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Tests and bugfixes for XOR encoder and decoder.

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This commit is contained in:
akwizgran
2012-01-20 19:09:27 +00:00
parent 74dd4e277f
commit 114ca203d8
6 changed files with 112 additions and 21 deletions
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10
components/net/sf/briar/transport/Frame.java
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@@ -4,10 +4,18 @@ import static net.sf.briar.api.transport.TransportConstants.MAX_FRAME_LENGTH;
class Frame {
private final byte[] buf = new byte[MAX_FRAME_LENGTH];
private final byte[] buf;
private int length = -1;
Frame() {
this(MAX_FRAME_LENGTH);
}
Frame(int length) {
buf = new byte[length];
}
public byte[] getBuffer() {
return buf;
}

14
components/net/sf/briar/transport/XorErasureDecoder.java
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@@ -36,27 +36,31 @@ class XorErasureDecoder implements ErasureDecoder {
// We don't need no stinkin' parity segment
for(int i = 0; i < n - 1; i++) {
byte[] src = set[i].getBuffer();
System.arraycopy(src, 0, dest, offset, length);
int copyLength = Math.min(length, dest.length - offset);
System.arraycopy(src, 0, dest, offset, copyLength);
offset += length;
}
} else {
// Reconstruct the missing segment
byte[] parity = new byte[length];
int missingOffset = -1;
for(int i = 0; i < n; i++) {
for(int i = 0; i < n - 1; i++) {
if(set[i] == null) {
missingOffset = offset;
} else {
byte[] src = set[i].getBuffer();
System.arraycopy(src, 0, dest, offset, length);
for(int j = 0; j < length; j++) parity[j] ^= src[j];
int copyLength = Math.min(length, dest.length - offset);
System.arraycopy(src, 0, dest, offset, copyLength);
}
offset += length;
}
byte[] src = set[n - 1].getBuffer();
for(int i = 0; i < length; i++) parity[i] ^= src[i];
assert missingOffset != -1;
System.arraycopy(parity, 0, dest, missingOffset, length);
int copyLength = Math.min(length, dest.length - missingOffset);
System.arraycopy(parity, 0, dest, missingOffset, copyLength);
}
assert offset == length * (n - 1);
// The frame length may not be an exact multiple of the segment length
int payload = HeaderEncoder.getPayloadLength(dest);
int padding = HeaderEncoder.getPaddingLength(dest);

5
components/net/sf/briar/transport/XorErasureEncoder.java
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@@ -21,8 +21,9 @@ class XorErasureEncoder implements ErasureEncoder {
byte[] src = f.getBuffer(), parity = set[n - 1].getBuffer();
int offset = 0;
for(int i = 0; i < n - 1; i++) {
System.arraycopy(src, offset, set[i].getBuffer(), 0, length);
for(int j = 0; j < length; j++) parity[j] ^= src[offset + j];
int copyLength = Math.min(length, src.length - offset);
System.arraycopy(src, offset, set[i].getBuffer(), 0, copyLength);
for(int j = 0; j < copyLength; j++) parity[j] ^= src[offset + j];
offset += length;
}
return set;

1
test/build.xml
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@@ -61,6 +61,7 @@
<test name='net.sf.briar.transport.IncomingSegmentedEncryptionLayerTest'/>
<test name='net.sf.briar.transport.OutgoingEncryptionLayerImplTest'/>
<test name='net.sf.briar.transport.OutgoingSegmentedEncryptionLayerTest'/>
<test name='net.sf.briar.transport.XorErasureCodeTest'/>
<test name='net.sf.briar.transport.XorErasureDecoderTest'/>
<test name='net.sf.briar.transport.XorErasureEncoderTest'/>
<test name='net.sf.briar.util.ByteUtilsTest'/>

50
test/net/sf/briar/transport/XorErasureCodeTest.java Normal file
View File

@@ -0,0 +1,50 @@
package net.sf.briar.transport;
import static net.sf.briar.api.transport.TransportConstants.FRAME_HEADER_LENGTH;
import static net.sf.briar.api.transport.TransportConstants.MAC_LENGTH;
import java.util.Random;
import net.sf.briar.BriarTestCase;
import net.sf.briar.api.transport.Segment;
import static org.junit.Assert.assertArrayEquals;
import org.junit.Test;
public class XorErasureCodeTest extends BriarTestCase {
@Test
public void testEncodingAndDecodingWithAllSegments() throws Exception {
XorErasureEncoder e = new XorErasureEncoder(5);
XorErasureDecoder d = new XorErasureDecoder(5);
Frame f = new Frame(1234);
new Random().nextBytes(f.getBuffer());
int payload = 1234 - FRAME_HEADER_LENGTH - MAC_LENGTH;
HeaderEncoder.encodeHeader(f.getBuffer(), 0L, payload, 0);
f.setLength(1234);
Segment[] set = e.encodeFrame(f);
assertEquals(5, set.length);
Frame f1 = new Frame(1234);
assertTrue(d.decodeFrame(f1, set));
assertArrayEquals(f.getBuffer(), f1.getBuffer());
}
@Test
public void testEncodingAndDecodingWithMissingSegment() throws Exception {
XorErasureEncoder e = new XorErasureEncoder(5);
XorErasureDecoder d = new XorErasureDecoder(5);
Frame f = new Frame(1234);
new Random().nextBytes(f.getBuffer());
int payload = 1234 - FRAME_HEADER_LENGTH - MAC_LENGTH;
HeaderEncoder.encodeHeader(f.getBuffer(), 0L, payload, 0);
f.setLength(1234);
for(int i = 0; i < 5; i++) {
Segment[] set = e.encodeFrame(f);
assertEquals(5, set.length);
set[i] = null;
Frame f1 = new Frame(1234);
assertTrue(d.decodeFrame(f1, set));
assertArrayEquals(f.getBuffer(), f1.getBuffer());
}
}
}

53
test/net/sf/briar/transport/XorErasureDecoderTest.java
View File

@@ -14,24 +14,15 @@ public class XorErasureDecoderTest extends BriarTestCase {
@Test
public void testMaximumLength() throws Exception {
XorErasureDecoder d = new XorErasureDecoder(5);
// A frame of the maximum length should be decoded successfully
Segment[] set = encodeEmptyFrame(MAX_FRAME_LENGTH / 4, 5);
XorErasureDecoder d = new XorErasureDecoder(5);
Frame f = new Frame();
assertTrue(d.decodeFrame(f, set));
// Check the header
byte[] b = f.getBuffer();
assertEquals(0L, HeaderEncoder.getFrameNumber(b));
int payload = MAX_FRAME_LENGTH - FRAME_HEADER_LENGTH - MAC_LENGTH;
assertEquals(payload, HeaderEncoder.getPayloadLength(b));
assertEquals(0, HeaderEncoder.getPaddingLength(b));
// Check the body
assertEquals(MAX_FRAME_LENGTH, f.getLength());
for(int i = FRAME_HEADER_LENGTH; i < MAX_FRAME_LENGTH; i++) {
assertEquals(0, b[i]);
}
checkFrame(f, MAX_FRAME_LENGTH);
// A frame larger than the maximum length should not be decoded
set = encodeEmptyFrame(MAX_FRAME_LENGTH / 4 + 1, 5);
f = new Frame();
try {
d.decodeFrame(f, set);
} catch(FormatException expected) {}
@@ -47,12 +38,35 @@ public class XorErasureDecoderTest extends BriarTestCase {
set[1].setLength(251);
// The frame should be decoded successfully
XorErasureDecoder d = new XorErasureDecoder(4);
Frame f = new Frame();
Frame f = new Frame(750);
assertTrue(d.decodeFrame(f, set));
// The minimum of the segments' lengths should have been used
assertEquals(750, f.getLength());
}
@Test
public void testDecodingWithMissingSegment() throws Exception {
XorErasureDecoder d = new XorErasureDecoder(4);
for(int i = 0; i < 4; i++) {
Segment[] set = encodeEmptyFrame(250, 4);
set[i] = null;
// The frame should be decoded successfully
Frame f = new Frame(750);
assertTrue(d.decodeFrame(f, set));
checkFrame(f, 750);
}
}
@Test
public void testDecodingWithTwoMissingSegments() throws Exception {
XorErasureDecoder d = new XorErasureDecoder(4);
Segment[] set = encodeEmptyFrame(250, 4);
set[0] = null;
set[1] = null;
Frame f = new Frame(750);
assertFalse(d.decodeFrame(f, set));
}
private Segment[] encodeEmptyFrame(int length, int n) {
Segment[] set = new Segment[n];
for(int i = 0; i < n; i++) {
@@ -64,4 +78,17 @@ public class XorErasureDecoderTest extends BriarTestCase {
HeaderEncoder.encodeHeader(set[n - 1].getBuffer(), 0L, payload, 0);
return set;
}
private void checkFrame(Frame f, int length) {
byte[] b = f.getBuffer();
assertEquals(0L, HeaderEncoder.getFrameNumber(b));
int payload = length - FRAME_HEADER_LENGTH - MAC_LENGTH;
assertEquals(payload, HeaderEncoder.getPayloadLength(b));
assertEquals(0, HeaderEncoder.getPaddingLength(b));
// Check the body
assertEquals(length, f.getLength());
for(int i = FRAME_HEADER_LENGTH; i < length; i++) {
assertEquals("" + i, 0, b[i]);
}
}
}