1 /*
2 * Licensed under the Apache License, Version 2.0 (the "License");
3 * you may not use this file except in compliance with the License.
4 * You may obtain a copy of the License at
5 *
6 * http://www.apache.org/licenses/LICENSE-2.0
7 *
8 * Unless required by applicable law or agreed to in writing, software
9 * distributed under the License is distributed on an "AS IS" BASIS,
10 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
11 * See the License for the specific language governing permissions and
12 * limitations under the License.
13 * under the License.
14 */
15
16 package org.apache.commons.imaging.formats.jpeg.decoder;
17
18 import java.util.Arrays;
19
20 import org.apache.commons.imaging.ImagingException;
21 import org.apache.commons.imaging.formats.jpeg.JpegConstants;
22
23 final class JpegInputStream {
24 static final int SHALLOW_SIZE = 32;
25 // Figure F.18, F.2.2.5, page 111 of ITU-T T.81
26 private final int[] interval;
27 // next position in the array to read
28 private int nextPos;
29 private int cnt;
30 private int b;
31
32 JpegInputStream(final int[] interval) {
33 this.interval = Arrays.copyOf(interval, interval.length);
34 this.nextPos = 0;
35 }
36
37 /**
38 * Returns {@code true} as long there are unread fields available, else {@code false}
39 *
40 * @return {@code true} as long there are unread fields available, else {@code false}
41 */
42 public boolean hasNext() {
43 return nextPos < this.interval.length;
44 }
45
46 public int nextBit() throws ImagingException {
47 if (cnt == 0) {
48 b = this.read();
49 if (b < 0) {
50 throw new ImagingException("Premature End of File");
51 }
52 cnt = 8;
53 if (b == 0xff) {
54 final int b2 = this.read();
55 if (b2 < 0) {
56 throw new ImagingException("Premature End of File");
57 }
58 if (b2 != 0) {
59 if (b2 == (0xff & JpegConstants.DNL_MARKER)) {
60 throw new ImagingException("DNL not yet supported");
61 }
62 throw new ImagingException("Invalid marker found " + "in entropy data: 0xFF " + Integer.toHexString(b2));
63 }
64 }
65 }
66 final int bit = b >> 7 & 0x1;
67 cnt--;
68 b <<= 1;
69 return bit;
70 }
71
72 /**
73 * Returns the value from current field (as {@code InputStream.read()} would do) and set the position of the pointer to the next field to read.
74 *
75 * @return the value from current field (as {@code InputStream.read()} would do).
76 * @throws IllegalStateException if the stream hasn't any other value.
77 */
78 int read() {
79 if (!this.hasNext()) {
80 throw new IllegalStateException("This stream hasn't any other value, all values were already read.");
81 }
82 final int value = this.interval[nextPos];
83 this.nextPos++;
84 return value;
85 }
86 }