Page 172 - ARM 64 Bit Assembly Language

Abstract data types 159

31 { int MaxWordLength = 1024;
32 char *nextword, *cleanword;
33 wordlist *list;
34 nextword = (char*)malloc(MaxWordLength*sizeof(char));
35 list = wl_alloc();
36 while(scanf("%s",nextword) == 1)
37 {
38 cleanword = remove_punctuation(nextword);
39 if(strlen(cleanword)>0)
40 wl_increment(list,cleanword);
41 free(cleanword);
42 }
43 printf("Alphabetical List\n");
44 wl_print(list);
45 printf("\nNumerical List\n");
46 wl_print_numerical(list);
47 wl_free(list);
48 return 0;
49 }

The interface for the ADT is shown in Listing 6.5. There are several ways that the ADT could
be implemented. Note that the interface given in the header file does not show the internal
fields of the word list data type. Thus, any file which includes this header are allowed to de-
clare pointers to wordlist data types, but cannot access or modify any internal fields. The
list of words could be stored in an array, a linked list, a binary tree, or some other data struc-
ture. Also, the subroutines could be implemented in C or in some other language, including
assembly. Listing 6.6 shows an implementation in C using a linked list. Note that the function
for printing the word frequency list in numerical order has not been implemented. It will be
written in assembly language. Since the program is split into multiple files, it is a good idea
to use the make utility to build the executable program. A basic makefile is shown in List-
ing 6.7.

Listing 6.5 C header for the wordlist ADT.

1 #ifndef LIST_H
2 #define LIST_H
3
4 /**********************************************************/
5 /* Define an opaque type, named wordlist */
6 typedef struct wlist wordlist;
7
8 /**********************************************************/
9 /* wl_alloc allocates and initializes a new word list. */
10 wordlist* wl_alloc();
11
12 /**********************************************************/