From 21d8194c7c578dcc9535f923d10abfc7c78e0322 Mon Sep 17 00:00:00 2001
From: Miodrag Milanovic <mmicko@gmail.com>
Date: Fri, 4 Dec 2015 12:32:42 +0100
Subject: [PATCH] placed cache back in new form, fixes listxml and similar (nw)

---
 src/emu/drivenum.cpp | 8 ++++++++
 src/emu/drivenum.h   | 3 +++
 2 files changed, 11 insertions(+)

diff --git a/src/emu/drivenum.cpp b/src/emu/drivenum.cpp
index a410c3fbd85..99d3498c6a4 100644
--- a/src/emu/drivenum.cpp
+++ b/src/emu/drivenum.cpp
@@ -189,7 +189,15 @@ machine_config &driver_enumerator::config(int index, emu_options &options) const
 	// if we don't have it cached, add it
 	if (m_config[index] == nullptr)
 	{
+		// if our cache is full, release the head entry
+		if (m_config_cache.size() == CONFIG_CACHE_COUNT)
+		{
+			int first = m_config_cache.front();
+			m_config[first] = nullptr;
+			m_config_cache.erase(m_config_cache.begin());
+		}
 		m_config[index] = std::make_unique<machine_config>(*s_drivers_sorted[index], options);
+		m_config_cache.push_back(index);
 	}
 	return *m_config[index];
 }
diff --git a/src/emu/drivenum.h b/src/emu/drivenum.h
index 4768623fa7c..e3bf3117861 100644
--- a/src/emu/drivenum.h
+++ b/src/emu/drivenum.h
@@ -119,12 +119,15 @@ private:
 	// internal helpers
 	void release_current() const;
 
+	static const int CONFIG_CACHE_COUNT = 100;
+	
 	// internal state
 	int                 m_current;
 	int                 m_filtered_count;
 	emu_options &       m_options;
 	std::vector<UINT8> m_included;
 	mutable std::vector<std::unique_ptr<machine_config>> m_config;
+	mutable std::vector<int> m_config_cache;
 };
 
 #endif