RTech: add GUID helper functions to fix a defect

Several instances of Pak_GetValidAssetGUID() in the engine are calling the hashing algorithm twice; once to get the guid, once to return the guid. The rewrite eliminates the bug by returning the cached guid. This is still pending a hook to effectively replace the defective function(s).

src/public/rtech/ipakfile.h

@@ -89,6 +89,9 @@
 // the handle that should be returned when a pak failed to load or process
 #define PAK_INVALID_HANDLE -1
 
+// the guid that should be returned for assets that do not exist in the runtime
+#define PAK_INVALID_GUID 0
+
 #define PAK_MAX_DISPATCH_LOAD_JOBS 4
 #define PAK_DEFAULT_JOB_GROUP_ID 0x3000
 

src/rtech/pak/paktools.cpp

@@ -282,6 +282,48 @@ const PakLoadedInfo_s* Pak_GetPakInfo(const char* const pakName)
 	return nullptr;
 }
 
+//-----------------------------------------------------------------------------
+// returns a pointer to the asset data by GUID, returns NULL if not found in
+// the runtime
+//-----------------------------------------------------------------------------
+void* Pak_FindAssetByGUID(const PakGuid_t guid)
+{
+	int assetIndex = guid & PAK_MAX_LOADED_ASSETS_MASK;
+	const PakAssetShort_s* asset = &g_pakGlobals->loadedAssets[assetIndex];
+
+	PakGuid_t assetGuid = asset->guid;
+
+	if (assetGuid == guid)
+		return asset->head;
+
+	while (assetGuid)
+	{
+		assetIndex = (assetIndex +1) & PAK_MAX_LOADED_ASSETS_MASK;
+		asset = &g_pakGlobals->loadedAssets[assetIndex];
+
+		assetGuid = asset->guid;
+
+		if (assetGuid == guid)
+			return asset->head;
+	}
+
+	return nullptr;
+}
+
+//-----------------------------------------------------------------------------
+// returns the guid of the asset if it exists in the runtime, returns
+// PAK_INVALID_GUID if not found in the runtime
+//-----------------------------------------------------------------------------
+PakGuid_t Pak_GetValidAssetGUID(const char* const name)
+{
+	const PakGuid_t guid = Pak_StringToGuid(name);
+
+	if (guid && Pak_FindAssetByGUID(guid))
+		return guid;
+
+	return PAK_INVALID_GUID;
+}
+
 //-----------------------------------------------------------------------------
 // returns a pointer to the patch data header
 //-----------------------------------------------------------------------------