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diff --git a/src/lib/util/endianness.h b/src/lib/util/endianness.h
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+// license:BSD-3-Clause
+// copyright-holders:Aaron Giles
+/***************************************************************************
+
+ endianness.h
+
+ Endianness types and utility functions.
+
+***************************************************************************/
+
+#ifndef MAME_LIB_UTIL_ENDIANNESS_H
+#define MAME_LIB_UTIL_ENDIANNESS_H
+
+#pragma once
+
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <string_view>
+#include <type_traits>
+
+
+namespace util {
+
+//**************************************************************************
+// TYPE DEFINITIONS
+//**************************************************************************
+
+// constants for expression endianness
+enum class endianness
+{
+ little,
+ big,
+#ifdef LSB_FIRST
+ native = little
+#else
+ native = big
+#endif
+};
+
+
+// helper for accessing data adjusted for endianness
+template <typename In, typename Out, endianness Endian>
+class offset_endian_cast
+{
+private:
+ static inline constexpr std::ptrdiff_t SWIZZLE = (sizeof(In) / sizeof(Out)) - 1;
+
+ static_assert(!(sizeof(In) % sizeof(Out)), "input size must be a multiple of output size");
+ static_assert(!((sizeof(In) / sizeof(Out)) & SWIZZLE), "ratio of input size to output size must be a power of two");
+
+ Out *m_ptr;
+ std::ptrdiff_t m_offs;
+
+public:
+ constexpr offset_endian_cast(In *ptr, std::ptrdiff_t offs) noexcept : m_ptr(reinterpret_cast<Out *>(ptr)), m_offs(offs) { }
+
+ constexpr Out &operator[](std::ptrdiff_t i) const noexcept { return m_ptr[(m_offs + i) ^ ((Endian != endianness::native) ? SWIZZLE : 0)]; }
+ constexpr Out &operator*() const noexcept { return m_ptr[m_offs ^ ((Endian != endianness::native) ? SWIZZLE : 0)]; }
+
+ constexpr offset_endian_cast operator+(std::ptrdiff_t i) const noexcept { return offset_endian_cast(*this) += i; }
+ constexpr offset_endian_cast operator-(std::ptrdiff_t i) const noexcept { return offset_endian_cast(*this) -= i; }
+
+ offset_endian_cast &operator+=(std::ptrdiff_t i) noexcept { m_offs += i; return *this; }
+ offset_endian_cast &operator-=(std::ptrdiff_t i) noexcept { m_offs -= i; return *this; }
+ offset_endian_cast &operator++() noexcept { ++m_offs; return *this; }
+ offset_endian_cast &operator--() noexcept { --m_offs; return *this; }
+ offset_endian_cast operator++(int) noexcept { offset_endian_cast result(*this); ++m_offs; return result; }
+ offset_endian_cast operator--(int) noexcept { offset_endian_cast result(*this); --m_offs; return result; }
+};
+
+
+// helper for accessing data adjusted for endianness
+template <typename In, typename Out, endianness Endian>
+class endian_cast
+{
+private:
+ static inline constexpr std::ptrdiff_t SWIZZLE = (sizeof(In) / sizeof(Out)) - 1;
+
+ static_assert(!(sizeof(In) % sizeof(Out)), "input size must be a multiple of output size");
+ static_assert(!((sizeof(In) / sizeof(Out)) & SWIZZLE), "ratio of input size to output size must be a power of two");
+
+ Out *m_ptr;
+
+public:
+ constexpr endian_cast(In *ptr) noexcept : m_ptr(reinterpret_cast<Out *>(ptr)) { }
+
+ constexpr Out &operator[](std::ptrdiff_t i) const noexcept { return m_ptr[i ^ ((Endian != endianness::native) ? SWIZZLE : 0)]; }
+
+ constexpr auto operator+(std::ptrdiff_t offs) const noexcept
+ {
+ using required_const = std::conditional_t<std::is_const_v<Out>, std::add_const_t<In>, In>;
+ using required_cv = std::conditional_t<std::is_volatile_v<Out>, std::add_volatile<required_const>, required_const>;
+ return offset_endian_cast<required_cv, Out, Endian>(reinterpret_cast<required_cv *>(m_ptr), offs);
+ }
+
+ constexpr auto operator-(std::ptrdiff_t offs) const noexcept
+ {
+ using required_const = std::conditional_t<std::is_const_v<Out>, std::add_const_t<In>, In>;
+ using required_cv = std::conditional_t<std::is_volatile_v<Out>, std::add_volatile<required_const>, required_const>;
+ return offset_endian_cast<required_cv, Out, Endian>(reinterpret_cast<required_cv *>(m_ptr), -offs);
+ }
+};
+
+
+
+//**************************************************************************
+// MACROS AND INLINE FUNCTIONS
+//**************************************************************************
+
+constexpr std::string_view endian_to_string_view(endianness e) { using namespace std::literals; return e == endianness::little ? "little"sv : "big"sv; }
+
+// endian-based value: first value is if native endianness is little-endian, second is if native is big-endian
+#define NATIVE_ENDIAN_VALUE_LE_BE(leval, beval) ((util::endianness::native == util::endianness::little) ? (leval) : (beval))
+
+
+// inline functions for accessing bytes and words within larger chunks
+
+template <typename T, typename U>
+auto big_endian_cast(U *ptr)
+{
+ using requested_const = std::conditional_t<std::is_const_v<U>, std::add_const_t<T>, T>;
+ using requested_cv = std::conditional_t<std::is_volatile_v<U>, std::add_volatile<requested_const>, requested_const>;
+ return endian_cast<U, requested_cv, endianness::big>(ptr);
+}
+
+template <typename T, typename U>
+auto little_endian_cast(U *ptr)
+{
+ using requested_const = std::conditional_t<std::is_const_v<U>, std::add_const_t<T>, T>;
+ using requested_cv = std::conditional_t<std::is_volatile_v<U>, std::add_volatile<requested_const>, requested_const>;
+ return endian_cast<U, requested_cv, endianness::little>(ptr);
+}
+
+// read/write a byte to a 16-bit space
+template <typename T> constexpr T BYTE_XOR_BE(T a) { return a ^ NATIVE_ENDIAN_VALUE_LE_BE(1,0); }
+template <typename T> constexpr T BYTE_XOR_LE(T a) { return a ^ NATIVE_ENDIAN_VALUE_LE_BE(0,1); }
+
+// read/write a byte to a 32-bit space
+template <typename T> constexpr T BYTE4_XOR_BE(T a) { return a ^ NATIVE_ENDIAN_VALUE_LE_BE(3,0); }
+template <typename T> constexpr T BYTE4_XOR_LE(T a) { return a ^ NATIVE_ENDIAN_VALUE_LE_BE(0,3); }
+
+// read/write a word to a 32-bit space
+template <typename T> constexpr T WORD_XOR_BE(T a) { return a ^ NATIVE_ENDIAN_VALUE_LE_BE(2,0); }
+template <typename T> constexpr T WORD_XOR_LE(T a) { return a ^ NATIVE_ENDIAN_VALUE_LE_BE(0,2); }
+
+// read/write a byte to a 64-bit space
+template <typename T> constexpr T BYTE8_XOR_BE(T a) { return a ^ NATIVE_ENDIAN_VALUE_LE_BE(7,0); }
+template <typename T> constexpr T BYTE8_XOR_LE(T a) { return a ^ NATIVE_ENDIAN_VALUE_LE_BE(0,7); }
+
+// read/write a word to a 64-bit space
+template <typename T> constexpr T WORD2_XOR_BE(T a) { return a ^ NATIVE_ENDIAN_VALUE_LE_BE(6,0); }
+template <typename T> constexpr T WORD2_XOR_LE(T a) { return a ^ NATIVE_ENDIAN_VALUE_LE_BE(0,6); }
+
+// read/write a dword to a 64-bit space
+template <typename T> constexpr T DWORD_XOR_BE(T a) { return a ^ NATIVE_ENDIAN_VALUE_LE_BE(4,0); }
+template <typename T> constexpr T DWORD_XOR_LE(T a) { return a ^ NATIVE_ENDIAN_VALUE_LE_BE(0,4); }
+
+} // namespace util
+
+#endif // MAME_LIB_UTIL_ENDIANNESS_H