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using System;
using System.Numerics;
namespace Ryujinx.Horizon.Sdk.Ngc.Detail
{
class SbvRank
{
private const int BitsPerWord = Set.BitsPerWord;
private const int Rank1Entries = 8;
private const int BitsPerRank0Entry = BitsPerWord * Rank1Entries;
private uint[] _rank0;
private byte[] _rank1;
public SbvRank()
{
}
public SbvRank(ReadOnlySpan<uint> bitmap, int setCapacity)
{
Build(bitmap, setCapacity);
}
public void Build(ReadOnlySpan<uint> bitmap, int setCapacity)
{
_rank0 = new uint[CalculateRank0Length(setCapacity)];
_rank1 = new byte[CalculateRank1Length(setCapacity)];
BuildRankDictionary(_rank0, _rank1, (setCapacity + BitsPerWord - 1) / BitsPerWord, bitmap);
}
private static void BuildRankDictionary(Span<uint> rank0, Span<byte> rank1, int length, ReadOnlySpan<uint> bitmap)
{
uint rank0Count;
uint rank1Count = 0;
for (int index = 0; index < length; index++)
{
if ((index % Rank1Entries) != 0)
{
rank0Count = rank0[index / Rank1Entries];
}
else
{
rank0[index / Rank1Entries] = rank1Count;
rank0Count = rank1Count;
}
rank1[index] = (byte)(rank1Count - rank0Count);
rank1Count += (uint)BitOperations.PopCount(bitmap[index]);
}
}
public bool Import(ref BinaryReader reader, int setCapacity)
{
if (setCapacity == 0)
{
return true;
}
int rank0Length = CalculateRank0Length(setCapacity);
int rank1Length = CalculateRank1Length(setCapacity);
return reader.AllocateAndReadArray(ref _rank0, rank0Length) == rank0Length &&
reader.AllocateAndReadArray(ref _rank1, rank1Length) == rank1Length;
}
public int CalcRank1(int index, uint[] membershipBitmap)
{
int rank0Index = index / BitsPerRank0Entry;
int rank1Index = index / BitsPerWord;
uint membershipBits = membershipBitmap[rank1Index] & (uint.MaxValue >> (BitsPerWord - 1 - (index % BitsPerWord)));
return (int)_rank0[rank0Index] + _rank1[rank1Index] + BitOperations.PopCount(membershipBits);
}
public int CalcSelect0(int index, int length, uint[] membershipBitmap)
{
int rank0Index;
if (length > BitsPerRank0Entry)
{
int left = 0;
int right = (length + BitsPerRank0Entry - 1) / BitsPerRank0Entry;
while (true)
{
int range = right - left;
if (range < 0)
{
range++;
}
int middle = left + (range / 2);
int foundIndex = middle * BitsPerRank0Entry - (int)_rank0[middle];
if ((uint)foundIndex <= (uint)index)
{
left = middle;
}
else
{
right = middle;
}
if (right <= left + 1)
{
break;
}
}
rank0Index = left;
}
else
{
rank0Index = 0;
}
int lengthInWords = (length + BitsPerWord - 1) / BitsPerWord;
int rank1WordsCount = rank0Index == (length / BitsPerRank0Entry) && (lengthInWords % Rank1Entries) != 0
? lengthInWords % Rank1Entries
: Rank1Entries;
int baseIndex = (int)_rank0[rank0Index] + rank0Index * -BitsPerRank0Entry + index;
int plainIndex;
int count;
int remainingBits;
uint membershipBits;
for (plainIndex = rank0Index * Rank1Entries - 1, count = 0; count < rank1WordsCount; plainIndex++, count++)
{
int currentIndex = baseIndex + count * -BitsPerWord;
if (_rank1[plainIndex + 1] + currentIndex < 0)
{
remainingBits = _rank1[plainIndex] + currentIndex + BitsPerWord;
membershipBits = ~membershipBitmap[plainIndex];
return plainIndex * BitsPerWord + SbvSelect.SelectPos(membershipBits, remainingBits);
}
}
remainingBits = _rank1[plainIndex] + baseIndex + (rank1WordsCount - 1) * -BitsPerWord;
membershipBits = ~membershipBitmap[plainIndex];
return plainIndex * BitsPerWord + SbvSelect.SelectPos(membershipBits, remainingBits);
}
private static int CalculateRank0Length(int setCapacity)
{
return (setCapacity / (BitsPerWord * Rank1Entries)) + 1;
}
private static int CalculateRank1Length(int setCapacity)
{
return (setCapacity / BitsPerWord) + 1;
}
}
}
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