Common: Replace ScanDirectoryTree with a non-recursive implementation.

This makes it do only what we need for our readdir implementation, thus
improving performances a lot in heavy trees and fixing bugs like #1115.

src/common/file_util.cpp

@@ -420,9 +420,7 @@ bool CreateEmptyFile(const std::string &filename)
 }
 
 
-// Scans the directory tree gets, starting from _Directory and adds the
-// results into parentEntry. Returns the number of files+directories found
-u32 ScanDirectoryTree(const std::string &directory, FSTEntry& parentEntry)
+u32 ReadDirectory(const std::string& directory, FSTEntry& parentEntry, int recursion)
 {
     LOG_TRACE(Common_Filesystem, "directory %s", directory.c_str());
     // How many files + directories we found
@@ -467,12 +465,14 @@ u32 ScanDirectoryTree(const std::string &directory, FSTEntry& parentEntry)
         if (IsDirectory(entry.physicalName.c_str()))
         {
             entry.isDirectory = true;
-            // is a directory, lets go inside
-            entry.size = ScanDirectoryTree(entry.physicalName, entry);
-            foundEntries += (u32)entry.size;
+            if (recursion > 0)
+            {
+                entry.size = ReadDirectory(entry.physicalName, entry, recursion - 1);
+                foundEntries += (u32)entry.size;
+            }
         }
         else
-        { // is a file
+        {
             entry.isDirectory = false;
             entry.size = GetSize(entry.physicalName.c_str());
         }

src/common/file_util.h

@@ -96,9 +96,15 @@ bool Copy(const std::string &srcFilename, const std::string &destFilename);
 // creates an empty file filename, returns true on success
 bool CreateEmptyFile(const std::string &filename);
 
-// Scans the directory tree gets, starting from _Directory and adds the
-// results into parentEntry. Returns the number of files+directories found
-u32 ScanDirectoryTree(const std::string &directory, FSTEntry& parentEntry);
+/**
+ * Reads the contents of a directory, and adds the results into
+ * parentEntry, optionally going down up to recursion levels.
+ * @param directory Path of the directory to scan.
+ * @param parentEntry Structure into which found files will be put.
+ * @param recursion Number of children directory to read before giving up.
+ * @returns u32 The number of files+directories found.
+ */
+u32 ReadDirectory(const std::string& directory, FSTEntry& parentEntry, int recursion = 0);
 
 // deletes the given directory and anything under it. Returns true on success.
 bool DeleteDirRecursively(const std::string &directory);

src/core/file_sys/disk_archive.cpp

@@ -144,7 +144,7 @@ DiskDirectory::DiskDirectory(const DiskArchive& archive, const Path& path) {
 bool DiskDirectory::Open() {
     if (!FileUtil::IsDirectory(path))
         return false;
-    FileUtil::ScanDirectoryTree(path, directory);
+    FileUtil::ReadDirectory(path, directory);
     children_iterator = directory.children.begin();
     return true;
 }