/*
    * Copyright (C) 2008-2010, Google Inc.
    * Copyright (C) 2008, Marek Zawirski <marek.zawirski@gmail.com>
    * and other copyright owners as documented in the project's IP log.
    *
    * This program and the accompanying materials are made available
    * under the terms of the Eclipse Distribution License v1.0 which
    * accompanies this distribution, is reproduced below, and is
    * available at http://www.eclipse.org/org/documents/edl-v10.php
   *
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or
   * without modification, are permitted provided that the following
   * conditions are met:
   *
   * - Redistributions of source code must retain the above copyright
   *   notice, this list of conditions and the following disclaimer.
   *
   * - Redistributions in binary form must reproduce the above
   *   copyright notice, this list of conditions and the following
   *   disclaimer in the documentation and/or other materials provided
   *   with the distribution.
   *
   * - Neither the name of the Eclipse Foundation, Inc. nor the
   *   names of its contributors may be used to endorse or promote
   *   products derived from this software without specific prior
   *   written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
   * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
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   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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  package org.eclipse.jgit.storage.pack;
  
  import java.util.concurrent.Executor;
  import java.util.zip.Deflater;
  
  import org.eclipse.jgit.internal.storage.file.PackIndexWriter;
  import org.eclipse.jgit.lib.Config;
  import org.eclipse.jgit.lib.Repository;
  
  /**
   * Configuration used by a pack writer when constructing the stream.
   *
   * A configuration may be modified once created, but should not be modified
   * while it is being used by a PackWriter. If a configuration is not modified it
   * is safe to share the same configuration instance between multiple concurrent
   * threads executing different PackWriters.
   */
  public class PackConfig {
  	/**
  	 * Default value of deltas reuse option: {@value}
  	 *
  	 * @see #setReuseDeltas(boolean)
  	 */
  	public static final boolean DEFAULT_REUSE_DELTAS = true;
  
  	/**
  	 * Default value of objects reuse option: {@value}
  	 *
  	 * @see #setReuseObjects(boolean)
  	 */
  	public static final boolean DEFAULT_REUSE_OBJECTS = true;
  
  	/**
  	 * Default value of delta compress option: {@value}
  	 *
  	 * @see #setDeltaCompress(boolean)
  	 */
  	public static final boolean DEFAULT_DELTA_COMPRESS = true;
  
  	/**
  	 * Default value of delta base as offset option: {@value}
  	 *
  	 * @see #setDeltaBaseAsOffset(boolean)
  	 */
  	public static final boolean DEFAULT_DELTA_BASE_AS_OFFSET = false;
  
  	/**
  	 * Default value of maximum delta chain depth: {@value}
  	 *
  	 * @see #setMaxDeltaDepth(int)
  	 */
  	public static final int DEFAULT_MAX_DELTA_DEPTH = 50;
  
  	/**
  	 * Default window size during packing: {@value}
 	 *
 	 * @see #setDeltaSearchWindowSize(int)
 	 */
 	public static final int DEFAULT_DELTA_SEARCH_WINDOW_SIZE = 10;
 
 	/**
 	 * Default big file threshold: {@value}
 	 *
 	 * @see #setBigFileThreshold(int)
 	 */
 	public static final int DEFAULT_BIG_FILE_THRESHOLD = 50 * 1024 * 1024;
 
 	/**
 	 * Default delta cache size: {@value}
 	 *
 	 * @see #setDeltaCacheSize(long)
 	 */
 	public static final long DEFAULT_DELTA_CACHE_SIZE = 50 * 1024 * 1024;
 
 	/**
 	 * Default delta cache limit: {@value}
 	 *
 	 * @see #setDeltaCacheLimit(int)
 	 */
 	public static final int DEFAULT_DELTA_CACHE_LIMIT = 100;
 
 	/**
 	 * Default index version: {@value}
 	 *
 	 * @see #setIndexVersion(int)
 	 */
 	public static final int DEFAULT_INDEX_VERSION = 2;
 
 	/**
 	 * Default value of the build bitmaps option: {@value}
 	 *
 	 * @see #setBuildBitmaps(boolean)
 	 * @since 3.0
 	 */
 	public static final boolean DEFAULT_BUILD_BITMAPS = true;
 
 	/**
 	 * Default count of most recent commits to select for bitmaps. Only applies
 	 * when bitmaps are enabled: {@value}
 	 *
 	 * @see #setBitmapContiguousCommitCount(int)
 	 * @since 4.2
 	 */
 	public static final int DEFAULT_BITMAP_CONTIGUOUS_COMMIT_COUNT = 100;
 
 	/**
 	 * Count at which the span between selected commits changes from
 	 * "bitmapRecentCommitSpan" to "bitmapDistantCommitSpan". Only applies when
 	 * bitmaps are enabled: {@value}
 	 *
 	 * @see #setBitmapRecentCommitCount(int)
 	 * @since 4.2
 	 */
 	public static final int DEFAULT_BITMAP_RECENT_COMMIT_COUNT = 20000;
 
 	/**
 	 * Default spacing between commits in recent history when selecting commits
 	 * for bitmaps. Only applies when bitmaps are enabled: {@value}
 	 *
 	 * @see #setBitmapRecentCommitSpan(int)
 	 * @since 4.2
 	 */
 	public static final int DEFAULT_BITMAP_RECENT_COMMIT_SPAN = 100;
 
 	/**
 	 * Default spacing between commits in distant history when selecting commits
 	 * for bitmaps. Only applies when bitmaps are enabled: {@value}
 	 *
 	 * @see #setBitmapDistantCommitSpan(int)
 	 * @since 4.2
 	 */
 	public static final int DEFAULT_BITMAP_DISTANT_COMMIT_SPAN = 5000;
 
 	/**
 	 * Default count of branches required to activate inactive branch commit
 	 * selection. If the number of branches is less than this then bitmaps for
 	 * the entire commit history of all branches will be created, otherwise
 	 * branches marked as "inactive" will have coverage for only partial
 	 * history: {@value}
 	 *
 	 * @see #setBitmapExcessiveBranchCount(int)
 	 * @since 4.2
 	 */
 	public static final int DEFAULT_BITMAP_EXCESSIVE_BRANCH_COUNT = 100;
 
 	/**
 	 * Default age at which a branch is considered inactive. Age is taken as the
 	 * number of days ago that the most recent commit was made to a branch. Only
 	 * affects bitmap processing if bitmaps are enabled and the
 	 * "excessive branch count" has been exceeded: {@value}
 	 *
 	 * @see #setBitmapInactiveBranchAgeInDays(int)
 	 * @since 4.2
 	 */
 	public static final int DEFAULT_BITMAP_INACTIVE_BRANCH_AGE_IN_DAYS = 90;
 
 	private int compressionLevel = Deflater.DEFAULT_COMPRESSION;
 
 	private boolean reuseDeltas = DEFAULT_REUSE_DELTAS;
 
 	private boolean reuseObjects = DEFAULT_REUSE_OBJECTS;
 
 	private boolean deltaBaseAsOffset = DEFAULT_DELTA_BASE_AS_OFFSET;
 
 	private boolean deltaCompress = DEFAULT_DELTA_COMPRESS;
 
 	private int maxDeltaDepth = DEFAULT_MAX_DELTA_DEPTH;
 
 	private int deltaSearchWindowSize = DEFAULT_DELTA_SEARCH_WINDOW_SIZE;
 
 	private long deltaSearchMemoryLimit;
 
 	private long deltaCacheSize = DEFAULT_DELTA_CACHE_SIZE;
 
 	private int deltaCacheLimit = DEFAULT_DELTA_CACHE_LIMIT;
 
 	private int bigFileThreshold = DEFAULT_BIG_FILE_THRESHOLD;
 
 	private int threads;
 
 	private Executor executor;
 
 	private int indexVersion = DEFAULT_INDEX_VERSION;
 
 	private boolean buildBitmaps = DEFAULT_BUILD_BITMAPS;
 
 	private int bitmapContiguousCommitCount = DEFAULT_BITMAP_CONTIGUOUS_COMMIT_COUNT;
 
 	private int bitmapRecentCommitCount = DEFAULT_BITMAP_RECENT_COMMIT_COUNT;
 
 	private int bitmapRecentCommitSpan = DEFAULT_BITMAP_RECENT_COMMIT_SPAN;
 
 	private int bitmapDistantCommitSpan = DEFAULT_BITMAP_DISTANT_COMMIT_SPAN;
 
 	private int bitmapExcessiveBranchCount = DEFAULT_BITMAP_EXCESSIVE_BRANCH_COUNT;
 
 	private int bitmapInactiveBranchAgeInDays = DEFAULT_BITMAP_INACTIVE_BRANCH_AGE_IN_DAYS;
 
 	private boolean cutDeltaChains;
 
 	/** Create a default configuration. */
 	public PackConfig() {
 		// Fields are initialized to defaults.
 	}
 
 	/**
 	 * Create a configuration honoring the repository's settings.
 	 *
 	 * @param db
 	 *            the repository to read settings from. The repository is not
 	 *            retained by the new configuration, instead its settings are
 	 *            copied during the constructor.
 	 */
 	public PackConfig(Repository db) {
 		fromConfig(db.getConfig());
 	}
 
 	/**
 	 * Create a configuration honoring settings in a {@link Config}.
 	 *
 	 * @param cfg
 	 *            the source to read settings from. The source is not retained
 	 *            by the new configuration, instead its settings are copied
 	 *            during the constructor.
 	 */
 	public PackConfig(Config cfg) {
 		fromConfig(cfg);
 	}
 
 	/**
 	 * Copy an existing configuration to a new instance.
 	 *
 	 * @param cfg
 	 *            the source configuration to copy from.
 	 */
 	public PackConfig(PackConfig cfg) {
 		this.compressionLevel = cfg.compressionLevel;
 		this.reuseDeltas = cfg.reuseDeltas;
 		this.reuseObjects = cfg.reuseObjects;
 		this.deltaBaseAsOffset = cfg.deltaBaseAsOffset;
 		this.deltaCompress = cfg.deltaCompress;
 		this.maxDeltaDepth = cfg.maxDeltaDepth;
 		this.deltaSearchWindowSize = cfg.deltaSearchWindowSize;
 		this.deltaSearchMemoryLimit = cfg.deltaSearchMemoryLimit;
 		this.deltaCacheSize = cfg.deltaCacheSize;
 		this.deltaCacheLimit = cfg.deltaCacheLimit;
 		this.bigFileThreshold = cfg.bigFileThreshold;
 		this.threads = cfg.threads;
 		this.executor = cfg.executor;
 		this.indexVersion = cfg.indexVersion;
 		this.buildBitmaps = cfg.buildBitmaps;
 		this.bitmapContiguousCommitCount = cfg.bitmapContiguousCommitCount;
 		this.bitmapRecentCommitCount = cfg.bitmapRecentCommitCount;
 		this.bitmapRecentCommitSpan = cfg.bitmapRecentCommitSpan;
 		this.bitmapDistantCommitSpan = cfg.bitmapDistantCommitSpan;
 		this.bitmapExcessiveBranchCount = cfg.bitmapExcessiveBranchCount;
 		this.bitmapInactiveBranchAgeInDays = cfg.bitmapInactiveBranchAgeInDays;
 		this.cutDeltaChains = cfg.cutDeltaChains;
 	}
 
 	/**
 	 * Check whether to reuse deltas existing in repository.
 	 *
 	 * Default setting: {@value #DEFAULT_REUSE_DELTAS}
 	 *
 	 * @return true if object is configured to reuse deltas; false otherwise.
 	 */
 	public boolean isReuseDeltas() {
 		return reuseDeltas;
 	}
 
 	/**
 	 * Set reuse deltas configuration option for the writer.
 	 *
 	 * When enabled, writer will search for delta representation of object in
 	 * repository and use it if possible. Normally, only deltas with base to
 	 * another object existing in set of objects to pack will be used. The
 	 * exception however is thin-packs where the base object may exist on the
 	 * other side.
 	 *
 	 * When raw delta data is directly copied from a pack file, its checksum is
 	 * computed to verify the data is not corrupt.
 	 *
 	 * Default setting: {@value #DEFAULT_REUSE_DELTAS}
 	 *
 	 * @param reuseDeltas
 	 *            boolean indicating whether or not try to reuse deltas.
 	 */
 	public void setReuseDeltas(boolean reuseDeltas) {
 		this.reuseDeltas = reuseDeltas;
 	}
 
 	/**
 	 * Checks whether to reuse existing objects representation in repository.
 	 *
 	 * Default setting: {@value #DEFAULT_REUSE_OBJECTS}
 	 *
 	 * @return true if writer is configured to reuse objects representation from
 	 *         pack; false otherwise.
 	 */
 	public boolean isReuseObjects() {
 		return reuseObjects;
 	}
 
 	/**
 	 * Set reuse objects configuration option for the writer.
 	 *
 	 * If enabled, writer searches for compressed representation in a pack file.
 	 * If possible, compressed data is directly copied from such a pack file.
 	 * Data checksum is verified.
 	 *
 	 * Default setting: {@value #DEFAULT_REUSE_OBJECTS}
 	 *
 	 * @param reuseObjects
 	 *            boolean indicating whether or not writer should reuse existing
 	 *            objects representation.
 	 */
 	public void setReuseObjects(boolean reuseObjects) {
 		this.reuseObjects = reuseObjects;
 	}
 
 	/**
 	 * True if writer can use offsets to point to a delta base.
 	 *
 	 * If true the writer may choose to use an offset to point to a delta base
 	 * in the same pack, this is a newer style of reference that saves space.
 	 * False if the writer has to use the older (and more compatible style) of
 	 * storing the full ObjectId of the delta base.
 	 *
 	 * Default setting: {@value #DEFAULT_DELTA_BASE_AS_OFFSET}
 	 *
 	 * @return true if delta base is stored as an offset; false if it is stored
 	 *         as an ObjectId.
 	 */
 	public boolean isDeltaBaseAsOffset() {
 		return deltaBaseAsOffset;
 	}
 
 	/**
 	 * Set writer delta base format.
 	 *
 	 * Delta base can be written as an offset in a pack file (new approach
 	 * reducing file size) or as an object id (legacy approach, compatible with
 	 * old readers).
 	 *
 	 * Default setting: {@value #DEFAULT_DELTA_BASE_AS_OFFSET}
 	 *
 	 * @param deltaBaseAsOffset
 	 *            boolean indicating whether delta base can be stored as an
 	 *            offset.
 	 */
 	public void setDeltaBaseAsOffset(boolean deltaBaseAsOffset) {
 		this.deltaBaseAsOffset = deltaBaseAsOffset;
 	}
 
 	/**
 	 * Check whether the writer will create new deltas on the fly.
 	 *
 	 * Default setting: {@value #DEFAULT_DELTA_COMPRESS}
 	 *
 	 * @return true if the writer will create a new delta when either
 	 *         {@link #isReuseDeltas()} is false, or no suitable delta is
 	 *         available for reuse.
 	 */
 	public boolean isDeltaCompress() {
 		return deltaCompress;
 	}
 
 	/**
 	 * Set whether or not the writer will create new deltas on the fly.
 	 *
 	 * Default setting: {@value #DEFAULT_DELTA_COMPRESS}
 	 *
 	 * @param deltaCompress
 	 *            true to create deltas when {@link #isReuseDeltas()} is false,
 	 *            or when a suitable delta isn't available for reuse. Set to
 	 *            false to write whole objects instead.
 	 */
 	public void setDeltaCompress(boolean deltaCompress) {
 		this.deltaCompress = deltaCompress;
 	}
 
 	/**
 	 * Get maximum depth of delta chain set up for the writer.
 	 *
 	 * Generated chains are not longer than this value.
 	 *
 	 * Default setting: {@value #DEFAULT_MAX_DELTA_DEPTH}
 	 *
 	 * @return maximum delta chain depth.
 	 */
 	public int getMaxDeltaDepth() {
 		return maxDeltaDepth;
 	}
 
 	/**
 	 * Set up maximum depth of delta chain for the writer.
 	 *
 	 * Generated chains are not longer than this value. Too low value causes low
 	 * compression level, while too big makes unpacking (reading) longer.
 	 *
 	 * Default setting: {@value #DEFAULT_MAX_DELTA_DEPTH}
 	 *
 	 * @param maxDeltaDepth
 	 *            maximum delta chain depth.
 	 */
 	public void setMaxDeltaDepth(int maxDeltaDepth) {
 		this.maxDeltaDepth = maxDeltaDepth;
 	}
 
 	/**
 	 * @return true if existing delta chains should be cut at
 	 *         {@link #getMaxDeltaDepth()}. Default is false, allowing existing
 	 *         chains to be of any length.
 	 * @since 3.0
 	 */
 	public boolean getCutDeltaChains() {
 		return cutDeltaChains;
 	}
 
 	/**
 	 * Enable cutting existing delta chains at {@link #getMaxDeltaDepth()}.
 	 *
 	 * By default this is disabled and existing chains are kept at whatever
 	 * length a prior packer was configured to create. This allows objects to be
 	 * packed one with a large depth (for example 250), and later to quickly
 	 * repack the repository with a shorter depth (such as 50), but reusing the
 	 * complete delta chains created by the earlier 250 depth.
 	 *
 	 * @param cut
 	 *            true to cut existing chains.
 	 * @since 3.0
 	 */
 	public void setCutDeltaChains(boolean cut) {
 		cutDeltaChains = cut;
 	}
 
 	/**
 	 * Get the number of objects to try when looking for a delta base.
 	 *
 	 * This limit is per thread, if 4 threads are used the actual memory used
 	 * will be 4 times this value.
 	 *
 	 * Default setting: {@value #DEFAULT_DELTA_SEARCH_WINDOW_SIZE}
 	 *
 	 * @return the object count to be searched.
 	 */
 	public int getDeltaSearchWindowSize() {
 		return deltaSearchWindowSize;
 	}
 
 	/**
 	 * Set the number of objects considered when searching for a delta base.
 	 *
 	 * Default setting: {@value #DEFAULT_DELTA_SEARCH_WINDOW_SIZE}
 	 *
 	 * @param objectCount
 	 *            number of objects to search at once. Must be at least 2.
 	 */
 	public void setDeltaSearchWindowSize(int objectCount) {
 		if (objectCount <= 2)
 			setDeltaCompress(false);
 		else
 			deltaSearchWindowSize = objectCount;
 	}
 
 	/**
 	 * Get maximum number of bytes to put into the delta search window.
 	 *
 	 * Default setting is 0, for an unlimited amount of memory usage. Actual
 	 * memory used is the lower limit of either this setting, or the sum of
 	 * space used by at most {@link #getDeltaSearchWindowSize()} objects.
 	 *
 	 * This limit is per thread, if 4 threads are used the actual memory limit
 	 * will be 4 times this value.
 	 *
 	 * @return the memory limit.
 	 */
 	public long getDeltaSearchMemoryLimit() {
 		return deltaSearchMemoryLimit;
 	}
 
 	/**
 	 * Set the maximum number of bytes to put into the delta search window.
 	 *
 	 * Default setting is 0, for an unlimited amount of memory usage. If the
 	 * memory limit is reached before {@link #getDeltaSearchWindowSize()} the
 	 * window size is temporarily lowered.
 	 *
 	 * @param memoryLimit
 	 *            Maximum number of bytes to load at once, 0 for unlimited.
 	 */
 	public void setDeltaSearchMemoryLimit(long memoryLimit) {
 		deltaSearchMemoryLimit = memoryLimit;
 	}
 
 	/**
 	 * Get the size of the in-memory delta cache.
 	 *
 	 * This limit is for the entire writer, even if multiple threads are used.
 	 *
 	 * Default setting: {@value #DEFAULT_DELTA_CACHE_SIZE}
 	 *
 	 * @return maximum number of bytes worth of delta data to cache in memory.
 	 *         If 0 the cache is infinite in size (up to the JVM heap limit
 	 *         anyway). A very tiny size such as 1 indicates the cache is
 	 *         effectively disabled.
 	 */
 	public long getDeltaCacheSize() {
 		return deltaCacheSize;
 	}
 
 	/**
 	 * Set the maximum number of bytes of delta data to cache.
 	 *
 	 * During delta search, up to this many bytes worth of small or hard to
 	 * compute deltas will be stored in memory. This cache speeds up writing by
 	 * allowing the cached entry to simply be dumped to the output stream.
 	 *
 	 * Default setting: {@value #DEFAULT_DELTA_CACHE_SIZE}
 	 *
 	 * @param size
 	 *            number of bytes to cache. Set to 0 to enable an infinite
 	 *            cache, set to 1 (an impossible size for any delta) to disable
 	 *            the cache.
 	 */
 	public void setDeltaCacheSize(long size) {
 		deltaCacheSize = size;
 	}
 
 	/**
 	 * Maximum size in bytes of a delta to cache.
 	 *
 	 * Default setting: {@value #DEFAULT_DELTA_CACHE_LIMIT}
 	 *
 	 * @return maximum size (in bytes) of a delta that should be cached.
 	 */
 	public int getDeltaCacheLimit() {
 		return deltaCacheLimit;
 	}
 
 	/**
 	 * Set the maximum size of a delta that should be cached.
 	 *
 	 * During delta search, any delta smaller than this size will be cached, up
 	 * to the {@link #getDeltaCacheSize()} maximum limit. This speeds up writing
 	 * by allowing these cached deltas to be output as-is.
 	 *
 	 * Default setting: {@value #DEFAULT_DELTA_CACHE_LIMIT}
 	 *
 	 * @param size
 	 *            maximum size (in bytes) of a delta to be cached.
 	 */
 	public void setDeltaCacheLimit(int size) {
 		deltaCacheLimit = size;
 	}
 
 	/**
 	 * Get the maximum file size that will be delta compressed.
 	 *
 	 * Files bigger than this setting will not be delta compressed, as they are
 	 * more than likely already highly compressed binary data files that do not
 	 * delta compress well, such as MPEG videos.
 	 *
 	 * Default setting: {@value #DEFAULT_BIG_FILE_THRESHOLD}
 	 *
 	 * @return the configured big file threshold.
 	 */
 	public int getBigFileThreshold() {
 		return bigFileThreshold;
 	}
 
 	/**
 	 * Set the maximum file size that should be considered for deltas.
 	 *
 	 * Default setting: {@value #DEFAULT_BIG_FILE_THRESHOLD}
 	 *
 	 * @param bigFileThreshold
 	 *            the limit, in bytes.
 	 */
 	public void setBigFileThreshold(int bigFileThreshold) {
 		this.bigFileThreshold = bigFileThreshold;
 	}
 
 	/**
 	 * Get the compression level applied to objects in the pack.
 	 *
 	 * Default setting: {@value java.util.zip.Deflater#DEFAULT_COMPRESSION}
 	 *
 	 * @return current compression level, see {@link java.util.zip.Deflater}.
 	 */
 	public int getCompressionLevel() {
 		return compressionLevel;
 	}
 
 	/**
 	 * Set the compression level applied to objects in the pack.
 	 *
 	 * Default setting: {@value java.util.zip.Deflater#DEFAULT_COMPRESSION}
 	 *
 	 * @param level
 	 *            compression level, must be a valid level recognized by the
 	 *            {@link java.util.zip.Deflater} class.
 	 */
 	public void setCompressionLevel(int level) {
 		compressionLevel = level;
 	}
 
 	/**
 	 * Get the number of threads used during delta compression.
 	 *
 	 * Default setting: 0 (auto-detect processors)
 	 *
 	 * @return number of threads used for delta compression. 0 will auto-detect
 	 *         the threads to the number of available processors.
 	 */
 	public int getThreads() {
 		return threads;
 	}
 
 	/**
 	 * Set the number of threads to use for delta compression.
 	 *
 	 * During delta compression, if there are enough objects to be considered
 	 * the writer will start up concurrent threads and allow them to compress
 	 * different sections of the repository concurrently.
 	 *
 	 * An application thread pool can be set by {@link #setExecutor(Executor)}.
 	 * If not set a temporary pool will be created by the writer, and torn down
 	 * automatically when compression is over.
 	 *
 	 * Default setting: 0 (auto-detect processors)
 	 *
 	 * @param threads
 	 *            number of threads to use. If &lt;= 0 the number of available
 	 *            processors for this JVM is used.
 	 */
 	public void setThreads(int threads) {
 		this.threads = threads;
 	}
 
 	/** @return the preferred thread pool to execute delta search on. */
 	public Executor getExecutor() {
 		return executor;
 	}
 
 	/**
 	 * Set the executor to use when using threads.
 	 *
 	 * During delta compression if the executor is non-null jobs will be queued
 	 * up on it to perform delta compression in parallel. Aside from setting the
 	 * executor, the caller must set {@link #setThreads(int)} to enable threaded
 	 * delta search.
 	 *
 	 * @param executor
 	 *            executor to use for threads. Set to null to create a temporary
 	 *            executor just for the writer.
 	 */
 	public void setExecutor(Executor executor) {
 		this.executor = executor;
 	}
 
 	/**
 	 * Get the pack index file format version this instance creates.
 	 *
 	 * Default setting: {@value #DEFAULT_INDEX_VERSION}
 	 *
 	 * @return the index version, the special version 0 designates the oldest
 	 *         (most compatible) format available for the objects.
 	 * @see PackIndexWriter
 	 */
 	public int getIndexVersion() {
 		return indexVersion;
 	}
 
 	/**
 	 * Set the pack index file format version this instance will create.
 	 *
 	 * Default setting: {@value #DEFAULT_INDEX_VERSION}
 	 *
 	 * @param version
 	 *            the version to write. The special version 0 designates the
 	 *            oldest (most compatible) format available for the objects.
 	 * @see PackIndexWriter
 	 */
 	public void setIndexVersion(int version) {
 		indexVersion = version;
 	}
 
 	/**
 	 * True if writer is allowed to build bitmaps for indexes.
 	 *
 	 * Default setting: {@value #DEFAULT_BUILD_BITMAPS}
 	 *
 	 * @return true if delta base is the writer can choose to output an index
 	 *         with bitmaps.
 	 * @since 3.0
 	 */
 	public boolean isBuildBitmaps() {
 		return buildBitmaps;
 	}
 
 	/**
 	 * Set writer to allow building bitmaps for supported pack files.
 	 *
 	 * Index files can include bitmaps to speed up future ObjectWalks.
 	 *
 	 * Default setting: {@value #DEFAULT_BUILD_BITMAPS}
 	 *
 	 * @param buildBitmaps
 	 *            boolean indicating whether bitmaps may be included in the
 	 *            index.
 	 * @since 3.0
 	 */
 	public void setBuildBitmaps(boolean buildBitmaps) {
 		this.buildBitmaps = buildBitmaps;
 	}
 
 	/**
 	 * Get the count of most recent commits for which to build bitmaps.
 	 *
 	 * Default setting: {@value #DEFAULT_BITMAP_CONTIGUOUS_COMMIT_COUNT}
 	 *
 	 * @return the count of most recent commits for which to build bitmaps
 	 * @since 4.2
 	 */
 	public int getBitmapContiguousCommitCount() {
 		return bitmapContiguousCommitCount;
 	}
 
 	/**
 	 * Set the count of most recent commits for which to build bitmaps.
 	 *
 	 * Default setting: {@value #DEFAULT_BITMAP_CONTIGUOUS_COMMIT_COUNT}
 	 *
 	 * @param count
 	 *            the count of most recent commits for which to build bitmaps
 	 * @since 4.2
 	 */
 	public void setBitmapContiguousCommitCount(int count) {
 		bitmapContiguousCommitCount = count;
 	}
 
 	/**
 	 * Get the count at which to switch from "bitmapRecentCommitSpan" to
 	 * "bitmapDistantCommitSpan".
 	 *
 	 * Default setting: {@value #DEFAULT_BITMAP_RECENT_COMMIT_COUNT}
 	 *
 	 * @return the count for switching between recent and distant spans
 	 * @since 4.2
 	 */
 	public int getBitmapRecentCommitCount() {
 		return bitmapRecentCommitCount;
 	}
 
 	/**
 	 * Set the count at which to switch from "bitmapRecentCommitSpan" to
 	 * "bitmapDistantCommitSpan".
 	 *
 	 * Default setting: {@value #DEFAULT_BITMAP_RECENT_COMMIT_COUNT}
 	 *
 	 * @param count
 	 *            the count for switching between recent and distant spans
 	 * @since 4.2
 	 */
 	public void setBitmapRecentCommitCount(int count) {
 		bitmapRecentCommitCount = count;
 	}
 
 	/**
 	 * Get the span of commits when building bitmaps for recent history.
 	 *
 	 * Default setting: {@value #DEFAULT_BITMAP_RECENT_COMMIT_SPAN}
 	 *
 	 * @return the span of commits when building bitmaps for recent history
 	 * @since 4.2
 	 */
 	public int getBitmapRecentCommitSpan() {
 		return bitmapRecentCommitSpan;
 	}
 
 	/**
 	 * Set the span of commits when building bitmaps for recent history.
 	 *
 	 * Default setting: {@value #DEFAULT_BITMAP_RECENT_COMMIT_SPAN}
 	 *
 	 * @param span
 	 *            the span of commits when building bitmaps for recent history
 	 * @since 4.2
 	 */
 	public void setBitmapRecentCommitSpan(int span) {
 		bitmapRecentCommitSpan = span;
 	}
 
 	/**
 	 * Get the span of commits when building bitmaps for distant history.
 	 *
 	 * Default setting: {@value #DEFAULT_BITMAP_DISTANT_COMMIT_SPAN}
 	 *
 	 * @return the span of commits when building bitmaps for distant history
 	 * @since 4.2
 	 */
 	public int getBitmapDistantCommitSpan() {
 		return bitmapDistantCommitSpan;
 	}
 
 	/**
 	 * Set the span of commits when building bitmaps for distant history.
 	 *
 	 * Default setting: {@value #DEFAULT_BITMAP_DISTANT_COMMIT_SPAN}
 	 *
 	 * @param span
 	 *            the span of commits when building bitmaps for distant history
 	 * @since 4.2
 	 */
 	public void setBitmapDistantCommitSpan(int span) {
 		bitmapDistantCommitSpan = span;
 	}
 
 	/**
 	 * Get the count of branches deemed "excessive". If the count of branches in
 	 * a repository exceeds this number and bitmaps are enabled, "inactive"
 	 * branches will have fewer bitmaps than "active" branches.
 	 *
 	 * Default setting: {@value #DEFAULT_BITMAP_EXCESSIVE_BRANCH_COUNT}
 	 *
 	 * @return the count of branches deemed "excessive"
 	 * @since 4.2
 	 */
 	public int getBitmapExcessiveBranchCount() {
 		return bitmapExcessiveBranchCount;
 	}
 
 	/**
 	 * Set the count of branches deemed "excessive". If the count of branches in
 	 * a repository exceeds this number and bitmaps are enabled, "inactive"
 	 * branches will have fewer bitmaps than "active" branches.
 	 *
 	 * Default setting: {@value #DEFAULT_BITMAP_EXCESSIVE_BRANCH_COUNT}
 	 *
 	 * @param count
 	 *            the count of branches deemed "excessive"
 	 * @since 4.2
 	 */
 	public void setBitmapExcessiveBranchCount(int count) {
 		bitmapExcessiveBranchCount = count;
 	}
 
 	/**
 	 * Get the the age in days that marks a branch as "inactive".
 	 *
 	 * Default setting: {@value #DEFAULT_BITMAP_INACTIVE_BRANCH_AGE_IN_DAYS}
 	 *
 	 * @return the age in days that marks a branch as "inactive"
 	 * @since 4.2
 	 */
 	public int getBitmapInactiveBranchAgeInDays() {
 		return bitmapInactiveBranchAgeInDays;
 	}
 
 	/**
 	 * Set the the age in days that marks a branch as "inactive".
 	 *
 	 * Default setting: {@value #DEFAULT_BITMAP_INACTIVE_BRANCH_AGE_IN_DAYS}
 	 *
 	 * @param ageInDays
 	 *            the age in days that marks a branch as "inactive"
 	 * @since 4.2
 	 */
 	public void setBitmapInactiveBranchAgeInDays(int ageInDays) {
 		bitmapInactiveBranchAgeInDays = ageInDays;
 	}
 
 	/**
 	 * Update properties by setting fields from the configuration.
 	 *
 	 * If a property's corresponding variable is not defined in the supplied
 	 * configuration, then it is left unmodified.
 	 *
 	 * @param rc
 	 *            configuration to read properties from.
 	 */
 	public void fromConfig(final Config rc) {
 		setMaxDeltaDepth(rc.getInt("pack", "depth", getMaxDeltaDepth())); //$NON-NLS-1$ //$NON-NLS-2$
 		setDeltaSearchWindowSize(rc.getInt(
 				"pack", "window", getDeltaSearchWindowSize())); //$NON-NLS-1$ //$NON-NLS-2$
 		setDeltaSearchMemoryLimit(rc.getLong(
 				"pack", "windowmemory", getDeltaSearchMemoryLimit())); //$NON-NLS-1$ //$NON-NLS-2$
 		setDeltaCacheSize(rc.getLong(
 				"pack", "deltacachesize", getDeltaCacheSize())); //$NON-NLS-1$ //$NON-NLS-2$
 		setDeltaCacheLimit(rc.getInt(
 				"pack", "deltacachelimit", getDeltaCacheLimit())); //$NON-NLS-1$ //$NON-NLS-2$
 		setCompressionLevel(rc.getInt("pack", "compression", //$NON-NLS-1$ //$NON-NLS-2$
 				rc.getInt("core", "compression", getCompressionLevel()))); //$NON-NLS-1$ //$NON-NLS-2$
 		setIndexVersion(rc.getInt("pack", "indexversion", getIndexVersion())); //$NON-NLS-1$ //$NON-NLS-2$
 		setBigFileThreshold(rc.getInt(
 				"core", "bigfilethreshold", getBigFileThreshold())); //$NON-NLS-1$ //$NON-NLS-2$
 		setThreads(rc.getInt("pack", "threads", getThreads())); //$NON-NLS-1$ //$NON-NLS-2$
 
 		// These variables aren't standardized
 		//
 		setReuseDeltas(rc.getBoolean("pack", "reusedeltas", isReuseDeltas())); //$NON-NLS-1$ //$NON-NLS-2$
 		setReuseObjects(
 				rc.getBoolean("pack", "reuseobjects", isReuseObjects())); //$NON-NLS-1$ //$NON-NLS-2$
 		setDeltaCompress(
 				rc.getBoolean("pack", "deltacompression", isDeltaCompress())); //$NON-NLS-1$ //$NON-NLS-2$
 		setCutDeltaChains(
 				rc.getBoolean("pack", "cutdeltachains", getCutDeltaChains())); //$NON-NLS-1$ //$NON-NLS-2$
 		setBuildBitmaps(
 				rc.getBoolean("pack", "buildbitmaps", isBuildBitmaps())); //$NON-NLS-1$ //$NON-NLS-2$
 		setBitmapContiguousCommitCount(
 				rc.getInt("pack", "bitmapcontiguouscommitcount", //$NON-NLS-1$ //$NON-NLS-2$
 						getBitmapContiguousCommitCount()));
 		setBitmapRecentCommitCount(rc.getInt("pack", "bitmaprecentcommitcount", //$NON-NLS-1$ //$NON-NLS-2$
 				getBitmapRecentCommitCount()));
 		setBitmapRecentCommitSpan(rc.getInt("pack", "bitmaprecentcommitspan", //$NON-NLS-1$ //$NON-NLS-2$
 				getBitmapRecentCommitSpan()));
 		setBitmapDistantCommitSpan(rc.getInt("pack", "bitmapdistantcommitspan", //$NON-NLS-1$ //$NON-NLS-2$
 				getBitmapDistantCommitSpan()));
 		setBitmapExcessiveBranchCount(rc.getInt("pack", //$NON-NLS-1$
 				"bitmapexcessivebranchcount", getBitmapExcessiveBranchCount())); //$NON-NLS-1$
 		setBitmapInactiveBranchAgeInDays(
 				rc.getInt("pack", "bitmapinactivebranchageindays", //$NON-NLS-1$ //$NON-NLS-2$
 						getBitmapInactiveBranchAgeInDays()));
 	}
 
 	public String toString() {
 		final StringBuilder b = new StringBuilder();
 		b.append("maxDeltaDepth=").append(getMaxDeltaDepth()); //$NON-NLS-1$
 		b.append(", deltaSearchWindowSize=").append(getDeltaSearchWindowSize()); //$NON-NLS-1$
 		b.append(", deltaSearchMemoryLimit=") //$NON-NLS-1$
 				.append(getDeltaSearchMemoryLimit());
 		b.append(", deltaCacheSize=").append(getDeltaCacheSize()); //$NON-NLS-1$
 		b.append(", deltaCacheLimit=").append(getDeltaCacheLimit()); //$NON-NLS-1$
 		b.append(", compressionLevel=").append(getCompressionLevel()); //$NON-NLS-1$
 		b.append(", indexVersion=").append(getIndexVersion()); //$NON-NLS-1$
 		b.append(", bigFileThreshold=").append(getBigFileThreshold()); //$NON-NLS-1$
 		b.append(", threads=").append(getThreads()); //$NON-NLS-1$
 		b.append(", reuseDeltas=").append(isReuseDeltas()); //$NON-NLS-1$
 		b.append(", reuseObjects=").append(isReuseObjects()); //$NON-NLS-1$
 		b.append(", deltaCompress=").append(isDeltaCompress()); //$NON-NLS-1$
 		b.append(", buildBitmaps=").append(isBuildBitmaps()); //$NON-NLS-1$
 		b.append(", bitmapContiguousCommitCount=") //$NON-NLS-1$
 				.append(getBitmapContiguousCommitCount());
 		b.append(", bitmapRecentCommitCount=") //$NON-NLS-1$
 				.append(getBitmapRecentCommitCount());
 		b.append(", bitmapRecentCommitSpan=") //$NON-NLS-1$
 				.append(getBitmapRecentCommitSpan());
 		b.append(", bitmapDistantCommitSpan=") //$NON-NLS-1$
 				.append(getBitmapDistantCommitSpan());
 		b.append(", bitmapExcessiveBranchCount=") //$NON-NLS-1$
 				.append(getBitmapExcessiveBranchCount());
 		b.append(", bitmapInactiveBranchAge=") //$NON-NLS-1$
 				.append(getBitmapInactiveBranchAgeInDays());
 		return b.toString();
 	}
 }