all: add README

README.md

@@ -0,0 +1,41 @@
+# libds
+
+Data structures implemented in C.
+
+## Map
+
+A hash map with support for dynamic resizing.
+
+```c
+map* m = map_new();
+
+map_get(m, "foo"); // -> NULL
+map_len(m);        // -> 0
+
+map_set(m, "foo", "bar"); // -> "bar"
+map_get(m, "foo");        // -> "bar"
+map_len(m);               // -> 1
+
+map_set(m, "foo", "baz"); // -> "bar"
+map_get(m, "foo");        // -> "baz"
+map_len(m);               // -> 1
+
+map_del(m, "foo"); // -> "baz"
+map_len(m);        // -> 0
+
+for (struct map_iter it = map_iter_new(m); map_iter_next(&it);) {
+    // it.key
+    // it.value
+}
+
+map_free(m);
+```
+
+There are two implementations: [open addressing][1] ([map_oa.c](map_oa.c)) and [separate chaining][2] ([map_sc.c](map_sc.c)).
+Both are based on information from Wikipedia and the book [Crafting interpreters][3].
+The hash function used is [FNV-1a][4].
+
+[1]: https://en.wikipedia.org/wiki/Hash_table#Open_addressing
+[2]: https://en.wikipedia.org/wiki/Hash_table#Separate_chaining
+[3]: https://craftinginterpreters.com/hash-tables.html
+[4]: https://en.wikipedia.org/wiki/Fowler–Noll–Vo_hash_function#FNV-1a_hash

map.h

@@ -5,7 +5,7 @@
 #include <stddef.h>
 
 /*
- * A hash map that supports dynamic resizing.
+ * A hash map with support for dynamic resizing.
  * The keys are strings, the values must not be NULL.
  * Must be created with map_new() and freed with map_free().
  *