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using System;
using System.Threading;
namespace Ryujinx.Memory.Tracking
{
/// <summary>
/// A bitmap that can be safely modified from multiple threads.
/// </summary>
internal class ConcurrentBitmap
{
public const int IntSize = 64;
public const int IntShift = 6;
public const int IntMask = IntSize - 1;
/// <summary>
/// Masks representing the bitmap. Least significant bit first, 64-bits per mask.
/// </summary>
public readonly long[] Masks;
/// <summary>
/// Create a new multithreaded bitmap.
/// </summary>
/// <param name="count">The number of bits to reserve</param>
/// <param name="set">Whether the bits should be initially set or not</param>
public ConcurrentBitmap(int count, bool set)
{
Masks = new long[(count + IntMask) / IntSize];
if (set)
{
Array.Fill(Masks, -1L);
}
}
/// <summary>
/// Check if any bit in the bitmap is set.
/// </summary>
/// <returns>True if any bits are set, false otherwise</returns>
public bool AnySet()
{
for (int i = 0; i < Masks.Length; i++)
{
if (Interlocked.Read(ref Masks[i]) != 0)
{
return true;
}
}
return false;
}
/// <summary>
/// Check if a bit in the bitmap is set.
/// </summary>
/// <param name="bit">The bit index to check</param>
/// <returns>True if the bit is set, false otherwise</returns>
public bool IsSet(int bit)
{
int wordIndex = bit >> IntShift;
int wordBit = bit & IntMask;
long wordMask = 1L << wordBit;
return (Interlocked.Read(ref Masks[wordIndex]) & wordMask) != 0;
}
/// <summary>
/// Check if any bit in a range of bits in the bitmap are set. (inclusive)
/// </summary>
/// <param name="start">The first bit index to check</param>
/// <param name="end">The last bit index to check</param>
/// <returns>True if a bit is set, false otherwise</returns>
public bool IsSet(int start, int end)
{
if (start == end)
{
return IsSet(start);
}
int startIndex = start >> IntShift;
int startBit = start & IntMask;
long startMask = -1L << startBit;
int endIndex = end >> IntShift;
int endBit = end & IntMask;
long endMask = (long)(ulong.MaxValue >> (IntMask - endBit));
long startValue = Interlocked.Read(ref Masks[startIndex]);
if (startIndex == endIndex)
{
return (startValue & startMask & endMask) != 0;
}
if ((startValue & startMask) != 0)
{
return true;
}
for (int i = startIndex + 1; i < endIndex; i++)
{
if (Interlocked.Read(ref Masks[i]) != 0)
{
return true;
}
}
long endValue = Interlocked.Read(ref Masks[endIndex]);
if ((endValue & endMask) != 0)
{
return true;
}
return false;
}
/// <summary>
/// Set a bit at a specific index to either true or false.
/// </summary>
/// <param name="bit">The bit index to set</param>
/// <param name="value">Whether the bit should be set or not</param>
public void Set(int bit, bool value)
{
int wordIndex = bit >> IntShift;
int wordBit = bit & IntMask;
long wordMask = 1L << wordBit;
if (value)
{
Interlocked.Or(ref Masks[wordIndex], wordMask);
}
else
{
Interlocked.And(ref Masks[wordIndex], ~wordMask);
}
}
/// <summary>
/// Clear the bitmap entirely, setting all bits to 0.
/// </summary>
public void Clear()
{
for (int i = 0; i < Masks.Length; i++)
{
Interlocked.Exchange(ref Masks[i], 0);
}
}
}
}
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