1 /*
2 * Copyright (C) 2017, Google Inc.
3 * and other copyright owners as documented in the project's IP log.
4 *
5 * This program and the accompanying materials are made available
6 * under the terms of the Eclipse Distribution License v1.0 which
7 * accompanies this distribution, is reproduced below, and is
8 * available at http://www.eclipse.org/org/documents/edl-v10.php
9 *
10 * All rights reserved.
11 *
12 * Redistribution and use in source and binary forms, with or
13 * without modification, are permitted provided that the following
14 * conditions are met:
15 *
16 * - Redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer.
18 *
19 * - Redistributions in binary form must reproduce the above
20 * copyright notice, this list of conditions and the following
21 * disclaimer in the documentation and/or other materials provided
22 * with the distribution.
23 *
24 * - Neither the name of the Eclipse Foundation, Inc. nor the
25 * names of its contributors may be used to endorse or promote
26 * products derived from this software without specific prior
27 * written permission.
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
30 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
31 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
33 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
34 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
35 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
36 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
37 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
38 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
40 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
41 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42 */
43
44 package org.eclipse.jgit.internal.storage.dfs;
45
46 import static org.eclipse.jgit.internal.storage.pack.PackExt.REFTABLE;
47
48 import java.io.IOException;
49 import java.nio.ByteBuffer;
50
51 import org.eclipse.jgit.internal.storage.io.BlockSource;
52 import org.eclipse.jgit.internal.storage.reftable.ReftableReader;
53
54 /** A reftable stored in {@link DfsBlockCache}. */
55 public class DfsReftable extends BlockBasedFile {
56 /**
57 * Construct a reader for an existing reftable.
58 *
59 * @param desc
60 * description of the reftable within the DFS.
61 */
62 public DfsReftable(DfsPackDescription desc) {
63 this(DfsBlockCache.getInstance(), desc);
64 }
65
66 /**
67 * Construct a reader for an existing reftable.
68 *
69 * @param cache
70 * cache that will store the reftable data.
71 * @param desc
72 * description of the reftable within the DFS.
73 */
74 public DfsReftable(DfsBlockCache cache, DfsPackDescription desc) {
75 super(cache, desc, REFTABLE);
76
77 int bs = desc.getBlockSize(REFTABLE);
78 if (bs > 0) {
79 setBlockSize(bs);
80 }
81
82 long sz = desc.getFileSize(REFTABLE);
83 length = sz > 0 ? sz : -1;
84 }
85
86 /** @return description that was originally used to configure this file. */
87 public DfsPackDescription getPackDescription() {
88 return desc;
89 }
90
91 /**
92 * Open reader on the reftable.
93 * <p>
94 * The returned reader is not thread safe.
95 *
96 * @param ctx
97 * reader to access the DFS storage.
98 * @return cursor to read the table; caller must close.
99 * @throws IOException
100 * table cannot be opened.
101 */
102 public ReftableReader open(DfsReader ctx) throws IOException {
103 return new ReftableReader(new CacheSource(this, cache, ctx));
104 }
105
106 private static final class CacheSource extends BlockSource {
107 private final DfsReftable file;
108 private final DfsBlockCache cache;
109 private final DfsReader ctx;
110 private ReadableChannel ch;
111 private int readAhead;
112
113 CacheSource(DfsReftable file, DfsBlockCache cache, DfsReader ctx) {
114 this.file = file;
115 this.cache = cache;
116 this.ctx = ctx;
117 }
118
119 @Override
120 public ByteBuffer read(long pos, int cnt) throws IOException {
121 if (ch == null && readAhead > 0 && notInCache(pos)) {
122 open().setReadAheadBytes(readAhead);
123 }
124
125 DfsBlock block = cache.getOrLoad(file, pos, ctx, ch);
126 if (block.start == pos && block.size() >= cnt) {
127 return block.zeroCopyByteBuffer(cnt);
128 }
129
130 byte[] dst = new byte[cnt];
131 ByteBuffer buf = ByteBuffer.wrap(dst);
132 buf.position(ctx.copy(file, pos, dst, 0, cnt));
133 return buf;
134 }
135
136 private boolean notInCache(long pos) {
137 return cache.get(file.key, file.alignToBlock(pos)) == null;
138 }
139
140 @Override
141 public long size() throws IOException {
142 long n = file.length;
143 if (n < 0) {
144 n = open().size();
145 file.length = n;
146 }
147 return n;
148 }
149
150 @Override
151 public void adviseSequentialRead(long start, long end) {
152 int sz = ctx.getOptions().getStreamPackBufferSize();
153 if (sz > 0) {
154 readAhead = (int) Math.min(sz, end - start);
155 }
156 }
157
158 private ReadableChannel open() throws IOException {
159 if (ch == null) {
160 ch = ctx.db.openFile(file.desc, file.ext);
161 }
162 return ch;
163 }
164
165 @Override
166 public void close() {
167 if (ch != null) {
168 try {
169 ch.close();
170 } catch (IOException e) {
171 // Ignore read close failures.
172 } finally {
173 ch = null;
174 }
175 }
176 }
177 }
178 }