|
1 package com.thaiopensource.validate.auto;
2
3 import java.io.InputStream  ;
4 import java.io.IOException ;
5
6 public class RewindableInputStream extends InputStream implements Rewindable {
7 static class Block {
8 Block next;
9 final byte[] buf;
10 int used = 0;
11 static final int MIN_SIZE = 1024;
12 Block(int minSize) {
13 buf = new byte[Math.max(MIN_SIZE, minSize)];
14 }
15
16 Block() {
17 this(0);
18 }
19
20 void append(byte b) {
21 buf[used++] = b;
22 }
23
24 void append(byte[] b, int off, int len) {
25 System.arraycopy(b, off, buf, used, len);
26 used += len;
27 }
28 }
29
30 private Block head;
31
35 private int curBlockAvail;
36 private Block curBlock;
37 private int curBlockPos;
38 private Block lastBlock;
39
42 private boolean saving = true;
43 private final InputStream in;
44 private boolean pretendClosed = false;
45
48 private boolean eof;
49
50 public RewindableInputStream(InputStream in) {
51 if (in == null)
52 throw new NullPointerException ();
53 this.in = in;
54 }
55
56 public void close() throws IOException {
57 if (saving) {
58 curBlockAvail = 0;
59 curBlock = null;
60 pretendClosed = true;
61 }
62 else {
63 head = null;
64 curBlock = null;
65 lastBlock = null;
66 saving = false;
67 curBlockAvail = 0;
68 in.close();
69 }
70 }
71
72 public void rewind() {
73 if (!saving)
74 throw new IllegalStateException ("rewind() after willNotRewind()");
75 pretendClosed = false;
76 if (head == null)
77 return;
78 curBlock = head;
79 curBlockPos = 0;
80 curBlockAvail = curBlock.used;
81 }
82
83 public boolean canRewind() {
84 return saving;
85 }
86
87 public void willNotRewind() {
88 saving = false;
89 head = null;
90 lastBlock = null;
91 if (pretendClosed) {
92 pretendClosed = false;
93 try {
94 in.close();
95 }
96 catch (IOException e) { }
97 }
98 }
99
100 public int read() throws IOException {
101 if (curBlockAvail > 0) {
102 int c = curBlock.buf[curBlockPos++] & 0xFF;
103 --curBlockAvail;
104 if (curBlockAvail == 0) {
105 curBlock = curBlock.next;
106 if (curBlock != null) {
107 curBlockPos = 0;
108 curBlockAvail = curBlock.used;
109 }
110 }
111 return c;
112 }
113 int c = in.read();
114 if (saving && c != -1) {
115 if (lastBlock == null)
116 lastBlock = head = new Block();
117 else if (lastBlock.used == lastBlock.buf.length)
118 lastBlock = lastBlock.next = new Block();
119 lastBlock.append((byte)c);
120 }
121 return c;
122 }
123
124 public int read(byte b[], int off, int len) throws IOException {
125 if (curBlockAvail == 0 && !saving)
126 return in.read(b, off, len);
127 if (b == null)
128 throw new NullPointerException ();
129 if (len < 0)
130 throw new IndexOutOfBoundsException ();
131 int nRead = 0;
132 if (curBlockAvail != 0) {
133 for (;;) {
134 if (len == 0)
135 return nRead;
136 b[off++] = curBlock.buf[curBlockPos++];
137 --len;
138 nRead++;
139 --curBlockAvail;
140 if (curBlockAvail == 0) {
141 curBlock = curBlock.next;
142 if (curBlock == null)
143 break;
144 curBlockAvail = curBlock.used;
145 curBlockPos = 0;
146 }
147 }
148 }
149 if (len == 0)
150 return nRead;
151 if (eof)
152 return nRead > 0 ? nRead : -1;
153 try {
154 int n = in.read(b, off, len);
155 if (n < 0) {
156 eof = true;
157 return nRead > 0 ? nRead : -1;
158 }
159 nRead += n;
160 if (saving) {
161 if (lastBlock == null)
162 lastBlock = head = new Block(n);
163 else if (lastBlock.buf.length - lastBlock.used < n) {
164 if (lastBlock.used != lastBlock.buf.length) {
165 int free = lastBlock.buf.length - lastBlock.used;
166 lastBlock.append(b, off, free);
167 off += free;
168 n -= free;
169 }
170 lastBlock = lastBlock.next = new Block(n);
171 }
172 lastBlock.append(b, off, n);
173 }
174 }
175 catch (IOException e) {
176 eof = true;
177 if (nRead == 0)
178 throw e;
179 }
180 return nRead;
181 }
182
183 public int available() throws IOException {
184 if (curBlockAvail == 0)
185 return in.available();
186 int n = curBlockAvail;
187 for (Block b = curBlock.next; b != null; b = b.next)
188 n += b.used;
189 return n + in.available();
190 }
191
192 }
193 |
Popular Tags |
Java API By Example, From Geeks To Geeks.