mdbx++: добавление slice::as_pod<typename>().

mdbx.h++

@@ -394,6 +394,16 @@ using path = ::std::wstring;
 using path = ::std::string;
 #endif /* mdbx::path */
 
+#if defined(__SIZEOF_INT128__) ||                                              \
+    (defined(_INTEGRAL_MAX_BITS) && _INTEGRAL_MAX_BITS >= 128)
+#ifndef MDBX_U128_TYPE
+#define MDBX_U128_TYPE __uint128_t
+#endif /* MDBX_U128_TYPE */
+#ifndef MDBX_I128_TYPE
+#define MDBX_I128_TYPE __int128_t
+#endif /* MDBX_I128_TYPE */
+#endif /* __SIZEOF_INT128__ || _INTEGRAL_MAX_BITS >= 128 */
+
 #if __cplusplus >= 201103L || defined(DOXYGEN)
 /// \brief Duration in 1/65536 units of second.
 using duration = ::std::chrono::duration<unsigned, ::std::ratio<1, 65536>>;
@@ -552,6 +562,7 @@ MDBX_DECLARE_EXCEPTION(transaction_overlapping);
 [[noreturn]] LIBMDBX_API void throw_max_length_exceeded();
 [[noreturn]] LIBMDBX_API void throw_out_range();
 [[noreturn]] LIBMDBX_API void throw_allocators_mismatch();
+[[noreturn]] LIBMDBX_API void throw_bad_value_size();
 static MDBX_CXX14_CONSTEXPR size_t check_length(size_t bytes);
 static MDBX_CXX14_CONSTEXPR size_t check_length(size_t headroom,
                                                 size_t payload);
@@ -1029,6 +1040,35 @@ struct LIBMDBX_API_TYPE slice : public ::MDBX_val {
     return slice(size_t(-1));
   }
 
+  template <typename POD> MDBX_CXX14_CONSTEXPR POD as_pod() const {
+    static_assert(::std::is_standard_layout<POD>::value &&
+                      !::std::is_pointer<POD>::value,
+                  "Must be a standard layout type!");
+    if (MDBX_LIKELY(size() == sizeof(POD)))
+      MDBX_CXX20_LIKELY {
+        POD r;
+        memcpy(&r, data(), sizeof(r));
+        return r;
+      }
+    throw_bad_value_size();
+  }
+
+#ifdef MDBX_U128_TYPE
+  MDBX_U128_TYPE as_uint128() const;
+#endif /* MDBX_U128_TYPE */
+  uint64_t as_uint64() const;
+  uint32_t as_uint32() const;
+  uint16_t as_uint16() const;
+  uint8_t as_uint8() const;
+
+#ifdef MDBX_I128_TYPE
+  MDBX_I128_TYPE as_int128() const;
+#endif /* MDBX_I128_TYPE */
+  int64_t as_int64() const;
+  int32_t as_int32() const;
+  int16_t as_int16() const;
+  int8_t as_int8() const;
+
 protected:
   MDBX_CXX11_CONSTEXPR slice(size_t invalid_length) noexcept
       : ::MDBX_val({nullptr, invalid_length}) {}
@@ -2292,6 +2332,10 @@ public:
     return buffer(::mdbx::slice::wrap(pod), make_reference, allocator);
   }
 
+  template <typename POD> MDBX_CXX14_CONSTEXPR POD as_pod() const {
+    return slice_.as_pod<POD>();
+  }
+
   /// \brief Reserves storage space.
   void reserve(size_t wanna_headroom, size_t wanna_tailroom) {
     wanna_headroom = ::std::min(::std::max(headroom(), wanna_headroom),

src/mdbx.c++

@@ -233,6 +233,10 @@ namespace mdbx {
       "into an incompatible memory allocation scheme.");
 }
 
+[[noreturn]] __cold void throw_bad_value_size() {
+  throw bad_value_size(MDBX_BAD_VALSIZE);
+}
+
 __cold exception::exception(const ::mdbx::error &error) noexcept
     : base(error.what()), error_(error) {}
 
@@ -483,6 +487,109 @@ bool slice::is_printable(bool disable_utf8) const noexcept {
   return true;
 }
 
+#ifdef MDBX_U128_TYPE
+MDBX_U128_TYPE slice::as_uint128() const {
+  static_assert(sizeof(MDBX_U128_TYPE) == 16, "WTF?");
+  if (size() == 16) {
+    MDBX_U128_TYPE r;
+    memcpy(&r, data(), sizeof(r));
+    return r;
+  } else
+    return as_uint64();
+}
+#endif /* MDBX_U128_TYPE */
+
+uint64_t slice::as_uint64() const {
+  static_assert(sizeof(uint64_t) == 8, "WTF?");
+  if (size() == 8) {
+    uint64_t r;
+    memcpy(&r, data(), sizeof(r));
+    return r;
+  } else
+    return as_uint32();
+}
+
+uint32_t slice::as_uint32() const {
+  static_assert(sizeof(uint32_t) == 4, "WTF?");
+  if (size() == 4) {
+    uint32_t r;
+    memcpy(&r, data(), sizeof(r));
+    return r;
+  } else
+    return as_uint16();
+}
+
+uint16_t slice::as_uint16() const {
+  static_assert(sizeof(uint16_t) == 2, "WTF?");
+  if (size() == 2) {
+    uint16_t r;
+    memcpy(&r, data(), sizeof(r));
+    return r;
+  } else
+    return as_uint8();
+}
+
+uint8_t slice::as_uint8() const {
+  static_assert(sizeof(uint8_t) == 1, "WTF?");
+  if (size() == 1)
+    return *static_cast<const uint8_t *>(data());
+  else if (size() == 0)
+    return 0;
+  else
+    MDBX_CXX20_UNLIKELY throw_bad_value_size();
+}
+
+#ifdef MDBX_I128_TYPE
+MDBX_I128_TYPE slice::as_int128() const {
+  static_assert(sizeof(MDBX_I128_TYPE) == 16, "WTF?");
+  if (size() == 16) {
+    MDBX_I128_TYPE r;
+    memcpy(&r, data(), sizeof(r));
+    return r;
+  } else
+    return as_int64();
+}
+#endif /* MDBX_I128_TYPE */
+
+int64_t slice::as_int64() const {
+  static_assert(sizeof(int64_t) == 8, "WTF?");
+  if (size() == 8) {
+    uint64_t r;
+    memcpy(&r, data(), sizeof(r));
+    return r;
+  } else
+    return as_int32();
+}
+
+int32_t slice::as_int32() const {
+  static_assert(sizeof(int32_t) == 4, "WTF?");
+  if (size() == 4) {
+    int32_t r;
+    memcpy(&r, data(), sizeof(r));
+    return r;
+  } else
+    return as_int16();
+}
+
+int16_t slice::as_int16() const {
+  static_assert(sizeof(int16_t) == 2, "WTF?");
+  if (size() == 2) {
+    int16_t r;
+    memcpy(&r, data(), sizeof(r));
+    return r;
+  } else
+    return as_int8();
+}
+
+int8_t slice::as_int8() const {
+  if (size() == 1)
+    return *static_cast<const int8_t *>(data());
+  else if (size() == 0)
+    return 0;
+  else
+    MDBX_CXX20_UNLIKELY throw_bad_value_size();
+}
+
 //------------------------------------------------------------------------------
 
 char *to_hex::write_bytes(char *__restrict const dest, size_t dest_size) const {