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BCJFilterRISCV.cs
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BCJFilterRISCV.cs
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using System;
using System.Buffers.Binary;
using System.IO;
namespace SharpCompress.Compressors.Filters;
internal class BCJFilterRISCV : Filter
{
private int _pos;
public BCJFilterRISCV(bool isEncoder, Stream baseStream)
: base(isEncoder, baseStream, 8) => _pos = 0;
private int Decode(byte[] buffer, int offset, int count)
{
if (count < 8)
{
return 0;
}
var end = offset + count - 8;
int i;
for (i = offset; i <= end; i += 2)
{
uint inst = buffer[i];
if (inst == 0xEF)
{
uint b1 = buffer[i + 1];
if ((b1 & 0x0D) != 0)
continue;
uint b2 = buffer[i + 2];
uint b3 = buffer[i + 3];
uint pc = (uint)(_pos + i);
uint addr = ((b1 & 0xF0) << 13) | (b2 << 9) | (b3 << 1);
addr -= pc;
buffer[i + 1] = (byte)((b1 & 0x0F) | ((addr >> 8) & 0xF0));
buffer[i + 2] = (byte)(
((addr >> 16) & 0x0F) | ((addr >> 7) & 0x10) | ((addr << 4) & 0xE0)
);
buffer[i + 3] = (byte)(((addr >> 4) & 0x7F) | ((addr >> 13) & 0x80));
i += 4 - 2;
}
else if ((inst & 0x7F) == 0x17)
{
uint inst2 = 0;
inst |= (uint)buffer[i + 1] << 8;
inst |= (uint)buffer[i + 2] << 16;
inst |= (uint)buffer[i + 3] << 24;
if ((inst & 0xE80) != 0)
{
inst2 = BinaryPrimitives.ReadUInt32LittleEndian(
new ReadOnlySpan<byte>(buffer, i + 4, 4)
);
if (((((inst) << 8) ^ (inst2)) & 0xF8003) != 3)
{
i += 6 - 2;
continue;
}
uint addr = inst & 0xFFFFF000;
addr += inst2 >> 20;
inst = 0x17 | (2 << 7) | (inst2 << 12);
inst2 = addr;
}
else
{
uint inst2_rs1 = inst >> 27;
if ((uint)(((inst) - 0x3117) << 18) >= ((inst2_rs1) & 0x1D))
{
i += 4 - 2;
continue;
}
uint addr = BinaryPrimitives.ReadUInt32BigEndian(
new ReadOnlySpan<byte>(buffer, i + 4, 4)
);
addr -= (uint)(_pos + i);
inst2 = (inst >> 12) | (addr << 20);
inst = 0x17 | (inst2_rs1 << 7) | ((addr + 0x800) & 0xFFFFF000);
}
BinaryPrimitives.WriteUInt32LittleEndian(new Span<byte>(buffer, i, 4), inst);
BinaryPrimitives.WriteUInt32LittleEndian(new Span<byte>(buffer, i + 4, 4), inst2);
i += 8 - 2;
}
}
i -= offset;
_pos += i;
return i;
}
private int Encode(byte[] buffer, int offset, int count)
{
if (count < 8)
{
return 0;
}
var end = offset + count - 8;
int i;
for (i = offset; i <= end; i += 2)
{
uint inst = buffer[i];
if (inst == 0xEF)
{
uint b1 = buffer[i + 1];
if ((b1 & 0x0D) != 0)
continue;
uint b2 = buffer[i + 2];
uint b3 = buffer[i + 3];
uint pc = (uint)(_pos + i);
uint addr =
((b1 & 0xF0) << 8)
| ((b2 & 0x0F) << 16)
| ((b2 & 0x10) << 7)
| ((b2 & 0xE0) >> 4)
| ((b3 & 0x7F) << 4)
| ((b3 & 0x80) << 13);
addr += pc;
buffer[i + 1] = (byte)((b1 & 0x0F) | ((addr >> 13) & 0xF0));
buffer[i + 2] = (byte)(addr >> 9);
buffer[i + 3] = (byte)(addr >> 1);
i += 4 - 2;
}
else if ((inst & 0x7F) == 0x17)
{
inst |= (uint)buffer[i + 1] << 8;
inst |= (uint)buffer[i + 2] << 16;
inst |= (uint)buffer[i + 3] << 24;
if ((inst & 0xE80) != 0)
{
uint inst2 = BinaryPrimitives.ReadUInt32LittleEndian(
new ReadOnlySpan<byte>(buffer, i + 4, 4)
);
if (((((inst) << 8) ^ (inst2)) & 0xF8003) != 3)
{
i += 6 - 2;
continue;
}
uint addr = inst & 0xFFFFF000;
addr += (inst2 >> 20) - ((inst2 >> 19) & 0x1000);
addr += (uint)(_pos + i);
inst = 0x17 | (2 << 7) | (inst2 << 12);
BinaryPrimitives.WriteUInt32LittleEndian(new Span<byte>(buffer, i, 4), inst);
BinaryPrimitives.WriteUInt32BigEndian(new Span<byte>(buffer, i + 4, 4), addr);
}
else
{
uint fake_rs1 = inst >> 27;
if ((uint)(((inst) - 0x3117) << 18) >= ((fake_rs1) & 0x1D))
{
i += 4 - 2;
continue;
}
uint fake_addr = BinaryPrimitives.ReadUInt32LittleEndian(
new ReadOnlySpan<byte>(buffer, i + 4, 4)
);
uint fake_inst2 = (inst >> 12) | (fake_addr << 20);
inst = 0x17 | (fake_rs1 << 7) | (fake_addr & 0xFFFFF000);
BinaryPrimitives.WriteUInt32LittleEndian(new Span<byte>(buffer, i, 4), inst);
BinaryPrimitives.WriteUInt32LittleEndian(
new Span<byte>(buffer, i + 4, 4),
fake_inst2
);
}
i += 8 - 2;
}
}
i -= offset;
_pos += i;
return i;
}
protected override int Transform(byte[] buffer, int offset, int count)
{
if (_isEncoder)
{
return Encode(buffer, offset, count);
}
else
{
return Decode(buffer, offset, count);
}
}
}