internal static FastRange Get(int start, int count)
{
var fr = _cachedRange ?? (_cachedRange = new FastRange());
fr._start = start;
fr._count = count;
return(fr);
}
private void InitTree(IPacket packet, IHuffman huffman)
{
bool sparse;
int total = 0;
int maxLen;
if (packet.ReadBit())
{
// ordered
var len = (int)packet.ReadBits(5) + 1;
for (var i = 0; i < Entries;)
{
var cnt = (int)packet.ReadBits(Utils.ilog(Entries - i));
while (--cnt >= 0)
{
_lengths[i++] = len;
}
++len;
}
total = 0;
sparse = false;
maxLen = len;
}
else
{
// unordered
maxLen = -1;
sparse = packet.ReadBit();
for (var i = 0; i < Entries; i++)
{
if (!sparse || packet.ReadBit())
{
_lengths[i] = (int)packet.ReadBits(5) + 1;
++total;
}
else
{
// mark the entry as unused
_lengths[i] = -1;
}
if (_lengths[i] > maxLen)
{
maxLen = _lengths[i];
}
}
}
// figure out the maximum bit size; if all are unused, don't do anything else
if ((_maxBits = maxLen) > -1)
{
int[] codewordLengths = null;
if (sparse && total >= Entries >> 2)
{
codewordLengths = new int[Entries];
Array.Copy(_lengths, codewordLengths, Entries);
sparse = false;
}
int sortedCount;
// compute size of sorted tables
if (sparse)
{
sortedCount = total;
}
else
{
sortedCount = 0;
}
int[] values = null;
int[] codewords = null;
if (!sparse)
{
codewords = new int[Entries];
}
else if (sortedCount != 0)
{
codewordLengths = new int[sortedCount];
codewords = new int[sortedCount];
values = new int[sortedCount];
}
if (!ComputeCodewords(sparse, codewords, codewordLengths, _lengths, Entries, values))
{
throw new InvalidDataException();
}
var valueList = (IReadOnlyList <int>)values ?? FastRange.Get(0, codewords.Length);
huffman.GenerateTable(valueList, codewordLengths ?? _lengths, codewords);
_prefixList = huffman.PrefixTree;
_prefixBitLength = huffman.TableBits;
_overflowList = huffman.OverflowList;
}
}
void InitTree(DataPacket packet)
{
bool sparse;
int total = 0;
if (packet.ReadBit())
{
// ordered
var len = (int)packet.ReadBits(5) + 1;
for (var i = 0; i < Entries;)
{
var cnt = (int)packet.ReadBits(Utils.ilog(Entries - i));
while (--cnt >= 0)
{
Lengths[i++] = len;
}
++len;
}
total = 0;
sparse = false;
}
else
{
// unordered
sparse = packet.ReadBit();
for (var i = 0; i < Entries; i++)
{
if (!sparse || packet.ReadBit())
{
Lengths[i] = (int)packet.ReadBits(5) + 1;
++total;
}
else
{
// mark the entry as unused
Lengths[i] = -1;
}
}
}
// figure out the maximum bit size; if all are unused, don't do anything else
if ((MaxBits = Lengths.Max()) > -1)
{
int sortedCount = 0;
int[] codewordLengths = null;
if (sparse && total >= Entries >> 2)
{
codewordLengths = new int[Entries];
Array.Copy(Lengths, codewordLengths, Entries);
sparse = false;
}
// compute size of sorted tables
if (sparse)
{
sortedCount = total;
}
else
{
sortedCount = 0;
}
int sortedEntries = sortedCount;
int[] values = null;
int[] codewords = null;
if (!sparse)
{
codewords = new int[Entries];
}
else if (sortedEntries != 0)
{
codewordLengths = new int[sortedEntries];
codewords = new int[sortedEntries];
values = new int[sortedEntries];
}
if (!ComputeCodewords(sparse, sortedEntries, codewords, codewordLengths, len: Lengths, n: Entries, values: values))
{
throw new InvalidDataException();
}
var valueList = (IReadOnlyList <int>)values ?? FastRange.Get(0, codewords.Length);
PrefixList = Huffman.BuildPrefixedLinkedList(valueList, codewordLengths ?? Lengths, codewords, out PrefixBitLength, out PrefixOverflowTree);
}
}
