PKHeX/PKHeX.Core/Saves/Substructures/Gen4/SAV4BlockDetection.cs
Kurt 47071b41f3
Refactoring: Span-based value writes and method signatures (#3361)
Existing `get`/`set` logic is flawed in that it doesn't work on Big Endian operating systems, and it allocates heap objects when it doesn't need to.

`System.Buffers.Binary.BinaryPrimitives` in the `System.Memory` NuGet package provides both Little Endian and Big Endian methods to read and write data; all the `get`/`set` operations have been reworked to use this new API. This removes the need for PKHeX's manual `BigEndian` class, as all functions are already covered by the BinaryPrimitives API.

The `StringConverter` has now been rewritten to accept a Span to read from & write to, no longer requiring a temporary StringBuilder.

Other Fixes included:
- The Super Training UI for Gen6 has been reworked according to the latest block structure additions.
- Cloning a Stadium2 Save File now works correctly (opening from the Folder browser list).
- Checksum & Sanity properties removed from parent PKM class, and is now implemented via interface.
2022-01-02 21:35:59 -08:00

52 lines
1.8 KiB
C#

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;
}
}
}