public override bool Equals(object obj)
{
if (this == obj)
{
return(true);
}
else if (!(obj is IndexCacheEntryKey))
{
return(false);
}
IndexCacheEntryKey other = (IndexCacheEntryKey)obj;
if (this.subFileParameter == null && other.subFileParameter != null)
{
return(false);
}
else if (this.subFileParameter != null && !this.subFileParameter.Equals(other.subFileParameter))
{
return(false);
}
else if (this.indexBlockNumber != other.indexBlockNumber)
{
return(false);
}
return(true);
}
/// <summary>
/// Returns the index entry of a block in the given map file. If the required index entry is not cached, it will be
/// read from the map file index and put in the cache.
/// </summary>
/// <param name="subFileParameter">
/// the parameters of the map file for which the index entry is needed. </param>
/// <param name="blockNumber">
/// the number of the block in the map file. </param>
/// <returns> the index entry. </returns>
/// <exception cref="IOException">
/// if an I/O error occurs during reading. </exception>
internal virtual long GetIndexEntry(SubFileParameter subFileParameter, long blockNumber)
{
// check if the block number is out of bounds
if (blockNumber >= subFileParameter.NumberOfBlocks)
{
throw new IOException("invalid block number: " + blockNumber);
}
// calculate the index block number
long indexBlockNumber = blockNumber / INDEX_ENTRIES_PER_BLOCK;
// create the cache entry key for this request
IndexCacheEntryKey indexCacheEntryKey = new IndexCacheEntryKey(subFileParameter, indexBlockNumber);
// check for cached index block
byte[] indexBlock = this.map.Get(indexCacheEntryKey);
if (indexBlock == null)
{
// cache miss, seek to the correct index block in the file and read it
long indexBlockPosition = subFileParameter.IndexStartAddress + indexBlockNumber * SIZE_OF_INDEX_BLOCK;
int remainingIndexSize = (int)(subFileParameter.IndexEndAddress - indexBlockPosition);
int indexBlockSize = Math.Min(SIZE_OF_INDEX_BLOCK, remainingIndexSize);
indexBlock = new byte[indexBlockSize];
lock (sync)
{
this.randomAccessFile.Seek(indexBlockPosition, SeekOrigin.Begin);
if (this.randomAccessFile.Read(indexBlock, 0, indexBlockSize) != indexBlockSize)
{
throw new IOException("could not read index block with size: " + indexBlockSize);
}
}
// put the index block in the map
this.map.Add(indexCacheEntryKey, indexBlock);
}
// calculate the address of the index entry inside the index block
long indexEntryInBlock = blockNumber % INDEX_ENTRIES_PER_BLOCK;
int addressInIndexBlock = (int)(indexEntryInBlock * SubFileParameter.BYTES_PER_INDEX_ENTRY);
// return the real index entry
return(Deserializer.GetFiveBytesLong((sbyte[])(Array)indexBlock, addressInIndexBlock));
}
