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/*
* Copyright (C) 2017, 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.internal.storage.pack.PackExt.REFTABLE;
import java.io.IOException;
import java.nio.ByteBuffer;
import org.eclipse.jgit.internal.storage.io.BlockSource;
import org.eclipse.jgit.internal.storage.reftable.ReftableReader;
/**
* A reftable stored in {@link org.eclipse.jgit.internal.storage.dfs.DfsBlockCache}.
*/
public class DfsReftable extends BlockBasedFile {
/**
* Construct a reader for an existing reftable.
*
* @param desc
* description of the reftable within the DFS.
*/
public DfsReftable(DfsPackDescription desc) {
this(DfsBlockCache.getInstance(), desc);
}
/**
* Construct a reader for an existing reftable.
*
* @param cache
* cache that will store the reftable data.
* @param desc
* description of the reftable within the DFS.
*/
public DfsReftable(DfsBlockCache cache, DfsPackDescription desc) {
super(cache, desc, REFTABLE);
int bs = desc.getBlockSize(REFTABLE);
if (bs > 0) {
setBlockSize(bs);
}
long sz = desc.getFileSize(REFTABLE);
length = sz > 0 ? sz : -1;
}
/**
* Get description that was originally used to configure this file.
*
* @return description that was originally used to configure this file.
*/
public DfsPackDescription getPackDescription() {
return desc;
}
/**
* Open reader on the reftable.
* <p>
* The returned reader is not thread safe.
*
* @param ctx
* reader to access the DFS storage.
* @return cursor to read the table; caller must close.
* @throws java.io.IOException
* table cannot be opened.
*/
public ReftableReader open(DfsReader ctx) throws IOException {
return new ReftableReader(new CacheSource(this, cache, ctx));
}
private static final class CacheSource extends BlockSource {
private final DfsReftable file;
private final DfsBlockCache cache;
private final DfsReader ctx;
private ReadableChannel ch;
private int readAhead;
CacheSource(DfsReftable file, DfsBlockCache cache, DfsReader ctx) {
this.file = file;
this.cache = cache;
this.ctx = ctx;
}
@Override
public ByteBuffer read(long pos, int cnt) throws IOException {
if (ch == null && readAhead > 0 && notInCache(pos)) {
open().setReadAheadBytes(readAhead);
}
DfsBlock block = cache.getOrLoad(file, pos, ctx, () -> open());
if (block.start == pos && block.size() >= cnt) {
return block.zeroCopyByteBuffer(cnt);
}
byte[] dst = new byte[cnt];
ByteBuffer buf = ByteBuffer.wrap(dst);
buf.position(ctx.copy(file, pos, dst, 0, cnt));
return buf;
}
private boolean notInCache(long pos) {
return cache.get(file.key, file.alignToBlock(pos)) == null;
}
@Override
public long size() throws IOException {
long n = file.length;
if (n < 0) {
n = open().size();
file.length = n;
}
return n;
}
@Override
public void adviseSequentialRead(long start, long end) {
int sz = ctx.getOptions().getStreamPackBufferSize();
if (sz > 0) {
readAhead = (int) Math.min(sz, end - start);
}
}
private ReadableChannel open() throws IOException {
if (ch == null) {
ch = ctx.db.openFile(file.desc, file.ext);
}
return ch;
}
@Override
public void close() {
if (ch != null) {
try {
ch.close();
} catch (IOException e) {
// Ignore read close failures.
} finally {
ch = null;
}
}
}
}
}
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