Build everything as C++ (#1176)

include/hashmap.hpp

@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: MIT */
+
+// Generic hashmap implementation (C++ templates are calling...)
+#ifndef RGBDS_LINK_HASHMAP_H
+#define RGBDS_LINK_HASHMAP_H
+
+#include <assert.h>
+#include <stdbool.h>
+
+#define HASH_NB_BITS 32
+#define HALF_HASH_NB_BITS 16
+static_assert(HALF_HASH_NB_BITS * 2 == HASH_NB_BITS, "");
+#define HASHMAP_NB_BUCKETS (1 << HALF_HASH_NB_BITS)
+
+// HashMapEntry is internal, please do not attempt to use it
+typedef struct HashMapEntry *HashMap[HASHMAP_NB_BUCKETS];
+
+/*
+ * Adds an element to a hashmap.
+ * @warning Adding a new element with an already-present key will not cause an
+ *          error, this must be handled externally.
+ * @warning Inserting a NULL will make `hash_GetElement`'s return ambiguous!
+ * @param map The HashMap to add the element to
+ * @param key The key with which the element will be stored and retrieved
+ * @param element The element to add
+ * @return A pointer to the pointer to the element.
+ */
+void **hash_AddElement(HashMap map, char const *key, void *element);
+
+/*
+ * Removes an element from a hashmap.
+ * @param map The HashMap to remove the element from
+ * @param key The key to search the element with
+ * @return True if the element was found and removed
+ */
+bool hash_RemoveElement(HashMap map, char const *key);
+
+/*
+ * Finds an element in a hashmap, and returns a pointer to its value field.
+ * @param map The map to consider the elements of
+ * @param key The key to search an element for
+ * @return A pointer to the pointer to the element, or NULL if not found.
+ */
+void **hash_GetNode(HashMap const map, char const *key);
+
+/*
+ * Finds an element in a hashmap.
+ * @param map The map to consider the elements of
+ * @param key The key to search an element for
+ * @return A pointer to the element, or NULL if not found. (NULL can be returned
+ *         if such an element was added, but that sounds pretty silly.)
+ */
+void *hash_GetElement(HashMap const map, char const *key);
+
+/*
+ * Executes a function on each element in a hashmap.
+ * @param map The map to consider the elements of
+ * @param func The function to run. The first argument will be the element,
+ *                                  the second will be `arg`.
+ * @param arg An argument to be passed to all function calls
+ */
+void hash_ForEach(HashMap const map, void (*func)(void *, void *), void *arg);
+
+/*
+ * Cleanly empties a hashmap from its contents.
+ * This does not `free` the data structure itself!
+ * @param map The map to empty
+ */
+void hash_EmptyMap(HashMap map);
+
+#endif // RGBDS_LINK_HASHMAP_H