API: Refactor: Implement api/handle module

This module will be used to implement remote management of objects through the
API. Object types to be registered must have a `uint64_t` field named 'handle'.

src/nvim/api/private/handle.c

@@ -0,0 +1,31 @@
+#include <stdint.h>
+
+#include "nvim/vim.h"
+#include "nvim/map.h"
+#include "nvim/api/private/handle.h"
+
+#define HANDLE_INIT(name) name##_handles = map_new(uint64_t)()
+
+#define HANDLE_IMPL(type, name)                                               \
+  static Map(uint64_t) *name##_handles = NULL;                                \
+                                                                              \
+  type *handle_get_##name(uint64_t handle)                                    \
+  {                                                                           \
+    return map_get(uint64_t)(name##_handles, handle);                         \
+  }                                                                           \
+                                                                              \
+  void handle_register_##name(type *name)                                     \
+  {                                                                           \
+    assert(!name->handle);                                                    \
+    name->handle = next_handle++;                                             \
+    map_put(uint64_t)(name##_handles, name->handle, name);                    \
+  }                                                                           \
+                                                                              \
+  void handle_unregister_##name(type *name)                                   \
+  {                                                                           \
+    map_del(uint64_t)(name##_handles, name->handle);                          \
+  }
+
+void handle_init()
+{
+}

src/nvim/api/private/handle.h

@@ -0,0 +1,14 @@
+#ifndef NVIM_API_HANDLE_H
+#define NVIM_API_HANDLE_H
+
+#include "nvim/vim.h"
+
+#define HANDLE_DECLS(type, name)                                              \
+  type *handle_get_##name(uint64_t handle);                                   \
+  void handle_register_##name(type *name);                                    \
+  void handle_unregister_##name(type *name);
+
+void handle_init(void);
+
+#endif  // NVIM_API_HANDLE_H
+

src/nvim/map.c

@@ -85,3 +85,4 @@
 
 MAP_IMPL(cstr_t)
 MAP_IMPL(ptr_t)
+MAP_IMPL(uint64_t)

src/nvim/map.h

@@ -21,6 +21,7 @@
 
 MAP_DECLS(cstr_t)
 MAP_DECLS(ptr_t)
+MAP_DECLS(uint64_t)
 
 #define map_new(T) map_##T##_new
 #define map_free(T) map_##T##_free

src/nvim/os_unix.c

@@ -27,6 +27,7 @@
 
 #include <string.h>
 
+#include "nvim/api/private/handle.h"
 #include "nvim/vim.h"
 #include "nvim/os_unix.h"
 #include "nvim/buffer.h"
@@ -542,6 +543,7 @@ int mch_nodetype(char_u *name)
 
 void mch_early_init()
 {
+  handle_init();
   time_init();
 }