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Remove a dynamically created stackalloc #966

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Merged
adamhathcock merged 4 commits into from
Oct 22, 2025
Merged

Remove a dynamically created stackalloc #966

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6de738f
reduce dynamic stackallocs in unpackv1
adamhathcock Oct 22, 2025
01021e1
remove some extra stackallocs
adamhathcock Oct 22, 2025
36c06c4
ugh, this is used because it shadows a field
adamhathcock Oct 22, 2025
74e27c0
fix the span length
adamhathcock Oct 22, 2025
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36 changes: 21 additions & 15 deletions src/SharpCompress/Compressors/Rar/UnpackV1/Unpack.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -205,9 +205,6 @@ private void UnstoreFile()

private void Unpack29(bool solid)
{
Span<int> DDecode = stackalloc int[PackDef.DC];
Span<byte> DBits = stackalloc byte[PackDef.DC];

int Bits;

if (DDecode[1] == 0)
Expand Down Expand Up @@ -1028,7 +1025,7 @@ private bool ReadVMCode()
vmCode.Add((byte)(GetBits() >> 8));
AddBits(8);
}
return (AddVMCode(FirstByte, vmCode, Length));
return AddVMCode(FirstByte, vmCode);
}

private bool ReadVMCodePPM()
Expand Down Expand Up @@ -1073,10 +1070,10 @@ private bool ReadVMCodePPM()
}
vmCode.Add((byte)Ch); // VMCode[I]=Ch;
}
return (AddVMCode(FirstByte, vmCode, Length));
return AddVMCode(FirstByte, vmCode);
}

private bool AddVMCode(int firstByte, List<byte> vmCode, int length)
private bool AddVMCode(int firstByte, List<byte> vmCode)
{
var Inp = new BitInput();
Inp.InitBitInput();
Expand Down Expand Up @@ -1199,19 +1196,28 @@ private bool AddVMCode(int firstByte, List<byte> vmCode, int length)
{
return (false);
}
Span<byte> VMCode = stackalloc byte[VMCodeSize];
for (var I = 0; I < VMCodeSize; I++)

var VMCode = ArrayPool<byte>.Shared.Rent(VMCodeSize);
try
{
if (Inp.Overflow(3))
for (var I = 0; I < VMCodeSize; I++)
{
return (false);
if (Inp.Overflow(3))
{
return (false);
}

VMCode[I] = (byte)(Inp.GetBits() >> 8);
Inp.AddBits(8);
}
VMCode[I] = (byte)(Inp.GetBits() >> 8);
Inp.AddBits(8);
}

// VM.Prepare(&VMCode[0],VMCodeSize,&Filter->Prg);
rarVM.prepare(VMCode, VMCodeSize, Filter.Program);
// VM.Prepare(&VMCode[0],VMCodeSize,&Filter->Prg);
rarVM.prepare(VMCode, VMCodeSize, Filter.Program);
}
finally
{
ArrayPool<byte>.Shared.Return(VMCode);
}
}
StackFilter.Program.AltCommands = Filter.Program.Commands; // StackFilter->Prg.AltCmd=&Filter->Prg.Cmd[0];
StackFilter.Program.CommandCount = Filter.Program.CommandCount;
Expand Down
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