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Fixed the frame reordering window.

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This commit is contained in:
akwizgran
2012-01-20 11:26:10 +00:00
parent 92b67d9881
commit 5a4505cb71
5 changed files with 106 additions and 114 deletions
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16
components/net/sf/briar/transport/FrameWindow.java
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@@ -2,21 +2,15 @@ package net.sf.briar.transport;
interface FrameWindow {
/** Returns true if the given number is too high to fit in the window. */
boolean isTooHigh(long frameNumber);
/** Returns true if the given number is in the window. */
boolean contains(long frameNumber);
/**
* Advances the window so it is centred on the given number, unless the
* centre is already greater than the number. Returns false if the window
* is unmodifiable.
*/
boolean advance(long frameNumber);
/**
* Removes the given number from the window and, if the number is greater
* than or equal to the window's centre, advances the centre to one greater
* than the given number. Returns false if the given number is not in the
* window or the window is unmodifiable.
* Removes the given number from the window and advances the window.
* Returns false if the given number is not in the window.
*/
boolean remove(long frameNumber);
}

60
components/net/sf/briar/transport/FrameWindowImpl.java
View File

@@ -5,18 +5,23 @@ import static net.sf.briar.util.ByteUtils.MAX_32_BIT_UNSIGNED;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
class FrameWindowImpl implements FrameWindow {
private final Collection<Long> window;
private long centre;
private long base;
FrameWindowImpl() {
window = new HashSet<Long>();
for(long l = 0; l < FRAME_WINDOW_SIZE / 2; l++) window.add(l);
centre = 0;
fill(0, FRAME_WINDOW_SIZE);
base = 0;
}
public boolean isTooHigh(long frameNumber) {
if(frameNumber < 0 || frameNumber > MAX_32_BIT_UNSIGNED)
throw new IllegalArgumentException();
return frameNumber >= base + FRAME_WINDOW_SIZE;
}
public boolean contains(long frameNumber) {
@@ -25,39 +30,32 @@ class FrameWindowImpl implements FrameWindow {
return window.contains(frameNumber);
}
public boolean advance(long frameNumber) {
if(frameNumber < 0 || frameNumber > MAX_32_BIT_UNSIGNED)
throw new IllegalArgumentException();
if(frameNumber <= centre) return true;
// Remove values that have passed out of the window
long newBottom = getBottom(frameNumber);
Iterator<Long> it = window.iterator();
while(it.hasNext()) if(it.next() < newBottom) it.remove();
// Add values that have passed into the window
long fillFrom = Math.max(newBottom, getTop(centre) + 1);
long newTop = getTop(frameNumber);
for(long l = fillFrom; l <= newTop; l++) window.add(l);
centre = frameNumber;
return true;
}
public boolean remove(long frameNumber) {
if(frameNumber < 0 || frameNumber > MAX_32_BIT_UNSIGNED)
throw new IllegalArgumentException();
if(!window.remove(frameNumber)) return false;
if(frameNumber >= centre && frameNumber < MAX_32_BIT_UNSIGNED)
advance(frameNumber + 1);
if(frameNumber == base) {
// Find the new base
if(window.isEmpty()) {
base += FRAME_WINDOW_SIZE;
fill(base, base + FRAME_WINDOW_SIZE);
} else {
for(long l = base; l < base + FRAME_WINDOW_SIZE; l++) {
if(window.contains(l)) {
fill(base + FRAME_WINDOW_SIZE, l + FRAME_WINDOW_SIZE);
base = l;
break;
}
}
}
}
return true;
}
// Returns the lowest value contained in a window with the given centre
private static long getBottom(long centre) {
return Math.max(0, centre - FRAME_WINDOW_SIZE / 2);
}
// Returns the highest value contained in a window with the given centre
private static long getTop(long centre) {
return Math.min(MAX_32_BIT_UNSIGNED,
centre + FRAME_WINDOW_SIZE / 2 - 1);
private void fill(long from, long to) {
for(long l = from; l < to; l++) {
if(l <= MAX_32_BIT_UNSIGNED) window.add(l);
else return;
}
}
}

22
components/net/sf/briar/transport/NullFrameWindow.java
View File

@@ -1,20 +1,28 @@
package net.sf.briar.transport;
import static net.sf.briar.util.ByteUtils.MAX_32_BIT_UNSIGNED;
class NullFrameWindow implements FrameWindow {
private long centre = 0L;
private long base = 0L;
public boolean contains(long frameNumber) {
return frameNumber == centre;
public boolean isTooHigh(long frameNumber) {
if(frameNumber < 0 || frameNumber > MAX_32_BIT_UNSIGNED)
throw new IllegalArgumentException();
return frameNumber != base;
}
public boolean advance(long frameNumber) {
return frameNumber == centre;
public boolean contains(long frameNumber) {
if(frameNumber < 0 || frameNumber > MAX_32_BIT_UNSIGNED)
throw new IllegalArgumentException();
return frameNumber == base;
}
public boolean remove(long frameNumber) {
if(frameNumber != centre) return false;
centre++;
if(frameNumber < 0 || frameNumber > MAX_32_BIT_UNSIGNED)
throw new IllegalArgumentException();
if(frameNumber != base) return false;
base++;
return true;
}
}

3
components/net/sf/briar/transport/NullIncomingReliabilityLayer.java
View File

@@ -15,8 +15,7 @@ class NullIncomingReliabilityLayer implements IncomingReliabilityLayer {
public boolean readFrame(Frame f) throws IOException, InvalidDataException {
if(!in.readFrame(f, window)) return false;
long frameNumber = HeaderEncoder.getFrameNumber(f.getBuffer());
if(!window.remove(frameNumber) && window.advance(frameNumber))
throw new RuntimeException();
if(!window.remove(frameNumber)) throw new IllegalStateException();
return true;
}
}