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/*
* Copyright (c) 2024, Google LLC 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
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.eclipse.jgit.internal.storage.dfs;
import java.io.IOException;
import java.util.List;
/**
* Block cache table.
*/
public interface DfsBlockCacheTable {
/**
* Quickly check if the cache contains block 0 of the given stream.
* <p>
* This can be useful for sophisticated pre-read algorithms to quickly
* determine if a file is likely already in cache, especially small
* reftables which may be smaller than a typical DFS block size.
*
* @param key
* the file to check.
* @return true if block 0 (the first block) is in the cache.
*/
boolean hasBlock0(DfsStreamKey key);
/**
* Look up a cached object, creating and loading it if it doesn't exist.
*
* @param file
* the pack that "contains" the cached object.
* @param position
* offset within <code>pack</code> of the object.
* @param dfsReader
* current thread's reader.
* @param fileChannel
* supplier for channel to read {@code pack}.
* @return the object reference.
* @throws IOException
* the reference was not in the cache and could not be loaded.
*/
DfsBlock getOrLoad(BlockBasedFile file, long position, DfsReader dfsReader,
DfsBlockCache.ReadableChannelSupplier fileChannel)
throws IOException;
/**
* Look up a cached object, creating and loading it if it doesn't exist.
*
* @param key
* the stream key of the pack.
* @param position
* the position in the key. The default should be 0.
* @param loader
* the function to load the reference.
* @return the object reference.
* @throws IOException
* the reference was not in the cache and could not be loaded.
*/
<T> DfsBlockCache.Ref<T> getOrLoadRef(DfsStreamKey key, long position,
DfsBlockCache.RefLoader<T> loader) throws IOException;
/**
* Put a block in the block cache.
*
* @param v
* the block to put in the cache.
*/
void put(DfsBlock v);
/**
* Put a block in the block cache.
*
* @param key
* the stream key of the pack.
* @param pos
* the position in the key.
* @param size
* the size of the object.
* @param v
* the object to put in the block cache.
* @return the object reference.
*/
<T> DfsBlockCache.Ref<T> put(DfsStreamKey key, long pos, long size, T v);
/**
* Put an object in the block cache.
*
* @param key
* the stream key of the pack.
* @param size
* the size of the object.
* @param v
* the object to put in the block cache.
* @return the object reference.
*/
<T> DfsBlockCache.Ref<T> putRef(DfsStreamKey key, long size, T v);
/**
* Check if the block cache contains an object identified by (key,
* position).
*
* @param key
* the stream key of the pack.
* @param position
* the position in the key.
* @return if the block cache contains the object identified by (key,
* position).
*/
boolean contains(DfsStreamKey key, long position);
/**
* Get the object identified by (key, position) from the block cache.
*
* @param key
* the stream key of the pack.
* @param position
* the position in the key.
* @return the object identified by (key, position).
*/
<T> T get(DfsStreamKey key, long position);
/**
* Get the list of {@link BlockCacheStats} held by this cache.
* <p>
* The returned list has a {@link BlockCacheStats} per configured cache
* table, with a minimum of 1 {@link BlockCacheStats} object returned.
*
* Use {@link AggregatedBlockCacheStats} to combine the results of the stats
* in the list for an aggregated view of the cache's stats.
*
* @return the list of {@link BlockCacheStats} held by this cache.
*/
List<BlockCacheStats> getBlockCacheStats();
/**
* Get the name of the table.
*
* @return this table's name.
*/
String getName();
/**
* Provides methods used with Block Cache statistics.
*/
interface BlockCacheStats {
/**
* Get the name of the block cache generating this instance.
*
* @return this cache's name.
*/
String getName();
/**
* Get total number of bytes in the cache, per pack file extension.
*
* @return total number of bytes in the cache, per pack file extension.
*/
long[] getCurrentSize();
/**
* Get number of requests for items in the cache, per pack file
* extension.
*
* @return the number of requests for items in the cache, per pack file
* extension.
*/
long[] getHitCount();
/**
* Get number of requests for items not in the cache, per pack file
* extension.
*
* @return the number of requests for items not in the cache, per pack
* file extension.
*/
long[] getMissCount();
/**
* Get total number of requests (hit + miss), per pack file extension.
*
* @return total number of requests (hit + miss), per pack file
* extension.
*/
long[] getTotalRequestCount();
/**
* Get hit ratios.
*
* @return hit ratios.
*/
long[] getHitRatio();
/**
* Get number of evictions performed due to cache being full, per pack
* file extension.
*
* @return the number of evictions performed due to cache being full,
* per pack file extension.
*/
long[] getEvictions();
}
}
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