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Create Overworld8RNG.cs

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Kurt 2021-02-13 18:18:14 -08:00
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commit 834d0d77ba
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PKHeX.Core/Legality/RNG/Overworld8RNG.cs Normal file
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namespace PKHeX.Core
{
public static class Overworld8RNG
{
public static bool ValidateOverworldEncounter(PKM pk, Shiny shiny = Shiny.FixedValue, int flawless = 0)
{
var seed = GetOriginalSeed(pk);
return ValidateOverworldEncounter(pk, seed, shiny, flawless);
}
public static bool ValidateOverworldEncounter(PKM pk, uint seed, Shiny shiny = Shiny.FixedValue, int flawless = 0)
{
// is the seed Xoroshiro determined, or just truncated state?
if (seed == uint.MaxValue)
return false;
var xoro = new Xoroshiro128Plus(seed);
var ec = xoro.NextInt(uint.MaxValue);
if (ec != pk.EncryptionConstant)
return false;
var pid = (uint) xoro.NextInt(uint.MaxValue);
if (!IsPIDValid(pk, pid, shiny))
return false;
var actualCount = flawless == 0 ? GetIsMatchEnd(pk, xoro) : GetIsMatchEnd(pk, xoro, flawless, flawless);
return actualCount != NoMatchIVs;
}
private static bool IsPIDValid(PKM pk, uint pid, Shiny shiny)
{
if (shiny == Shiny.Random)
return pid == pk.PID;
if (pid == pk.PID)
return true;
// Check forced shiny
if (pk.IsShiny)
{
if (GetIsShiny(pk.TID, pk.SID, pid))
return false;
pid = GetShinyPID(pk.TID, pk.SID, pid, 0);
return pid == pk.PID;
}
// Check forced non-shiny
if (!GetIsShiny(pk.TID, pk.SID, pid))
return false;
pid ^= 0x1000_0000;
return pid == pk.PID;
}
private const int NoMatchIVs = -1;
private static int GetIsMatchEnd(PKM pk, Xoroshiro128Plus xoro, int start = 0, int end = 3)
{
for (int iv_count = start; iv_count <= end; iv_count++)
{
var copy = xoro;
int[] ivs = {31, 31, 31, 31, 31, 31};
const int UNSET = -1;
const int MAX = 31;
for (int i = 0; i < iv_count; i++)
{
int index;
do { index = (int)copy.NextInt(6); } while (ivs[index] != UNSET);
ivs[index] = MAX;
}
if (pk is not IScaledSize s)
continue;
var height = (int) copy.NextInt(0x81) + (int) copy.NextInt(0x80);
if (s.HeightScalar != height)
continue;
var weight = (int) copy.NextInt(0x81) + (int) copy.NextInt(0x80);
if (s.WeightScalar != weight)
continue;
return iv_count;
}
return NoMatchIVs;
}
private static uint GetShinyPID(int tid, int sid, uint pid, int type)
{
return (uint)(((tid ^ sid ^ (pid & 0xFFFF) ^ type) << 16) | (pid & 0xFFFF));
}
private static bool GetIsShiny(int tid, int sid, uint pid)
{
return GetShinyXor(pid, (uint)((sid << 16) | tid)) < 16;
}
private static uint GetShinyXor(uint pid, uint oid)
{
var xor = pid ^ oid;
return (xor ^ (xor >> 16)) & 0xFFFF;
}
/// <summary>
/// Obtains the original seed for the Generation 8 overworld wild encounter.
/// </summary>
/// <param name="pk">Entity to check for</param>
/// <returns>Seed</returns>
private static uint GetOriginalSeed(PKM pk)
{
var seed = pk.EncryptionConstant - unchecked((uint)Xoroshiro128Plus.XOROSHIRO_CONST);
if (seed == 0xD5B9C463) // Collision seed with the 0xFFFFFFFF re-roll.
{
var xoro = new Xoroshiro128Plus(seed);
/* ec */ xoro.NextInt(uint.MaxValue);
var pid = xoro.NextInt(uint.MaxValue);
if (pid != pk.PID)
return 0xDD6295A4;
}
return seed;
}
}
}