Find asset usages in prefabs and scenes (Unity3d)

FindUsages.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Text;
using System.Threading;
using UnityEditor;
using UnityEngine;
using Debug = UnityEngine.Debug;

namespace Code.Editor
{
    public class FindUsages : EditorWindow
    {
        private struct SearchResult
        {
            public string Name;
            public string Path;
        }
        
        private class DatabaseRefreshListener : AssetPostprocessor
        {
            private static void OnPostprocessAllAssets(
                string[] importedAssets, 
                string[] deletedAssets, 
                string[] movedAssets,
                string[] movedFromAssetPaths)
            {
                NeedCacheRefresh = true;
            }
        }
        
        private static readonly List<SearchResult> PrefabNames = new List<SearchResult>();
        private static readonly List<SearchResult> SceneNames = new List<SearchResult>();
        private static readonly List<string> FilesWithAsset = new List<string>();
        private const string MenuItemName = "Assets/- Find usages";
        private const string YAMLHeader = "%YAML";
        private static readonly string[] SearchTypes = { ".prefab", ".asset", ".unity" };
        private static readonly Encoding AsciiEncoding = Encoding.ASCII;
        private static bool NeedCacheRefresh = true;
        private static string[] FilesCache;
        private static long ProcessedFiles;
        private static int ThreadsActive;
        private static byte[] TargetAsciiGuid;
        private static byte[] TargetHexGuid;
        private Vector2 _scrollPosition;
        private GUIStyle _buttonStyle;

        [MenuItem(MenuItemName, true, 10)]
        private static bool MenuItemCheck()
        {
            if (Selection.activeObject == null)
                return false;
            //skip directories
            return !Directory.Exists(AssetDatabase.GetAssetPath(Selection.activeObject));
        }

        private static void SearchThread(object _)
        {
            byte[] binaryData = new byte[1024];
            while (true)
            {
                long i = Interlocked.Increment(ref ProcessedFiles) - 1;
                if (i >= FilesCache.Length)
                    break;
                
                using (var fileStream = new FileStream(FilesCache[i], FileMode.Open))
                {
                    int fileLength = (int)fileStream.Length;
                    if (binaryData.Length < fileLength)
                        binaryData = new byte[fileLength];
                    int readCount = fileStream.Read(binaryData, 0, fileLength);
                    if (readCount < YAMLHeader.Length)
                        continue;
                
                    var byteSequence = AsciiEncoding.GetString(binaryData, 0, YAMLHeader.Length) == YAMLHeader
                        ? TargetAsciiGuid
                        : TargetHexGuid;
           
                    for (int j = YAMLHeader.Length; j < readCount - byteSequence.Length; j++)
                    {
                        int k;
                        for (k = 0; k < byteSequence.Length; k++)
                        {
                            if (binaryData[j + k] != byteSequence[k])
                                break;
                        }
                        if (k == byteSequence.Length)
                        {
                            lock (FilesWithAsset)
                                FilesWithAsset.Add(FilesCache[i]);
                            break;
                        }
                    }
                }
            }
            Interlocked.Decrement(ref ThreadsActive);
        }

        [MenuItem(MenuItemName, false, 30)]
        static void MenuItem()
        {
            string guid = Selection.assetGUIDs[0];
            TargetAsciiGuid = AsciiEncoding.GetBytes($"guid: {guid}");
            TargetHexGuid = new byte[guid.Length / 2];
            for (int i = 0; i < guid.Length; i += 2)
                TargetHexGuid[i/2] = byte.Parse(new string(new [] { guid[i+1], guid[i] }), NumberStyles.HexNumber);

            if (NeedCacheRefresh || FilesCache == null)
            {
                var filesList = new List<string>();
                foreach (string file in Directory.EnumerateFiles("Assets", "*.*", SearchOption.AllDirectories))
                {
                    for (int i = 0; i < SearchTypes.Length; i++)
                    {
                        if (file.EndsWith(SearchTypes[i]))
                        {
                            filesList.Add(file);
                            break;
                        }
                    }
                }
                FilesCache = filesList.ToArray();
            }
            
            ProcessedFiles = 0;
            FilesWithAsset.Clear();
            PrefabNames.Clear();
            SceneNames.Clear();
            int processorCount = Environment.ProcessorCount;
            ThreadsActive = processorCount;
            Debug.Log($"FindUsages. GUID: {guid} Cores: {processorCount}, Files: {FilesCache.Length}");
            for (int i = 0; i < processorCount; i++)
                ThreadPool.QueueUserWorkItem(SearchThread);

            var sw = new Stopwatch();
            sw.Start();
            while (ThreadsActive > 0)
            {
                EditorUtility.DisplayProgressBar("Find usages", $"File: {Selection.activeObject.name}", (float)ProcessedFiles / FilesCache.Length);
                Thread.Sleep(1);
            }
            EditorUtility.ClearProgressBar();
            sw.Stop();
            Debug.Log($"Search time: {sw.ElapsedMilliseconds} ms");

            for (int i = 0; i < FilesWithAsset.Count; i++)
            {
                var prefabPath = FilesWithAsset[i];
                var strWihtouPath = prefabPath.Substring(prefabPath.LastIndexOf(Path.DirectorySeparatorChar) + 1);
                var targetList = prefabPath.EndsWith(".unity") ? SceneNames : PrefabNames;
                targetList.Add(new SearchResult
                {
                    Name = strWihtouPath.Substring(0, strWihtouPath.IndexOf(".", StringComparison.InvariantCulture)) + " ",
                    Path = prefabPath
                });
            }

            if (PrefabNames.Count > 0 || SceneNames.Count > 0)
                GetWindow<FindUsages>().Show();
            else
                EditorUtility.DisplayDialog("Find usages", "Nothing found", "OK");
        }

        private void OnGUI()
        {
            _buttonStyle ??= new(GUI.skin.button) { alignment = TextAnchor.MiddleLeft };
            _scrollPosition = EditorGUILayout.BeginScrollView(_scrollPosition);
            GUILayout.Label("Prefabs");
            DrawSearchResults(PrefabNames);
            GUILayout.Label("Scenes");
            DrawSearchResults(SceneNames);
            EditorGUILayout.EndScrollView();

            return;

            void DrawSearchResults(List<SearchResult> searchResults)
            {
                for (int i = 0; i < searchResults.Count; i++)
                {
                    if (GUILayout.Button($"{searchResults[i].Name} ({searchResults[i].Path})", _buttonStyle, GUILayout.Height(20), GUILayout.ExpandWidth(true)))
                    {
                        Selection.activeObject = AssetDatabase.LoadAssetAtPath<UnityEngine.Object>(searchResults[i].Path);
                        EditorGUIUtility.PingObject(Selection.activeObject);
                    }
                }
            }
        }
    }
}

Very cool script!
Little addition: you could add EditorGUIUtility.PingObject(Selection.activeObject); after line 171 for even more convenience :)

@muellerat91interactive updated!