Hide directories games should not know about from them.

Stops some games from spending lots of time iterating over files they
should not care about. Helps the performance issues in #13847 quite a bit.

Core/HLE/sceIo.cpp

@@ -21,6 +21,7 @@
 #include <memory>
 
 #include "Common/Thread/ThreadUtil.h"
+#include "Common/TimeUtil.h"
 #include "Common/Profiler/Profiler.h"
 
 #include "Common/File/FileUtil.h"
@@ -2321,10 +2322,48 @@ static u32 sceIoDopen(const char *path) {
 	DirListing *dir = new DirListing();
 	SceUID id = kernelObjects.Create(dir);
 
+	double time = time_now_d();
 	dir->listing = pspFileSystem.GetDirListing(path);
 	dir->index = 0;
 	dir->name = std::string(path);
 
+	// Blacklist some directories that games should not be able to find out about.
+	// Speeds up directory iteration on slow Android Scoped Storage implementations :(
+	// Might also want to filter out PSP/GAME if not a homebrew, maybe also irrelevant directories
+	// in PSP/SAVEDATA, though iffy to know which ones are irrelevant..
+	if (!strcmp(path, "ms0:/PSP")) {
+		static const char *const pspFolderBlacklist[] = {
+			"CHEATS",
+			"PPSSPP_STATE",
+			"PLUGINS",
+			"SYSTEM",
+			"SCREENSHOT",
+			"TEXTURES",
+			"DUMP",
+		};
+		std::vector<PSPFileInfo> filtered;
+		for (const auto &entry : dir->listing) {
+			bool blacklisted = false;
+			for (auto black : pspFolderBlacklist) {
+				if (!strcasecmp(entry.name.c_str(), black)) {
+					blacklisted = true;
+					break;
+				}
+			}
+
+			if (!blacklisted) {
+				filtered.push_back(entry);
+			}
+		}
+
+		dir->listing = filtered;
+	}
+
+	double diff = time_now_d() - time;
+	//if (diff > 0.01) {
+		ERROR_LOG(IO, "sceIoDopen(%s) took %0.3f seconds", path, diff);
+	//}
+
 	// TODO: The result is delayed only from the memstick, it seems.
 	return id;
 }
@@ -2349,7 +2388,7 @@ static u32 sceIoDread(int id, u32 dirent_addr) {
 		SceIoDirEnt *entry = (SceIoDirEnt*) Memory::GetPointer(dirent_addr);
 
 		if (dir->index == (int) dir->listing.size()) {
-			DEBUG_LOG(SCEIO, "sceIoDread( %d %08x ) - end of the line", id, dirent_addr);
+			DEBUG_LOG(SCEIO, "sceIoDread( %d %08x ) - end", id, dirent_addr);
 			entry->d_name[0] = '\0';
 			return 0;
 		}