From c27c8c232a89edba59f89a73f32f429fabb994da Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@users.noreply.github.com>
Date: Tue, 12 Dec 2023 20:35:03 +0100
Subject: [PATCH] handle RFF encryption like compression.

This allows simplifiying the code a lot by moving the decrypter to OpenDecompressor and handling it with generic code in the base class.
---
 src/common/filesystem/include/fs_files.h      |  5 +--
 src/common/filesystem/source/file_rff.cpp     | 33 +++----------------
 .../filesystem/source/files_decompress.cpp    | 23 +++++++++++--
 3 files changed, 28 insertions(+), 33 deletions(-)

diff --git a/src/common/filesystem/include/fs_files.h b/src/common/filesystem/include/fs_files.h
index 5bc2d77021..c9a0479e6e 100644
--- a/src/common/filesystem/include/fs_files.h
+++ b/src/common/filesystem/include/fs_files.h
@@ -83,8 +83,9 @@ enum
 	METHOD_LZMA = 14,
 	METHOD_XZ = 95,
 	METHOD_PPMD = 98,
-	METHOD_LZSS = 1337,	// not used in Zips - this is for Console Doom compression
-	METHOD_ZLIB = 1338,	// Zlib stream with header, used by compressed nodes.
+	METHOD_LZSS = 1337,			// not used in Zips - this is for Console Doom compression
+	METHOD_ZLIB = 1338,			// Zlib stream with header, used by compressed nodes.
+	METHOD_RFFCRYPT = 1339,		// not actual compression but can be put in here to make handling easier.
 	METHOD_IMPLODE_MIN = 1000, // having discrete types for these avoids keeping around the GPFlags word in Zips.
 	METHOD_IMPLODE_0 = 1000,
 	METHOD_IMPLODE_2 = 1002,
diff --git a/src/common/filesystem/source/file_rff.cpp b/src/common/filesystem/source/file_rff.cpp
index ef74d7f83a..cd6ae7a7a6 100644
--- a/src/common/filesystem/source/file_rff.cpp
+++ b/src/common/filesystem/source/file_rff.cpp
@@ -90,7 +90,7 @@ void BloodCrypt (void *data, int key, int len)
 //
 //==========================================================================
 
-class FRFFFile : public FResourceFile
+class FRFFFile : public FUncompressedFile
 {
 
 public:
@@ -106,7 +106,7 @@ public:
 //==========================================================================
 
 FRFFFile::FRFFFile(const char *filename, FileReader &file, StringPool* sp)
-: FResourceFile(filename, file, sp)
+: FUncompressedFile(filename, file, sp)
 {
 }
 
@@ -139,8 +139,8 @@ bool FRFFFile::Open(LumpFilterInfo*)
 		Entries[i].Method = METHOD_STORED;
 		if (lumps[i].Flags & 0x10)
 		{
-			Entries[i].Flags = RESFF_COMPRESSED;	// flags the lump as not directly usable
-			Entries[i].Method = METHOD_INVALID;
+			Entries[i].Flags = RESFF_COMPRESSED;	// for purposes of decoding, compression and encryption are equivalent.
+			Entries[i].Method = METHOD_RFFCRYPT;
 		}
 		else
 		{
@@ -168,31 +168,6 @@ bool FRFFFile::Open(LumpFilterInfo*)
 	return true;
 }
 
-//==========================================================================
-//
-// Fills the lump cache and performs decryption
-//
-//==========================================================================
-#if 0
-int FRFFLump::FillCache()
-{
-	int res = FUncompressedLump::FillCache();
-
-	if (Flags & LUMPF_COMPRESSED)
-	{
-		int cryptlen = std::min<int> (LumpSize, 256);
-		uint8_t *data = (uint8_t *)Cache;
-
-		for (int i = 0; i < cryptlen; ++i)
-		{
-			data[i] ^= i >> 1;
-		}
-	}
-	return res;
-}
-#endif
-
-
 //==========================================================================
 //
 // File open
diff --git a/src/common/filesystem/source/files_decompress.cpp b/src/common/filesystem/source/files_decompress.cpp
index 7af2788bcb..62c85b3a25 100644
--- a/src/common/filesystem/source/files_decompress.cpp
+++ b/src/common/filesystem/source/files_decompress.cpp
@@ -952,6 +952,24 @@ bool FileReader::OpenDecompressor(FileReader &parent, Size length, int method, b
 			break;
 		}
 
+		// While this could be msde a buffering reader it isn't worth the effort because only stock RFFs are encrypted and they do not contain large files.
+		case METHOD_RFFCRYPT:
+		{
+			auto idec = new MemoryArrayReader<FileData>;
+			fr = idec;
+			auto& buffer = idec->GetArray();
+			auto bufr = (uint8_t*)buffer.allocate(length);
+			p->Read(bufr, length);
+
+			Size cryptlen = std::min<Size>(length, 256);
+
+			for (Size i = 0; i < cryptlen; ++i)
+			{
+				bufr[i] ^= i >> 1;
+			}
+			break;
+		}
+
 		default:
 			return false;
 		}
@@ -974,13 +992,13 @@ bool FileReader::OpenDecompressor(FileReader &parent, Size length, int method, b
 			mReader = new BufferingReader(fr);
 		}
 		return true;
-	}
+			}
 	catch (...)
 	{
 		if (fr) delete fr;
 		throw;
 	}
-}
+		}
 
 
 bool FCompressedBuffer::Decompress(char* destbuffer)
@@ -1001,3 +1019,4 @@ bool FCompressedBuffer::Decompress(char* destbuffer)
 	}
 	return false;
 }
+}
\ No newline at end of file