public CompressionProcessor()
{
_requestHeadersStorage = CompressionInitialHeaders.RequestInitialHeaders;
_responseHeadersStorage = CompressionInitialHeaders.ResponseInitialHeaders;
InitCompressor();
InitDecompressor();
}
public CompressionProcessor(ConnectionEnd end)
{
if (end == ConnectionEnd.Client)
{
_localHeaderTable = CompressionInitialHeaders.ResponseInitialHeaders;
_remoteHeaderTable = CompressionInitialHeaders.RequestInitialHeaders;
}
else
{
_localHeaderTable = CompressionInitialHeaders.RequestInitialHeaders;
_remoteHeaderTable = CompressionInitialHeaders.ResponseInitialHeaders;
}
_localRefSet = new SizedHeadersList();
_remoteRefSet = new SizedHeadersList();
InitCompressor();
InitDecompressor();
}
//Method retypes as many headers as it can to be Indexed
//and checks if headers marked as indexed are present in the headers table
/*private void OptimizeInputAndSendOptimized(List<KeyValuePair<string, string>> headers)
{
for (int i = 0; i < headers.Count; i++ )
{
var headerKv = new KeyValuePair<string, string>(headers[i].Item1, headers[i].Item2);
IndexationType headerType = (headers[i].Item3 as Indexation).Type;
int index = _remoteHeaderTable.IndexOf(headerKv);
//case headerType == IndexationType.Incremental
//must not be considered because headers table can contain duplicates
if (index != -1 && headerType == IndexationType.Substitution)
{
CompressIndexed(headerKv);
headers.Remove(headers[i--]);
}
//If header marked as indexed, but not found in the table, compress it as incremental.
if (index == -1 && headerType == IndexationType.Indexed)
{
CompressNonIndexed(headerKv.Key, headerKv.Value, IndexationType.Incremental, 5);
headers.Remove(headers[i--]);
}
}
}*/
public byte[] Compress(HeadersList headers)
{
var toSend = new SizedHeadersList();
var toDelete = new SizedHeadersList(_remoteRefSet);
ClearStream(_serializerStream, (int) _serializerStream.Position);
//OptimizeInputAndSendOptimized(headersCopy); - dont need this?
foreach (var header in headers)
{
if (header.Key == null || header.Value == null)
{
throw new InvalidHeaderException(header);
}
if (!_remoteRefSet.Contains(header))
{
//Not there, Will send
toSend.Add(header);
}
else
{
//Already there, don't delete
toDelete.Remove(header);
}
}
foreach (var header in toDelete)
{
//Anything left in toDelete, should send, so it is deleted from ref set.
CompressIndexed(header);
_remoteRefSet.Remove(header); //Update our copy
}
foreach (var header in toSend)
{
//Send whatever was left in headersCopy
if (_remoteHeaderTable.Contains(header))
{
CompressIndexed(header);
}
else
{
CompressHeader(header, new Indexation(IndexationType.Incremental));
}
_remoteRefSet.Add(header); //Update our copy
}
_serializerStream.Flush();
var result = new byte[_serializerStream.Position];
var streamBuffer = _serializerStream.GetBuffer();
Buffer.BlockCopy(streamBuffer, 0, result, 0, (int)_serializerStream.Position);
return result;
}
private void ModifyTable(string headerName, string headerValue, IndexationType headerType,
SizedHeadersList useHeadersTable, int index)
{
int headerLen = headerName.Length + headerValue.Length;
switch (headerType)
{
case IndexationType.Incremental:
if (useHeadersTable.Count > HeadersLimit - 1)
{
useHeadersTable.RemoveAt(0);
}
while (useHeadersTable.StoredHeadersSize + headerLen > MaxHeaderByteSize)
{
useHeadersTable.RemoveAt(0);
}
useHeadersTable.Add(new KeyValuePair<string, string>(headerName, headerValue));
break;
case IndexationType.Substitution:
if (index != -1)
{
useHeadersTable[index] = new KeyValuePair<string, string>(headerName, headerValue);
}
else
{
if (useHeadersTable.Count > HeadersLimit - 1)
{
useHeadersTable.RemoveAt(0);
}
while (useHeadersTable.StoredHeadersSize + headerLen > MaxHeaderByteSize)
{
useHeadersTable.RemoveAt(0);
}
//If header wasn't found then add it to the table
useHeadersTable.Add(new KeyValuePair<string, string>(headerName, headerValue));
}
break;
default:
return;
}
}
public HeadersList Decompress(byte[] serializedHeaders)
{
try
{
var workingSet = new SizedHeadersList(_localRefSet);
_currentOffset = 0;
while (_currentOffset != serializedHeaders.Length)
{
var entry = ParseHeader(serializedHeaders);
var header = new KeyValuePair<string, string>(entry.Item1, entry.Item2);
if (entry.Item3 == IndexationType.Indexed)
{
if (workingSet.Contains(header))
workingSet.RemoveAll(h => h.Equals(header));
else
workingSet.Add(header);
}
else
{
workingSet.Add(header);
}
}
_localRefSet = new SizedHeadersList(workingSet);
for (int i = _localRefSet.Count - 1; i >= 0; --i)
{
var header = _localRefSet[i];
if (!_localHeaderTable.Contains(header))
_localRefSet.RemoveAll(h => h.Equals(header));
}
return workingSet;
}
catch (Exception e)
{
throw new CompressionError(e);
}
}
private void CompressHeader(Tuple<string, string, IAdditionalHeaderInfo> header,
SizedHeadersList useHeadersTable)
{
byte prefix = 0;
var headerName = header.Item1;
var headerValue = header.Item2;
var headerType = (header.Item3 as Indexation).Type;
switch (headerType)
{
case IndexationType.WithoutIndexation:
case IndexationType.Incremental:
prefix = 5;
break;
case IndexationType.Substitution:
prefix = 6;
break;
case IndexationType.Indexed:
CompressIndexed(new KeyValuePair<string, string>(headerName, headerValue), useHeadersTable);
return;
}
CompressNonIndexed(headerName, headerValue, headerType, prefix, useHeadersTable);
}
private Tuple<string, string, IAdditionalHeaderInfo> ParseHeader(byte[] bytes, SizedHeadersList useHeadersTable)
{
var type = GetHeaderType(bytes);
int index = GetIndex(bytes, type);
string name;
string value;
byte valueLen;
byte nameLen;
switch (type)
{
case IndexationType.Indexed:
var kv = useHeadersTable[index];
return new Tuple<string, string, IAdditionalHeaderInfo>(kv.Key, kv.Value, new Indexation(type));
case IndexationType.Incremental:
case IndexationType.WithoutIndexation:
case IndexationType.Substitution:
//get replaced entry index. It's equal with the found index in our case
if (type == IndexationType.Substitution)
{
index = GetIndex(bytes, type);
}
if (index == 0)
{
nameLen = bytes[_currentOffset++];
name = Encoding.UTF8.GetString(bytes, _currentOffset, nameLen);
_currentOffset += nameLen;
}
else
{
//Index increased by 1 was sent
name = useHeadersTable[index - 1].Key;
}
valueLen = bytes[_currentOffset++];
value = Encoding.UTF8.GetString(bytes, _currentOffset, valueLen);
_currentOffset += valueLen;
ModifyTable(name, value, type, useHeadersTable, index - 1);
return new Tuple<string, string, IAdditionalHeaderInfo>(name, value, new Indexation(type));
}
return default(Tuple<string, string, IAdditionalHeaderInfo>);
}
//Method retypes as many headers as it can to be Indexed
//and checks if headers marked as indexed are present in the headers table
private void OptimizeInputAndSendOptimized(List<Tuple<string, string, IAdditionalHeaderInfo>> headers, SizedHeadersList useHeadersTable)
{
for (int i = 0; i < headers.Count; i++ )
{
var headerKv = new KeyValuePair<string, string>(headers[i].Item1, headers[i].Item2);
IndexationType headerType = (headers[i].Item3 as Indexation).Type;
int index = useHeadersTable.IndexOf(headerKv);
//case headerType == IndexationType.Incremental
//must not be considered because headers table can contain duplicates
if (index != -1 && headerType == IndexationType.Substitution)
{
CompressIndexed(headerKv, useHeadersTable);
headers.Remove(headers[i--]);
}
//If header marked as indexed, but not found in the table, compress it as incremental.
if (index == -1 && headerType == IndexationType.Indexed)
{
CompressNonIndexed(headerKv.Key, headerKv.Value, IndexationType.Incremental, 5, useHeadersTable);
headers.Remove(headers[i--]);
}
}
}
private void CompressNonIndexed(string headerName, string headerValue, IndexationType headerType, byte prefix,
SizedHeadersList useHeadersTable)
{
int index = useHeadersTable.FindIndex(kv => kv.Key == headerName);
byte nameLenBinary = 0; // headers cant be more then 255 characters length
byte[] nameBinary = new byte[0];
//It's necessary to form result array because partial writeToOutput stream can cause problems because of multithreading
using (var stream = new MemoryStream(64))
{
byte[] indexBinary;
byte valueLenBinary;
byte[] valueBinary;
if (index != -1)
{
indexBinary = (index + 1).ToUVarInt(prefix);
}
else
{
indexBinary = 0.ToUVarInt(prefix);
nameBinary = Encoding.UTF8.GetBytes(headerName);
nameLenBinary = (byte)nameBinary.Length;
}
//Set without index type
indexBinary[0] |= (byte)headerType;
valueBinary = Encoding.UTF8.GetBytes(headerValue);
valueLenBinary = (byte)valueBinary.Length;
stream.Write(indexBinary, 0, indexBinary.Length);
//write replaced index. It's equal with the found index in our case
if (headerType == IndexationType.Substitution)
{
stream.Write(indexBinary, 0, indexBinary.Length);
}
if (index == -1)
{
stream.WriteByte(nameLenBinary);
stream.Write(nameBinary, 0, nameBinary.Length);
}
stream.WriteByte(valueLenBinary);
stream.Write(valueBinary, 0, valueBinary.Length);
WriteToOutput(stream.GetBuffer(), 0, (int)stream.Position);
}
ModifyTable(headerName, headerValue, headerType, useHeadersTable, index);
}
private void CompressIndexed(KeyValuePair<string, string> header, SizedHeadersList useHeadersTable)
{
int index = useHeadersTable.FindIndex(kv => kv.Key == header.Key && kv.Value == header.Value);
const byte prefix = 7;
var bytes = index.ToUVarInt(prefix);
//Set indexed type
bytes[0] |= (byte) IndexationType.Indexed;
WriteToOutput(bytes, 0, bytes.Length);
}
