1g3EWFfr

1/*!
2 * \file use_hash_table.c
3 * \brief Example code of using a hash table for key-value pairs.
4 */
5
6#include <glib.h>
7
8/*!
9 * \brief Create a hash table from file.
10 */
11int
12create_hash_table_from_file (gchar *filename)
13{
14    FILE *fp
15    char buf[1024];
16
17    /* Intialise the hash table. */
18    table = g_hash_table_new (g_str_hash, g_str_equal);
19    /* Just a standard way to open files. */
20    fp = fopen (filename, "r");
21    /* If file does not exist, exit. */
22    if (!fp)
23    {
24        exit (1);
25    }
26    /* Read file line by line. */
27    while (fgets (buf, sizeof (buf), fp))
28    {
29        char *key;
30        char *value;
31        /* Get the first and the second field. */
32        key = strtok (buf, "\t");
33        if (!key) continue;
34        value = strtok (NULL, "\t");
35        if (!value) continue;
36        /* Look up the table for an existing key.
37         * If it exists replace it by inserting the new ke-value pair and
38         * freeing the old key-value pair */
39        char *old_key;
40        char *old_value;
41        /* Try looking up this key. */
42        if (g_hash_table_lookup_extended (table, key, &old_key, &old_value))
43        {
44            /* Insert the new value */
45            g_hash_table_insert (table, g_strdup (key), g_strdup (value));
46            /* Just free the key and value */
47            g_free (old_key);
48            g_free (old_value);
49        }
50        else
51        {
52            /* Insert into our hash table it is not a duplicate. */
53            g_hash_table_insert (table, g_strdup (key), g_strdup (value));
54        }
55    }
56    /* Close the file when done. */
57    fclose (fp);
58    return (EXIT_SUCCESS);
59}
60
61/*!
62 * \brief Dispose of the hash table.
63 */
64int
65destroy_hash_table ()
66{
67    g_hash_table_destroy (table);
68    return (EXIT_SUCCESS);
69}
70
71
72/*!
73 * \brief Remove the entry with the passed key from the hash table.
74 */
75int
76remove_entry (char *key)
77{
78    int result = EXIT_FAILURE;
79    char *old_key;
80    char *old_value;
81    /* Try looking up this key */
82    if (g_hash_table_lookup_extended (table, key, &old_key, &old_value))
83    {
84        /* Remove the entry in the hash table. */
85        g_hash_table_remove (table, key);
86        /* Just free the key and value. */
87        g_free( old_key);
88        g_free (old_value);
89        result = EXIT_SUCCESS;
90    }
91    return (result);
92}
93
94
95/*!
96 * \brief Free a key-value pair inside the hash table.
97 */
98static void
99free_a_hash_table_entry (gpointer key, gpointer value, gpointer user_data)
100{
101    g_free (key);
102    g_free (value);
103}
104
105
106/*!
107 * \brief Free all key-value entries in the hash table.
108 */
109int
110free_all_key_value_entries ()
111{
112    g_hash_table_foreach (table, free_a_hash_table_entry, NULL);
113}
114
115
116static gboolean
117remove_keys_with_A (gpointer key, gpointer value, gpointer user_data)
118{
119    char *char_value = (char *) value;
120
121    if (char_value[0] == 'A')
122    {
123        g_free (key);
124        g_free (value);
125        return TRUE;
126    }
127    else
128    {
129        return FALSE;
130    }
131}
132
133
134/*!
135 * \brief Let's have a main function.
136 */
137int
138main ()
139{
140    GHashTable *table;
141    int deleted;
142    gchar file_name = test.txt";
143
144    create_hash_table_from_file (file_name);
145    /* Do something with the hash table here. */
146    deleted = g_hash_table_foreach_remove (table, remove_keys_with_A, NULL);
147    printf ("Deleted %d items!\n", deleted);
148    free_all_key_value_entries ();
149    destroy_hash_table ();
150}
151
152
153/* EOF */