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 /**
55 * A reftable stored in {@link org.eclipse.jgit.internal.storage.dfs.DfsBlockCache}.
56 */
57 public class DfsReftable extends BlockBasedFile {
58 /**
59 * Construct a reader for an existing reftable.
60 *
61 * @param desc
62 * description of the reftable within the DFS.
63 */
64 public DfsReftable(DfsPackDescription desc) {
65 this(DfsBlockCache.getInstance(), desc);
66 }
67
68 /**
69 * Construct a reader for an existing reftable.
70 *
71 * @param cache
72 * cache that will store the reftable data.
73 * @param desc
74 * description of the reftable within the DFS.
75 */
76 public DfsReftable(DfsBlockCache cache, DfsPackDescription desc) {
77 super(cache, desc, REFTABLE);
78
79 int bs = desc.getBlockSize(REFTABLE);
80 if (bs > 0) {
81 setBlockSize(bs);
82 }
83
84 long sz = desc.getFileSize(REFTABLE);
85 length = sz > 0 ? sz : -1;
86 }
87
88 /**
89 * Get description that was originally used to configure this file.
90 *
91 * @return description that was originally used to configure this file.
92 */
93 public DfsPackDescription getPackDescription() {
94 return desc;
95 }
96
97 /**
98 * Open reader on the reftable.
99 * <p>
100 * The returned reader is not thread safe.
101 *
102 * @param ctx
103 * reader to access the DFS storage.
104 * @return cursor to read the table; caller must close.
105 * @throws java.io.IOException
106 * table cannot be opened.
107 */
108 public ReftableReader open(DfsReader ctx) throws IOException {
109 return new ReftableReader(new CacheSource(this, cache, ctx));
110 }
111
112 private static final class CacheSource extends BlockSource {
113 private final DfsReftable file;
114 private final DfsBlockCache cache;
115 private final DfsReader ctx;
116 private ReadableChannel ch;
117 private int readAhead;
118
119 CacheSource(DfsReftable file, DfsBlockCache cache, DfsReader ctx) {
120 this.file = file;
121 this.cache = cache;
122 this.ctx = ctx;
123 }
124
125 @Override
126 public ByteBuffer read(long pos, int cnt) throws IOException {
127 if (ch == null && readAhead > 0 && notInCache(pos)) {
128 open().setReadAheadBytes(readAhead);
129 }
130
131 DfsBlock block = cache.getOrLoad(file, pos, ctx, () -> open());
132 if (block.start == pos && block.size() >= cnt) {
133 return block.zeroCopyByteBuffer(cnt);
134 }
135
136 byte[] dst = new byte[cnt];
137 ByteBuffer buf = ByteBuffer.wrap(dst);
138 buf.position(ctx.copy(file, pos, dst, 0, cnt));
139 return buf;
140 }
141
142 private boolean notInCache(long pos) {
143 return cache.get(file.key, file.alignToBlock(pos)) == null;
144 }
145
146 @Override
147 public long size() throws IOException {
148 long n = file.length;
149 if (n < 0) {
150 n = open().size();
151 file.length = n;
152 }
153 return n;
154 }
155
156 @Override
157 public void adviseSequentialRead(long start, long end) {
158 int sz = ctx.getOptions().getStreamPackBufferSize();
159 if (sz > 0) {
160 readAhead = (int) Math.min(sz, end - start);
161 }
162 }
163
164 private ReadableChannel open() throws IOException {
165 if (ch == null) {
166 ch = ctx.db.openFile(file.desc, file.ext);
167 }
168 return ch;
169 }
170
171 @Override
172 public void close() {
173 if (ch != null) {
174 try {
175 ch.close();
176 } catch (IOException e) {
177 // Ignore read close failures.
178 } finally {
179 ch = null;
180 }
181 }
182 }
183 }
184 }