- 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

@@ -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;
 }

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;
 }

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;
 }
 

src/gamedata/resourcefiles/file_rff.cpp

@@ -184,6 +184,7 @@ bool FRFFFile::Open(bool quiet)
 		}
 	}
 	delete[] lumps;
+	GenerateHash();
 	return true;
 }
 

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)
 	{

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;
 }

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

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: