PKHeX/PKHeX.Core/Saves/Substructures/Gen4/SAV4BlockDetection.cs

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using System;
using static System.Buffers.Binary.BinaryPrimitives;
namespace PKHeX.Core;
/// <summary>
/// Finds the index of the most recent save block for <see cref="SAV4"/> blocks.
/// </summary>
public static class SAV4BlockDetection
{
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)
{
// Major Counters
var major1 = ReadUInt32LittleEndian(data[offset1..]);
var major2 = ReadUInt32LittleEndian(data[offset2..]);
var result1 = CompareCounters(major1, major2);
if (result1 != Same)
return result1;
// Minor Counters
var minor1 = ReadUInt32LittleEndian(data[(offset1 + 4)..]);
var minor2 = ReadUInt32LittleEndian(data[(offset2 + 4)..]);
var result2 = CompareCounters(minor1, minor2);
return result2 == 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;
}
/// <summary>
/// Compares two extra blocks to determine which is newest.
/// </summary>
/// <returns>0=Primary, 1=Secondary, -1=Uninitialized.</returns>
public static int CompareExtra(ReadOnlySpan<byte> data1, ReadOnlySpan<byte> data2, BlockInfo4 block)
{
// The Hall of Fame block uses a counter in the footer to determine which copy is used.
// Entering the Hall of Fame overwrites both copies with the new data.
var rev1 = block.GetRevision(data1);
var rev2 = block.GetRevision(data2);
var valid1 = rev1 != 0xFFFFFFFF && block.SizeValid(data1);
var valid2 = rev2 != 0xFFFFFFFF && block.SizeValid(data2);
if (valid1 && (rev1 >= rev2 || !valid2))
return First;
if (valid2 && (rev2 > rev1 || !valid1))
return Second;
return -1; // Uninitialized
}
public static int CompareExtra(ReadOnlySpan<byte> data1, ReadOnlySpan<byte> data2, BlockInfo4 block, uint key, uint keyBackup, byte prefer)
{
// The Battle Hall/Battle Videos use a key in the General block to check if the block is valid.
// If the key is 0xFFFFFFFF, the block is uninitialized or deleted.
// Which partition is checked first is determined by a byte in the General block.
var key1 = block.GetKey(data1);
var key2 = block.GetKey(data2);
var valid1 = key1 != 0xFFFFFFFF && block.SizeValid(data1);
var valid2 = key2 != 0xFFFFFFFF && block.SizeValid(data2);
if (prefer == First)
{
if (valid1 && key == key1)
return First;
if (valid2 && key == key2)
return Second;
if (valid1 && keyBackup == key1)
return First;
if (valid2 && keyBackup == key2)
return Second;
}
else
{
if (valid2 && key == key2)
return Second;
if (valid1 && key == key1)
return First;
if (valid2 && keyBackup == key2)
return Second;
if (valid1 && keyBackup == key1)
return First;
}
return -1; // Uninitialized
}
}