blob: e6f02a8a1d023fbd289cafa02dd61186ed843e0c (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
|
// The BitOutputStream and BitInputStream classes provide the ability to
// write and read individual bits to a file in a compact form. One major
// limitation of this approach is that the resulting file will always have
// a number of bits that is a multiple of 8. In effect, whatever bits are
// output to the file are padded at the end with 0's to make the total
// number of bits a multiple of 8.
//
// BitInputStream has the following public methods:
// public BitInputStream(String file)
// opens an input stream with the given file name
// public int nextBit()
// reads the next bit from input (throws exception if at end of file)
// public boolean hasNextBit()
// returns true if there's another bit in the input stream to be read
// public void close()
// closes the input
import java.io.*;
import java.util.*;
@SuppressWarnings("deprecation")
public class BitInputStream {
private FileInputStream input;
private int currentByte; // current set of bits (buffer)
private int nextByte; // next set of bits (buffer)
private int numBits; // how many bits from buffer have been used
private int remainingAtEnd; // how many bits will be remaining at the end
// after we're done
private static final int BYTE_SIZE = 8; // bits per byte
// pre : given file name is legal
// post: creates a BitInputStream reading input from the file
public BitInputStream(String file) {
try {
this.input = new FileInputStream(file);
// Read in the number of remaining bits at the end
this.remainingAtEnd = this.input.read();
// Set up the nextByte field.
this.nextByte = this.input.read();
} catch (IOException ex) {
throw new RuntimeException(ex.toString());
}
this.nextByte();
}
public boolean hasNextBit() {
boolean atEnd = this.currentByte == -1;
boolean onlyRemaining = this.nextByte == -1
&& BYTE_SIZE - this.numBits == this.remainingAtEnd;
return !atEnd && !onlyRemaining;
}
// post: reads next bit from input
// throws NoSuchElementException if there is no bit to return
public int nextBit() {
// if at eof, throw exception
if (!this.hasNextBit()) {
throw new NoSuchElementException();
}
int result = this.currentByte % 2;
this.currentByte /= 2;
this.numBits++;
if (this.numBits == BYTE_SIZE) {
this.nextByte();
}
return result;
}
// post: refreshes the internal buffer with the next BYTE_SIZE bits
private void nextByte() {
this.currentByte = this.nextByte;
if (this.currentByte != -1) {
try {
this.nextByte = this.input.read();
} catch (IOException e) {
throw new RuntimeException(e.toString());
}
}
this.numBits = 0;
}
// post: input is closed
public void close() {
try {
this.input.close();
} catch (IOException e) {
throw new RuntimeException(e.toString());
}
}
// included to ensure that the stream is closed
protected void finalize() {
this.close();
}
}
|
