From 1f080be047557a548f23927e17a7e6c55e117283 Mon Sep 17 00:00:00 2001 From: YoshiRulz Date: Thu, 8 Apr 2021 15:30:23 +1000 Subject: [PATCH] Extract byte swapping helpers from RomGame, cleanup, and add tests --- src/BizHawk.Client.Common/RomGame.cs | 57 +++---------------- src/BizHawk.Common/EndiannessUtils.cs | 57 +++++++++++++++++++ .../EndiannessUtils/EndiannessUtilsTests.cs | 30 ++++++++++ 3 files changed, 94 insertions(+), 50 deletions(-) create mode 100644 src/BizHawk.Common/EndiannessUtils.cs create mode 100644 src/BizHawk.Tests/Common/EndiannessUtils/EndiannessUtilsTests.cs diff --git a/src/BizHawk.Client.Common/RomGame.cs b/src/BizHawk.Client.Common/RomGame.cs index 737b480829..244b157100 100644 --- a/src/BizHawk.Client.Common/RomGame.cs +++ b/src/BizHawk.Client.Common/RomGame.cs @@ -86,7 +86,13 @@ namespace BizHawk.Client.Common if (file.Extension == ".z64" || file.Extension == ".n64" || file.Extension == ".v64") { - RomData = MutateSwapN64(RomData); + // Use a simple magic number to detect N64 rom format, then byteswap the ROM to ensure a consistent endianness/order + RomData = RomData[0] switch + { + 0x37 => EndiannessUtils.ByteSwap16(RomData), // V64 format (byte swapped) + 0x40 => EndiannessUtils.ByteSwap32(RomData), // N64 format (word swapped) + _ => RomData // Z64 format (no swap), or something unexpected; in either case do nothing + }; } // note: this will be taking several hashes, of a potentially large amount of data.. yikes! @@ -137,55 +143,6 @@ namespace BizHawk.Client.Common return output; } - private static unsafe byte[] MutateSwapN64(byte[] source) - { - // N64 roms are in one of the following formats: - // .Z64 = No swapping - // .N64 = Word Swapped - // .V64 = Byte Swapped - - // File extension does not always match the format - int size = source.Length; - - // V64 format - fixed (byte* pSource = &source[0]) - { - if (pSource[0] == 0x37) - { - for (int i = 0; i < size; i += 2) - { - byte temp = pSource[i]; - pSource[i] = pSource[i + 1]; - pSource[i + 1] = temp; - } - } - - // N64 format - else if (pSource[0] == 0x40) - { - for (int i = 0; i < size; i += 4) - { - // output[i] = source[i + 3]; - // output[i + 3] = source[i]; - // output[i + 1] = source[i + 2]; - // output[i + 2] = source[i + 1]; - byte temp = pSource[i]; - pSource[i] = pSource[i + 3]; - pSource[i + 3] = temp; - - temp = pSource[i + 1]; - pSource[i + 1] = pSource[i + 2]; - pSource[i + 2] = temp; - } - } - else // Z64 format (or some other unknown format) - { - } - } - - return source; - } - private void CheckForPatchOptions() { try diff --git a/src/BizHawk.Common/EndiannessUtils.cs b/src/BizHawk.Common/EndiannessUtils.cs new file mode 100644 index 0000000000..2da5288a27 --- /dev/null +++ b/src/BizHawk.Common/EndiannessUtils.cs @@ -0,0 +1,57 @@ +using System; +using System.Diagnostics; + +namespace BizHawk.Common +{ + public static unsafe class EndiannessUtils + { + /// reverses pairs of octets: 0xAABBIIJJPPQQYYZZ <=> 0xBBAAJJIIQQPPZZYY + public static byte[] ByteSwap16(byte[] a) + { + var l = a.Length; + var copy = new byte[l]; + Array.Copy(a, copy, l); + MutatingByteSwap16(copy); + return copy; + } + + /// reverses groups of 4 octets: 0xAABBCCDDWWXXYYZZ <=> 0xDDCCBBAAZZYYXXWW + public static byte[] ByteSwap32(byte[] a) + { + var l = a.Length; + var copy = new byte[l]; + Array.Copy(a, copy, l); + MutatingByteSwap32(copy); + return copy; + } + + /// reverses pairs of octets in-place: 0xAABBIIJJPPQQYYZZ <=> 0xBBAAJJIIQQPPZZYY + public static void MutatingByteSwap16(byte[] a) + { + var l = a.Length; + Debug.Assert(l % 2 == 0); + fixed (byte* p = &a[0]) for (var i = 0; i < l; i += 2) + { + var b = p[i]; + p[i] = p[i + 1]; + p[i + 1] = b; + } + } + + /// reverses groups of 4 octets in-place: 0xAABBCCDDWWXXYYZZ <=> 0xDDCCBBAAZZYYXXWW + public static void MutatingByteSwap32(byte[] a) + { + var l = a.Length; + Debug.Assert(l % 4 == 0); + fixed (byte* p = &a[0]) for (var i = 0; i < l; i += 4) + { + var b = p[i]; + p[i] = p[i + 3]; + p[i + 3] = b; + b = p[i + 1]; + p[i + 1] = p[i + 2]; + p[i + 2] = b; + } + } + } +} diff --git a/src/BizHawk.Tests/Common/EndiannessUtils/EndiannessUtilsTests.cs b/src/BizHawk.Tests/Common/EndiannessUtils/EndiannessUtilsTests.cs new file mode 100644 index 0000000000..05038f872f --- /dev/null +++ b/src/BizHawk.Tests/Common/EndiannessUtils/EndiannessUtilsTests.cs @@ -0,0 +1,30 @@ +using System.Linq; + +using BizHawk.Common; + +using Microsoft.VisualStudio.TestTools.UnitTesting; + +namespace BizHawk.Tests.Common +{ + [TestClass] + public sealed class EndiannessUtilsTests + { + private static readonly byte[] expected = { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF }; + + [TestMethod] + public void TestByteSwap16() + { + var a = new byte[] { 0x23, 0x01, 0x67, 0x45, 0xAB, 0x89, 0xEF, 0xCD }; + EndiannessUtils.MutatingByteSwap16(a); + Assert.IsTrue(a.SequenceEqual(expected)); + } + + [TestMethod] + public void TestByteSwap32() + { + var a = new byte[] { 0x67, 0x45, 0x23, 0x01, 0xEF, 0xCD, 0xAB, 0x89 }; + EndiannessUtils.MutatingByteSwap32(a); + Assert.IsTrue(a.SequenceEqual(expected)); + } + } +}