UMBC CMSC 313, Computer Organization & Assembly Language, Fall 2012

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Tuesday, November 6, 2012

Assigned:         Due:   

Polymorphism in C

Assigned Reading in Null & Lobur:   

Assigned Reading in Duntemann:   

Preview Slides (in PDF): none

Topics Covered:

• Example of assembly language program passing a function pointer to a C program (for Project 7):
  • The C function: doarray.c
  • The assembly language program: main.asm
  • Sample run: typescript

• Using void * pointers and function pointers to achieve genericity. (Programs posted below.)

Programs Shown: These are all different implementations of a simple singly linked list ADT.

• Version 1: plain vanilla linked list. Each node is has an int data field.

  Files: README.txt   ll.c   ll.h   main01.c  

• Version 2: uses #define constants DATA_TYPE and DATA_TYPE_FORMAT for linked list of int.

  Files: README.txt   ll.c   ll.h   main02.c  

• Version 3: this time define constants DATA_TYPE and DATA_TYPE_FORMAT for linked list of double.

  Files: README.txt   ll.c   ll.h   main03.c  

• Version 4: uses void * pointers that allow linked list functions to point to different types of nodes. This works as long as the next field is the first field in all the nodes. Note that ll.c does not have to be recompiled to use it with another node type.

  Files: README.txt   ll.c   ll.h   main04.c   main05.c   main06.c   main07.c   void_ptr.c  

• Version 5: This version allows us to have both int and double nodes in one linked list. Each node now stores a pointer to a function that knows how to print that node.

  Files: README.txt   ll.c   ll.h   main08.c   main09.c   main10.c   main11.c  

• Version 6: Previous version allowed only constant strings in string nodes because of deallocation issues. In this version, each node also has a delete function attached. Instead of storing another function pointer in each node, we store a pointer to an array of function pointers. Thus we have only one table for each type. Increasing the number of functions in the table would not increase the size of each node.

  Files: README.txt   ll.c   ll.h   main12.c   main13.c   main14.c   main15.c   main16.c  

• Version 7: Clean up the code and make header files for each type of linked list. The implemenations can be compiled separately and placed in a library using the ar command.

  We also make a linked list node that points to a linked list. (See ll_list.c and ll_list.h.) This allows you to have linked lists of linked lists. Notice that print_ll_node() and del_ll_node() can be implemented quite simply using the linked list functions in ll.h.

  Files: README.txt   ll.c   ll.h   ll_double.c   ll_double.h   ll_int.c   ll_int.h   ll_list.c   ll_list.h   ll_string.c   ll_string.h   main17.c   main18.c   main19.c   main20.c   main21.c