[struct_pack][bugfix] fix broken container size cause program crash

include/ylt/struct_pack.hpp

@@ -309,26 +309,16 @@ template <uint64_t conf = sp_config::DEFAULT, typename T, typename... Args,
   auto old_pos = reader.tellg();
   auto ret = in.deserialize_with_len(consume_len, t, args...);
   std::size_t delta = reader.tellg() - old_pos;
-  if SP_LIKELY (ret == errc{}) {
-    if SP_LIKELY (consume_len > 0) {
-      if SP_UNLIKELY (delta > consume_len) {
-        ret = struct_pack::errc::invalid_buffer;
-        if constexpr (struct_pack::seek_reader_t<Reader>)
-          if SP_UNLIKELY (!reader.seekg(old_pos)) {
-            return struct_pack::errc::seek_failed;
-          }
-      }
-      else {
-        reader.ignore(consume_len - delta);
-      }
+  if SP_LIKELY (consume_len > 0) {
+    if SP_UNLIKELY (delta > consume_len) {
+      // TODO test this branch
+      ret = struct_pack::errc::invalid_buffer;
+    }
+    else {
+      reader.ignore(consume_len - delta);
     }
   }
-  else {
-    if constexpr (struct_pack::seek_reader_t<Reader>)
-      if SP_UNLIKELY (!reader.seekg(old_pos)) {
-        return struct_pack::errc::seek_failed;
-      }
-  }
+
   return ret;
 }
 #if __cpp_concepts >= 201907L

include/ylt/struct_pack/error_code.hpp

@@ -23,8 +23,7 @@ enum class errc {
   no_buffer_space,
   invalid_buffer,
   hash_conflict,
-  seek_failed,
-  too_width_size
+  invalid_width_of_container_length,
 };
 
 namespace detail {

include/ylt/struct_pack/reflection.hpp

@@ -106,11 +106,6 @@ concept view_reader_t = reader_t<T> && requires(T t) {
   { t.read_view(std::size_t{}) } -> std::convertible_to<const char *>;
 };
 
-template <typename T>
-concept seek_reader_t = reader_t<T> && requires(T t) {
-  t.seekg(std::size_t{});
-};
-
 #else
 
 template <typename T, typename = void>
@@ -147,17 +142,59 @@ struct view_reader_t_impl<
 
 template <typename T>
 constexpr bool view_reader_t = reader_t<T> &&view_reader_t_impl<T>::value;
+#endif
+
+#if __cpp_concepts >= 201907L
+
+template <typename T>
+concept check_reader_t = reader_t<T> && requires(T t) {
+  t.check(std::size_t{});
+};
+
+template <typename T>
+concept can_reserve = requires(T t) {
+  t.reserve(std::size_t{});
+};
+
+template <typename T>
+concept can_shrink_to_fit = requires(T t) {
+  t.shrink_to_fit();
+};
+
+#else
+
+template <typename T, typename = void>
+struct check_reader_t_impl : std::false_type {};
+
+template <typename T>
+struct check_reader_t_impl<
+    T, std::void_t<decltype(std::declval<T>().check(std::size_t{}))>>
+    : std::true_type {};
+
+template <typename T>
+constexpr bool check_reader_t = reader_t<T> &&check_reader_t_impl<T>::value;
+
+template <typename T, typename = void>
+struct can_reserve_impl : std::false_type {};
+
+template <typename T>
+struct can_reserve_impl<
+    T, std::void_t<decltype(std::declval<T>().reserve(std::size_t{}))>>
+    : std::true_type {};
+
+template <typename T>
+constexpr bool can_reserve = can_reserve_impl<T>::value;
 
 template <typename T, typename = void>
-struct seek_reader_t_impl : std::false_type {};
+struct can_shrink_to_fit_impl : std::false_type {};
 
 template <typename T>
-struct seek_reader_t_impl<
-    T, std::void_t<decltype(std::declval<T>().seekg(std::size_t{}))>>
+struct can_shrink_to_fit_impl<
+    T, std::void_t<decltype(std::declval<T>().shrink_to_fit())>>
     : std::true_type {};
 
 template <typename T>
-constexpr bool seek_reader_t = reader_t<T> &&seek_reader_t_impl<T>::value;
+constexpr bool can_shrink_to_fit = can_shrink_to_fit_impl<T>::value;
 
 #endif