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ShrinkItArchive
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Added some masking to prevent a byte with the high bit set (0x80 or more) to flip into negative numbers; also altered to use an int in update.

This commit is contained in:
Robert Greene 2008-06-17 04:09:03 +00:00
parent 27ee990c43
commit 6c241ea036
2 changed files with 8 additions and 3 deletions
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4
src/com/webcodepro/shrinkit/CRC16.java
View File

@ -40,7 +40,7 @@ public class CRC16 implements Checksum {
*/
private int update(int crc, byte[] bytes, int off, int len) {
for (int i = off; i < (off + len); i++) {
byte b = bytes[i];
int b = (bytes[i] & 0xff);
crc = (table[((crc >> 8) & 0xff) ^ b] ^ (crc << 8)) & 0xffff;
}
return crc;
@ -64,7 +64,7 @@ public class CRC16 implements Checksum {
* @param b input byte
*/
public void update(int b) {
byte[] ba = { (byte) b };
byte[] ba = { (byte) (b & 0xff) };
value = update(value, ba, 0, 1);
}

7
test_src/com/webcodepro/shrinkit/CRC16Test.java
View File

@ -5,7 +5,6 @@ import java.io.UnsupportedEncodingException;
import junit.framework.TestCase;
public class CRC16Test extends TestCase {
public void testTable() {
int[] table = CRC16.getTable();
assertEquals(0, table[0]);
@ -30,4 +29,10 @@ public class CRC16Test extends TestCase {
assertEquals(0x31c3, crc16.getValue());
}
public void testVariousValues() throws UnsupportedEncodingException {
CRC16 crc16 = new CRC16();
byte[] data = new byte[] { 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, (byte)0x80 };
crc16.update(data);
assertEquals(0x2299, crc16.getValue());
}
}