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Add counter overflow check

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Never will happen, but not worth arguing over because this is essentially what the ROM does. Entry to this method requires both OK.
91c040b081/src/save.c (L587-L605)
Closes #3805
This commit is contained in:
Kurt 2023-02-23 00:48:03 -08:00
parent 77cac48d34
commit 552676ed3a
2 changed files with 44 additions and 4 deletions
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5
PKHeX.Core/Saves/SAV3.cs
View file

@ -123,10 +123,7 @@ public abstract class SAV3 : SaveFile, ILangDeviantSave, IEventFlag37
if (!v1)
return 0;
var count0 = ReadUInt32LittleEndian(data[(sectorZero0 + 0x0FFC)..]);
var count1 = ReadUInt32LittleEndian(data[(sectorZero1 + 0x0FFC)..]);
// don't care about 32bit overflow. a 10 second save would take 1,000 years to overflow!
return count1 > count0 ? 1 : 0;
return SAV3BlockDetection.CompareFooters(data, sectorZero0, sectorZero1);
}
protected sealed override byte[] GetFinalData()

43
PKHeX.Core/Saves/Substructures/Gen3/SAV3BlockDetection.cs Normal file
View file

@ -0,0 +1,43 @@
using System;
using System.Buffers.Binary;
namespace PKHeX.Core;
/// <summary>
/// Finds the index of the most recent save block for <see cref="SAV3"/> blocks.
/// </summary>
public static class SAV3BlockDetection
{
private const int First = 0;
private const int Second = 1;
private const int Same = 2;
/// <summary>
/// Compares the footers of the two blocks to determine which is newest.
/// </summary>
/// <returns>0=Primary, 1=Secondary.</returns>
public static int CompareFooters(ReadOnlySpan<byte> data, int offset1, int offset2)
{
var counter1 = BinaryPrimitives.ReadUInt32LittleEndian(data[(offset1 + 0x0FFC)..]);
var counter2 = BinaryPrimitives.ReadUInt32LittleEndian(data[(offset2 + 0x0FFC)..]);
var result = CompareCounters(counter1, counter2);
return result == Second ? Second : First; // Same -> First, shouldn't happen for valid saves.
}
private static int CompareCounters(uint counter1, uint counter2)
{
// Uninitialized -- only continue if a rollover case (humanly impossible)
if (counter1 == uint.MaxValue && counter2 != uint.MaxValue - 1)
return Second;
if (counter2 == uint.MaxValue && counter1 != uint.MaxValue - 1)
return First;
// Different
if (counter1 > counter2)
return First;
if (counter1 < counter2)
return Second;
return Same;
}
}