mirror of
https://github.com/kwsch/PKHeX
synced 2024-12-13 22:22:34 +00:00
104 lines
3.8 KiB
C#
104 lines
3.8 KiB
C#
using System;
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using static System.Buffers.Binary.BinaryPrimitives;
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namespace PKHeX.Core;
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/// <summary>
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/// Finds the index of the most recent save block for <see cref="SAV4"/> blocks.
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/// </summary>
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public static class SAV4BlockDetection
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{
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private const int First = 0;
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private const int Second = 1;
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private const int Same = 2;
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/// <summary>
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/// Compares the footers of the two blocks to determine which is newest.
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/// </summary>
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/// <returns>0=Primary, 1=Secondary.</returns>
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public static int CompareFooters(ReadOnlySpan<byte> data, int offset1, int offset2)
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{
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// Major Counters
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var major1 = ReadUInt32LittleEndian(data[offset1..]);
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var major2 = ReadUInt32LittleEndian(data[offset2..]);
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var result1 = CompareCounters(major1, major2);
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if (result1 != Same)
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return result1;
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// Minor Counters
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var minor1 = ReadUInt32LittleEndian(data[(offset1 + 4)..]);
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var minor2 = ReadUInt32LittleEndian(data[(offset2 + 4)..]);
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var result2 = CompareCounters(minor1, minor2);
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return result2 == Second ? Second : First; // Same -> First, shouldn't happen for valid saves.
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}
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private static int CompareCounters(uint counter1, uint counter2)
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{
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// Uninitialized -- only continue if a rollover case (humanly impossible)
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if (counter1 == uint.MaxValue && counter2 != uint.MaxValue - 1)
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return Second;
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if (counter2 == uint.MaxValue && counter1 != uint.MaxValue - 1)
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return First;
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// Different
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if (counter1 > counter2)
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return First;
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if (counter1 < counter2)
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return Second;
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return Same;
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}
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/// <summary>
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/// Compares two extra blocks to determine which is newest.
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/// </summary>
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/// <returns>0=Primary, 1=Secondary, -1=Uninitialized.</returns>
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public static int CompareExtra(ReadOnlySpan<byte> data1, ReadOnlySpan<byte> data2, BlockInfo4 block)
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{
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// The Hall of Fame block uses a counter in the footer to determine which copy is used.
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// Entering the Hall of Fame overwrites both copies with the new data.
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var rev1 = block.GetRevision(data1);
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var rev2 = block.GetRevision(data2);
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var valid1 = rev1 != 0xFFFFFFFF && block.SizeValid(data1);
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var valid2 = rev2 != 0xFFFFFFFF && block.SizeValid(data2);
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if (valid1 && (rev1 >= rev2 || !valid2))
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return First;
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if (valid2 && (rev2 > rev1 || !valid1))
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return Second;
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return -1; // Uninitialized
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}
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public static int CompareExtra(ReadOnlySpan<byte> data1, ReadOnlySpan<byte> data2, BlockInfo4 block, uint key, uint keyBackup, byte prefer)
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{
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// The Battle Hall/Battle Videos use a key in the General block to check if the block is valid.
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// If the key is 0xFFFFFFFF, the block is uninitialized or deleted.
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// Which partition is checked first is determined by a byte in the General block.
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var key1 = block.GetKey(data1);
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var key2 = block.GetKey(data2);
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var valid1 = key1 != 0xFFFFFFFF && block.SizeValid(data1);
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var valid2 = key2 != 0xFFFFFFFF && block.SizeValid(data2);
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if (prefer == First)
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{
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if (valid1 && key == key1)
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return First;
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if (valid2 && key == key2)
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return Second;
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if (valid1 && keyBackup == key1)
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return First;
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if (valid2 && keyBackup == key2)
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return Second;
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}
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else
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{
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if (valid2 && key == key2)
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return Second;
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if (valid1 && key == key1)
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return First;
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if (valid2 && keyBackup == key2)
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return Second;
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if (valid1 && keyBackup == key1)
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return First;
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}
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return -1; // Uninitialized
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}
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}
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