xref: /dports/java/eclipse/eclipse.platform.releng.aggregator-R4_16/eclipse.jdt.core/org.eclipse.jdt.core/search/org/eclipse/jdt/internal/core/nd/db/Database.java

/*******************************************************************************
 * Copyright (c) 2005, 2016 QNX Software Systems and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     QNX - Initial API and implementation
 *     Symbian - Add some non-javadoc implementation notes
 *     Markus Schorn (Wind River Systems)
 *     IBM Corporation
 *     Sergey Prigogin (Google)
 *     Stefan Xenos (Google)
 *******************************************************************************/
package org.eclipse.jdt.internal.core.nd.db;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.ClosedByInterruptException;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.FileChannel;
import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Set;

import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.OperationCanceledException;
import org.eclipse.core.runtime.Status;
import org.eclipse.jdt.internal.core.nd.IndexExceptionBuilder;
import org.eclipse.jdt.internal.core.nd.db.ModificationLog.Tag;
import org.eclipse.osgi.util.NLS;

/**
 * Database encapsulates access to a flat binary format file with a memory-manager-like API for
 * obtaining and releasing areas of storage (memory).
 * <p>
 * Some terminology is used throughout this class: A block is a variable-size piece of
 * contiguous memory returned by malloc. A chunk is a fixed-size piece of contiguous memory
 * that is the atomic unit for paging, caching, reads, and writes. A free block is contiguous
 * variable-length piece of memory that is created by free and is potentially usable by malloc.
 * Most chunks contain multiple blocks and free blocks, but it is possible for a single block
 * to use multiple chunks. Such blocks are referred to as "large blocks". A free block is always
 * smaller than a chunk.
 */
/*
 * The file encapsulated is divided into Chunks of size CHUNK_SIZE, and a table of contents
 * mapping chunk index to chunk address is maintained. Chunk structure exists only conceptually -
 * it is not a structure that appears in the file.
 *
 * ===== The first chunk is used by Database itself for house-keeping purposes and has structure
 *
 * offset                content
 * 	                     _____________________________
 * 0                    | version number
 * INT_SIZE             | pointer to head of linked list of blocks of size MIN_BLOCK_DELTAS*BLOCK_SIZE_DELTA
 * ..                   | ...
 * INT_SIZE * (M + 1)   | pointer to head of linked list of blocks of size (M + MIN_BLOCK_DELTAS) * BLOCK_SIZE_DELTA
 * FREE_BLOCK_OFFSET    | chunk number for the root of the large block free space trie
 * WRITE_NUMBER_OFFSET  | long integer which is incremented on every write
 * MALLOC_STATS_OFFSET  | memory usage statistics
 * DATA_AREA            | The database singletons are stored here and use the remainder of chunk 0
 *
 * M = CHUNK_SIZE / BLOCK_SIZE_DELTA - MIN_BLOCK_DELTAS
 *
 * ===== block structure (for free/unused blocks)
 *
 * offset            content
 * 	                 _____________________________
 * 0                | size of block (positive indicates an unused block) (2 bytes)
 * PREV_OFFSET      | pointer to previous block (of same size) (only in free blocks)
 * NEXT_OFFSET      | pointer to next block (of same size) (only in free blocks)
 * ...              | unused space
 *
 *====== block structure (for allocated blocks)
 *
 * offset            content
 * 	                 _____________________________
 * 0                | size of block (negative indicates the block is in use) (2 bytes)
 * 2                | content of the struct
 *
 */
public class Database {
	public static final int CHAR_SIZE = 2;
	public static final int BYTE_SIZE = 1;
	public static final int SHORT_SIZE = 2;
	public static final int INT_SIZE = 4;
	public static final int LONG_SIZE = 8;
	public static final int CHUNK_SIZE = 1024 * 4;
	public static final int OFFSET_IN_CHUNK_MASK= CHUNK_SIZE - 1;
	public static final int BLOCK_HEADER_SIZE = SHORT_SIZE;

	public static final int BLOCK_SIZE_DELTA_BITS = 3;
	public static final int BLOCK_SIZE_DELTA= 1 << BLOCK_SIZE_DELTA_BITS;

	// Fields that are only used by free blocks
	private static final int BLOCK_PREV_OFFSET = BLOCK_HEADER_SIZE;
	private static final int BLOCK_NEXT_OFFSET = BLOCK_HEADER_SIZE + INT_SIZE;
	private static final int FREE_BLOCK_HEADER_SIZE = BLOCK_NEXT_OFFSET + INT_SIZE;

	// Must be enough multiples of BLOCK_SIZE_DELTA in order to fit the free block header
	public static final int MIN_BLOCK_DELTAS = (FREE_BLOCK_HEADER_SIZE + BLOCK_SIZE_DELTA - 1) / BLOCK_SIZE_DELTA;
	public static final int MAX_BLOCK_DELTAS = (CHUNK_SIZE - LargeBlock.HEADER_SIZE - LargeBlock.FOOTER_SIZE)
			/ BLOCK_SIZE_DELTA;
	public static final int MAX_SINGLE_BLOCK_MALLOC_SIZE = MAX_BLOCK_DELTAS * BLOCK_SIZE_DELTA - BLOCK_HEADER_SIZE;
	public static final int PTR_SIZE = 4; // size of a pointer in the database in bytes
	public static final int STRING_SIZE = PTR_SIZE;
	public static final int FLOAT_SIZE = INT_SIZE;
	public static final int DOUBLE_SIZE = LONG_SIZE;
	public static final long MAX_DB_SIZE= ((long) 1 << (Integer.SIZE + BLOCK_SIZE_DELTA_BITS));

	public static final long MAX_MALLOC_SIZE = MAX_DB_SIZE - LargeBlock.HEADER_SIZE - LargeBlock.FOOTER_SIZE
			- CHUNK_SIZE - BLOCK_HEADER_SIZE;

	public static final int VERSION_OFFSET = 0;
	public static final int MALLOC_TABLE_OFFSET = VERSION_OFFSET + INT_SIZE;
	public static final int FREE_BLOCK_OFFSET = MALLOC_TABLE_OFFSET
			+ (CHUNK_SIZE / BLOCK_SIZE_DELTA - MIN_BLOCK_DELTAS + 1) * INT_SIZE;
	public static final int WRITE_NUMBER_OFFSET = FREE_BLOCK_OFFSET + PTR_SIZE;
	public static final int MALLOC_STATS_OFFSET = WRITE_NUMBER_OFFSET + LONG_SIZE;
	public static final int DATA_AREA_OFFSET = MALLOC_STATS_OFFSET + MemoryStats.SIZE;
	public static final int NUM_HEADER_CHUNKS = 1;

	// Malloc pool IDs (used for classifying memory allocations and recording statistics about them)
	/** Misc pool -- may be used for any purpose that doesn't fit the IDs below. */
	public static final short POOL_MISC 			= 0x0000;
	public static final short POOL_BTREE 			= 0x0001;
	public static final short POOL_DB_PROPERTIES 	= 0x0002;
	public static final short POOL_STRING_LONG 		= 0x0003;
	public static final short POOL_STRING_SHORT		= 0x0004;
	public static final short POOL_LINKED_LIST		= 0x0005;
	public static final short POOL_STRING_SET 		= 0x0006;
	public static final short POOL_GROWABLE_ARRAY	= 0x0007;
	/** Id for the first node type. All node types will record their stats in a pool whose ID is POOL_FIRST_NODE_TYPE + node_id*/
	public static final short POOL_FIRST_NODE_TYPE	= 0x0100;

	public static class ChunkStats {
		public final int totalChunks;
		public final int chunksInMemory;
		public final int dirtyChunks;
		public final int nonDirtyChunksNotInCache;

		public ChunkStats(int totalChunks, int chunksInMemory, int dirtyChunks, int nonDirtyChunksNotInCache) {
			this.totalChunks = totalChunks;
			this.chunksInMemory = chunksInMemory;
			this.dirtyChunks = dirtyChunks;
			this.nonDirtyChunksNotInCache = nonDirtyChunksNotInCache;
		}

		@Override
		public String toString() {
			return "Chunks: total = " + this.totalChunks + ", in memory = " + this.chunksInMemory //$NON-NLS-1$//$NON-NLS-2$
					+ ", dirty = " + this.dirtyChunks + ", not in cache = " + this.nonDirtyChunksNotInCache;  //$NON-NLS-1$//$NON-NLS-2$
		}
	}

	/**
	 * For loops that scan through the chunks list, this imposes a maximum number of iterations before the loop must
	 * release the chunk cache mutex.
	 */
	private static final int MAX_ITERATIONS_PER_LOCK = 256;
	private static final int WRITE_BUFFER_SIZE = CHUNK_SIZE * 32;

	/**
	 * True iff large chunk self-diagnostics should be enabled.
	 */
	public static boolean DEBUG_FREE_SPACE;

	public static boolean DEBUG_PAGE_CACHE;

	private final File fLocation;
	private final boolean fReadOnly;
	private RandomAccessFile fFile;
	private boolean fExclusiveLock;	 // Necessary for any write operation.
	private boolean fLocked;		 // Necessary for any operation.
	private boolean fIsMarkedIncomplete;

	private int fVersion;
	private final Chunk fHeaderChunk;
	/**
	 * Stores the {@link Chunk} associated with each page number or null if the chunk isn't loaded. Synchronize on
	 * {@link #fCache} before accessing.
	 */
	Chunk[] fChunks;
	private int fChunksUsed;
	private ChunkCache fCache;

	private long malloced;
	private long freed;
	private long cacheHits;
	private long cacheMisses;
	private long bytesWritten;
	private long totalReadTimeMs;

	private MemoryStats memoryUsage;
	public Chunk fMostRecentlyFetchedChunk;
	/**
	 * Contains the set of Chunks in this Database for which the Chunk.dirty flag is set to true.
	 * Protected by the database write lock. This set does not contain the header chunk, which is
	 * always handled as a special case by the code that flushes chunks.
	 */
	private HashSet<Chunk> dirtyChunkSet = new HashSet<>();
	private long totalFlushTime;
	private long totalWriteTimeMs;
	private long pageWritesBytes;
	private long nextValidation;
	private long validateCounter;
	public static final double MIN_BYTES_PER_MILLISECOND = 20480.0;

	private final ModificationLog log = new ModificationLog(0);
	private final Tag mallocTag;
	private final Tag freeTag;

	/**
	 * Construct a new Database object, creating a backing file if necessary.
	 * @param location the local file path for the database
	 * @param cache the cache to be used optimization
	 * @param version the version number to store in the database (only applicable for new databases)
	 * @param openReadOnly whether this Database object will ever need writing to
	 * @throws IndexException
	 */
	public Database(File location, ChunkCache cache, int version, boolean openReadOnly) throws IndexException {
		this.mallocTag = ModificationLog.createTag("Calling Database.malloc"); //$NON-NLS-1$
		this.freeTag = ModificationLog.createTag("Calling Database.free"); //$NON-NLS-1$
		try {
			this.fLocation = location;
			this.fReadOnly= openReadOnly;
			this.fCache= cache;
			openFile();

			int nChunksOnDisk = (int) (this.fFile.length() / CHUNK_SIZE);
			this.fHeaderChunk= new Chunk(this, 0);
			if (nChunksOnDisk <= 0) {
				this.fVersion= version;
				this.fChunks= new Chunk[1];
				this.fChunksUsed = this.fChunks.length;
			} else {
				this.fHeaderChunk.read();
				this.fVersion= this.fHeaderChunk.getInt(VERSION_OFFSET);
				this.fChunks = new Chunk[nChunksOnDisk];	// chunk[0] is unused.
				this.fChunksUsed = nChunksOnDisk;
			}
		} catch (IOException e) {
			throw new IndexException(new DBStatus(e));
		}
		this.memoryUsage = new MemoryStats(this.fHeaderChunk, MALLOC_STATS_OFFSET);
	}

	private static int divideRoundingUp(long num, long den) {
		return (int) ((num + den - 1) / den);
	}

	private void openFile() throws FileNotFoundException {
		this.fFile = new RandomAccessFile(this.fLocation, this.fReadOnly ? "r" : "rw"); //$NON-NLS-1$ //$NON-NLS-2$
	}

	void read(ByteBuffer buf, long position) throws IOException {
		int retries= 0;
		do {
			try {
				this.fFile.getChannel().read(buf, position);
				return;
			} catch (ClosedChannelException e) {
				// Always reopen the file if possible or subsequent reads will fail.
				openFile();

				// This is the most common type of interruption. If another thread called Thread.interrupt,
				// throw an OperationCanceledException.
				if (e instanceof ClosedByInterruptException) {
					throw new OperationCanceledException();
				}

				// If we've retried too many times, just rethrow the exception.
				if (++retries >= 20) {
					throw e;
				}

				// Otherwise, retry
			}
		} while (true);
	}

	public ModificationLog getLog() {
		return this.log;
	}

	/**
	 * Attempts to write to the given position in the file. Will retry if interrupted by Thread.interrupt() until,
	 * the write succeeds. It will return true if any call to Thread.interrupt() was detected.
	 *
	 * @return true iff a call to Thread.interrupt() was detected at any point during the operation.
	 * @throws IOException
	 */
	boolean write(ByteBuffer buf, long position) throws IOException {
		this.bytesWritten += buf.limit();
		return performUninterruptableWrite(() -> {this.fFile.getChannel().write(buf, position);});
	}

	private static interface IORunnable {
		void run() throws IOException;
	}

	/**
	 * Attempts to perform an uninterruptable write operation on the database. Returns true if an attempt was made
	 * to interrupt it.
	 *
	 * @throws IOException
	 */
	private boolean performUninterruptableWrite(IORunnable runnable) throws IOException {
		boolean interrupted = false;
		int retries= 0;
		while (true) {
			try {
				runnable.run();
				return interrupted;
			} catch (ClosedChannelException e) {
				openFile();

				if (e instanceof ClosedByInterruptException) {
					// Retry forever if necessary as long as another thread is calling Thread.interrupt
					interrupted = true;
				} else {
					if (++retries > 20) {
						throw e;
					}
				}
			}
		}
	}

	public void transferTo(FileChannel target) throws IOException {
		assert this.fLocked;
        final FileChannel from= this.fFile.getChannel();
        long nRead = 0;
        long position = 0;
        long size = from.size();
        while (position < size) {
        	nRead = from.transferTo(position, 4096 * 16, target);
        	if (nRead == 0) {
        		break;		// Should not happen.
        	} else {
        		position+= nRead;
        	}
        }
	}

	public int getVersion() {
		return this.fVersion;
	}

	public void setVersion(int version) throws IndexException {
		assert this.fExclusiveLock;
		this.fHeaderChunk.putInt(VERSION_OFFSET, version);
		this.fVersion= version;
	}

	/**
	 * Empty the contents of the Database, make it ready to start again. Interrupting the thread with
	 * {@link Thread#interrupt()} won't interrupt the write. Returns true iff the thread was interrupted
	 * with {@link Thread#interrupt()}.
	 *
	 * @throws IndexException
	 */
	public boolean clear(int version) throws IndexException {
		assert this.fExclusiveLock;
		boolean wasCanceled = false;
		removeChunksFromCache();

		this.log.clear();
		this.fVersion= version;
		// Clear the first chunk.
		this.fHeaderChunk.clear(0, CHUNK_SIZE);
		// Chunks have been removed from the cache, so we may just reset the array of chunks.
		this.fChunks = new Chunk[] {null};
		this.dirtyChunkSet.clear();
		this.fChunksUsed = this.fChunks.length;
		try {
			wasCanceled = this.fHeaderChunk.flush() || wasCanceled; // Zero out header chunk.
			wasCanceled = performUninterruptableWrite(() -> {
				this.fFile.getChannel().truncate(CHUNK_SIZE);
			}) || wasCanceled;
			this.bytesWritten += CHUNK_SIZE;
		} catch (IOException e) {
			Package.log(e);
		}
		this.malloced = this.freed = 0;
		/*
		 * This is for debugging purposes in order to simulate having a very large Nd database.
		 * This will set aside the specified number of chunks.
		 * Nothing uses these chunks so subsequent allocations come after these fillers.
		 * The special function createNewChunks allocates all of these chunks at once.
		 * 524288 for a file starting at 2G
		 * 8388608 for a file starting at 32G
		 *
		 */
		long setasideChunks = Long.getLong("org.eclipse.jdt.core.parser.nd.chunks", 0); //$NON-NLS-1$
		if (setasideChunks != 0) {
			setVersion(getVersion());
			createNewChunks((int) setasideChunks);
			wasCanceled = flush() || wasCanceled;
		}
		this.memoryUsage.refresh();
		this.fHeaderChunk.makeDirty();
		return wasCanceled;
	}

	private void removeChunksFromCache() {
		int scanIndex = NUM_HEADER_CHUNKS;
		while (scanIndex < this.fChunksUsed) {
			synchronized (this.fCache) {
				int countMax = Math.min(MAX_ITERATIONS_PER_LOCK, this.fChunksUsed - scanIndex);
				for (int count = 0; count < countMax; count++) {
					Chunk chunk = this.fChunks[scanIndex++];
					if (chunk != null) {
						this.fCache.remove(chunk);
						if (DEBUG_PAGE_CACHE) {
							System.out.println("CHUNK " + chunk.fSequenceNumber //$NON-NLS-1$
									+ ": removing from vector in removeChunksFromCache - instance " //$NON-NLS-1$
									+ System.identityHashCode(chunk));
						}
						this.fChunks[chunk.fSequenceNumber] = null;
					}
				}
			}
		}
	}

	/**
	 * Return the Chunk that contains the given offset.
	 *
	 * @throws IndexException
	 */
	public Chunk getChunk(long offset) throws IndexException {
		assert offset >= 0;
		assertLocked();
		if (offset < CHUNK_SIZE) {
			this.fMostRecentlyFetchedChunk = this.fHeaderChunk;
			return this.fHeaderChunk;
		}
		long long_index = offset / CHUNK_SIZE;
		assert long_index < Integer.MAX_VALUE;

		final int index = (int) long_index;
		Chunk chunk;
		synchronized (this.fCache) {
			assert this.fLocked;
			if (index < 0 || index >= this.fChunks.length) {
				databaseCorruptionDetected();
			}
			chunk = this.fChunks[index];
		}

		long readStartMs = 0;
		long readEndMs = 0;
		// Read the new chunk outside of any synchronized block (this allows parallel reads and prevents background
		// threads from retaining a lock that blocks the UI while the background thread performs I/O).
		boolean cacheMiss = (chunk == null);
		if (cacheMiss) {
			readStartMs = System.currentTimeMillis();
			chunk = new Chunk(this, index);
			chunk.read();
			readEndMs = System.currentTimeMillis();
		}

		synchronized (this.fCache) {
			if (cacheMiss) {
				this.cacheMisses++;
				this.totalReadTimeMs += (readEndMs - readStartMs);
			} else {
				this.cacheHits++;
			}
			Chunk newChunk = this.fChunks[index];
			if (newChunk != chunk && newChunk != null) {
				// Another thread fetched this chunk in the meantime. In this case, we should use the chunk fetched
				// by the other thread.
				if (DEBUG_PAGE_CACHE) {
					System.out.println("CHUNK " + chunk.fSequenceNumber //$NON-NLS-1$
							+ ": already fetched by another thread - instance " //$NON-NLS-1$
							+ System.identityHashCode(chunk));
				}
				chunk = newChunk;
			} else if (cacheMiss) {
				if (DEBUG_PAGE_CACHE) {
					System.out.println("CHUNK " + chunk.fSequenceNumber + ": inserted into vector - instance " //$NON-NLS-1$//$NON-NLS-2$
							+ System.identityHashCode(chunk));
				}
				this.fChunks[index] = chunk;
			}
			this.fCache.add(chunk);
			this.fMostRecentlyFetchedChunk = chunk;
		}

		return chunk;
	}

	public void assertLocked() {
		if (!this.fLocked) {
			throw new IllegalStateException("Database not locked!"); //$NON-NLS-1$
		}
	}

	private void databaseCorruptionDetected() throws IndexException {
		String msg = "Corrupted database: " + this.fLocation.getName(); //$NON-NLS-1$
		throw new IndexException(new DBStatus(msg));
	}

	/**
	 * Copies numBytes from source to destination
	 */
	public void memcpy(long dest, long source, int numBytes) {
		assert numBytes >= 0;
		long endAddress = source + numBytes;
		assert endAddress <= (long) this.fChunksUsed * CHUNK_SIZE;
		// TODO: make use of lower-level System.arrayCopy
		for (int count = 0; count < numBytes; count++) {
			putByte(dest + count, getByte(source + count));
		}
	}

	/**
	 * Allocate a block out of the database.
	 */
	public long malloc(final long datasize, final short poolId) throws IndexException {
		assert this.fExclusiveLock;
		assert datasize >= 0;
		assert datasize <= MAX_MALLOC_SIZE;

		long result;
		int usedSize;
		this.log.start(this.mallocTag);
		try {
			if (datasize >= MAX_SINGLE_BLOCK_MALLOC_SIZE) {
				int newChunkNum = createLargeBlock(datasize);
				usedSize = Math.abs(getBlockHeaderForChunkNum(newChunkNum)) * CHUNK_SIZE;
				result = (long) newChunkNum * CHUNK_SIZE + LargeBlock.HEADER_SIZE;
				// Note that we identify large blocks by setting their block size to 0.
				clearRange(result, usedSize - LargeBlock.HEADER_SIZE - LargeBlock.FOOTER_SIZE);
				result = result + BLOCK_HEADER_SIZE;
			} else {
				long freeBlock = 0;
				int needDeltas = divideRoundingUp(datasize + BLOCK_HEADER_SIZE, BLOCK_SIZE_DELTA);
				if (needDeltas < MIN_BLOCK_DELTAS) {
					needDeltas = MIN_BLOCK_DELTAS;
				}

				// Which block size.
				int useDeltas;
				for (useDeltas = needDeltas; useDeltas <= MAX_BLOCK_DELTAS; useDeltas++) {
					freeBlock = getFirstBlock(useDeltas * BLOCK_SIZE_DELTA);
					if (freeBlock != 0)
						break;
				}

				// Get the block.
				Chunk chunk;
				if (freeBlock == 0) {
					// Allocate a new chunk.
					freeBlock = (long) (createLargeBlock(datasize)) * (long) CHUNK_SIZE + LargeBlock.HEADER_SIZE;
					useDeltas = MAX_BLOCK_DELTAS;
					chunk = getChunk(freeBlock);
				} else {
					chunk = getChunk(freeBlock);
					chunk.makeDirty();
					int blockReportedSize = chunk.getShort(freeBlock);
					if (blockReportedSize != useDeltas * BLOCK_SIZE_DELTA) {
						throw describeProblem()
							.addProblemAddress("block size", freeBlock, SHORT_SIZE) //$NON-NLS-1$
							.build(
								"Heap corruption detected in free space list. Block " + freeBlock //$NON-NLS-1$
								+ " reports a size of " + blockReportedSize + " but was in the list for blocks of size "  //$NON-NLS-1$//$NON-NLS-2$
								+ useDeltas * BLOCK_SIZE_DELTA);
					}
					removeBlock(chunk, useDeltas * BLOCK_SIZE_DELTA, freeBlock);
				}

				final int unusedDeltas = useDeltas - needDeltas;
				if (unusedDeltas >= MIN_BLOCK_DELTAS) {
					// Add in the unused part of our block.
					addBlock(chunk, unusedDeltas * BLOCK_SIZE_DELTA, freeBlock + needDeltas * BLOCK_SIZE_DELTA);
					useDeltas = needDeltas;
				}

				// Make our size negative to show in use.
				usedSize = useDeltas * BLOCK_SIZE_DELTA;
				chunk.putShort(freeBlock, (short) -usedSize);

				// Clear out the block, lots of people are expecting this.
				chunk.clear(freeBlock + BLOCK_HEADER_SIZE, usedSize - BLOCK_HEADER_SIZE);
				result = freeBlock + BLOCK_HEADER_SIZE;
			}
		} finally {
			this.log.end(this.mallocTag);
		}

		this.log.recordMalloc(result, usedSize - BLOCK_HEADER_SIZE);
		this.malloced += usedSize;
		this.memoryUsage.recordMalloc(poolId, usedSize);

		if (DEBUG_FREE_SPACE) {
			boolean performedValidation = periodicValidateFreeSpace();

			if (performedValidation) {
				verifyNotInFreeSpaceList(result);
			}
		}

		return result;
	}

	/**
	 * Clears all the bytes in the given range by setting them to zero.
	 *
	 * @param startAddress first address to clear
	 * @param bytesToClear number of addresses to clear
	 */
	public void clearRange(long startAddress, long bytesToClear) {
		if (bytesToClear == 0) {
			return;
		}
		long endAddress = startAddress + bytesToClear;
		assert endAddress <= (long) this.fChunksUsed * CHUNK_SIZE;
		int blockNumber = (int) (startAddress / CHUNK_SIZE);
		int firstBlockBytesToClear = (int) Math.min((((long) (blockNumber + 1) * CHUNK_SIZE) - startAddress), bytesToClear);

		Chunk firstBlock = getChunk(startAddress);
		firstBlock.clear(startAddress, firstBlockBytesToClear);
		startAddress += firstBlockBytesToClear;
		bytesToClear -= firstBlockBytesToClear;
		while (bytesToClear > CHUNK_SIZE) {
			Chunk nextBlock = getChunk(startAddress);
			nextBlock.clear(startAddress, CHUNK_SIZE);
			startAddress += CHUNK_SIZE;
			bytesToClear -= CHUNK_SIZE;
		}

		if (bytesToClear > 0) {
			Chunk nextBlock = getChunk(startAddress);
			nextBlock.clear(startAddress, (int) bytesToClear);
		}
	}

	/**
	 * Obtains a new block that can fit the given number of bytes (at minimum). Returns the
	 * chunk number.
	 *
	 * @param datasize minimum number of bytes needed
	 * @return the chunk number
	 */
	private int createLargeBlock(long datasize) {
		final int neededChunks = getChunksNeededForBytes(datasize);
		int freeBlockChunkNum = getFreeBlockFromTrie(neededChunks);
		final int numChunks;

		if (freeBlockChunkNum == 0) {
			final int lastChunkNum = this.fChunksUsed;

			numChunks = neededChunks;

			// Check if the last block in the database is free. If so, unlink and expand it.
			int lastBlockSize = getBlockFooterForChunkBefore(lastChunkNum);
			if (lastBlockSize > 0) {
				int startChunkNum = getFirstChunkOfBlockBefore(lastChunkNum);

				unlinkFreeBlock(startChunkNum);
				// Allocate additional new chunks such that the new chunk is large enough to
				// handle this allocation.
				createNewChunks(neededChunks - lastBlockSize);
				freeBlockChunkNum = startChunkNum;
			} else {
				freeBlockChunkNum = createNewChunks(numChunks);
			}
		} else {
			numChunks = getBlockHeaderForChunkNum(freeBlockChunkNum);

			if (numChunks < neededChunks) {
				throw describeProblem()
					.addProblemAddress("chunk header", (long) freeBlockChunkNum * CHUNK_SIZE, INT_SIZE) //$NON-NLS-1$
					.build("A block in the free space trie was too small or wasn't actually free. Reported size = " //$NON-NLS-1$
							+ numChunks + " chunks, requested size = " + neededChunks + " chunks");  //$NON-NLS-1$//$NON-NLS-2$
			}

			int footer = getBlockFooterForChunkBefore(freeBlockChunkNum + numChunks);
			if (footer != numChunks) {
				throw describeProblem()
					.addProblemAddress("chunk header", (long) freeBlockChunkNum * CHUNK_SIZE, INT_SIZE) //$NON-NLS-1$
					.addProblemAddress("chunk footer", (long) (freeBlockChunkNum + numChunks) * CHUNK_SIZE - INT_SIZE, INT_SIZE) //$NON-NLS-1$
					.build("The header and footer didn't match for a block in the free space trie. Expected " //$NON-NLS-1$
							+ numChunks + " but found " + footer); //$NON-NLS-1$
			}

			unlinkFreeBlock(freeBlockChunkNum);
		}

		final int resultChunkNum;
		if (numChunks > neededChunks) {
			// If the chunk we've selected is larger than necessary, split it. We have the
			// choice of using either half of the block. In the interest of leaving more
			// opportunities of merging large blocks, we leave the unused half of the block
			// next to the larger adjacent block.
			final int nextBlockChunkNum = freeBlockChunkNum + numChunks;

			final int nextBlockSize = Math.abs(getBlockHeaderForChunkNum(nextBlockChunkNum));
			final int prevBlockSize = Math.abs(getBlockFooterForChunkBefore(freeBlockChunkNum));

			final int unusedChunks = numChunks - neededChunks;
			if (nextBlockSize >= prevBlockSize) {
				// Use the start of the block
				resultChunkNum = freeBlockChunkNum;
				// Return the last half of the block to the free block pool
				linkFreeBlockToTrie(freeBlockChunkNum + neededChunks, unusedChunks);
			} else {
				// Use the end of the block
				resultChunkNum = freeBlockChunkNum + unusedChunks;
				// Return the first half of the block to the free block pool
				linkFreeBlockToTrie(freeBlockChunkNum, unusedChunks);
			}
		} else {
			resultChunkNum = freeBlockChunkNum;
		}

		// Fill in the header and footer
		setBlockHeader(resultChunkNum, -neededChunks);
		return resultChunkNum;
	}

	/**
	 * Unlinks a free block (which currently belongs to the free block trie) so that it may
	 * be reused.
	 *
	 * @param freeBlockChunkNum chunk number of the block to be unlinked
	 */
	private void unlinkFreeBlock(int freeBlockChunkNum) {
		long freeBlockAddress = (long) freeBlockChunkNum * CHUNK_SIZE;
		int anotherBlockOfSameSize = 0;
		int nextBlockChunkNum = getInt(freeBlockAddress + LargeBlock.NEXT_BLOCK_OFFSET);
		int prevBlockChunkNum = getInt(freeBlockAddress + LargeBlock.PREV_BLOCK_OFFSET);
		// Relink the linked list
		if (nextBlockChunkNum != 0) {
			anotherBlockOfSameSize = nextBlockChunkNum;
			putInt((long) nextBlockChunkNum * CHUNK_SIZE + LargeBlock.PREV_BLOCK_OFFSET, prevBlockChunkNum);
		}
		if (prevBlockChunkNum != 0) {
			anotherBlockOfSameSize = prevBlockChunkNum;
			putInt((long) prevBlockChunkNum * CHUNK_SIZE + LargeBlock.NEXT_BLOCK_OFFSET, nextBlockChunkNum);
		}

		/**
		 * True iff this block was a block in the trie. False if it was attached to to the list of siblings but some
		 * other node in the list is the one in the trie.
		 */
		boolean wasInTrie = false;
		long root = getInt(FREE_BLOCK_OFFSET);
		if (root == freeBlockChunkNum) {
			putInt(FREE_BLOCK_OFFSET, 0);
			wasInTrie = true;
		}

		int freeBlockSize = getBlockHeaderForChunkNum(freeBlockChunkNum);
		int parentChunkNum = getInt(freeBlockAddress + LargeBlock.PARENT_OFFSET);
		if (parentChunkNum != 0) {
			int currentSize = getBlockHeaderForChunkNum(parentChunkNum);
			int difference = currentSize ^ freeBlockSize;
			if (difference != 0) {
				int firstDifference = LargeBlock.SIZE_OF_SIZE_FIELD * 8 - Integer.numberOfLeadingZeros(difference) - 1;
				long locationOfChildPointer = (long) parentChunkNum * CHUNK_SIZE + LargeBlock.CHILD_TABLE_OFFSET
						+ (firstDifference * INT_SIZE);
				int childChunkNum = getInt(locationOfChildPointer);
				if (childChunkNum == freeBlockChunkNum) {
					wasInTrie = true;
					putInt(locationOfChildPointer, 0);
				}
			}
		}

		// If the removed block was the head of the linked list, we need to reinsert the following entry as the
		// new head.
		if (wasInTrie && anotherBlockOfSameSize != 0) {
			insertChild(parentChunkNum, anotherBlockOfSameSize);
		}

		int currentParent = parentChunkNum;
		for (int childIdx = 0; childIdx < LargeBlock.ENTRIES_IN_CHILD_TABLE; childIdx++) {
			long childAddress = freeBlockAddress + LargeBlock.CHILD_TABLE_OFFSET + (childIdx * INT_SIZE);
			int nextChildChunkNum = getInt(childAddress);
			if (nextChildChunkNum != 0) {
				if (!wasInTrie) {
					throw describeProblem()
						.addProblemAddress("non-null child pointer", childAddress, INT_SIZE) //$NON-NLS-1$
						.build("All child pointers should be null for a free chunk that is in the sibling list but" //$NON-NLS-1$
								+ " not part of the trie. Problematic chunk number: " + freeBlockChunkNum); //$NON-NLS-1$
				}
				insertChild(currentParent, nextChildChunkNum);
				// Parent all subsequent children under the child that was most similar to the old parent
				if (currentParent == parentChunkNum) {
					currentParent = nextChildChunkNum;
				}
			}
		}

	}

	/**
	 * Returns the chunk number of a free block that contains at least the given number of chunks, or
	 * 0 if there is no existing contiguous free block containing at least the given number of chunks.
	 *
	 * @param numChunks minumum number of chunks desired
	 * @return the chunk number of a free block containing at least the given number of chunks or 0
	 * if there is no existing free block containing that many chunks.
	 */
	private int getFreeBlockFromTrie(int numChunks) {
		int currentChunkNum = getInt(FREE_BLOCK_OFFSET);

		int resultChunkNum = getSmallestChildNoSmallerThan(currentChunkNum, numChunks);
		if (resultChunkNum == 0) {
			return 0;
		}

		// Try not to return the trie node itself if there is a linked list entry available, since unlinking
		// something from the linked list is faster than unlinking a trie node.
		int nextResultChunkNum = getInt((long) resultChunkNum * CHUNK_SIZE + LargeBlock.NEXT_BLOCK_OFFSET);
		if (nextResultChunkNum != 0) {
			return nextResultChunkNum;
		}
		return resultChunkNum;
	}

	/**
	 * Given the chunk number of a block somewhere in the free space trie, this returns the smallest
	 * child in the subtree that is no smaller than the given number of chunks.
	 *
	 * @param trieNodeChunkNum chunk number of a block in the free space trie
	 * @param numChunks desired number of chunks
	 * @return the chunk number of the first chunk in a contiguous free block containing at least the
	 * given number of chunks
	 */
	private int getSmallestChildNoSmallerThan(int trieNodeChunkNum, int numChunks) {
		if (trieNodeChunkNum == 0) {
			return 0;
		}
		int currentSize = getBlockHeaderForChunkNum(trieNodeChunkNum);
		assert (currentSize >= 0);
		int difference = currentSize ^ numChunks;
		if (difference == 0) {
			return trieNodeChunkNum;
		}

		int bitMask = Integer.highestOneBit(difference);
		int firstDifference = LargeBlock.SIZE_OF_SIZE_FIELD * 8 - Integer.numberOfLeadingZeros(bitMask) - 1;
		boolean lookingForSmallerChild = (currentSize > numChunks);
		for (int testPosition = firstDifference; testPosition < LargeBlock.ENTRIES_IN_CHILD_TABLE; testPosition++) {
			if (((currentSize & bitMask) != 0) == lookingForSmallerChild) {
				int nextChildChunkNum = getInt(
						(long) trieNodeChunkNum * CHUNK_SIZE + LargeBlock.CHILD_TABLE_OFFSET + (testPosition * INT_SIZE));
				int childResultChunkNum = getSmallestChildNoSmallerThan(nextChildChunkNum, numChunks);
				if (childResultChunkNum != 0) {
					return childResultChunkNum;
				}
			}
			bitMask <<= 1;
		}

		if (lookingForSmallerChild) {
			return trieNodeChunkNum;
		} else {
			return 0;
		}
	}

	/**
	 * Link the given unused block into the free block tries. The block does not need to have
	 * its header filled in already.
	 *
	 * @param freeBlockChunkNum chunk number of the start of the block
	 * @param numChunks number of chunks in the block
	 */
	private void linkFreeBlockToTrie(int freeBlockChunkNum, int numChunks) {
		setBlockHeader(freeBlockChunkNum, numChunks);
		long freeBlockAddress = (long) freeBlockChunkNum * CHUNK_SIZE;
		Chunk chunk = getChunk(freeBlockAddress);
		chunk.clear(freeBlockAddress + LargeBlock.HEADER_SIZE,
				LargeBlock.UNALLOCATED_HEADER_SIZE - LargeBlock.HEADER_SIZE);

		insertChild(getInt(FREE_BLOCK_OFFSET), freeBlockChunkNum);
	}

	public void validateFreeSpace() {
		validateFreeSpaceLists();
		validateFreeSpaceTries();
	}

	/**
	 * Performs a self-test on the free space lists used by malloc to check for corruption
	 */
	private void validateFreeSpaceLists() {
		int useDeltas;
		for (useDeltas = MIN_BLOCK_DELTAS; useDeltas <= MAX_BLOCK_DELTAS; useDeltas++) {
			validateFreeBlocksFor(useDeltas);
		}
	}

	private void verifyNotInFreeSpaceList(long result) {
		int useDeltas;
		for (useDeltas = MIN_BLOCK_DELTAS; useDeltas <= MAX_BLOCK_DELTAS; useDeltas++) {
			int correctSize = useDeltas * BLOCK_SIZE_DELTA;
			long block = getFirstBlock(correctSize);
			long addressOfPrevBlockPointer = getAddressOfFirstBlockPointer(correctSize);
			while (block != 0) {
				if (block == result) {
					throw describeProblem()
						.addProblemAddress("incoming pointer", addressOfPrevBlockPointer, PTR_SIZE) //$NON-NLS-1$
						.build("Block " + result  //$NON-NLS-1$
							+ " was found in the free space list, even though it wasn't free"); //$NON-NLS-1$
				}
				addressOfPrevBlockPointer = block + BLOCK_NEXT_OFFSET;
				long followingBlock = getFreeRecPtr(addressOfPrevBlockPointer);
				block = followingBlock;
			}
		}

		int currentChunkNum = getInt(FREE_BLOCK_OFFSET);

		if (currentChunkNum == 0) {
			return;
		}
		int targetChunkNum = (int) (result / CHUNK_SIZE);

		if (currentChunkNum == targetChunkNum) {
			throw describeProblem().build("Block " + result  //$NON-NLS-1$
					+ " was not supposed to be in the free space list, but was linked as the root of the list"); //$NON-NLS-1$
		}

		verifyNotInLargeBlockFreeSpaceTrie(targetChunkNum, currentChunkNum, 0);
	}

	private void verifyNotInLargeBlockFreeSpaceTrie(int targetChunkNum, int chunkNum, int parent) {
		long chunkStart = (long) chunkNum * CHUNK_SIZE;

		for (int testPosition = 0; testPosition < LargeBlock.ENTRIES_IN_CHILD_TABLE; testPosition++) {
			long chunkAddress = chunkStart + LargeBlock.CHILD_TABLE_OFFSET + (testPosition * INT_SIZE);
			int nextChildChunkNum = getInt(chunkAddress);

			if (nextChildChunkNum == 0) {
				continue;
			}

			if (nextChildChunkNum == targetChunkNum) {
				throw describeProblem()
					.addProblemAddress("trie child address", chunkAddress, INT_SIZE) //$NON-NLS-1$
					.build("Chunk number " + nextChildChunkNum  //$NON-NLS-1$
						+ " was found in the free space trie even though it was in use"); //$NON-NLS-1$
			}

			verifyNotInLargeBlockFreeSpaceTrie(targetChunkNum, nextChildChunkNum, chunkNum);
		}
	}

	private void validateFreeBlocksFor(int numberOfDeltas) {
		int correctSize = numberOfDeltas * BLOCK_SIZE_DELTA;
		long lastBlock = 0;
		long block = getFirstBlock(correctSize);
		long addressOfPrevBlockPointer = getAddressOfFirstBlockPointer(correctSize);
		while (block != 0) {
			long measuredLastBlock = getFreeRecPtr(block + BLOCK_PREV_OFFSET);
			int blockReportedSize = getShort(block);
			long followingBlock = getFreeRecPtr(block + BLOCK_NEXT_OFFSET);
			if (measuredLastBlock != lastBlock) {
				throw describeProblem()
					.addProblemAddress("last block", block + BLOCK_PREV_OFFSET, PTR_SIZE) //$NON-NLS-1$
					.addProblemAddress("incoming pointer", addressOfPrevBlockPointer, PTR_SIZE) //$NON-NLS-1$
					.build("The free space block (" + block //$NON-NLS-1$
						+ ") of size " + correctSize + " had an incorrect prev pointer to "  //$NON-NLS-1$//$NON-NLS-2$
						+ measuredLastBlock + ", but it should have been pointing to " //$NON-NLS-1$
						+ lastBlock);
			}
			if (blockReportedSize != correctSize) {
				throw describeProblem()
					.addProblemAddress("block size", block, SHORT_SIZE) //$NON-NLS-1$
					.addProblemAddress("incoming pointer", addressOfPrevBlockPointer, PTR_SIZE) //$NON-NLS-1$
					.build("A block (" + block + ") of size " + measuredLastBlock //$NON-NLS-1$ //$NON-NLS-2$
						+ " was in the free space list for blocks of size " + correctSize); //$NON-NLS-1$
			}
			addressOfPrevBlockPointer = block + BLOCK_NEXT_OFFSET;
			lastBlock = block;
			block = followingBlock;
		}
	}

	/**
	 * Performs a self-test on the free space trie list (used by the large block allocator) to check for corruption
	 */
	private void validateFreeSpaceTries() {
		int currentChunkNum = getInt(FREE_BLOCK_OFFSET);

		if (currentChunkNum == 0) {
			return;
		}

		Set<Integer> visited = new HashSet<>();
		validateFreeSpaceNode(visited, currentChunkNum, 0);
	}

	private void validateFreeSpaceNode(Set<Integer> visited, int chunkNum, int parent) {
		if (visited.contains(chunkNum)) {
			throw describeProblem().build("Chunk " + chunkNum + "(parent = " + parent //$NON-NLS-1$//$NON-NLS-2$
					+ " appeared twice in the free space tree"); //$NON-NLS-1$
		}

		long chunkStart = (long) chunkNum * CHUNK_SIZE;
		int parentChunk = getInt(chunkStart + LargeBlock.PARENT_OFFSET);
		if (parentChunk != parent) {
			throw describeProblem()
				.addProblemAddress("parent pointer", chunkStart + LargeBlock.PARENT_OFFSET, Database.INT_SIZE) //$NON-NLS-1$
				.build("Chunk " + chunkNum + " has the wrong parent. Expected " + parent  //$NON-NLS-1$//$NON-NLS-2$
					+ " but found  " + parentChunk); //$NON-NLS-1$
		}

		visited.add(chunkNum);
		int numChunks = getBlockHeaderForChunkNum(chunkNum);
		for (int testPosition = 0; testPosition < LargeBlock.ENTRIES_IN_CHILD_TABLE; testPosition++) {
			long nextChildChunkNumAddress = chunkStart + LargeBlock.CHILD_TABLE_OFFSET + (testPosition * INT_SIZE);
			int nextChildChunkNum = getInt(nextChildChunkNumAddress);

			if (nextChildChunkNum == 0) {
				continue;
			}

			int nextSize = getBlockHeaderForChunkNum(nextChildChunkNum);
			int sizeDifference = nextSize ^ numChunks;
			int firstDifference = LargeBlock.SIZE_OF_SIZE_FIELD * 8 - Integer.numberOfLeadingZeros(
					Integer.highestOneBit(sizeDifference)) - 1;

			if (firstDifference != testPosition) {
				IndexExceptionBuilder descriptor = describeProblem();
				attachBlockHeaderForChunkNum(descriptor, chunkNum);
				attachBlockHeaderForChunkNum(descriptor, nextChildChunkNum);
				throw descriptor.build("Chunk " + nextChildChunkNum + " contained an incorrect size of "  //$NON-NLS-1$//$NON-NLS-2$
						+ nextSize + ". It was at position " + testPosition + " in parent " + chunkNum //$NON-NLS-1$ //$NON-NLS-2$
						+ " which had size " + numChunks); //$NON-NLS-1$
			}

			try {
				validateFreeSpaceNode(visited, nextChildChunkNum, chunkNum);
			} catch (IndexException e) {
				describeProblem()
					.addProblemAddress("child pointer from parent " + chunkNum, nextChildChunkNumAddress,  //$NON-NLS-1$
							Database.INT_SIZE)
					.attachTo(e);
				throw e;
			}
		}
	}

	/**
	 * Adds the given child block to the given parent subtree of the free space trie. Any existing
	 * subtree under the given child block will be retained.
	 *
	 * @param parentChunkNum root of the existing tree, or 0 if the child is going to be the new root
	 * @param newChildChunkNum the new child to insert
	 */
	private void insertChild(int parentChunkNum, int newChildChunkNum) {
		if (parentChunkNum == 0) {
			putInt((long) newChildChunkNum * CHUNK_SIZE + LargeBlock.PARENT_OFFSET, parentChunkNum);
			putInt(FREE_BLOCK_OFFSET, newChildChunkNum);
			return;
		}
		int numChunks = getBlockHeaderForChunkNum(newChildChunkNum);
		for (;;) {
			int currentSize = getBlockHeaderForChunkNum(parentChunkNum);
			int difference = currentSize ^ numChunks;
			if (difference == 0) {
				// The newly added item is exactly the same size as this trie node
				insertFreeBlockAfter(parentChunkNum, newChildChunkNum);
				return;
			}

			int firstDifference = LargeBlock.SIZE_OF_SIZE_FIELD * 8 - Integer.numberOfLeadingZeros(difference) - 1;
			long locationOfChildPointer = (long) parentChunkNum * CHUNK_SIZE + LargeBlock.CHILD_TABLE_OFFSET
					+ (firstDifference * INT_SIZE);
			int childChunkNum = getInt(locationOfChildPointer);
			if (childChunkNum == 0) {
				putInt(locationOfChildPointer, newChildChunkNum);
				putInt((long) newChildChunkNum * CHUNK_SIZE + LargeBlock.PARENT_OFFSET, parentChunkNum);
				return;
			}
			parentChunkNum = childChunkNum;
		}
	}

	/**
	 * Adds the given block to the linked list of equally-sized free chunks in the free space trie.
	 * Both chunks must be unused, must be the same size, and the previous chunk must already
	 * be linked into the free space trie. The newly-added chunk must not have any children.
	 *
	 * @param prevChunkNum chunk number of previous block in the existing list
	 * @param newChunkNum new chunk to be added to the list
	 */
	private void insertFreeBlockAfter(int prevChunkNum, int newChunkNum) {
		long prevChunkAddress = (long) prevChunkNum * CHUNK_SIZE;
		int nextChunkNum = getInt(prevChunkAddress + LargeBlock.NEXT_BLOCK_OFFSET);
		long nextChunkAddress = (long) nextChunkNum * CHUNK_SIZE;
		long newLockAddress = (long) newChunkNum * CHUNK_SIZE;

		putInt(prevChunkAddress + LargeBlock.NEXT_BLOCK_OFFSET, newChunkNum);
		if (nextChunkNum != 0) {
			putInt(nextChunkAddress + LargeBlock.PREV_BLOCK_OFFSET, newChunkNum);
		}
		putInt(newLockAddress + LargeBlock.PREV_BLOCK_OFFSET, prevChunkNum);
		putInt(newLockAddress + LargeBlock.NEXT_BLOCK_OFFSET, nextChunkNum);
	}

	/**
	 * Returns the chunk number of the chunk at the start of a block, given the
	 * chunk number of the chunk at the start of the following block.
	 *
	 * @param chunkNum the chunk number of the chunk immediately following the
	 * chunk being queried
	 * @return the chunk number of the chunk at the start of the previous block
	 */
	private int getFirstChunkOfBlockBefore(int chunkNum) {
		int blockChunks = Math.abs(getBlockFooterForChunkBefore(chunkNum));
		return chunkNum - blockChunks;
	}

	/**
	 * Sets the block header and footer for the given range of chunks which make
	 * up a contiguous block.
	 *
	 * @param firstChunkNum chunk number of the first chunk in the block
	 * @param headerContent the content of the header. Its magnitude is the number of
	 * chunks in the block. It is positive if the chunk is free and negative if
	 * the chunk is in use.
	 */
	private void setBlockHeader(int firstChunkNum, int headerContent) {
		assert headerContent != 0;
		assert firstChunkNum < this.fChunksUsed;
		int numBlocks = Math.abs(headerContent);
		long firstChunkAddress = (long) firstChunkNum * CHUNK_SIZE;
		putInt(firstChunkAddress, headerContent);
		putInt(firstChunkAddress + ((long) numBlocks * CHUNK_SIZE) - LargeBlock.FOOTER_SIZE, headerContent);
	}

	/**
	 * Returns the size of the block (in number of chunks) starting at the given address. The return value is positive
	 * if the block is free and negative if the block is allocated.
	 */
	private int getBlockHeaderForChunkNum(int firstChunkNum) {
		if (firstChunkNum >= this.fChunksUsed) {
			return 0;
		}
		return getInt((long) firstChunkNum * CHUNK_SIZE);
	}

	private void attachBlockHeaderForChunkNum(IndexExceptionBuilder builder, int firstChunkNum) {
		if (firstChunkNum >= this.fChunksUsed) {
			return;
		}
		builder.addProblemAddress("block header for chunk " + firstChunkNum, ((long) firstChunkNum * CHUNK_SIZE), //$NON-NLS-1$
				Database.INT_SIZE);
	}

	/**
	 * Returns the size of the block (in number of chunks), given the (non-inclusive) address that the block ends at.
	 * The return value is positive if the block is free and negative if the block is allocated.
	 */
	private int getBlockFooterForChunkBefore(int chunkNum) {
		if (chunkNum < 2) {
			// Don't report the database header as a normal chunk.
			return 0;
		}
		return getInt((long) chunkNum * CHUNK_SIZE - LargeBlock.FOOTER_SIZE);
	}

	private int createNewChunks(int numChunks) throws IndexException {
		assert this.fExclusiveLock;
		synchronized (this.fCache) {
			final int firstChunkIndex = this.fChunksUsed;
			final int lastChunkIndex = firstChunkIndex + numChunks - 1;

			final Chunk lastChunk = new Chunk(this, lastChunkIndex);

			if (lastChunkIndex >= this.fChunks.length) {
				int increment = Math.max(1024, this.fChunks.length / 20);
				int newNumChunks = Math.max(lastChunkIndex + 1, this.fChunks.length + increment);
				Chunk[] newChunks = new Chunk[newNumChunks];
				System.arraycopy(this.fChunks, 0, newChunks, 0, this.fChunks.length);
				this.fChunks = newChunks;
			}

			this.fChunksUsed = lastChunkIndex + 1;
			if (DEBUG_PAGE_CACHE) {
				System.out.println("CHUNK " + lastChunk.fSequenceNumber + ": inserted into vector - instance "  //$NON-NLS-1$//$NON-NLS-2$
						+ System.identityHashCode(lastChunk));
			}
			this.fChunks[lastChunkIndex] = lastChunk;
			this.fMostRecentlyFetchedChunk = lastChunk;
			lastChunk.makeDirty();
			this.fCache.add(lastChunk);
			long result = (long) firstChunkIndex * CHUNK_SIZE;

			/*
			 * Non-dense pointers are at most 31 bits dense pointers are at most 35 bits Check the sizes here and throw
			 * an exception if the address is too large. By throwing the IndexException with the special status, the
			 * indexing operation should be stopped. This is desired since generally, once the max size is exceeded,
			 * there are lots of errors.
			 */
			long endAddress = result + ((long) numChunks * CHUNK_SIZE);
			if (endAddress > MAX_DB_SIZE) {
				Object bindings[] = { this.getLocation().getAbsolutePath(), MAX_DB_SIZE };
				throw new IndexException(new Status(IStatus.ERROR, Package.PLUGIN_ID, Package.STATUS_DATABASE_TOO_LARGE,
						NLS.bind("Database too large! Address = " + endAddress + ", max size = " + MAX_DB_SIZE, //$NON-NLS-1$ //$NON-NLS-2$
								bindings), null));
			}

			return firstChunkIndex;
		}
	}

	private long getAddressOfFirstBlockPointer(int blockSize) {
		return MALLOC_TABLE_OFFSET + (blockSize / BLOCK_SIZE_DELTA - MIN_BLOCK_DELTAS) * INT_SIZE;
	}

	/**
	 * @param blockSize (must be a multiple of BLOCK_SIZE_DELTA)
	 */
	private long getFirstBlock(int blockSize) throws IndexException {
		assert this.fLocked;
		return this.fHeaderChunk.getFreeRecPtr(getAddressOfFirstBlockPointer(blockSize));
	}

	private void setFirstBlock(int blockSize, long block) throws IndexException {
		assert this.fExclusiveLock;
		this.fHeaderChunk.putFreeRecPtr(getAddressOfFirstBlockPointer(blockSize), block);
	}

	private void removeBlock(Chunk chunk, int blocksize, long block) throws IndexException {
		assert this.fExclusiveLock;

		long prevblock = chunk.getFreeRecPtr(block + BLOCK_PREV_OFFSET);
		long nextblock = chunk.getFreeRecPtr(block + BLOCK_NEXT_OFFSET);
		if (prevblock != 0) {
			putFreeRecPtr(prevblock + BLOCK_NEXT_OFFSET, nextblock);
		} else { // We were the head.
			setFirstBlock(blocksize, nextblock);
		}

		if (nextblock != 0)
			putFreeRecPtr(nextblock + BLOCK_PREV_OFFSET, prevblock);
	}

	private void addBlock(Chunk chunk, int blocksize, long block) throws IndexException {
		assert this.fExclusiveLock;
		// Mark our size
		chunk.putShort(block, (short) blocksize);

		// Add us to the head of the list.
		long prevfirst = getFirstBlock(blocksize);
		chunk.putFreeRecPtr(block + BLOCK_PREV_OFFSET, 0);
		chunk.putFreeRecPtr(block + BLOCK_NEXT_OFFSET, prevfirst);
		if (prevfirst != 0)
			putFreeRecPtr(prevfirst + BLOCK_PREV_OFFSET, block);
		setFirstBlock(blocksize, block);
	}

	/**
	 * Free an allocated block.
	 *
	 * @param address
	 *            memory address to be freed
	 * @param poolId
	 *            the same ID that was previously passed into malloc when allocating this memory address
	 */
	public void free(long address, short poolId) throws IndexException {
		getLog().start(this.freeTag);
		try {
			assert this.fExclusiveLock;
			if (address == 0) {
				return;
			}
			long blockSize;
			long block = address - BLOCK_HEADER_SIZE;
			Chunk chunk = getChunk(block);
			blockSize = -chunk.getShort(block);
			// We use a block size of 0 to indicate a large block that fills a range of chunks
			if (blockSize == 0) {
				int offsetIntoChunk = (int) (address % CHUNK_SIZE);
				assert offsetIntoChunk == LargeBlock.HEADER_SIZE + BLOCK_HEADER_SIZE;
				// Deallocating a large block
				// This was a large block. It uses a sequence of full chunks.
				int chunkNum = (int) (address / CHUNK_SIZE);
				int numChunks = -getBlockHeaderForChunkNum(chunkNum);
				if (numChunks < 0) {
					IndexExceptionBuilder builder = describeProblem();
					if (chunkNum < this.fChunksUsed) {
						builder.addProblemAddress("block header", (long) chunkNum * CHUNK_SIZE, INT_SIZE); //$NON-NLS-1$
					}
					throw builder.build("Already freed large block " + address); //$NON-NLS-1$
				}
				blockSize = (long) numChunks * CHUNK_SIZE;
				this.log.recordFree(address, (int)(blockSize - BLOCK_HEADER_SIZE));
				freeLargeChunk(chunkNum, numChunks);
			} else {
				// Deallocating a normal block
				// TODO Look for opportunities to merge small blocks
				if (blockSize < 0) {
					throw describeProblem()
						.addProblemAddress("block size", block, SHORT_SIZE) //$NON-NLS-1$
						.build("Already freed record " + address); //$NON-NLS-1$
				}
				this.log.recordFree(address, (int)(blockSize - BLOCK_HEADER_SIZE));
				int offset = Chunk.recPtrToIndex(address);
				if (offset + blockSize > CHUNK_SIZE) {
					throw describeProblem()
						.addProblemAddress("block size", block, SHORT_SIZE) //$NON-NLS-1$
						.build("Attempting to free chunk of impossible size. The block at address " //$NON-NLS-1$
								+ address + " in chunk " + chunk.fSequenceNumber + " offset " + offset //$NON-NLS-1$//$NON-NLS-2$
								+ " can't be as large as " //$NON-NLS-1$
								+ blockSize + " bytes since that would make it extend beyond the end of the chunk"); //$NON-NLS-1$
				}
				addBlock(chunk, (int) blockSize, block);
			}

			if (DEBUG_FREE_SPACE) {
				periodicValidateFreeSpace();
			}

			this.freed += blockSize;
			this.memoryUsage.recordFree(poolId, blockSize);
		} finally {
			getLog().end(this.freeTag);
		}
	}

	/**
	 * Periodically performs validation of the free space in the database. Validation is very expensive, so the
	 * validation period uses exponential falloff so validations happen less and less frequently over
	 * time. Returns true iff validation happened on this iteration.
	 */
	private boolean periodicValidateFreeSpace() {
		this.validateCounter++;
		if (this.validateCounter > this.nextValidation) {
			validateFreeSpace();
			this.nextValidation = this.validateCounter * 2;
			return true;
		}
		return false;
	}

	private void freeLargeChunk(int chunkNum, int numChunks) {
		assert chunkNum > 0;
		assert numChunks > 0;
		int prevBlockHeader = getBlockFooterForChunkBefore(chunkNum);
		int nextBlockChunkNum = chunkNum + numChunks;
		int nextBlockHeader = getBlockHeaderForChunkNum(nextBlockChunkNum);

		// If the previous block is unused, merge with it
		if (prevBlockHeader > 0) {
			int prevBlockChunkNum = getFirstChunkOfBlockBefore(chunkNum);

			unlinkFreeBlock(prevBlockChunkNum);
			chunkNum = prevBlockChunkNum;
			numChunks += prevBlockHeader;
		}

		// If the next block is unused, merge with it
		if (nextBlockHeader > 0) {
			unlinkFreeBlock(nextBlockChunkNum);
			numChunks += nextBlockHeader;
		}

		// Block merging is done. Now reinsert the merged block into the free space trie
		linkFreeBlockToTrie(chunkNum, numChunks);
	}

	public void putByte(long offset, byte value) throws IndexException {
		getChunk(offset).putByte(offset, value);
	}

	public byte getByte(long offset) throws IndexException {
		return getChunk(offset).getByte(offset);
	}

	public void putInt(long offset, int value) throws IndexException {
		getChunk(offset).putInt(offset, value);
	}

	public int getInt(long offset) throws IndexException {
		return getChunk(offset).getInt(offset);
	}

	public void putRecPtr(long offset, long value) throws IndexException {
		getChunk(offset).putRecPtr(offset, value);
	}

	public long getRecPtr(long offset) throws IndexException {
		return getChunk(offset).getRecPtr(offset);
	}

	private void putFreeRecPtr(long offset, long value) throws IndexException {
		getChunk(offset).putFreeRecPtr(offset, value);
	}

	private long getFreeRecPtr(long offset) throws IndexException {
		return getChunk(offset).getFreeRecPtr(offset);
	}

	public void put3ByteUnsignedInt(long offset, int value) throws IndexException {
		getChunk(offset).put3ByteUnsignedInt(offset, value);
	}

	public int get3ByteUnsignedInt(long offset) throws IndexException {
		return getChunk(offset).get3ByteUnsignedInt(offset);
	}

	public void putShort(long offset, short value) throws IndexException {
		getChunk(offset).putShort(offset, value);
	}

	public short getShort(long offset) throws IndexException {
		return getChunk(offset).getShort(offset);
	}

	public void putLong(long offset, long value) throws IndexException {
		getChunk(offset).putLong(offset, value);
	}

	public void putDouble(long offset, double value) throws IndexException {
		getChunk(offset).putDouble(offset, value);
	}

	public void putFloat(long offset, float value) throws IndexException {
		getChunk(offset).putFloat(offset, value);
	}

	public long getLong(long offset) throws IndexException {
		return getChunk(offset).getLong(offset);
	}

	public double getDouble(long offset) throws IndexException {
		return getChunk(offset).getDouble(offset);
	}

	public float getFloat(long offset) throws IndexException {
		return getChunk(offset).getFloat(offset);
	}

	public void putChar(long offset, char value) throws IndexException {
		getChunk(offset).putChar(offset, value);
	}

	public char getChar(long offset) throws IndexException {
		return getChunk(offset).getChar(offset);
	}

	public void clearBytes(long offset, int byteCount) throws IndexException {
		getChunk(offset).clear(offset, byteCount);
	}

	public void putBytes(long offset, byte[] data, int len) throws IndexException {
		getChunk(offset).put(offset, data, len);
	}

	public void putBytes(long offset, byte[] data, int dataPos, int len) throws IndexException {
		getChunk(offset).put(offset, data, dataPos, len);
	}

	public void getBytes(long offset, byte[] data) throws IndexException {
		getChunk(offset).get(offset, data);
	}

	public void getBytes(long offset, byte[] data, int dataPos, int len) throws IndexException {
		getChunk(offset).get(offset, data, dataPos, len);
	}

	public IString newString(String string) throws IndexException {
		return newString(string.toCharArray());
	}

	public IString newString(char[] chars) throws IndexException {
		int len= chars.length;
		int bytelen;
		final boolean useBytes = useBytes(chars);
		if (useBytes) {
			bytelen= len;
		} else {
			bytelen= 2 * len;
		}

		if (bytelen > ShortString.MAX_BYTE_LENGTH) {
			return new LongString(this, chars, useBytes);
		} else {
			return new ShortString(this, chars, useBytes);
		}
	}

	private boolean useBytes(char[] chars) {
		for (char c : chars) {
			if ((c & 0xff00) != 0)
				return false;
		}
		return true;
	}

	public IString getString(long offset) throws IndexException {
		final int l = getInt(offset);
		int bytelen= l < 0 ? -l : 2 * l;
		if (bytelen > ShortString.MAX_BYTE_LENGTH) {
			return new LongString(this, offset);
		}
		return new ShortString(this, offset);
	}

	public long getDatabaseSize() {
		return (long) this.fChunksUsed * CHUNK_SIZE;
	}

	/**
	 * Returns the number of bytes freed by {@link #free(long, short)} since this {@link Database} instance was
	 * instantiated. Intended for use in unit tests.
	 */
	public long getBytesFreed() {
		return this.freed;
	}

	/**
	 * Returns the number of bytes allocated by {@link #malloc(long, short)} since this {@link Database} instance was
	 * instantiated. Intended for use in unit tests.
	 */
	public long getBytesAllocated() {
		return this.malloced;
	}

	/**
	 * For debugging purposes, only.
	 */
	public void reportFreeBlocks() throws IndexException {
		System.out.println("Allocated size: " + formatByteString(getDatabaseSize())); //$NON-NLS-1$
		System.out.println("malloc'ed: " + formatByteString(this.malloced)); //$NON-NLS-1$
		System.out.println("free'd: " + formatByteString(this.freed)); //$NON-NLS-1$
		System.out.println("wasted: " + formatByteString((getDatabaseSize() - (this.malloced - this.freed)))); //$NON-NLS-1$
		System.out.println("Free blocks"); //$NON-NLS-1$
		for (int bs = MIN_BLOCK_DELTAS*BLOCK_SIZE_DELTA; bs <= CHUNK_SIZE; bs += BLOCK_SIZE_DELTA) {
			int count = 0;
			long block = getFirstBlock(bs);
			while (block != 0) {
				++count;
				block = getFreeRecPtr(block + BLOCK_NEXT_OFFSET);
			}
			if (count != 0)
				System.out.println("Block size: " + bs + "=" + count); //$NON-NLS-1$ //$NON-NLS-2$
		}
	}

	/**
	 * Closes the database.
	 * <p>
	 * The behavior of any further calls to the Database is undefined
	 * @throws IndexException
	 */
	public void close() throws IndexException {
		assert this.fExclusiveLock;
		flush();
		removeChunksFromCache();

		this.log.clear();
		// Chunks have been removed from the cache, so we are fine.
		this.fHeaderChunk.clear(0, CHUNK_SIZE);
		this.memoryUsage.refresh();
		this.fHeaderChunk.fDirty= false;
		this.dirtyChunkSet.clear();
		this.fChunks= new Chunk[] { null };
		this.fChunksUsed = this.fChunks.length;
		try {
			this.fFile.close();
		} catch (IOException e) {
			throw new IndexException(new DBStatus(e));
		}
	}

	/**
     * This method is public for testing purposes only.
     */
	public File getLocation() {
		return this.fLocation;
	}

	/**
	 * Called from any thread via the cache, protected by {@link #fCache}.
	 */
	void checkIfChunkReleased(final Chunk chunk) {
		if (!chunk.fDirty && chunk.fCacheIndex < 0) {
			if (DEBUG_PAGE_CACHE) {
				System.out.println("CHUNK " + chunk.fSequenceNumber //$NON-NLS-1$
						+ ": removing from vector in releaseChunk - instance " + System.identityHashCode(chunk)); //$NON-NLS-1$
			}
			this.fChunks[chunk.fSequenceNumber]= null;
		}
	}

	void chunkDirtied(final Chunk chunk) {
		if (chunk.fSequenceNumber < NUM_HEADER_CHUNKS) {
			return;
		}
		this.dirtyChunkSet.add(chunk);
	}

	void chunkCleaned(final Chunk chunk) {
		if (chunk.fSequenceNumber < NUM_HEADER_CHUNKS) {
			return;
		}
		this.dirtyChunkSet.remove(chunk);
		checkIfChunkReleased(chunk);
	}

	/**
	 * Returns the cache used for this database.
	 * @since 4.0
	 */
	public ChunkCache getChunkCache() {
		return this.fCache;
	}

	/**
	 * Asserts that database is used by one thread exclusively. This is necessary when doing
	 * write operations.
	 */
	public void setExclusiveLock() {
		this.fExclusiveLock= true;
		this.fLocked= true;
	}

	public void setLocked(boolean val) {
		this.fLocked= val;
	}

	public void giveUpExclusiveLock() {
		this.fExclusiveLock = false;
	}

	public boolean flush() throws IndexException {
		boolean wasInterrupted = false;
		assert this.fLocked;
		ArrayList<Chunk> dirtyChunks= new ArrayList<>();
		synchronized (this.fCache) {
			dirtyChunks.addAll(this.dirtyChunkSet);
		}
		sortBySequenceNumber(dirtyChunks);

		long startTime = System.currentTimeMillis();
		// Also handles header chunk.
		wasInterrupted = flushAndUnlockChunks(dirtyChunks, true) || wasInterrupted;
		long elapsedTime = System.currentTimeMillis() - startTime;
		this.totalFlushTime += elapsedTime;

		return wasInterrupted;
	}

	private void sortBySequenceNumber(ArrayList<Chunk> dirtyChunks) {
		dirtyChunks.sort((a, b) -> {return a.fSequenceNumber - b.fSequenceNumber;});
	}

	/**
	 * Interrupting the thread with {@link Thread#interrupt()} won't interrupt the write. Returns true iff an attempt
	 * was made to interrupt the thread with {@link Thread#interrupt()}.
	 *
	 * @throws IndexException
	 */
	private boolean flushAndUnlockChunks(final ArrayList<Chunk> dirtyChunks, boolean isComplete) throws IndexException {
		boolean wasInterrupted = false;
		assert !Thread.holdsLock(this.fCache);
		final boolean haveDirtyChunks = !dirtyChunks.isEmpty();
		if (haveDirtyChunks || this.fHeaderChunk.fDirty) {
			wasInterrupted = markFileIncomplete() || wasInterrupted;
		}
		if (haveDirtyChunks) {
			double desiredWriteBytesPerMs = Database.MIN_BYTES_PER_MILLISECOND;
			synchronized (this.fCache) {
				if (this.cacheMisses > 100) {
					double measuredReadBytesPerMs = getAverageReadBytesPerMs();
					if (measuredReadBytesPerMs > 0) {
						desiredWriteBytesPerMs = measuredReadBytesPerMs / 2;
					}
				}
			}
			desiredWriteBytesPerMs = Math.max(desiredWriteBytesPerMs, Database.MIN_BYTES_PER_MILLISECOND);
			ChunkWriter writer = new ChunkWriter(WRITE_BUFFER_SIZE, desiredWriteBytesPerMs, this::write);
			try {
				for (Chunk chunk : dirtyChunks) {
					if (chunk.fDirty) {
						boolean wasCanceled = false;
						if (DEBUG_PAGE_CACHE) {
							System.out.println("CHUNK " + chunk.fSequenceNumber + ": flushing - instance " //$NON-NLS-1$//$NON-NLS-2$
									+ System.identityHashCode(chunk));
						}
						byte[] nextBytes;
						synchronized (this.fCache) {
							nextBytes = chunk.getBytes();
							chunk.fDirty = false;
							chunkCleaned(chunk);
						}
						wasCanceled = writer.write((long) chunk.fSequenceNumber * Database.CHUNK_SIZE, nextBytes);

						wasInterrupted = wasCanceled || wasInterrupted;
					}
				}
				writer.flush();
				synchronized (this.fCache) {
					this.pageWritesBytes += writer.getBytesWritten();
					this.totalWriteTimeMs += writer.getTotalWriteTimeMs();
				}
			} catch (IOException e) {
				throw new IndexException(new DBStatus(e));
			}
		}

		if (isComplete) {
			if (this.fHeaderChunk.fDirty || this.fIsMarkedIncomplete) {
				this.fHeaderChunk.putInt(VERSION_OFFSET, this.fVersion);
				wasInterrupted = this.fHeaderChunk.flush() || wasInterrupted;
				this.fIsMarkedIncomplete= false;
			}
		}
		return wasInterrupted;
	}

	private boolean markFileIncomplete() throws IndexException {
		boolean wasInterrupted = false;
		if (!this.fIsMarkedIncomplete) {
			this.fIsMarkedIncomplete= true;
			try {
				final ByteBuffer buf= ByteBuffer.wrap(new byte[4]);
				wasInterrupted = performUninterruptableWrite(() -> this.fFile.getChannel().write(buf, 0));
				this.bytesWritten += 4;
			} catch (IOException e) {
				throw new IndexException(new DBStatus(e));
			}
		}
		return wasInterrupted;
	}

	public void resetCacheCounters() {
		this.cacheHits = 0;
		this.cacheMisses = 0;
		this.bytesWritten = 0;
		this.totalFlushTime = 0;
		this.pageWritesBytes = 0;
		this.totalWriteTimeMs = 0;
		this.totalReadTimeMs = 0;
	}

	public long getBytesWritten() {
		return this.bytesWritten;
	}

	public double getAverageReadBytesPerMs() {
		long reads = this.cacheMisses;
		long time = this.totalReadTimeMs;

		if (time == 0) {
			return 0;
		}

		return (double)(reads * CHUNK_SIZE) / (double) time;
	}

	public double getAverageWriteBytesPerMs() {
		long time = this.totalWriteTimeMs;
		long writes = this.pageWritesBytes;

		return ((double) writes / (double) time);
	}

	public long getBytesRead() {
		return this.cacheMisses * CHUNK_SIZE;
	}

	public long getCacheHits() {
		return this.cacheHits;
	}

	public long getCacheMisses() {
		return this.cacheMisses;
	}

	public long getCumulativeFlushTimeMs() {
		return this.totalFlushTime;
	}

	public long getSizeBytes() throws IOException {
		return this.fFile.length();
	}

	public int getChunkCount() {
		return this.fChunksUsed;
	}

	/**
	 * A Record Pointer is a pointer as returned by Database.malloc().
	 * This is a pointer to a block + BLOCK_HEADER_SIZE.
	 */
	public static void putRecPtr(final long value, byte[] buffer, int idx) {
		final int denseValue = value == 0 ? 0 : Chunk.compressFreeRecPtr(value - BLOCK_HEADER_SIZE);
		Chunk.putInt(denseValue, buffer, idx);
	}

	/**
	 * A Record Pointer is a pointer as returned by Database.malloc().
	 * This is a pointer to a block + BLOCK_HEADER_SIZE.
	 */
	public static long getRecPtr(byte[] buffer, final int idx) {
		int value = Chunk.getInt(buffer, idx);
		long address = Chunk.expandToFreeRecPtr(value);
		return address != 0 ? (address + BLOCK_HEADER_SIZE) : address;
	}

	public MemoryStats getMemoryStats() {
		return this.memoryUsage;
	}

	/**
	 * Returns the number of bytes that can fit in the payload of the given number of chunks.
	 */
	public static long getBytesThatFitInChunks(int numChunks) {
		return CHUNK_SIZE * (long) numChunks - LargeBlock.HEADER_SIZE - LargeBlock.FOOTER_SIZE - BLOCK_HEADER_SIZE;
	}

	/**
	 * Returns the number of chunks needed to fit the given number of bytes of payload.
	 */
	public static int getChunksNeededForBytes(long datasize) {
		return divideRoundingUp(datasize + BLOCK_HEADER_SIZE + LargeBlock.HEADER_SIZE + LargeBlock.FOOTER_SIZE,
				CHUNK_SIZE);
	}

	public ChunkCache getCache() {
		return this.fCache;
	}

	public int getDirtyChunkCount() {
		return this.dirtyChunkSet.size();
	}

	public static String formatByteString(long valueInBytes) {
		final double MB = 1024 * 1024;
		double value = valueInBytes;
		String suffix = "B"; //$NON-NLS-1$

		if (value > 1024) {
			suffix = "MiB"; //$NON-NLS-1$
			value /= MB;
		}

		DecimalFormat mbFormat = new DecimalFormat("#0.###"); //$NON-NLS-1$
		return mbFormat.format(value) + suffix;
	}

	public ChunkStats getChunkStats() {
		synchronized (this.fCache) {
			int count = 0;
			int dirtyChunks = 0;
			int nonDirtyChunksNotInCache = 0;
			for (Chunk next : this.fChunks) {
				if (next != null) {
					count++;
					if (next.fDirty) {
						dirtyChunks++;
					} else if (next.fCacheIndex < 0) {
						nonDirtyChunksNotInCache++;
					}
				}
			}
			return new ChunkStats(this.fChunks.length, count, dirtyChunks, nonDirtyChunksNotInCache);
		}
	}

	public IndexExceptionBuilder describeProblem() {
		return new IndexExceptionBuilder(this);
	}
}