[space-maps/core] rewrite the core space map to use less memory.

persistent-data/space-maps/core.h

@@ -21,112 +21,12 @@
 
 #include "persistent-data/space_map.h"
 
+#include <map>
+
 //----------------------------------------------------------------
 
 namespace persistent_data {
-	class core_map : public checked_space_map {
-	public:
-		typedef std::shared_ptr<core_map> ptr;
-
-		core_map(block_address nr_blocks)
-			: counts_(nr_blocks, 0),
-			  nr_free_(nr_blocks),
-			  search_start_(0ull) {
-		}
-
-		block_address get_nr_blocks() const {
-			return counts_.size();
-		}
-
-		block_address get_nr_free() const {
-			return nr_free_;
-		}
-
-		ref_t get_count(block_address b) const {
-			return counts_[b];
-		}
-
-		void set_count(block_address b, ref_t c) {
-			if (counts_[b] == 0 && c > 0)
-				nr_free_--;
-
-			else if (counts_[b] > 0 && c == 0) {
-				if (b < search_start_)
-					search_start_ = b;
-
-				nr_free_++;
-			}
-
-			counts_[b] = c;
-		}
-
-		void commit() {
-		}
-
-		void inc(block_address b, ref_t count) override {
-			if (counts_[b] == 0)
-				nr_free_--;
-
-			counts_[b] += count;
-		}
-
-		void dec(block_address b, ref_t count) override {
-			counts_[b] -= count;
-
-			if (counts_[b] == 0) {
-				if (b < search_start_)
-					search_start_ = b;
-				nr_free_++;
-			}
-		}
-
-		maybe_block find_free(span_iterator &it) {
-			for (maybe_span ms = it.first(); ms; ms = it.next()) {
-				if (search_start_ >= ms->second)
-					continue;
-
-				for (block_address b = std::max(search_start_, ms->first); b < ms->second; b++) {
-					if (b >= counts_.size())
-						throw std::runtime_error("block out of bounds");
-
-					if (!counts_[b])
-						return maybe_block(b);
-				}
-			}
-
-			return maybe_block();
-		}
-
-		bool count_possibly_greater_than_one(block_address b) const {
-			return counts_[b] > 1;
-		}
-
-		void extend(block_address extra_blocks) {
-			throw std::runtime_error("'extend' not implemented");
-		}
-
-		void count_metadata(block_counter &bc) const {
-		}
-
-		// FIXME: meaningless, but this class is only used for testing
-		size_t root_size() const {
-			return 0;
-		}
-
-		// FIXME: meaningless, but this class is only used for testing
-		virtual void copy_root(void *dest, size_t len) const {
-			throw std::runtime_error("'copy root' not implemented");
-		}
-
-		checked_space_map::ptr clone() const {
-			return ptr(new core_map(*this));
-		}
-
-	private:
-		std::vector<ref_t> counts_;
-		unsigned nr_free_;
-		block_address search_start_;
-	};
+	checked_space_map::ptr create_core_map(block_address nr_blocks);
 }
 
 //----------------------------------------------------------------