1 /* OutputWindow.java --
2 Copyright (C) 2001, 2004 Free Software Foundation, Inc.
3
4 This file is part of GNU Classpath.
5
6 GNU Classpath is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
9 any later version.
10
11 GNU Classpath is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with GNU Classpath; see the file COPYING. If not, write to the
18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
19 02110-1301 USA.
20
21 Linking this library statically or dynamically with other modules is
22 making a combined work based on this library. Thus, the terms and
23 conditions of the GNU General Public License cover the whole
24 combination.
25
26 As a special exception, the copyright holders of this library give you
27 permission to link this library with independent modules to produce an
28 executable, regardless of the license terms of these independent
29 modules, and to copy and distribute the resulting executable under
30 terms of your choice, provided that you also meet, for each linked
31 independent module, the terms and conditions of the license of that
32 module. An independent module is a module which is not derived from
33 or based on this library. If you modify this library, you may extend
34 this exception to your version of the library, but you are not
35 obligated to do so. If you do not wish to do so, delete this
36 exception statement from your version. */
37
38 package java.util.zip;
39
40 /**
41 * Contains the output from the Inflation process.
42 *
43 * We need to have a window so that we can refer backwards into the output stream
44 * to repeat stuff.
45 *
46 * @author John Leuner
47 * @since 1.1
48 */
49 class OutputWindow
50 {
51 private static final int WINDOW_SIZE = 1 << 15;
52 private static final int WINDOW_MASK = WINDOW_SIZE - 1;
53
54 private byte[] window = new byte[WINDOW_SIZE]; //The window is 2^15 bytes
55 private int window_end = 0;
56 private int window_filled = 0;
57
58 public void write(int abyte)
59 {
60 if (window_filled++ == WINDOW_SIZE)
61 throw new IllegalStateException("Window full");
62 window[window_end++] = (byte) abyte;
63 window_end &= WINDOW_MASK;
64 }
65
66 private void slowRepeat(int rep_start, int len, int dist)
67 {
68 while (len-- > 0)
69 {
70 window[window_end++] = window[rep_start++];
71 window_end &= WINDOW_MASK;
72 rep_start &= WINDOW_MASK;
73 }
74 }
75
76 public void repeat(int len, int dist)
77 {
78 if ((window_filled += len) > WINDOW_SIZE)
79 throw new IllegalStateException("Window full");
80
81 int rep_start = (window_end - dist) & WINDOW_MASK;
82 int border = WINDOW_SIZE - len;
83 if (rep_start <= border && window_end < border)
84 {
85 if (len <= dist)
86 {
87 System.arraycopy(window, rep_start, window, window_end, len);
88 window_end += len;
89 }
90 else
91 {
92 /* We have to copy manually, since the repeat pattern overlaps.
93 */
94 while (len-- > 0)
95 window[window_end++] = window[rep_start++];
96 }
97 }
98 else
99 slowRepeat(rep_start, len, dist);
100 }
101
102 public int copyStored(StreamManipulator input, int len)
103 {
104 len = Math.min(Math.min(len, WINDOW_SIZE - window_filled),
105 input.getAvailableBytes());
106 int copied;
107
108 int tailLen = WINDOW_SIZE - window_end;
109 if (len > tailLen)
110 {
111 copied = input.copyBytes(window, window_end, tailLen);
112 if (copied == tailLen)
113 copied += input.copyBytes(window, 0, len - tailLen);
114 }
115 else
116 copied = input.copyBytes(window, window_end, len);
117
118 window_end = (window_end + copied) & WINDOW_MASK;
119 window_filled += copied;
120 return copied;
121 }
122
123 public void copyDict(byte[] dict, int offset, int len)
124 {
125 if (window_filled > 0)
126 throw new IllegalStateException();
127
128 if (len > WINDOW_SIZE)
129 {
130 offset += len - WINDOW_SIZE;
131 len = WINDOW_SIZE;
132 }
133 System.arraycopy(dict, offset, window, 0, len);
134 window_end = len & WINDOW_MASK;
135 }
136
137 public int getFreeSpace()
138 {
139 return WINDOW_SIZE - window_filled;
140 }
141
142 public int getAvailable()
143 {
144 return window_filled;
145 }
146
147 public int copyOutput(byte[] output, int offset, int len)
148 {
149 int copy_end = window_end;
150 if (len > window_filled)
151 len = window_filled;
152 else
153 copy_end = (window_end - window_filled + len) & WINDOW_MASK;
154
155 int copied = len;
156 int tailLen = len - copy_end;
157
158 if (tailLen > 0)
159 {
160 System.arraycopy(window, WINDOW_SIZE - tailLen,
161 output, offset, tailLen);
162 offset += tailLen;
163 len = copy_end;
164 }
165 System.arraycopy(window, copy_end - len, output, offset, len);
166 window_filled -= copied;
167 if (window_filled < 0)
168 throw new IllegalStateException();
169 return copied;
170 }
171
172 public void reset() {
173 window_filled = window_end = 0;
174 }
175 }
176
177
178
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