From 38a4135bcda3edfeaecae91ec32abfb3d41b7e6d Mon Sep 17 00:00:00 2001
From: Kurt <kaphotics@gmail.com>
Date: Mon, 20 Dec 2021 18:37:45 -0800
Subject: [PATCH] Span-ify the unpacking of mini arcs

cuts out some of the internal c# sanity checking for better perf
---
 PKHeX.Core/Legality/BinLinker.cs | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/PKHeX.Core/Legality/BinLinker.cs b/PKHeX.Core/Legality/BinLinker.cs
index 393420ef7..f894a279a 100644
--- a/PKHeX.Core/Legality/BinLinker.cs
+++ b/PKHeX.Core/Legality/BinLinker.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Runtime.InteropServices;
 
 namespace PKHeX.Core
 {
@@ -10,22 +11,22 @@ public static class BinLinker
         /// <param name="fileData">Packed data</param>
         /// <param name="identifier">Signature expected in the first two bytes (ASCII)</param>
         /// <returns>Unpacked array containing all files that were packed.</returns>
-        public static byte[][] Unpack(byte[] fileData, string identifier)
+        public static byte[][] Unpack(ReadOnlySpan<byte> fileData, string identifier)
         {
 #if DEBUG
             System.Diagnostics.Debug.Assert(fileData.Length > 4);
             System.Diagnostics.Debug.Assert(identifier[0] == fileData[0] && identifier[1] == fileData[1]);
 #endif
-            int count = BitConverter.ToUInt16(fileData, 2); int ctr = 4;
-            int start = BitConverter.ToInt32(fileData, ctr); ctr += 4;
+            MemoryMarshal.TryRead(fileData[4..], out int start);
+            MemoryMarshal.TryRead(fileData[2..], out ushort count);
+            var offsetBytes = fileData[8..(8 + (count * sizeof(int)))];
+            var offsets = MemoryMarshal.Cast<byte, int>(offsetBytes);
+
             byte[][] returnData = new byte[count][];
-            for (int i = 0; i < count; i++)
+            for (int i = 0; i < offsets.Length; i++)
             {
-                int end = BitConverter.ToInt32(fileData, ctr); ctr += 4;
-                int len = end - start;
-                byte[] data = new byte[len];
-                Buffer.BlockCopy(fileData, start, data, 0, len);
-                returnData[i] = data;
+                int end = offsets[i];
+                returnData[i] = fileData[start..end].ToArray();
                 start = end;
             }
             return returnData;