/// <summary>
/// Decompress the zero-compressed data present in the reader's position.
/// Every zero-compressed data begins with an extended size indicator
/// <seealso cref="Extensions.WriteSizeEx(BinaryWriter,uint)"/>
/// </summary>
/// <param name="reader">The reader to read the compressed data from</param>
/// <returns>The decompressed data as a MemoryStream for further usage</returns>
public static MemoryStream LoadZeroCompressed(BinaryReader reader)
{
MemoryStream outputStream = new MemoryStream();
BinaryWriter outputWriter = new BinaryWriter(outputStream);
uint packedLen = reader.ReadSizeEx();
long max = reader.BaseStream.Position + packedLen;
while (reader.BaseStream.Position < max)
{
ZeroCompressionOpcode opcode = reader.ReadByte();
if (opcode.FirstIsZero)
{
for (int n = 0; n < (opcode.FirstLength + 1); n++)
{
outputWriter.Write((byte)0);
}
}
else
{
int bytes = (int)(Math.Min(8 - opcode.FirstLength, max - reader.BaseStream.Position));
for (int n = 0; n < bytes; n++)
{
outputWriter.Write(reader.ReadByte());
}
}
if (opcode.SecondIsZero)
{
for (int n = 0; n < (opcode.SecondLength + 1); n++)
{
outputWriter.Write((byte)0);
}
}
else
{
int bytes = (int)(Math.Min(8 - opcode.SecondLength, max - reader.BaseStream.Position));
for (int n = 0; n < bytes; n++)
{
outputWriter.Write(reader.ReadByte());
}
}
}
// add some extra empty bytes at the end as CCP's implementation seems to use a fixed buffer size
// and thus already includes them
outputWriter.Write(new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 });
// go to the beginning of the stream to properly parse the data
outputStream.Seek(0, SeekOrigin.Begin);
return(outputStream);
}
/// <summary>
/// Decompress the zero-compressed data present in the reader's position.
/// Every zero-compressed data begins with an extended size indicator
/// <seealso cref="Extensions.WriteSizeEx(BinaryWriter,uint)"/>
/// </summary>
/// <param name="reader">The reader to read the compressed data from</param>
/// <returns>The decompressed data as a MemoryStream for further usage</returns>
public static MemoryStream LoadZeroCompressed(BinaryReader reader)
{
MemoryStream outputStream = new MemoryStream();
BinaryWriter outputWriter = new BinaryWriter(outputStream);
uint packedLen = reader.ReadSizeEx();
long max = reader.BaseStream.Position + packedLen;
while (reader.BaseStream.Position < max)
{
ZeroCompressionOpcode opcode = reader.ReadByte();
if (opcode.FirstIsZero)
{
for (int n = 0; n < (opcode.FirstLength + 1); n++)
{
outputWriter.Write((byte)0);
}
}
else
{
int bytes = (int)(Math.Min(8 - opcode.FirstLength, max - reader.BaseStream.Position));
for (int n = 0; n < bytes; n++)
{
outputWriter.Write(reader.ReadByte());
}
}
if (opcode.SecondIsZero)
{
for (int n = 0; n < (opcode.SecondLength + 1); n++)
{
outputWriter.Write((byte)0);
}
}
else
{
int bytes = (int)(Math.Min(8 - opcode.SecondLength, max - reader.BaseStream.Position));
for (int n = 0; n < bytes; n++)
{
outputWriter.Write(reader.ReadByte());
}
}
}
// go to the beginning of the stream to properly parse the data
return(outputStream);
}
/// <summary>
/// Compresses all the data present in the <paramref name="reader" /> and saves it to the writer on <paramref name="output" />
/// </summary>
/// <param name="reader">The reader to read the data from</param>
/// <param name="output">The writer to write the data to</param>
public static void ZeroCompress(BinaryReader reader, BinaryWriter output)
{
// create temporal memory buffer to store the compressed data as we require
// seek capability and not all the streams have it
MemoryStream newStream = new MemoryStream();
BinaryWriter newWriter = new BinaryWriter(newStream);
byte b = reader.ReadByte();
while (reader.BaseStream.Position < reader.BaseStream.Length)
{
ZeroCompressionOpcode opcode = (byte)0;
int opcodeStartShift = 1;
// reserve space for opcode
newWriter.Write(opcode);
// when the first byte found is a zero we actually do compression
// count the number of zeros present up to 7 and update the opcode accordingly
if (b == 0x00)
{
opcode.FirstIsZero = true;
int firstLen = -1;
while ((b == 0x00) && (firstLen < 7) && (reader.BaseStream.Position < reader.BaseStream.Length))
{
firstLen++;
b = reader.ReadByte();
}
// Very stupid, but fixes a big problem with them
if (reader.BaseStream.Position == reader.BaseStream.Length)
{
opcode.FirstLength = (byte)(firstLen + 1);
}
else
{
opcode.FirstLength = (byte)(firstLen);
}
}
// when the first byte read is not 0 the only option is to update the opcode and write
// to the stream the bytes that are not being compressed
else
{
opcode.FirstIsZero = false;
opcode.FirstLength = 8;
while ((b != 0x00) && (opcode.FirstLength > 0))
{
opcode.FirstLength--;
opcodeStartShift++;
newWriter.Write(b);
if (reader.BaseStream.Position < reader.BaseStream.Length)
{
b = reader.ReadByte();
}
else
{
break;
}
}
}
// special situation, if the input stream is shorter than a double block do not try to compress further
// mark the second part as zeros, with zero length and finish the compression
if (reader.BaseStream.Position == reader.BaseStream.Length)
{
opcode.SecondIsZero = true;
opcode.SecondLength = 0;
}
else if (b == 0x00)
{
opcode.SecondIsZero = true;
int secondLength = -1;
while ((b == 0x00) && (opcode.SecondLength < 7) &&
(reader.BaseStream.Position < reader.BaseStream.Length))
{
secondLength++;
b = reader.ReadByte();
}
opcode.SecondLength = (byte)(secondLength);
}
else
{
opcode.SecondIsZero = false;
opcode.SecondLength = 8;
while ((b != 0x00) && (opcode.SecondLength > 0))
{
opcode.SecondLength--;
opcodeStartShift++;
newWriter.Write(b);
if (reader.BaseStream.Position < reader.BaseStream.Length)
{
b = reader.ReadByte();
}
else
{
break;
}
}
}
// seek back to where the opcode position was reserved
newWriter.Seek(-opcodeStartShift, SeekOrigin.Current);
// write the updated opcode
newWriter.Write(opcode);
// seek back to where the last write ended
newWriter.Seek(opcodeStartShift - 1, SeekOrigin.Current);
}
// once all the data is compressed write it to the actual output stream
output.WriteSizeEx((int)(newStream.Length));
if (newStream.Length > 0)
{
newStream.WriteTo(output.BaseStream);
}
}
