From 937e3d6f680ba598fea213d960d29d760007116c Mon Sep 17 00:00:00 2001
From: Billy Laws <blaws05@gmail.com>
Date: Sat, 13 Feb 2021 12:51:22 +0000
Subject: [PATCH] Add endiannes swapping helper functions

Avoid using compiler functions manually to create a cleaner interface,
and allow swapping the endianness of arbritary lengths.
---
 app/src/main/cpp/skyline/common.h              | 18 ++++++++++++++++++
 app/src/main/cpp/skyline/crypto/aes_cipher.h   |  2 +-
 .../cpp/skyline/vfs/ctr_encrypted_backing.cpp  |  2 +-
 app/src/main/cpp/skyline/vfs/nca.cpp           |  4 ++--
 4 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/app/src/main/cpp/skyline/common.h b/app/src/main/cpp/skyline/common.h
index a0e77323..9328e4a1 100644
--- a/app/src/main/cpp/skyline/common.h
+++ b/app/src/main/cpp/skyline/common.h
@@ -311,6 +311,24 @@ namespace skyline {
             return result >> (offset + 4);
         }
 
+        template<size_t N>
+        constexpr std::array<u8, N> SwapEndianness(std::array<u8, N> in) {
+            std::reverse(in.begin(), in.end());
+            return in;
+        }
+
+        constexpr u64 SwapEndianness(u64 in) {
+            return __builtin_bswap64(in);
+        }
+
+        constexpr u32 SwapEndianness(u32 in) {
+            return __builtin_bswap32(in);
+        }
+
+        constexpr u16 SwapEndianness(u16 in) {
+            return __builtin_bswap16(in);
+        }
+
         /**
          * @brief A compile-time hash function as std::hash isn't constexpr
          */
diff --git a/app/src/main/cpp/skyline/crypto/aes_cipher.h b/app/src/main/cpp/skyline/crypto/aes_cipher.h
index 211f7d03..b6c6c048 100644
--- a/app/src/main/cpp/skyline/crypto/aes_cipher.h
+++ b/app/src/main/cpp/skyline/crypto/aes_cipher.h
@@ -21,7 +21,7 @@ namespace skyline::crypto {
          */
         static std::array<u8, 0x10> GetTweak(size_t sector) {
             std::array<u8, 0x10> tweak{};
-            size_t le{__builtin_bswap64(sector)};
+            size_t le{util::SwapEndianness(sector)};
             std::memcpy(tweak.data() + 8, &le, 8);
             return tweak;
         }
diff --git a/app/src/main/cpp/skyline/vfs/ctr_encrypted_backing.cpp b/app/src/main/cpp/skyline/vfs/ctr_encrypted_backing.cpp
index d36f946a..9cfb93d0 100644
--- a/app/src/main/cpp/skyline/vfs/ctr_encrypted_backing.cpp
+++ b/app/src/main/cpp/skyline/vfs/ctr_encrypted_backing.cpp
@@ -13,7 +13,7 @@ namespace skyline::vfs {
 
     void CtrEncryptedBacking::UpdateCtr(u64 offset) {
         offset >>= 4;
-        size_t le{__builtin_bswap64(offset)};
+        size_t le{util::SwapEndianness(offset)};
         std::memcpy(ctr.data() + 8, &le, 8);
         cipher.SetIV(ctr);
     }
diff --git a/app/src/main/cpp/skyline/vfs/nca.cpp b/app/src/main/cpp/skyline/vfs/nca.cpp
index 6871eca3..9b19e81d 100644
--- a/app/src/main/cpp/skyline/vfs/nca.cpp
+++ b/app/src/main/cpp/skyline/vfs/nca.cpp
@@ -81,8 +81,8 @@ namespace skyline::vfs {
                 auto key{!(rightsIdEmpty || useKeyArea) ? GetTitleKey() : GetKeyAreaKey(sectionHeader.encryptionType)};
 
                 std::array<u8, 0x10> ctr{};
-                u32 secureValueLE{__builtin_bswap32(sectionHeader.secureValue)};
-                u32 generationLE{__builtin_bswap32(sectionHeader.generation)};
+                u32 secureValueLE{util::SwapEndianness(sectionHeader.secureValue)};
+                u32 generationLE{util::SwapEndianness(sectionHeader.generation)};
                 std::memcpy(ctr.data(), &secureValueLE, 4);
                 std::memcpy(ctr.data() + 4, &generationLE, 4);