From 84d54ba34035c35937968d96b6fe4e1bf11b49d2 Mon Sep 17 00:00:00 2001
From: Gary Talent <gary@drinkingtea.net>
Date: Sat, 13 Aug 2022 01:35:17 -0500
Subject: [PATCH] [ox/mc] Fix decoding of int64s

---
 deps/ox/src/ox/mc/intops.hpp    | 30 ++++++++++++++++++------------
 deps/ox/src/ox/std/byteswap.hpp | 16 +++++++++++++++-
 2 files changed, 33 insertions(+), 13 deletions(-)

diff --git a/deps/ox/src/ox/mc/intops.hpp b/deps/ox/src/ox/mc/intops.hpp
index d2da8255..0740c478 100644
--- a/deps/ox/src/ox/mc/intops.hpp
+++ b/deps/ox/src/ox/mc/intops.hpp
@@ -8,6 +8,7 @@
 
 #pragma once
 
+#include <ox/std/array.hpp>
 #include <ox/std/assert.hpp>
 #include <ox/std/bit.hpp>
 #include <ox/std/byteswap.hpp>
@@ -55,7 +56,7 @@ static_assert(highestBit(uint64_t(1) << 31) == 31);
 static_assert(highestBit(uint64_t(1) << 63) == 63);
 
 struct McInt {
-	uint8_t data[9] = {0};
+	uint8_t data[9] = {};
 	// length of integer in bytes
 	std::size_t length = 0;
 };
@@ -113,7 +114,7 @@ constexpr McInt encodeInteger(I input) noexcept {
  * length integer.
  */
 [[nodiscard]]
-static constexpr std::size_t countBytes(uint8_t b) noexcept {
+static constexpr std::size_t countBytes(unsigned b) noexcept {
 	std::size_t i = 0;
 	while ((b >> i) & 1) ++i;
 	return i + 1;
@@ -130,13 +131,13 @@ static_assert(countBytes(0b0111'1111) == 8);
 static_assert(countBytes(0b1111'1111) == 9);
 
 template<typename I>
-Result<I> decodeInteger(const uint8_t buff[9], std::size_t buffLen, std::size_t *bytesRead) noexcept {
+constexpr Result<I> decodeInteger(const uint8_t buff[9], std::size_t buffLen, std::size_t *bytesRead) noexcept {
 	const auto bytes = countBytes(buff[0]);
 	if (bytes == 9) {
 		*bytesRead = bytes;
 		I out = 0;
 		ox_memcpy(&out, &buff[1], sizeof(I));
-		return static_cast<I>(LittleEndian<I>(out));
+		return fromLittleEndian<I>(out);
 	} else if (buffLen >= bytes) {
 		*bytesRead = bytes;
 		uint64_t decoded = 0;
@@ -150,28 +151,33 @@ Result<I> decodeInteger(const uint8_t buff[9], std::size_t buffLen, std::size_t
 			if (negative) {
 				// fill in all bits between encoded sign and real sign with 1s
 				// split it up because the 32-bit ARM can't shift more than 32 bits
-				uint32_t *d = reinterpret_cast<uint32_t*>(&decoded);
+				ox::Array<uint32_t, 2> d = {};
+				ox_memcpy(d.data(), &decoded, sizeof(decoded));
 				auto bit = negBit;
 				for (; bit < ox::min<std::size_t>(Bits<I>, 32); ++bit) {
 					d[0] |= 1 << bit;
 				}
+				bit -= 32;
 				for (; bit < Bits<I>; ++bit) {
 					d[1] |= 1 << bit;
 				}
+				I out = 0;
+				if constexpr(ox::defines::BigEndian) {
+					const auto d0Tmp = d[0];
+					d[0] = d[1];
+					d[1] = d0Tmp;
+				}
+				ox_memcpy(&out, d.data(), sizeof(out));
+				return out;
 			}
-			I out = 0;
-			ox_memcpy(&out, &decoded, sizeof(out));
-			return out;
-		} else {
-			auto out = static_cast<I>(decoded);
-			return out;
 		}
+		return static_cast<I>(decoded);
 	}
 	return OxError(1);
 }
 
 template<typename I>
-Result<I> decodeInteger(McInt m) noexcept {
+constexpr Result<I> decodeInteger(McInt m) noexcept {
 	std::size_t bytesRead;
 	return decodeInteger<I>(m.data, 9, &bytesRead);
 }
diff --git a/deps/ox/src/ox/std/byteswap.hpp b/deps/ox/src/ox/std/byteswap.hpp
index 494d00a6..68365d44 100644
--- a/deps/ox/src/ox/std/byteswap.hpp
+++ b/deps/ox/src/ox/std/byteswap.hpp
@@ -64,13 +64,27 @@ constexpr T conditionalByteSwap(T i) noexcept {
 }
 
 template<typename T>
+[[nodiscard]]
+constexpr T fromLittleEndian(T i) noexcept {
+	return conditionalByteSwap<T, defines::BigEndian>(i);
+}
+
+template<typename T>
+[[nodiscard]]
+constexpr T fromBigEndian(T i) noexcept {
+	return conditionalByteSwap<T, defines::LittleEndian>(i);
+}
+
+template<typename T>
+[[nodiscard]]
 constexpr T toLittleEndian(T i) noexcept {
 	return conditionalByteSwap<T, defines::BigEndian>(i);
 }
 
 template<typename T>
+[[nodiscard]]
 constexpr T toBigEndian(T i) noexcept {
-	return conditionalByteSwap<T, defines::BigEndian>(i);
+	return conditionalByteSwap<T, defines::LittleEndian>(i);
 }
 
 template<typename T, bool byteSwap>