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If there's space for a partial final frame, use it.

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This commit is contained in:
akwizgran
2012-08-29 18:11:30 +01:00
parent a104548f7c
commit 88e7cc786f
2 changed files with 117 additions and 8 deletions
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28
components/net/sf/briar/transport/OutgoingEncryptionLayer.java
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@@ -24,7 +24,7 @@ class OutgoingEncryptionLayer implements FrameWriter {
private final AuthenticatedCipher frameCipher;
private final ErasableKey tagKey, frameKey;
private final byte[] iv, aad, ciphertext;
private final int frameLength;
private final int frameLength, maxPayloadLength;
private long capacity, frameNumber;
private boolean writeTag;
@@ -40,6 +40,7 @@ class OutgoingEncryptionLayer implements FrameWriter {
this.tagKey = tagKey;
this.frameKey = frameKey;
this.frameLength = frameLength;
maxPayloadLength = frameLength - HEADER_LENGTH - MAC_LENGTH;
iv = new byte[IV_LENGTH];
aad = new byte[AAD_LENGTH];
ciphertext = new byte[frameLength];
@@ -56,6 +57,7 @@ class OutgoingEncryptionLayer implements FrameWriter {
this.frameCipher = frameCipher;
this.frameKey = frameKey;
this.frameLength = frameLength;
maxPayloadLength = frameLength - HEADER_LENGTH - MAC_LENGTH;
tagCipher = null;
tagKey = null;
iv = new byte[IV_LENGTH];
@@ -125,10 +127,26 @@ class OutgoingEncryptionLayer implements FrameWriter {
}
public long getRemainingCapacity() {
long capacityExcludingTag = writeTag ? capacity - TAG_LENGTH : capacity;
long frames = capacityExcludingTag / frameLength;
// How many frame numbers can we use?
long frameNumbers = MAX_32_BIT_UNSIGNED - frameNumber + 1;
int maxPayloadLength = frameLength - HEADER_LENGTH - MAC_LENGTH;
return maxPayloadLength * Math.min(frames, frameNumbers);
// How many full frames do we have space for?
long bytes = writeTag ? capacity - TAG_LENGTH : capacity;
long fullFrames = bytes / frameLength;
// Are we limited by frame numbers or space?
if(frameNumbers > fullFrames) {
// Can we send a partial frame after the full frames?
int partialFrame = (int) (bytes - fullFrames * frameLength);
if(partialFrame > HEADER_LENGTH + MAC_LENGTH) {
// Send full frames and a partial frame, limited by space
int partialPayload = partialFrame - HEADER_LENGTH - MAC_LENGTH;
return maxPayloadLength * fullFrames + partialPayload;
} else {
// Send full frames only, limited by space
return maxPayloadLength * fullFrames;
}
} else {
// Send full frames only, limited by frame numbers
return maxPayloadLength * frameNumbers;
}
}
}