Change MapBlock content cache to a vector

src/benchmark/benchmark_mapblock.cpp

@@ -118,11 +118,13 @@ static u32 workOnBoth(const MBContainer &vec)
 			content_t c = n.getContent();
 
 			if (!block->contents_cached && !block->do_not_cache_contents) {
-				block->contents.insert(c);
+				if (!CONTAINS(block->contents, c))
+					block->contents.push_back(c);
 				if (block->contents.size() > 10) {
 					// Too many different nodes... don't try to cache
 					block->do_not_cache_contents = true;
 					block->contents.clear();
+					block->contents.shrink_to_fit();
 				}
 			}
 		}

src/mapblock.h

@@ -19,7 +19,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #pragma once
 
-#include <set>
+#include <vector>
 #include "irr_v3d.h"
 #include "mapnode.h"
 #include "exceptions.h"
@@ -476,7 +476,9 @@ public:
 
 	//// ABM optimizations ////
 	// Cache of content types
-	std::unordered_set<content_t> contents;
+	// This is actually a set but for the small sizes we have a vector should be
+	// more efficient.
+	std::vector<content_t> contents;
 	// True if content types are cached
 	bool contents_cached = false;
 	// True if we never want to cache content types for this block

src/serverenvironment.cpp

@@ -782,6 +782,8 @@ struct ActiveABM
 	s16 max_y;
 };
 
+#define CONTENT_TYPE_CACHE_MAX 64
+
 class ABMHandler
 {
 private:
@@ -922,13 +924,16 @@ public:
 		{
 			MapNode n = block->getNodeNoCheck(p0);
 			content_t c = n.getContent();
+
 			// Cache content types as we go
 			if (!block->contents_cached && !block->do_not_cache_contents) {
-				block->contents.insert(c);
+				if (!CONTAINS(block->contents, c))
-				if (block->contents.size() > 64) {
+					block->contents.push_back(c);
+				if (block->contents.size() > CONTENT_TYPE_CACHE_MAX) {
 					// Too many different nodes... don't try to cache
 					block->do_not_cache_contents = true;
 					block->contents.clear();
+					block->contents.shrink_to_fit();
 				}
 			}