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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System;
using System.Reflection;
using System.Reflection.Emit;
using System.Security;
namespace System.Runtime.Serialization
{
internal sealed class BitFlagsGenerator
{
private readonly int _bitCount;
private readonly CodeGenerator _ilg;
private readonly LocalBuilder[] _locals;
public BitFlagsGenerator(int bitCount, CodeGenerator ilg)
{
_ilg = ilg;
_bitCount = bitCount;
int localCount = (bitCount + 7) / 8;
_locals = new LocalBuilder[localCount];
for (int i = 0; i < _locals.Length; i++)
{
_locals[i] = ilg.DeclareLocal(typeof(byte), (byte)0);
}
}
public static bool IsBitSet(byte[] bytes, int bitIndex)
{
int byteIndex = GetByteIndex(bitIndex);
byte bitValue = GetBitValue(bitIndex);
return (bytes[byteIndex] & bitValue) == bitValue;
}
public static void SetBit(byte[] bytes, int bitIndex)
{
int byteIndex = GetByteIndex(bitIndex);
byte bitValue = GetBitValue(bitIndex);
bytes[byteIndex] |= bitValue;
}
public int GetBitCount()
{
return _bitCount;
}
public LocalBuilder GetLocal(int i)
{
return _locals[i];
}
public int GetLocalCount()
{
return _locals.Length;
}
public void Load(int bitIndex)
{
LocalBuilder local = _locals[GetByteIndex(bitIndex)];
byte bitValue = GetBitValue(bitIndex);
_ilg.Load(local);
_ilg.Load(bitValue);
_ilg.And();
_ilg.Load(bitValue);
_ilg.Ceq();
}
public void LoadArray()
{
LocalBuilder localArray = _ilg.DeclareLocal(Globals.TypeOfByteArray);
_ilg.NewArray(typeof(byte), _locals.Length);
_ilg.Store(localArray);
for (int i = 0; i < _locals.Length; i++)
{
_ilg.StoreArrayElement(localArray, i, _locals[i]);
}
_ilg.Load(localArray);
}
public void Store(int bitIndex, bool value)
{
LocalBuilder local = _locals[GetByteIndex(bitIndex)];
byte bitValue = GetBitValue(bitIndex);
if (value)
{
_ilg.Load(local);
_ilg.Load(bitValue);
_ilg.Or();
_ilg.Stloc(local);
}
else
{
_ilg.Load(local);
_ilg.Load(bitValue);
_ilg.Not();
_ilg.And();
_ilg.Stloc(local);
}
}
private static byte GetBitValue(int bitIndex)
{
return (byte)(1 << (bitIndex & 7));
}
private static int GetByteIndex(int bitIndex)
{
return bitIndex >> 3;
}
}
}
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