1 /*
2 * Copyright (C) 2007, Robin Rosenberg <robin.rosenberg@dewire.com>
3 * Copyright (C) 2006-2008, Shawn O. Pearce <spearce@spearce.org>
4 * and other copyright owners as documented in the project's IP log.
5 *
6 * This program and the accompanying materials are made available
7 * under the terms of the Eclipse Distribution License v1.0 which
8 * accompanies this distribution, is reproduced below, and is
9 * available at http://www.eclipse.org/org/documents/edl-v10.php
10 *
11 * All rights reserved.
12 *
13 * Redistribution and use in source and binary forms, with or
14 * without modification, are permitted provided that the following
15 * conditions are met:
16 *
17 * - Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 *
20 * - Redistributions in binary form must reproduce the above
21 * copyright notice, this list of conditions and the following
22 * disclaimer in the documentation and/or other materials provided
23 * with the distribution.
24 *
25 * - Neither the name of the Eclipse Foundation, Inc. nor the
26 * names of its contributors may be used to endorse or promote
27 * products derived from this software without specific prior
28 * written permission.
29 *
30 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
31 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
32 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
33 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
34 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
35 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
36 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
37 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
38 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
39 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
40 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
41 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
42 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
43 */
44
45 package org.eclipse.jgit.internal.storage.file;
46
47 import java.io.IOException;
48 import java.util.zip.DataFormatException;
49 import java.util.zip.Inflater;
50
51 import org.eclipse.jgit.internal.storage.pack.PackOutputStream;
52
53 /**
54 * A window of data currently stored within a cache.
55 * <p>
56 * All bytes in the window can be assumed to be "immediately available", that is
57 * they are very likely already in memory, unless the operating system's memory
58 * is very low and has paged part of this process out to disk. Therefore copying
59 * bytes from a window is very inexpensive.
60 * </p>
61 */
62 abstract class ByteWindow {
63 protected final PackFile pack;
64
65 protected final long start;
66
67 protected final long end;
68
69 /**
70 * Constructor for ByteWindow.
71 *
72 * @param p
73 * a {@link org.eclipse.jgit.internal.storage.file.PackFile}.
74 * @param s
75 * where the byte window starts in the pack file
76 * @param n
77 * size of the byte window
78 */
79 protected ByteWindow(PackFile p, long s, int n) {
80 pack = p;
81 start = s;
82 end = start + n;
83 }
84
85 final int size() {
86 return (int) (end - start);
87 }
88
89 final boolean contains(PackFile neededFile, long neededPos) {
90 return pack == neededFile && start <= neededPos && neededPos < end;
91 }
92
93 /**
94 * Copy bytes from the window to a caller supplied buffer.
95 *
96 * @param pos
97 * offset within the file to start copying from.
98 * @param dstbuf
99 * destination buffer to copy into.
100 * @param dstoff
101 * offset within <code>dstbuf</code> to start copying into.
102 * @param cnt
103 * number of bytes to copy. This value may exceed the number of
104 * bytes remaining in the window starting at offset
105 * <code>pos</code>.
106 * @return number of bytes actually copied; this may be less than
107 * <code>cnt</code> if <code>cnt</code> exceeded the number of
108 * bytes available.
109 */
110 final int copy(long pos, byte[] dstbuf, int dstoff, int cnt) {
111 return copy((int) (pos - start), dstbuf, dstoff, cnt);
112 }
113
114 /**
115 * Copy bytes from the window to a caller supplied buffer.
116 *
117 * @param pos
118 * offset within the window to start copying from.
119 * @param dstbuf
120 * destination buffer to copy into.
121 * @param dstoff
122 * offset within <code>dstbuf</code> to start copying into.
123 * @param cnt
124 * number of bytes to copy. This value may exceed the number of
125 * bytes remaining in the window starting at offset
126 * <code>pos</code>.
127 * @return number of bytes actually copied; this may be less than
128 * <code>cnt</code> if <code>cnt</code> exceeded the number of
129 * bytes available.
130 */
131 protected abstract int copy(int pos, byte[] dstbuf, int dstoff, int cnt);
132
133 abstract void write(PackOutputStream out, long pos, int cnt)
134 throws IOException;
135
136 final int setInput(long pos, Inflater inf) throws DataFormatException {
137 return setInput((int) (pos - start), inf);
138 }
139
140 /**
141 * Set the input
142 *
143 * @param pos
144 * position
145 * @param inf
146 * an {@link java.util.zip.Inflater} object.
147 * @return size of the byte window
148 * @throws java.util.zip.DataFormatException
149 * if any.
150 */
151 protected abstract int setInput(int pos, Inflater inf)
152 throws DataFormatException;
153 }