DfsBlockCacheConfig

/*
 * Copyright (C) 2011, Google Inc.
 * 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
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package org.eclipse.jgit.internal.storage.dfs;

import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_CORE_SECTION;
import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_DFS_SECTION;
import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_BLOCK_LIMIT;
import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_BLOCK_SIZE;
import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_CONCURRENCY_LEVEL;
import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_STREAM_RATIO;

import java.text.MessageFormat;

import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.lib.Config;

/**
 * Configuration parameters for
 * {@link org.eclipse.jgit.internal.storage.dfs.DfsBlockCache}.
 */
public class DfsBlockCacheConfig {
	/** 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 long blockLimit;
	private int blockSize;
	private double streamRatio;
	private int concurrencyLevel;

	/**
	 * Create a default configuration.
	 */
	public DfsBlockCacheConfig() {
		setBlockLimit(32 * MB);
		setBlockSize(64 * KB);
		setStreamRatio(0.30);
		setConcurrencyLevel(32);
	}

	/**
	 * 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 32 MB.</b>
	 */
	public long getBlockLimit() {
		return blockLimit;
	}

	/**
	 * Set maximum number bytes of heap memory to dedicate to caching pack file
	 * data.
	 * <p>
	 * It is strongly recommended to set the block limit to be an integer multiple
	 * of the block size. This constraint is not enforced by this method (since
	 * it may be called before {@link #setBlockSize(int)}), but it is enforced by
	 * {@link #fromConfig(Config)}.
	 *
	 * @param newLimit
	 *            maximum number bytes of heap memory to dedicate to caching
	 *            pack file data; must be positive.
	 * @return {@code this}
	 */
	public DfsBlockCacheConfig setBlockLimit(long newLimit) {
		if (newLimit <= 0) {
			throw new IllegalArgumentException(MessageFormat.format(
					JGitText.get().blockLimitNotPositive,
					Long.valueOf(newLimit)));
		}
		blockLimit = newLimit;
		return this;
	}

	/**
	 * 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 64 KB.</b>
	 */
	public int getBlockSize() {
		return blockSize;
	}

	/**
	 * 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.
	 *            The value must be a power of 2.
	 * @return {@code this}
	 */
	public DfsBlockCacheConfig setBlockSize(int newSize) {
		int size = Math.max(512, newSize);
		if ((size & (size - 1)) != 0) {
			throw new IllegalArgumentException(
					JGitText.get().blockSizeNotPowerOf2);
		}
		blockSize = size;
		return this;
	}

	/**
	 * Get the estimated number of threads concurrently accessing the cache.
	 *
	 * @return the estimated number of threads concurrently accessing the cache.
	 *         <b>Default is 32.</b>
	 */
	public int getConcurrencyLevel() {
		return concurrencyLevel;
	}

	/**
	 * Set the estimated number of threads concurrently accessing the cache.
	 *
	 * @param newConcurrencyLevel
	 *            the estimated number of threads concurrently accessing the
	 *            cache.
	 * @return {@code this}
	 */
	public DfsBlockCacheConfig setConcurrencyLevel(
			final int newConcurrencyLevel) {
		concurrencyLevel = newConcurrencyLevel;
		return this;
	}

	/**
	 * Get highest percentage of {@link #getBlockLimit()} a single pack can
	 * occupy while being copied by the pack reuse strategy.
	 *
	 * @return highest percentage of {@link #getBlockLimit()} a single pack can
	 *         occupy while being copied by the pack reuse strategy. <b>Default
	 *         is 0.30, or 30%</b>.
	 */
	public double getStreamRatio() {
		return streamRatio;
	}

	/**
	 * Set percentage of cache to occupy with a copied pack.
	 *
	 * @param ratio
	 *            percentage of cache to occupy with a copied pack.
	 * @return {@code this}
	 */
	public DfsBlockCacheConfig setStreamRatio(double ratio) {
		streamRatio = Math.max(0, Math.min(ratio, 1.0));
		return this;
	}

	/**
	 * Update properties by setting fields from the configuration.
	 * <p>
	 * If a property is not defined in the configuration, then it is left
	 * unmodified.
	 * <p>
	 * Enforces certain constraints on the combination of settings in the config,
	 * for example that the block limit is a multiple of the block size.
	 *
	 * @param rc
	 *            configuration to read properties from.
	 * @return {@code this}
	 */
	public DfsBlockCacheConfig fromConfig(Config rc) {
		long cfgBlockLimit = rc.getLong(
				CONFIG_CORE_SECTION,
				CONFIG_DFS_SECTION,
				CONFIG_KEY_BLOCK_LIMIT,
				getBlockLimit());
		int cfgBlockSize = rc.getInt(
				CONFIG_CORE_SECTION,
				CONFIG_DFS_SECTION,
				CONFIG_KEY_BLOCK_SIZE,
				getBlockSize());
		if (cfgBlockLimit % cfgBlockSize != 0) {
			throw new IllegalArgumentException(MessageFormat.format(
					JGitText.get().blockLimitNotMultipleOfBlockSize,
					Long.valueOf(cfgBlockLimit),
					Long.valueOf(cfgBlockSize)));
		}

		setBlockLimit(cfgBlockLimit);
		setBlockSize(cfgBlockSize);

		setConcurrencyLevel(rc.getInt(
				CONFIG_CORE_SECTION,
				CONFIG_DFS_SECTION,
				CONFIG_KEY_CONCURRENCY_LEVEL,
				getConcurrencyLevel()));

		String v = rc.getString(
				CONFIG_CORE_SECTION,
				CONFIG_DFS_SECTION,
				CONFIG_KEY_STREAM_RATIO);
		if (v != null) {
			try {
				setStreamRatio(Double.parseDouble(v));
			} catch (NumberFormatException e) {
				throw new IllegalArgumentException(MessageFormat.format(
						JGitText.get().enumValueNotSupported3,
						CONFIG_CORE_SECTION,
						CONFIG_DFS_SECTION,
						CONFIG_KEY_STREAM_RATIO, v));
			}
		}
		return this;
	}
}