org.jitsi.impl.neomedia.codec.REDBlockIterator Maven / Gradle / Ivy
/*
* Copyright @ 2015 Atlassian Pty Ltd
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jitsi.impl.neomedia.codec;
import java.util.*;
import java.util.function.*;
import org.jitsi.utils.logging.*;
/**
* An Iterator that iterates RED blocks (primary and non-primary).
*
* @author George Politis
*/
public class REDBlockIterator
implements Iterator
{
/**
* The Logger used by the REDBlockIterator class and
* its instances to print debug information.
*/
private static final Logger logger
= Logger.getLogger(REDBlockIterator.class);
/**
* The byte buffer that holds the RED payload that this instance is
* dissecting.
*/
private final byte[] buffer;
/**
* The offset in the buffer where the RED payload begin.
*/
private final int offset;
/**
* The length of the RED payload in the buffer.
*/
private final int length;
/**
* The number of RED blocks inside the RED payload.
*/
private int cntRemainingBlocks = -1;
/**
* The offset of the next RED block header inside the RED payload.
*/
private int offNextBlockHeader = -1;
/**
* The offset of the next RED block payload inside the RED payload.
*/
private int offNextBlockPayload = -1;
/**
* Matches a RED block in the RED payload.
*
* @param predicate the predicate that is used to match the RED block.
* @param buffer the byte buffer that contains the RED payload.
* @param offset the offset in the buffer where the RED payload begins.
* @param length the length of the RED payload.
* @return the first RED block that matches the given predicate, null
* otherwise.
*/
public static REDBlock matchFirst(
Predicate predicate,
byte[] buffer, int offset, int length)
{
if (isMultiBlock(buffer, offset, length))
{
REDBlockIterator it = new REDBlockIterator(buffer, offset, length);
while (it.hasNext())
{
REDBlock b = it.next();
if (b != null && predicate.test(b))
{
return b;
}
}
return null;
}
else
{
REDBlock b = getPrimaryBlock(buffer, offset, length);
if (b != null && predicate.test(b))
{
return b;
}
else
{
return null;
}
}
}
/**
* Gets the first RED block in the RED payload.
*
* @param buffer the byte buffer that contains the RED payload.
* @param offset the offset in the buffer where the RED payload begins.
* @param length the length of the RED payload.
* @return the primary RED block if it exists, null otherwise.
*/
public static REDBlock getPrimaryBlock(
byte[] buffer, int offset, int length)
{
// Chrome is typically sending RED packets with a single block carrying
// either VP8 or FEC. This is unusual, and probably wrong as it messes
// up the sequence numbers and packet loss computations but it's just
// the way it is. Here we detect this situation and avoid looping
// through the blocks if there is a single block.
if (isMultiBlock(buffer, offset, length))
{
REDBlock block = null;
REDBlockIterator redBlockIterator
= new REDBlockIterator(buffer, offset, length);
while (redBlockIterator.hasNext())
{
block = redBlockIterator.next();
}
if (block == null)
{
logger.warn("No primary block found.");
}
return block;
}
else
{
// we need at least one byte to read the RED block payload type.
if (buffer == null || offset < 0 || length < 1
|| buffer.length < offset + length)
{
logger.warn("Prevented an array out of bounds exception."
+ " offset: " + offset + ", length: " + length);
return null;
}
byte blockPT = (byte) (buffer[offset] & 0x7f);
int blockOff = offset + 1; // + 1 for the primary block header.
int blockLen = length - 1;
return new REDBlock(buffer, blockOff, blockLen, blockPT);
}
}
/**
* Returns {@code true} if a specific RED packet contains multiple blocks;
* {@code false}, otherwise.
*
* @param buffer the byte buffer that contains the RED payload.
* @param offset the offset in the buffer where the RED payload begins.
* @param length the length of the RED payload.
* @return {@code true} if {@code pkt} contains multiple RED blocks; otherwise,
* {@code false}
*/
public static boolean isMultiBlock(byte[] buffer, int offset, int length)
{
if (buffer == null || buffer.length == 0)
{
logger.warn("The buffer appears to be empty.");
return false;
}
if (offset < 0 || buffer.length <= offset)
{
logger.warn("Prevented array out of bounds exception.");
return false;
}
return (buffer[offset] & 0x80) != 0;
}
/**
* Ctor.
*
* @param buffer the byte buffer that contains the RED payload.
* @param offset the offset in the buffer where the RED payload begins.
* @param length the length of the RED payload.
*/
public REDBlockIterator(byte[] buffer, int offset, int length)
{
this.buffer = buffer;
this.offset = offset;
this.length = length;
this.initialize();
}
@Override
public boolean hasNext()
{
return cntRemainingBlocks > 0;
}
@Override
public REDBlock next()
{
if (!hasNext())
{
throw new NoSuchElementException();
}
cntRemainingBlocks--;
if (buffer == null || buffer.length <= offNextBlockHeader)
{
logger.warn("Prevented an array out of bounds exception.");
return null;
}
byte blockPT = (byte) (buffer[offNextBlockHeader] & 0x7f);
int blockLen;
if (hasNext())
{
if (buffer.length < offNextBlockHeader + 4)
{
logger.warn("Prevented an array out of bounds exception.");
return null;
}
// 0 1 2 3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
//+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//|F| block PT | timestamp offset | block length |
//+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
blockLen = (buffer[offNextBlockHeader + 2] & 0x03) << 8
| (buffer[offNextBlockHeader + 3] & 0xFF);
offNextBlockHeader += 4; // next RED header
offNextBlockPayload += blockLen;
}
else
{
// 0 1 2 3 4 5 6 7
//+-+-+-+-+-+-+-+-+
//|0| Block PT |
//+-+-+-+-+-+-+-+-+
blockLen = length - (offNextBlockPayload + 1);
offNextBlockHeader = -1;
offNextBlockPayload = -1;
}
return new REDBlock(buffer, offNextBlockPayload, blockLen, blockPT);
}
@Override
public void remove()
{
throw new UnsupportedOperationException();
}
/**
* Initializes this instance.
*/
private void initialize()
{
if (buffer == null || buffer.length == 0)
{
return;
}
//beginning of RTP payload
offNextBlockHeader = offset;
// Number of packets inside RED.
cntRemainingBlocks = 0;
// 0 1 2 3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
//+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//|F| block PT | timestamp offset | block length |
//+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
while ((buffer[offNextBlockHeader] & 0x80) != 0)
{
cntRemainingBlocks++;
offNextBlockHeader += 4;
}
// 0 1 2 3 4 5 6 7
//+-+-+-+-+-+-+-+-+
//|0| Block PT |
//+-+-+-+-+-+-+-+-+
if (buffer.length >= offNextBlockHeader + 8)
{
cntRemainingBlocks++;
}
//back to beginning of RTP payload
offNextBlockHeader = offset;
if (cntRemainingBlocks > 0)
{
offNextBlockPayload
= offNextBlockHeader + (cntRemainingBlocks - 1) * 4 + 1;
}
}
}
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