[Scummvm-git-logs] scummvm master -> 8f5741a37ae1a202d0600c4dc44f000ade832fcc

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Summary:
8f5741a37a AD: Skip detection for engines with no matching filenames


Commit: 8f5741a37ae1a202d0600c4dc44f000ade832fcc
    https://github.com/scummvm/scummvm/commit/8f5741a37ae1a202d0600c4dc44f000ade832fcc
Author: Miro Kropacek (miro.kropacek at gmail.com)
Date: 2026-04-19T13:36:54+02:00

Commit Message:
AD: Skip detection for engines with no matching filenames

When adding a game, every engine's detection table is traversed twice
(once for MD5 pre-computation, once for matching) even if the game
folder contains none of the files that engine cares about.

Build a set of all unique filenames referenced by each engine's
detection entries during preprocessDescriptions() (called once and
cached). Before entering the expensive detection loops, check if any
file in the game folder exists in this set. If not, skip the engine
entirely.

On the Atari backend with ~60 statically linked engines, this reduces
the "Add game" time by about 30-40%.

Changed paths:
    engines/advancedDetector.cpp
    engines/advancedDetector.h


diff --git a/engines/advancedDetector.cpp b/engines/advancedDetector.cpp
index 04c16a0ddb2..555309eb2c9 100644
--- a/engines/advancedDetector.cpp
+++ b/engines/advancedDetector.cpp
@@ -718,6 +718,20 @@ ADDetectedGames AdvancedMetaEngineDetectionBase::detectGame(const Common::FSNode
 
 	preprocessDescriptions();
 
+	// Early rejection: if none of the file names referenced by this engine's
+	// detection entries exist in the game folder, there is no chance of a match.
+	bool anyFileFound = false;
+	for (auto it = allFiles.begin(); it != allFiles.end(); ++it) {
+		if (_fileNamesMap.contains(it->_key)) {
+			anyFileFound = true;
+			break;
+		}
+	}
+	if (!anyFileFound) {
+		debugC(3, kDebugGlobalDetection, "Skipping engine '%s': no matching file names in directory", getName());
+		return matched;
+	}
+
 	// Check which files are included in some ADGameDescription *and* whether
 	// they are present. Compute MD5s and file sizes for the available files.
 	for (descPtr = _gameDescriptors; ((const ADGameDescription *)descPtr)->gameId != nullptr; descPtr += _descItemSize) {
@@ -1004,6 +1018,27 @@ void AdvancedMetaEngineDetectionBase::preprocessDescriptions() {
 	for (const byte *descPtr = _gameDescriptors; ((const ADGameDescription *)descPtr)->gameId != nullptr; descPtr += _descItemSize) {
 		const ADGameDescription *g = (const ADGameDescription *)descPtr;
 
+		// Collect all unique file names for early rejection
+		for (const ADGameFileDescription *fileDesc = g->filesDescriptions; fileDesc->fileName; fileDesc++) {
+			Common::String fname = fileDesc->fileName;
+
+			// For archive entries, extract the archive name
+			if (gameFileToMD5Props(fileDesc, g->flags) & kMD5Archive) {
+				Common::StringTokenizer tok(fname, ":");
+				tok.nextToken(); // skip archive type
+				fname = tok.nextToken(); // archive name
+			}
+
+			// For paths with directory components, extract the leaf filename
+			// unless kADFlagMatchFullPaths is set
+			if (!(_flags & kADFlagMatchFullPaths) && fname.contains('/')) {
+				fname = Common::Path(fname).baseName();
+			}
+
+			_fileNamesMap.setVal(Common::Path(fname, fname.contains('/')
+				? '/' : Common::Path::kNoSeparator), true);
+		}
+
 		// Scan for potential directory globs
 		for (const ADGameFileDescription *fileDesc = g->filesDescriptions; fileDesc->fileName; fileDesc++) {
 			if (strchr(fileDesc->fileName, '/')) {
diff --git a/engines/advancedDetector.h b/engines/advancedDetector.h
index fc9ef3a81b8..535f50a13c6 100644
--- a/engines/advancedDetector.h
+++ b/engines/advancedDetector.h
@@ -554,6 +554,7 @@ private:
 private:
 	Common::HashMap<Common::String, bool, Common::IgnoreCase_Hash, Common::IgnoreCase_EqualTo> _grayListMap;
 	Common::HashMap<Common::String, bool, Common::IgnoreCase_Hash, Common::IgnoreCase_EqualTo> _globsMap;
+	Common::HashMap<Common::Path, bool, Common::Path::IgnoreCase_Hash, Common::Path::IgnoreCase_EqualTo> _fileNamesMap;
 	bool _hashMapsInited;
 
 protected: