mirror of
https://github.com/aaru-dps/Aaru.git
synced 2025-12-16 19:24:25 +00:00
112 lines
3.6 KiB
C#
112 lines
3.6 KiB
C#
// /***************************************************************************
|
|
// Aaru Data Preservation Suite
|
|
// ----------------------------------------------------------------------------
|
|
//
|
|
// Filename : Helpers.cs
|
|
// Author(s) : Natalia Portillo <claunia@claunia.com>
|
|
//
|
|
// Component : Acorn filesystem plugin.
|
|
//
|
|
// --[ License ] --------------------------------------------------------------
|
|
//
|
|
// This library is free software; you can redistribute it and/or modify
|
|
// it under the terms of the GNU Lesser General Public License as
|
|
// published by the Free Software Foundation; either version 2.1 of the
|
|
// License, or (at your option) any later version.
|
|
//
|
|
// This library is distributed in the hope that it will be useful, but
|
|
// WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
// Lesser General Public License for more details.
|
|
//
|
|
// You should have received a copy of the GNU Lesser General Public
|
|
// License along with this library; if not, see <http://www.gnu.org/licenses/>.
|
|
//
|
|
// ----------------------------------------------------------------------------
|
|
// Copyright © 2011-2025 Natalia Portillo
|
|
// ****************************************************************************/
|
|
|
|
using System.Collections.Generic;
|
|
|
|
namespace Aaru.Filesystems;
|
|
|
|
/// <inheritdoc />
|
|
/// <summary>Implements detection of Acorn's Advanced Data Filing System (ADFS)</summary>
|
|
public sealed partial class AcornADFS
|
|
{
|
|
static byte AcornMapChecksum(byte[] data, int length)
|
|
{
|
|
var sum = 0;
|
|
var carry = 0;
|
|
|
|
if(length > data.Length) length = data.Length;
|
|
|
|
// ADC r0, r0, r1
|
|
// MOVS r0, r0, LSL #24
|
|
// MOV r0, r0, LSR #24
|
|
for(int i = length - 1; i >= 0; i--)
|
|
{
|
|
sum += data[i] + carry;
|
|
|
|
if(sum > 0xFF)
|
|
{
|
|
carry = 1;
|
|
sum &= 0xFF;
|
|
}
|
|
else
|
|
carry = 0;
|
|
}
|
|
|
|
return (byte)(sum & 0xFF);
|
|
}
|
|
|
|
static byte NewMapChecksum(byte[] mapBase)
|
|
{
|
|
uint rover;
|
|
uint sumVector0 = 0;
|
|
uint sumVector1 = 0;
|
|
uint sumVector2 = 0;
|
|
uint sumVector3 = 0;
|
|
|
|
for(rover = (uint)(mapBase.Length - 4); rover > 0; rover -= 4)
|
|
{
|
|
sumVector0 += mapBase[rover + 0] + (sumVector3 >> 8);
|
|
sumVector3 &= 0xff;
|
|
sumVector1 += mapBase[rover + 1] + (sumVector0 >> 8);
|
|
sumVector0 &= 0xff;
|
|
sumVector2 += mapBase[rover + 2] + (sumVector1 >> 8);
|
|
sumVector1 &= 0xff;
|
|
sumVector3 += mapBase[rover + 3] + (sumVector2 >> 8);
|
|
sumVector2 &= 0xff;
|
|
}
|
|
|
|
/*
|
|
Don't add the check byte when calculating its value
|
|
*/
|
|
sumVector0 += sumVector3 >> 8;
|
|
sumVector1 += mapBase[1] + (sumVector0 >> 8);
|
|
sumVector2 += mapBase[2] + (sumVector1 >> 8);
|
|
sumVector3 += mapBase[3] + (sumVector2 >> 8);
|
|
|
|
return (byte)((sumVector0 ^ sumVector1 ^ sumVector2 ^ sumVector3) & 0xff);
|
|
}
|
|
|
|
// TODO: This is not correct...
|
|
static byte AcornDirectoryChecksum(IList<byte> data, int length)
|
|
{
|
|
uint sum = 0;
|
|
|
|
if(length > data.Count) length = data.Count;
|
|
|
|
// EOR r0, r1, r0, ROR #13
|
|
for(var i = 0; i < length; i++)
|
|
{
|
|
uint carry = sum & 0x1FFF;
|
|
sum >>= 13;
|
|
sum ^= data[i];
|
|
sum += carry << 19;
|
|
}
|
|
|
|
return (byte)((sum & 0xFF000000) >> 24 ^ (sum & 0xFF0000) >> 16 ^ (sum & 0xFF00) >> 8 ^ sum & 0xFF);
|
|
}
|
|
} |