1 |
import java.io.File; |
2 |
import java.io.FileInputStream; |
3 |
import java.io.FileOutputStream; |
4 |
import java.io.InputStream; |
5 |
import java.io.OutputStream; |
6 |
import java.io.IOException; |
7 |
|
8 |
/** |
9 |
An encryptor encrypts files using the Caesar cipher. |
10 |
For decryption, use an encryptor whose key is the |
11 |
negative of the encryption key. |
12 |
*/ |
13 |
public class Encryptor |
14 |
{ |
15 |
/** |
16 |
Constructs an encryptor. |
17 |
@param aKey the encryption key |
18 |
*/ |
19 |
public Encryptor(int aKey) |
20 |
{ |
21 |
key = aKey; |
22 |
} |
23 |
|
24 |
/** |
25 |
Encrypts the contents of a file. |
26 |
@param inFile the input file |
27 |
@param outFile the output file |
28 |
*/ |
29 |
public void encryptFile(File inFile, File outFile) |
30 |
throws IOException |
31 |
{ |
32 |
InputStream in = null; |
33 |
OutputStream out = null; |
34 |
|
35 |
try |
36 |
{ |
37 |
in = new FileInputStream(inFile); |
38 |
out = new FileOutputStream(outFile); |
39 |
encryptStream(in, out); |
40 |
} |
41 |
finally |
42 |
{ |
43 |
if (in != null) in.close(); |
44 |
if (out != null) out.close(); |
45 |
} |
46 |
} |
47 |
|
48 |
/** |
49 |
Encrypts the contents of a stream. |
50 |
@param in the input stream |
51 |
@param out the output stream |
52 |
*/ |
53 |
public void encryptStream(InputStream in, OutputStream out) |
54 |
throws IOException |
55 |
{ |
56 |
boolean done = false; |
57 |
while (!done) |
58 |
{ |
59 |
int next = in.read(); |
60 |
if (next == -1) done = true; |
61 |
else |
62 |
{ |
63 |
byte b = (byte)next; |
64 |
byte c = encrypt(b); |
65 |
out.write(c); |
66 |
} |
67 |
} |
68 |
} |
69 |
|
70 |
/** |
71 |
Encrypts a byte. |
72 |
@param b the byte to encrypt |
73 |
@return the encrypted byte |
74 |
*/ |
75 |
public byte encrypt(byte b) |
76 |
{ |
77 |
return (byte)(b + key); |
78 |
} |
79 |
|
80 |
private int key; |
81 |
} |