private static void Encode(Stream input, Stream output, bool with_size)
{
int input_size = (int)(input.Length - input.Position);
byte[] input_buffer = new byte[input_size];
input.Read(input_buffer, 0, input_size);
long outputInitialPosition = output.Position;
if (with_size)
{
output.Seek(2, SeekOrigin.Current);
}
/*
* Here we create and populate the "LZSS graph":
*
* Each value in the uncompressed file forms a node in this graph.
* The various edges between these nodes represent LZSS matches.
*
* Using a shortest-path algorithm, these edges can be used to
* find the optimal combination of matches needed to produce the
* smallest possible file.
*
* The outputted array only contains one edge per node: the optimal
* one. This means, in order to produce the smallest file, you just
* have to traverse the graph from one edge to the next, encoding
* each match as you go along.
*/
LZSSGraphEdge[] node_meta_array = new LZSSGraphEdge[input_size + 1];
// Initialise the array
node_meta_array[0].cost = 0;
for (int i = 1; i < input_size + 1; ++i)
{
node_meta_array[i].cost = int.MaxValue;
}
// Find matches
for (int i = 0; i < input_size; ++i)
{
int max_read_ahead = Math.Min(0xF + 3, input_size - i);
int max_read_behind = Math.Max(0, i - 0x1000);
// Search for zero-fill matches
if (i < 0x1000)
{
for (int k = 0; k < 0xF + 3; ++k)
{
if (input_buffer[i + k] == 0)
{
int length = k + 1;
// Update this node's optimal edge if this one is better
if (length >= 3 && node_meta_array[i + k + 1].cost > node_meta_array[i].cost + 1 + 16)
{
node_meta_array[i + k + 1].cost = node_meta_array[i].cost + 1 + 16;
node_meta_array[i + k + 1].previous_node_index = i;
node_meta_array[i + k + 1].match_length = k + 1;
node_meta_array[i + k + 1].match_offset = 0xFFF;
}
}
else
{
break;
}
}
}
// Search for dictionary matches
for (int j = i; j-- > max_read_behind;)
{
for (int k = 0; k < max_read_ahead; ++k)
{
if (input_buffer[i + k] == input_buffer[j + k])
{
int distance = i - j;
int length = k + 1;
// Update this node's optimal edge if this one is better
if (length >= 3 && node_meta_array[i + k + 1].cost > node_meta_array[i].cost + 1 + 16)
{
node_meta_array[i + k + 1].cost = node_meta_array[i].cost + 1 + 16;
node_meta_array[i + k + 1].previous_node_index = i;
node_meta_array[i + k + 1].match_length = k + 1;
node_meta_array[i + k + 1].match_offset = j;
}
}
else
{
break;
}
}
}
// Do literal match
// Update this node's optimal edge if this one is better (or the same, since literal matches usually decode faster)
if (node_meta_array[i + 1].cost >= node_meta_array[i].cost + 1 + 8)
{
node_meta_array[i + 1].cost = node_meta_array[i].cost + 1 + 8;
node_meta_array[i + 1].previous_node_index = i;
node_meta_array[i + 1].match_length = 0;
}
}
// Reverse the edge link order, so the array can be traversed from start to end, rather than vice versa
node_meta_array[0].previous_node_index = int.MaxValue;
node_meta_array[input_size].next_node_index = int.MaxValue;
for (int node_index = input_size; node_meta_array[node_index].previous_node_index != int.MaxValue; node_index = node_meta_array[node_index].previous_node_index)
{
node_meta_array[node_meta_array[node_index].previous_node_index].next_node_index = node_index;
}
/*
* LZSS graph complete
*/
UInt8_NE_L_OutputBitStream bitStream = new UInt8_NE_L_OutputBitStream(output);
MemoryStream data = new MemoryStream();
for (int node_index = 0; node_meta_array[node_index].next_node_index != int.MaxValue; node_index = node_meta_array[node_index].next_node_index)
{
int next_index = node_meta_array[node_index].next_node_index;
if (node_meta_array[next_index].match_length != 0)
{
// Compressed
Push(bitStream, false, output, data);
int match_offset_adjusted = node_meta_array[next_index].match_offset - 0x12; // I don't think there's any reason for this, the format's just stupid
NeutralEndian.Write1(data, (byte)(match_offset_adjusted & 0xFF));
NeutralEndian.Write1(data, (byte)(((match_offset_adjusted & 0xF00) >> 4) | ((node_meta_array[next_index].match_length - 3) & 0x0F)));
}
else
{
// Uncompressed
Push(bitStream, true, output, data);
NeutralEndian.Write1(data, input_buffer[node_index]);
}
}
// Write remaining data (normally we don't flush until we have a full descriptor byte)
bitStream.Flush(true);
byte[] dataArray = data.ToArray();
output.Write(dataArray, 0, dataArray.Length);
if (with_size)
{
ushort size = (ushort)(outputInitialPosition - output.Position - 2);
output.Seek(outputInitialPosition, SeekOrigin.Begin);
LittleEndian.Write2(output, size);
}
}
private static void Encode(Stream input, Stream output, bool with_size)
{
long input_size = input.Length - input.Position;
byte[] input_buffer = new byte[input_size];
input.Read(input_buffer, 0, (int)input_size);
long outputInitialPosition = output.Position;
if (with_size)
{
output.Seek(2, SeekOrigin.Current);
}
List <byte> data = new List <byte>();
UInt8_NE_L_OutputBitStream bitStream = new UInt8_NE_L_OutputBitStream(output);
long input_pointer = 0;
while (input_pointer < input_size)
{
// The maximum recurrence length that can be encoded is 0x12
// Of course, if the remaining file is smaller, cap to that instead
long maximum_match_length = Math.Min(input_size - input_pointer, 0x12);
// The furthest back Saxman can address is 0x1000 bytes
// Again, if there's less than 0x1000 bytes of data available, then cap at that instead
long maximum_backsearch = Math.Min(input_pointer, 0x1000);
// These are our default values for the longest match found
long longest_match_offset = input_pointer; // This one doesn't really need initialising, but it does shut up some moronic warnings
long longest_match_length = 1;
// First, look for dictionary matches
for (long backsearch_pointer = input_pointer - 1; backsearch_pointer >= input_pointer - maximum_backsearch; --backsearch_pointer)
{
long match_length = 0;
while (input_buffer[backsearch_pointer + match_length] == input_buffer[input_pointer + match_length] && ++match_length < maximum_match_length)
{
;
}
if (match_length > longest_match_length)
{
longest_match_length = match_length;
longest_match_offset = backsearch_pointer;
}
}
// Then, look for zero-fill matches
if (input_pointer < 0xFFF) // Saxman cannot perform zero-fills past the first 0xFFF bytes (it relies on some goofy logic in the decompressor)
{
long match_length = 0;
while (input_buffer[input_pointer + match_length] == 0 && ++match_length < maximum_match_length)
{
;
}
if (match_length > longest_match_length)
{
longest_match_length = match_length;
// Saxman detects zero-fills by checking if the dictionary reference offset is somehow
// pointing to *after* the decompressed data, so we set it to the highest possible value here
longest_match_offset = 0xFFF;
}
}
// We cannot compress runs shorter than three bytes
if (longest_match_length < 3)
{
// Uncompressed
Push(bitStream, true, output, data);
data.Add(input_buffer[input_pointer]);
longest_match_length = 1;
}
else
{
// Compressed
Push(bitStream, false, output, data);
long match_offset_adjusted = longest_match_offset - 0x12; // I don't think there's any reason for this, the format's just stupid
data.Add((byte)(match_offset_adjusted & 0xFF));
data.Add((byte)(((match_offset_adjusted & 0xF00) >> 4) | ((longest_match_length - 3) & 0x0F)));
}
input_pointer += longest_match_length;
}
// Write remaining data (normally we don't flush until we have a full descriptor byte)
bitStream.Flush(true);
byte[] dataArray = data.ToArray();
output.Write(dataArray, 0, dataArray.Length);
if (with_size)
{
ushort size = (ushort)(output.Position - 2);
output.Seek(outputInitialPosition, SeekOrigin.Begin);
LittleEndian.Write2(output, size);
}
}