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using System;
using System.Runtime.InteropServices;
namespace Ryujinx.Horizon.Sdk.Ngc.Detail
{
class CompressedArray
{
private const int MaxUncompressedEntries = 64;
private const int CompressedEntriesPerBlock = 64;
private const int BitsPerWord = Set.BitsPerWord;
private readonly struct BitfieldRange
{
private readonly uint _range;
private readonly int _baseValue;
public int BitfieldIndex => (int)(_range & 0x7ffffff);
public int BitfieldLength => (int)(_range >> 27) + 1;
public int BaseValue => _baseValue;
public BitfieldRange(uint range, int baseValue)
{
_range = range;
_baseValue = baseValue;
}
}
private uint[] _bitfieldRanges;
private uint[] _bitfields;
private int[] _uncompressedArray;
public int Length => (_bitfieldRanges.Length / 2) * CompressedEntriesPerBlock + _uncompressedArray.Length;
public int this[int index]
{
get
{
var ranges = GetBitfieldRanges();
int rangeBlockIndex = index / CompressedEntriesPerBlock;
if (rangeBlockIndex < ranges.Length)
{
var range = ranges[rangeBlockIndex];
int bitfieldLength = range.BitfieldLength;
int bitfieldOffset = (index % CompressedEntriesPerBlock) * bitfieldLength;
int bitfieldIndex = range.BitfieldIndex + (bitfieldOffset / BitsPerWord);
int bitOffset = bitfieldOffset % BitsPerWord;
ulong bitfieldValue = _bitfields[bitfieldIndex];
// If the bit fields crosses the word boundary, let's load the next one to ensure we
// have access to the full value.
if (bitOffset + bitfieldLength > BitsPerWord)
{
bitfieldValue |= (ulong)_bitfields[bitfieldIndex + 1] << 32;
}
int value = (int)(bitfieldValue >> bitOffset) & ((1 << bitfieldLength) - 1);
// Sign-extend.
int remainderBits = BitsPerWord - bitfieldLength;
value <<= remainderBits;
value >>= remainderBits;
return value + range.BaseValue;
}
else if (rangeBlockIndex < _uncompressedArray.Length + _bitfieldRanges.Length * BitsPerWord)
{
return _uncompressedArray[index % MaxUncompressedEntries];
}
return 0;
}
}
private ReadOnlySpan<BitfieldRange> GetBitfieldRanges()
{
return MemoryMarshal.Cast<uint, BitfieldRange>(_bitfieldRanges);
}
public bool Import(ref BinaryReader reader)
{
if (!reader.Read(out int bitfieldRangesCount) ||
reader.AllocateAndReadArray(ref _bitfieldRanges, bitfieldRangesCount) != bitfieldRangesCount)
{
return false;
}
if (!reader.Read(out int bitfieldsCount) || reader.AllocateAndReadArray(ref _bitfields, bitfieldsCount) != bitfieldsCount)
{
return false;
}
return reader.Read(out byte uncompressedArrayLength) &&
reader.AllocateAndReadArray(ref _uncompressedArray, uncompressedArrayLength, MaxUncompressedEntries) == uncompressedArrayLength;
}
}
}
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