add bjson library & update /doc/en/scripting/filesystem.md

src/logic/scripting/lua/libs/libbjson.cpp

@@ -0,0 +1,40 @@
+#include "coders/binary_json.hpp"
+#include "api_lua.hpp"
+#include "util/Buffer.hpp"
+#include "../lua_custom_types.hpp"
+
+static int l_tobytes(lua::State* L) {
+    auto value = lua::tovalue(L, 1);
+    bool compress = true;
+    if (lua::gettop(L) >= 2) {
+        compress = lua::toboolean(L, 2);
+    }
+    return lua::newuserdata<lua::LuaBytearray>(
+        L, json::to_binary(value, compress)
+    );
+}
+
+static int l_frombytes(lua::State* L) {
+    if (lua::istable(L, 1)) {
+        size_t len = lua::objlen(L, 1);
+        util::Buffer<ubyte> buffer(len);
+        for (size_t i = 0; i < len; i++) {
+            lua::rawgeti(L, i + 1);
+            buffer[i] = lua::tointeger(L, -1);
+            lua::pop(L);
+        }
+        return lua::pushvalue(L, json::from_binary(buffer.data(), len));
+    } else if (auto bytes = lua::touserdata<lua::LuaBytearray>(L, -1)) {
+        const auto& buffer = bytes->data();
+        return lua::pushvalue(
+            L, json::from_binary(buffer.data(), buffer.size())
+        );
+    } else {
+        throw std::runtime_error("table or Bytearray expected");
+    }
+}
+
+const luaL_Reg bjsonlib[] = {
+    {"tobytes", lua::wrap<l_tobytes>},
+    {"frombytes", lua::wrap<l_frombytes>},
+    {NULL, NULL}};