| /* |
| * 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; |
| } |
| } |
| } |
| } |
| } |