How to use

CacheLongKeyLIRS

in

org.h2.mvstore.cache

/**
 * Set the read cache size in MB.
 *
 * @param mb the cache size in MB.
 */
public void setCacheSize(int mb) {
  final long bytes = (long) mb * 1024 * 1024;
  if (cache != null) {
    cache.setMaxMemory(bytes);
    cache.clear();
  }
  if (cacheChunkRef != null) {
    cacheChunkRef.setMaxMemory(bytes / 4);
    cacheChunkRef.clear();
  }
}

int len = CACHE_BLOCK_SIZE - off;
len = Math.min(len, dst.remaining());
ByteBuffer buff = cache.get(cachePos);
if (buff == null) {
  buff = ByteBuffer.allocate(CACHE_BLOCK_SIZE);
    cache.put(cachePos, buff, CACHE_BLOCK_SIZE);
  } else {
    if (read <= 0) {

/**
 * Get the maximum cache size, in MB.
 * Note that this does not include the page chunk references cache, which is
 * 25% of the size of the page cache.
 *
 * @return the cache size
 */
public int getCacheSize() {
  if (cache == null) {
    return 0;
  }
  return (int) (cache.getMaxMemory() / 1024 / 1024);
}

/**
 * Add an entry to the cache using the average memory size.
 *
 * @param key the key (may not be null)
 * @param value the value (may not be null)
 * @return the old value, or null if there was no resident entry
 */
public V put(long key, V value) {
  return put(key, value, sizeOf(value));
}

/**
 * Get the entry set for all resident entries.
 *
 * @return the entry set
 */
public synchronized Set<Map.Entry<Long, V>> entrySet() {
  HashMap<Long, V> map = new HashMap<>();
  for (long k : keySet()) {
    map.put(k,  find(k).value);
  }
  return map.entrySet();
}

/**
 * Get the value for the given key if the entry is cached. This method
 * adjusts the internal state of the cache sometimes, to ensure commonly
 * used entries stay in the cache.
 *
 * @param key the key (may not be null)
 * @return the value, or null if there is no resident entry
 */
public V get(long key) {
  int hash = getHash(key);
  return getSegment(hash).get(key, hash);
}

private void clearCache(ByteBuffer src, long position) {
  if (cache.size() > 0) {
    int len = src.remaining();
    long p = getCachePos(position);
    while (len > 0) {
      cache.remove(p);
      p += CACHE_BLOCK_SIZE;
      len -= CACHE_BLOCK_SIZE;
    }
  }
}

/**
 * Remove an entry. Both resident and non-resident entries can be
 * removed.
 *
 * @param key the key (may not be null)
 * @return the old value, or null if there was no resident entry
 */
public V remove(long key) {
  int hash = getHash(key);
  int segmentIndex = getSegmentIndex(hash);
  Segment<V> s = segments[segmentIndex];
  // check whether resize is required: synchronize on s, to avoid
  // concurrent resizes (concurrent reads read
  // from the old segment)
  synchronized (s) {
    s = resizeIfNeeded(s, segmentIndex);
    return s.remove(key, hash);
  }
}

/**
 * Put the page in the cache.
 *
 * @param pos the page position
 * @param page the page
 * @param memory the memory used
 */
void cachePage(long pos, Page page, int memory) {
  if (cache != null) {
    cache.put(pos, page, memory);
  }
}

@Override
public synchronized FileChannel truncate(long newSize) throws IOException {
  cache.clear();
  base.truncate(newSize);
  return this;
}

/**
 * Get the amount of memory used for caching, in MB.
 * Note that this does not include the page chunk references cache, which is
 * 25% of the size of the page cache.
 *
 * @return the amount of memory used for caching
 */
public int getCacheSizeUsed() {
  if (cache == null) {
    return 0;
  }
  return (int) (cache.getUsedMemory() / 1024 / 1024);
}

/**
 * Read a page.
 *
 * @param map the map
 * @param pos the page position
 * @return the page
 */
Page readPage(MVMap<?, ?> map, long pos) {
  if (pos == 0) {
    throw DataUtils.newIllegalStateException(
        DataUtils.ERROR_FILE_CORRUPT, "Position 0");
  }
  Page p = cache == null ? null : cache.get(pos);
  if (p == null) {
    Chunk c = getChunk(pos);
    long filePos = c.block * BLOCK_SIZE;
    filePos += DataUtils.getPageOffset(pos);
    if (filePos < 0) {
      throw DataUtils.newIllegalStateException(
          DataUtils.ERROR_FILE_CORRUPT,
          "Negative position {0}", filePos);
    }
    long maxPos = (c.block + c.len) * BLOCK_SIZE;
    p = Page.read(fileStore, pos, map, filePos, maxPos);
    cachePage(pos, p, p.getMemory());
  }
  return p;
}

cache.remove(pos);

  cache = new CacheLongKeyLIRS<>(cc);
  cc.maxMemory /= 4;
  cacheChunkRef = new CacheLongKeyLIRS<>(cc);
} else {
  cache = null;
if (cache != null && pgSplitSize > cache.getMaxItemSize()) {
  pgSplitSize = (int)cache.getMaxItemSize();

private void addToMap(Entry<V> e) {
  int index = getHash(e.key) & mask;
  e.mapNext = entries[index];
  entries[index] = e;
  usedMemory += e.memory;
  mapSize++;
}

/**
 * Specifies max allowed size of cache for deserialized offheap rows to avoid deserialization costs for most
 * frequently used ones. In general performance is better with greater cache size. Must be more than 128 items.
 *
 * @param size Cache size in items.
 */
@GridSpiConfiguration(optional = true)
public void setMaxOffheapRowsCacheSize(int size) {
  A.ensure(size >= 128, "Offheap rows cache size must be not less than 128.");
  rowCache = new CacheLongKeyLIRS<>(size, 1, 128, 256);
}

/**
 * Get the value for the given key if the entry is cached. This method does
 * not modify the internal state.
 *
 * @param key the key (may not be null)
 * @return the value, or null if there is no resident entry
 */
public V peek(long key) {
  Entry<V> e = find(key);
  return e == null ? null : e.value;
}

/**
 * Check whether the given value is stored.
 *
 * @param value the value
 * @return true if it is stored
 */
public boolean containsValue(Object value) {
  return getMap().containsValue(value);
}

/**
 * Get the values for all resident entries.
 *
 * @return the entry set
 */
public List<V> values() {
  ArrayList<V> list = new ArrayList<>();
  for (long k : keySet()) {
    V value = find(k).value;
    if (value != null) {
      list.add(value);
    }
  }
  return list;
}

/**
 * Check whether there is a resident entry for the given key. This
 * method does not adjust the internal state of the cache.
 *
 * @param key the key (may not be null)
 * @return true if there is a resident entry
 */
public boolean containsKey(long key) {
  int hash = getHash(key);
  return getSegment(hash).containsKey(key, hash);
}