1 files changed, 96 insertions, 0 deletions
diff --git a/src/w_checksum.c b/src/w_checksum.c
new file mode 100644
index 00000000..faa6108a
--- /dev/null
+++ b/src/w_checksum.c
@@ -0,0 +1,96 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// $Id: w_wad.h 596 2006-09-02 19:10:07Z fraggle $
+//
+// Copyright(C) 1993-1996 Id Software, Inc.
+// Copyright(C) 2005 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//       Generate a checksum of the WAD directory.
+//
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "md5.h"
+#include "w_checksum.h"
+#include "w_wad.h"
+
+static FILE **open_wadfiles = NULL;
+static int num_open_wadfiles = 0;
+
+static int GetFileNumber(FILE *handle)
+{
+    int i;
+    int result;
+
+    for (i=0; i<num_open_wadfiles; ++i)
+    {
+        if (open_wadfiles[i] == handle)
+        {
+            return i;
+        }
+    }
+
+    // Not found in list.  This is a new file we haven't seen yet.
+    // Allocate another slot for this file.
+
+    open_wadfiles = realloc(open_wadfiles,
+                            sizeof(FILE *) * (num_open_wadfiles + 1));
+    open_wadfiles[num_open_wadfiles] = handle;
+
+    result = num_open_wadfiles;
+    ++num_open_wadfiles;
+
+    return result;
+}
+
+static void ChecksumAddLump(md5_context_t *md5_context, lumpinfo_t *lump)
+{
+    char buf[9];
+
+    strncpy(buf, lump->name, 8);
+    buf[8] = '\0';
+    MD5_UpdateString(md5_context, buf);
+    MD5_UpdateInt32(md5_context, GetFileNumber(lump->handle));
+    MD5_UpdateInt32(md5_context, lump->position);
+    MD5_UpdateInt32(md5_context, lump->size);
+}
+
+void W_Checksum(byte digest[16])
+{
+    md5_context_t md5_context;
+    int i;
+
+    MD5_Init(&md5_context);
+
+    num_open_wadfiles = 0;
+
+    // Go through each entry in the WAD directory, adding information
+    // about each entry to the MD5 hash.
+
+    for (i=0; i<numlumps; ++i)
+    {
+        ChecksumAddLump(&md5_context, &lumpinfo[i]);
+    }
+    
+    MD5_Final(digest, &md5_context);
+}
+