DfsReaderOptions.java

/*
 * Copyright (C) 2011, Google Inc. and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

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_DELTA_BASE_CACHE_LIMIT;
import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_STREAM_BUFFER;
import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_STREAM_FILE_TRESHOLD;

import org.eclipse.jgit.lib.Config;
import org.eclipse.jgit.storage.pack.PackConfig;

/**
 * Options controlling how objects are read from a DFS stored repository.
 */
public class DfsReaderOptions {
    /** 1024 (number of bytes in one kibibyte/kilobyte) */
    public static final int KiB = 1024;

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

    private int deltaBaseCacheLimit;
    private int streamFileThreshold;

    private int streamPackBufferSize;

    /**
     * Create a default reader configuration.
     */
    public DfsReaderOptions() {
        setDeltaBaseCacheLimit(10 * MiB);
        setStreamFileThreshold(PackConfig.DEFAULT_BIG_FILE_THRESHOLD);
    }

    /**
     * Get maximum number of bytes to hold in per-reader DeltaBaseCache.
     *
     * @return maximum number of bytes to hold in per-reader DeltaBaseCache.
     */
    public int getDeltaBaseCacheLimit() {
        return deltaBaseCacheLimit;
    }

    /**
     * Set the maximum number of bytes in the DeltaBaseCache.
     *
     * @param maxBytes
     *            the new limit.
     * @return {@code this}
     */
    public DfsReaderOptions setDeltaBaseCacheLimit(int maxBytes) {
        deltaBaseCacheLimit = Math.max(0, maxBytes);
        return this;
    }

    /**
     * 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}.
     * @return {@code this}
     */
    public DfsReaderOptions setStreamFileThreshold(int newLimit) {
        streamFileThreshold = Math.max(0, newLimit);
        return this;
    }

    /**
     * Get number of bytes to use for buffering when streaming a pack file
     * during copying.
     *
     * @return number of bytes to use for buffering when streaming a pack file
     *         during copying. If 0 the block size of the pack is used.
     */
    public int getStreamPackBufferSize() {
        return streamPackBufferSize;
    }

    /**
     * Set new buffer size in bytes for buffers used when streaming pack files
     * during copying.
     *
     * @param bufsz
     *            new buffer size in bytes for buffers used when streaming pack
     *            files during copying.
     * @return {@code this}
     */
    public DfsReaderOptions setStreamPackBufferSize(int bufsz) {
        streamPackBufferSize = Math.max(0, bufsz);
        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.
     *
     * @param rc
     *            configuration to read properties from.
     * @return {@code this}
     */
    public DfsReaderOptions fromConfig(Config rc) {
        setDeltaBaseCacheLimit(rc.getInt(
                CONFIG_CORE_SECTION,
                CONFIG_DFS_SECTION,
                CONFIG_KEY_DELTA_BASE_CACHE_LIMIT,
                getDeltaBaseCacheLimit()));

        long maxMem = Runtime.getRuntime().maxMemory();
        long sft = rc.getLong(
                CONFIG_CORE_SECTION,
                CONFIG_DFS_SECTION,
                CONFIG_KEY_STREAM_FILE_TRESHOLD,
                getStreamFileThreshold());
        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);

        setStreamPackBufferSize(rc.getInt(
                CONFIG_CORE_SECTION,
                CONFIG_DFS_SECTION,
                CONFIG_KEY_STREAM_BUFFER,
                getStreamPackBufferSize()));
        return this;
    }
}