-
Notifications
You must be signed in to change notification settings - Fork 4
/
queue_example.c
112 lines (99 loc) · 2.78 KB
/
queue_example.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
// gcc queue_example.c -o queue_example
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "queue.h" // queue taken from FreeBSD 10
// Note the standard typedef of struct node to node_t for convenient use but
// the TAILQ_ENTRY macro uses the struct name.
typedef struct node
{
char c;
TAILQ_ENTRY(node) nodes;
} node_t;
// This typedef creates a head_t that makes it easy for us to pass pointers to
// head_t without the compiler complaining.
typedef TAILQ_HEAD(head_s, node) head_t;
// Takes a string and puts in in the queue on character at a time.
static void _fill_queue(head_t * head, const char * string)
{
int c = 0;
for (c = 0; c < strlen(string); ++c)
{
struct node * e = malloc(sizeof(struct node));
if (e == NULL)
{
fprintf(stderr, "malloc failed");
exit(EXIT_FAILURE);
}
e->c = string[c];
TAILQ_INSERT_TAIL(head, e, nodes);
e = NULL;
}
}
// Removes all of the elements from the queue before free()ing them.
static void _free_queue(head_t * head)
{
struct node * e = NULL;
while (!TAILQ_EMPTY(head))
{
e = TAILQ_FIRST(head);
TAILQ_REMOVE(head, e, nodes);
free(e);
e = NULL;
}
}
// Prints the queue by traversing the queue forwards.
static void _print_queue(head_t * head)
{
struct node * e = NULL;
TAILQ_FOREACH(e, head, nodes)
{
printf("%c", e->c);
}
}
// Prints the queue while traversing the queue backwards.
static void _print_queue_backwards(head_t * head)
{
struct node * e = NULL;
TAILQ_FOREACH_REVERSE(e, head, head_s, nodes)
{
printf("%c", e->c);
}
}
// Safely removes the vowels from the queue
static void _remove_vowels(head_t * head)
{
struct node * e = NULL;
struct node * next = NULL;
TAILQ_FOREACH_SAFE(e, head, nodes, next)
{
if (e->c == 'a' || e->c == 'A' || e->c == 'e' || e->c == 'E' ||
e->c == 'i' || e->c == 'I' || e->c == 'o' || e->c == 'O' ||
e->c == 'u' || e->c == 'U')
{
TAILQ_REMOVE(head, e, nodes);
free(e);
e = NULL;
}
}
}
int main (int arc, char * argv [])
{
// declare the head
head_t head;
TAILQ_INIT(&head); // initialize the head
// fill the queue with "Hello World\n"
_fill_queue(&head, "Hello World!\n");
printf("Forwards: ");
_print_queue(&head); // prints "Hello World!\n"
printf("Backwards: ");
_print_queue_backwards(&head); // prints "\n!dlroW olleH"
// remove the vowels from the queue
_remove_vowels(&head);
printf("\nForwards, vowels removed: ");
_print_queue(&head); // prints "Hll Wrld!\n"
// free the queue
_free_queue(&head);
_print_queue(&head); // prints ""
return EXIT_SUCCESS;
}