A Save is used to send ChunkPtrStructs from one module to another in a thread save way (one writer and one reader). pushFront Input module uses this function to push a ChunkPtrStruct on the stack. popBack Output module uses this function to receive a ChunkPtrStruct. If the stack is empty, the module (its thread) waits until data is available. diarrhea Output module uses this function to receive all ChunkPtrStructs that are currently on the stack. If the stack is empty, function will return without stalling execution.