feat(stdlib): add vim.base64 module (#25843)

Add base64 encode() and decode() functions to a vim.base64 module.

src/nvim/lua/base64.c

@@ -0,0 +1,65 @@
+#include <assert.h>
+#include <lauxlib.h>
+#include <lua.h>
+
+#include "nvim/base64.h"
+#include "nvim/lua/base64.h"
+#include "nvim/memory.h"
+
+static int nlua_base64_encode(lua_State *L)
+{
+  if (lua_gettop(L) < 1) {
+    return luaL_error(L, "Expected 1 argument");
+  }
+
+  if (lua_type(L, 1) != LUA_TSTRING) {
+    luaL_argerror(L, 1, "expected string");
+  }
+
+  size_t src_len = 0;
+  const char *src = lua_tolstring(L, 1, &src_len);
+
+  const char *ret = base64_encode(src, src_len);
+  assert(ret != NULL);
+  lua_pushstring(L, ret);
+  xfree((void *)ret);
+
+  return 1;
+}
+
+static int nlua_base64_decode(lua_State *L)
+{
+  if (lua_gettop(L) < 1) {
+    return luaL_error(L, "Expected 1 argument");
+  }
+
+  if (lua_type(L, 1) != LUA_TSTRING) {
+    luaL_argerror(L, 1, "expected string");
+  }
+
+  size_t src_len = 0;
+  const char *src = lua_tolstring(L, 1, &src_len);
+
+  const char *ret = base64_decode(src, src_len);
+  if (ret == NULL) {
+    return luaL_error(L, "Invalid input");
+  }
+
+  lua_pushstring(L, ret);
+  xfree((void *)ret);
+
+  return 1;
+}
+
+static const luaL_Reg base64_functions[] = {
+  { "encode", nlua_base64_encode },
+  { "decode", nlua_base64_decode },
+  { NULL, NULL },
+};
+
+int luaopen_base64(lua_State *L)
+{
+  lua_newtable(L);
+  luaL_register(L, NULL, base64_functions);
+  return 1;
+}

src/nvim/lua/base64.h

@@ -0,0 +1,12 @@
+#ifndef NVIM_LUA_BASE64_H
+#define NVIM_LUA_BASE64_H
+
+#include <lauxlib.h>
+#include <lua.h>
+#include <lualib.h>
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "lua/base64.h.generated.h"
+#endif
+
+#endif  // NVIM_LUA_BASE64_H

src/nvim/lua/stdlib.c

@@ -26,6 +26,7 @@
 #include "nvim/ex_eval.h"
 #include "nvim/fold.h"
 #include "nvim/globals.h"
+#include "nvim/lua/base64.h"
 #include "nvim/lua/converter.h"
 #include "nvim/lua/spell.h"
 #include "nvim/lua/stdlib.h"
@@ -606,6 +607,10 @@ void nlua_state_add_stdlib(lua_State *const lstate, bool is_thread)
     lua_pushcfunction(lstate, &nlua_iconv);
     lua_setfield(lstate, -2, "iconv");
 
+    // vim.base64
+    luaopen_base64(lstate);
+    lua_setfield(lstate, -2, "base64");
+
     nlua_state_add_internal(lstate);
   }