Update MaxMind DB library to current master.

external/MaxmindDB/data-pool.h

@@ -0,0 +1,52 @@
+#ifndef DATA_POOL_H
+#define DATA_POOL_H
+
+#include "maxminddb.h"
+
+#include <stdbool.h>
+#include <stddef.h>
+
+// This should be large enough that we never need to grow the array of pointers
+// to blocks. 32 is enough. Even starting out of with size 1 (1 struct), the
+// 32nd element alone will provide 2**32 structs as we exponentially increase
+// the number in each block. Being confident that we do not have to grow the
+// array lets us avoid writing code to do that. That code would be risky as it
+// would rarely be hit and likely not be well tested.
+#define DATA_POOL_NUM_BLOCKS 32
+
+// A pool of memory for MMDB_entry_data_list_s structs. This is so we can
+// allocate multiple up front rather than one at a time for performance
+// reasons.
+//
+// The order you add elements to it (by calling data_pool_alloc()) ends up as
+// the order of the list.
+//
+// The memory only grows. There is no support for releasing an element you take
+// back to the pool.
+typedef struct MMDB_data_pool_s {
+    // Index of the current block we're allocating out of.
+    size_t index;
+
+    // The size of the current block, counting by structs.
+    size_t size;
+
+    // How many used in the current block, counting by structs.
+    size_t used;
+
+    // The current block we're allocating out of.
+    MMDB_entry_data_list_s *block;
+
+    // The size of each block.
+    size_t sizes[DATA_POOL_NUM_BLOCKS];
+
+    // An array of pointers to blocks of memory holding space for list
+    // elements.
+    MMDB_entry_data_list_s *blocks[DATA_POOL_NUM_BLOCKS];
+} MMDB_data_pool_s;
+
+MMDB_data_pool_s *data_pool_new(size_t const);
+void data_pool_destroy(MMDB_data_pool_s *const);
+MMDB_entry_data_list_s *data_pool_alloc(MMDB_data_pool_s *const);
+MMDB_entry_data_list_s *data_pool_to_list(MMDB_data_pool_s *const);
+
+#endif