
        return cacheEntry;
    }
    public void load(CacheEntry entry) {
        if (entry.exists) {
            if (insertCache(entry)) {
                 += entry.size;
            }
        } else {
            int sizeIncrement = (.get(entry.name) == null) ? 1 : 0;
            .put(entry.nameentry);
             += sizeIncrement;
        }
    }
    public boolean unload(String name) {
        CacheEntry removedEntry = removeCache(name);
        if (removedEntry != null) {
             -= removedEntry.size;
            return true;
        } else if (.remove(name) != null) {
            --;
            return true;
        }
        return false;
    }


    
Find a map elemnt given its name in a sorted array of map elements. This will return the index for the closest inferior or equal item in the given array.
    private static final int find(CacheEntry[] mapString name) {
        int a = 0;
        int b = map.length - 1;
        // Special cases: -1 and 0
        if (b == -1) {
            return -1;
        }
        if (name.compareTo(map[0].) < 0) {
            return -1;
        }
        if (b == 0) {
            return 0;
        }
        int i = 0;
        while (true) {
            i = (b + a) / 2;
            int result = name.compareTo(map[i].);
            if (result > 0) {
                a = i;
            } else if (result == 0) {
                return i;
            } else {
                b = i;
            }
            if ((b - a) == 1) {
                int result2 = name.compareTo(map[b].);
                if (result2 < 0) {
                    return a;
                } else {
                    return b;
                }
            }
        }
    }


    
Insert into the right place in a sorted MapElement array, and prevent duplicates.
    private final boolean insertCache(CacheEntry newElement) {
        CacheEntry[] oldCache = ;
        int pos = find(oldCachenewElement.name);
        if ((pos != -1) && (newElement.name.equals(oldCache[pos].))) {
            return false;
        }
        CacheEntry[] newCache = new CacheEntry[. + 1];
        System.arraycopy(oldCache, 0, newCache, 0, pos + 1);
        newCache[pos + 1] = newElement;
        System.arraycopy
            (oldCachepos + 1, newCachepos + 2, oldCache.length - pos - 1);
         = newCache;
        return true;
    }


    
Insert into the right place in a sorted MapElement array.
    private final CacheEntry removeCache(String name) {
        CacheEntry[] oldCache = ;
        int pos = find(oldCachename);
        if ((pos != -1) && (name.equals(oldCache[pos].))) {
            CacheEntry[] newCache = new CacheEntry[. - 1];
            System.arraycopy(oldCache, 0, newCache, 0, pos);
            System.arraycopy(oldCachepos + 1, newCachepos
                             oldCache.length - pos - 1);
             = newCache;
            return oldCache[pos];
        }
        return null;
    }
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