From 31aa855a51be2184d405eb63d689aa94c4dd6608 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@users.noreply.github.com>
Date: Fri, 13 Sep 2019 12:29:17 +0200
Subject: [PATCH] - generate a hash identifier for each loaded resource file.

This is not useful by itself but can be used for adding new features later, e.g. mod-wide compatibility settings or file specific lump replacement or injection.
---
 src/gamedata/resourcefiles/file_7z.cpp      |  1 +
 src/gamedata/resourcefiles/file_grp.cpp     |  2 +-
 src/gamedata/resourcefiles/file_pak.cpp     |  2 +-
 src/gamedata/resourcefiles/file_rff.cpp     |  1 +
 src/gamedata/resourcefiles/file_wad.cpp     |  1 +
 src/gamedata/resourcefiles/file_zip.cpp     |  1 +
 src/gamedata/resourcefiles/resourcefile.cpp | 34 +++++++++++++++++++++
 src/gamedata/resourcefiles/resourcefile.h   |  2 ++
 8 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/src/gamedata/resourcefiles/file_7z.cpp b/src/gamedata/resourcefiles/file_7z.cpp
index 01bd043ef..27b596341 100644
--- a/src/gamedata/resourcefiles/file_7z.cpp
+++ b/src/gamedata/resourcefiles/file_7z.cpp
@@ -316,6 +316,7 @@ bool F7ZFile::Open(bool quiet)
 
 	if (!quiet && !batchrun) Printf(", %d lumps\n", NumLumps);
 
+	GenerateHash();
 	PostProcessArchive(&Lumps[0], sizeof(F7ZLump));
 	return true;
 }
diff --git a/src/gamedata/resourcefiles/file_grp.cpp b/src/gamedata/resourcefiles/file_grp.cpp
index 936490177..81657a3c5 100644
--- a/src/gamedata/resourcefiles/file_grp.cpp
+++ b/src/gamedata/resourcefiles/file_grp.cpp
@@ -120,7 +120,7 @@ bool FGrpFile::Open(bool quiet)
 		Lumps[i].LumpNameSetup(fileinfo[i].NameWithZero);
 	}
 	if (!quiet && !batchrun) Printf(", %d lumps\n", NumLumps);
-
+	GenerateHash();
 	delete[] fileinfo;
 	return true;
 }
diff --git a/src/gamedata/resourcefiles/file_pak.cpp b/src/gamedata/resourcefiles/file_pak.cpp
index d69c5673d..2b4d39658 100644
--- a/src/gamedata/resourcefiles/file_pak.cpp
+++ b/src/gamedata/resourcefiles/file_pak.cpp
@@ -113,7 +113,7 @@ bool FPakFile::Open(bool quiet)
 		Lumps[i].LumpSize = LittleLong(fileinfo[i].filelen);
 		Lumps[i].CheckEmbedded();
 	}
-
+	GenerateHash();
 	return true;
 }
 
diff --git a/src/gamedata/resourcefiles/file_rff.cpp b/src/gamedata/resourcefiles/file_rff.cpp
index 056379c7b..35402c3ad 100644
--- a/src/gamedata/resourcefiles/file_rff.cpp
+++ b/src/gamedata/resourcefiles/file_rff.cpp
@@ -184,6 +184,7 @@ bool FRFFFile::Open(bool quiet)
 		}
 	}
 	delete[] lumps;
+	GenerateHash();
 	return true;
 }
 
diff --git a/src/gamedata/resourcefiles/file_wad.cpp b/src/gamedata/resourcefiles/file_wad.cpp
index f6db35f14..169cd975d 100644
--- a/src/gamedata/resourcefiles/file_wad.cpp
+++ b/src/gamedata/resourcefiles/file_wad.cpp
@@ -203,6 +203,7 @@ bool FWadFile::Open(bool quiet)
 	}
 
 	delete[] fileinfo;
+	GenerateHash(); // Do this before the lump processing below.
 
 	if (!quiet)
 	{
diff --git a/src/gamedata/resourcefiles/file_zip.cpp b/src/gamedata/resourcefiles/file_zip.cpp
index 8ee031ae0..d661a8158 100644
--- a/src/gamedata/resourcefiles/file_zip.cpp
+++ b/src/gamedata/resourcefiles/file_zip.cpp
@@ -363,6 +363,7 @@ bool FZipFile::Open(bool quiet)
 
 	if (!quiet && !batchrun) Printf(TEXTCOLOR_NORMAL ", %d lumps\n", NumLumps);
 	
+	GenerateHash();
 	PostProcessArchive(&Lumps[0], sizeof(FZipLump));
 	return true;
 }
diff --git a/src/gamedata/resourcefiles/resourcefile.cpp b/src/gamedata/resourcefiles/resourcefile.cpp
index 68a17058c..d934c98f2 100644
--- a/src/gamedata/resourcefiles/resourcefile.cpp
+++ b/src/gamedata/resourcefiles/resourcefile.cpp
@@ -41,6 +41,7 @@
 #include "gi.h"
 #include "doomstat.h"
 #include "doomtype.h"
+#include "md5.h"
 
 
 //==========================================================================
@@ -353,6 +354,39 @@ int lumpcmp(const void * a, const void * b)
 	return rec1->FullName.CompareNoCase(rec2->FullName);
 }
 
+//==========================================================================
+//
+// FResourceFile :: GenerateHash
+//
+// Generates a hash identifier for use in file identification.
+// Potential uses are mod-wide compatibility settings or localization add-ons.
+// This only hashes the lump directory but not the actual content
+//
+//==========================================================================
+
+void FResourceFile::GenerateHash()
+{
+	// hash the lump directory after sorting
+	
+	Hash.Format(("%08X-%04X-"), (unsigned)Reader.GetLength(), NumLumps);
+	
+	MD5Context md5;
+	
+	uint8_t digest[16];
+	for(uint32_t i = 0; i < NumLumps; i++)
+	{
+		auto lump = GetLump(i);
+		md5.Update((const uint8_t*)lump->Name, strlen(lump->Name) + 1); // +1 to hash the terminating 0 as well.
+		md5.Update((const uint8_t*)lump->FullName.GetChars(), lump->FullName.Len() + 1);
+		md5.Update((const uint8_t*)&lump->LumpSize, 4);
+	}
+	md5.Final(digest);
+	for (auto c : digest)
+	{
+		Hash.AppendFormat("%02X", c);
+	}
+}
+
 //==========================================================================
 //
 // FResourceFile :: PostProcessArchive
diff --git a/src/gamedata/resourcefiles/resourcefile.h b/src/gamedata/resourcefiles/resourcefile.h
index 4903441bd..65e0ef3f1 100644
--- a/src/gamedata/resourcefiles/resourcefile.h
+++ b/src/gamedata/resourcefiles/resourcefile.h
@@ -85,11 +85,13 @@ public:
 	FString FileName;
 protected:
 	uint32_t NumLumps;
+	FString Hash;
 
 	FResourceFile(const char *filename);
 	FResourceFile(const char *filename, FileReader &r);
 
 	// for archives that can contain directories
+	void GenerateHash();
 	void PostProcessArchive(void *lumps, size_t lumpsize);
 
 private: