WindowCacheConfig

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package org.eclipse.jgit.storage.file;

import org.eclipse.jgit.internal.storage.file.WindowCache;
import org.eclipse.jgit.lib.Config;
import org.eclipse.jgit.storage.pack.PackConfig;

/**
 * Configuration parameters for JVM-wide buffer cache used by JGit.
 */
public class WindowCacheConfig {
	/** 1024 (number of bytes in one kibibyte/kilobyte) */
	public static final int KB = 1024;

	/** 1024 {@link #KB} (number of bytes in one mebibyte/megabyte) */
	public static final int MB = 1024 * KB;

	private int packedGitOpenFiles;

	private long packedGitLimit;

	private int packedGitWindowSize;

	private boolean packedGitMMAP;

	private int deltaBaseCacheLimit;

	private int streamFileThreshold;

	/**
	 * Create a default configuration.
	 */
	public WindowCacheConfig() {
		packedGitOpenFiles = 128;
		packedGitLimit = 10 * MB;
		packedGitWindowSize = 8 * KB;
		packedGitMMAP = false;
		deltaBaseCacheLimit = 10 * MB;
		streamFileThreshold = PackConfig.DEFAULT_BIG_FILE_THRESHOLD;
	}

	/**
	 * Get maximum number of streams to open at a time.
	 *
	 * @return maximum number of streams to open at a time. Open packs count
	 *         against the process limits. <b>Default is 128.</b>
	 */
	public int getPackedGitOpenFiles() {
		return packedGitOpenFiles;
	}

	/**
	 * Set maximum number of streams to open at a time.
	 *
	 * @param fdLimit
	 *            maximum number of streams to open at a time. Open packs count
	 *            against the process limits
	 */
	public void setPackedGitOpenFiles(int fdLimit) {
		packedGitOpenFiles = fdLimit;
	}

	/**
	 * Get maximum number bytes of heap memory to dedicate to caching pack file
	 * data.
	 *
	 * @return maximum number bytes of heap memory to dedicate to caching pack
	 *         file data. <b>Default is 10 MB.</b>
	 */
	public long getPackedGitLimit() {
		return packedGitLimit;
	}

	/**
	 * Set maximum number bytes of heap memory to dedicate to caching pack file
	 * data.
	 *
	 * @param newLimit
	 *            maximum number bytes of heap memory to dedicate to caching
	 *            pack file data.
	 */
	public void setPackedGitLimit(long newLimit) {
		packedGitLimit = newLimit;
	}

	/**
	 * Get size in bytes of a single window mapped or read in from the pack
	 * file.
	 *
	 * @return size in bytes of a single window mapped or read in from the pack
	 *         file. <b>Default is 8 KB.</b>
	 */
	public int getPackedGitWindowSize() {
		return packedGitWindowSize;
	}

	/**
	 * Set size in bytes of a single window read in from the pack file.
	 *
	 * @param newSize
	 *            size in bytes of a single window read in from the pack file.
	 */
	public void setPackedGitWindowSize(int newSize) {
		packedGitWindowSize = newSize;
	}

	/**
	 * Whether to use Java NIO virtual memory mapping for windows
	 *
	 * @return {@code true} enables use of Java NIO virtual memory mapping for
	 *         windows; false reads entire window into a byte[] with standard
	 *         read calls. <b>Default false.</b>
	 */
	public boolean isPackedGitMMAP() {
		return packedGitMMAP;
	}

	/**
	 * Set whether to enable use of Java NIO virtual memory mapping for windows
	 *
	 * @param usemmap
	 *            {@code true} enables use of Java NIO virtual memory mapping
	 *            for windows; false reads entire window into a byte[] with
	 *            standard read calls.
	 */
	public void setPackedGitMMAP(boolean usemmap) {
		packedGitMMAP = usemmap;
	}

	/**
	 * Get maximum number of bytes to cache in delta base cache for inflated,
	 * recently accessed objects, without delta chains.
	 *
	 * @return maximum number of bytes to cache in delta base cache for
	 *         inflated, recently accessed objects, without delta chains.
	 *         <b>Default 10 MB.</b>
	 */
	public int getDeltaBaseCacheLimit() {
		return deltaBaseCacheLimit;
	}

	/**
	 * Set maximum number of bytes to cache in delta base cache for inflated,
	 * recently accessed objects, without delta chains.
	 *
	 * @param newLimit
	 *            maximum number of bytes to cache in delta base cache for
	 *            inflated, recently accessed objects, without delta chains.
	 */
	public void setDeltaBaseCacheLimit(int newLimit) {
		deltaBaseCacheLimit = newLimit;
	}

	/**
	 * Get the size threshold beyond which objects must be streamed.
	 *
	 * @return the size threshold beyond which objects must be streamed.
	 */
	public int getStreamFileThreshold() {
		return streamFileThreshold;
	}

	/**
	 * Set new byte limit for objects that must be streamed.
	 *
	 * @param newLimit
	 *            new byte limit for objects that must be streamed. Objects
	 *            smaller than this size can be obtained as a contiguous byte
	 *            array, while objects bigger than this size require using an
	 *            {@link org.eclipse.jgit.lib.ObjectStream}.
	 */
	public void setStreamFileThreshold(int newLimit) {
		streamFileThreshold = newLimit;
	}

	/**
	 * Update properties by setting fields from the configuration.
	 * <p>
	 * If a property is not defined in the configuration, then it is left
	 * unmodified.
	 *
	 * @param rc
	 *            configuration to read properties from.
	 * @return {@code this}.
	 * @since 3.0
	 */
	public WindowCacheConfig fromConfig(Config rc) {
		setPackedGitOpenFiles(rc.getInt(
				"core", null, "packedgitopenfiles", getPackedGitOpenFiles())); //$NON-NLS-1$ //$NON-NLS-2$
		setPackedGitLimit(rc.getLong(
				"core", null, "packedgitlimit", getPackedGitLimit())); //$NON-NLS-1$ //$NON-NLS-2$
		setPackedGitWindowSize(rc.getInt(
				"core", null, "packedgitwindowsize", getPackedGitWindowSize())); //$NON-NLS-1$ //$NON-NLS-2$
		setPackedGitMMAP(rc.getBoolean(
				"core", null, "packedgitmmap", isPackedGitMMAP())); //$NON-NLS-1$ //$NON-NLS-2$
		setDeltaBaseCacheLimit(rc.getInt(
				"core", null, "deltabasecachelimit", getDeltaBaseCacheLimit())); //$NON-NLS-1$ //$NON-NLS-2$

		long maxMem = Runtime.getRuntime().maxMemory();
		long sft = rc.getLong(
				"core", null, "streamfilethreshold", getStreamFileThreshold()); //$NON-NLS-1$ //$NON-NLS-2$
		sft = Math.min(sft, maxMem / 4); // don't use more than 1/4 of the heap
		sft = Math.min(sft, Integer.MAX_VALUE); // cannot exceed array length
		setStreamFileThreshold((int) sft);
		return this;
	}

	/**
	 * Install this configuration as the live settings.
	 * <p>
	 * The new configuration is applied immediately. If the new limits are
	 * smaller than what is currently cached, older entries will be purged
	 * as soon as possible to allow the cache to meet the new limit.
	 *
	 * @since 3.0
	 */
	@SuppressWarnings("deprecation")
	public void install() {
		WindowCache.reconfigure(this);
	}
}