aboutsummaryrefslogtreecommitdiff
path: root/ht.c
blob: d23e141d6d40002e915b48595ea6b912bc3974aa (plain)
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
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
#include "ht.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define SIZE 1024

struct node {
    char        *key;
    void        *val;
    struct node *next;
};

struct hash_table {
    struct node **vals;
    int           max_size;
    int           size;

    int          curr_index;
    struct node *curr_node;
    bool         iterating;
};

static unsigned long djb2_hash(char *str)
{
    unsigned long hash = 5381;
    int           c;

    // hash * 33 + c
    while ((c = *str++)) hash = ((hash << 5) + hash) + c;

    return hash;
}

ht_t *ht_create(void)
{
    ht_t *h       = malloc(sizeof(ht_t));
    h->max_size   = SIZE;
    h->size       = 0;
    h->vals       = malloc(sizeof(struct node) * h->max_size);
    h->curr_index = 0;
    h->curr_node  = NULL;
    h->iterating  = false;

    return h;
}

void ht_destroy(ht_t *h)
{
    // only destroy if h isn't NULL
    if (h) {
        // only destroy vals if it isn't NULL
        if (h->vals) {
            // iterate through the hash values
            for (int i = 0; i < h->max_size; ++i) {
                // iterate through the linked list and remove the value
                struct node *curr = h->vals[i];
                struct node *prev;
                while (curr) {
                    prev = curr;
                    curr = curr->next;
                    free(prev->key);
                    free(prev);
                }
            }
            free(h->vals);
        }
        free(h);
    }
}

void *ht_find(ht_t *h, char *key)
{
    unsigned int hash = djb2_hash(key) % h->max_size;

    // exit early if hash isn't in table
    if (!h->vals[hash])
        return NULL;

    // iterate through values stored at `hash`; exit early if found
    struct node *curr = h->vals[hash];
    while (curr) {
        if (strcmp(key, curr->key) == 0)
            return curr->val;
        curr = curr->next;
    }

    return NULL;
}

void ht_insert(ht_t *h, char *key, void *val)
{
    unsigned int hash = djb2_hash(key) % h->max_size;

    // create a node
    int len          = strlen(key);
    struct node *new = malloc(sizeof(struct node));
    new->key         = malloc(sizeof(char) * (len + 1));
    for (int i = 0; i < len; ++i) {
        new->key[i] = key[i];
    }
    new->key[len] = 0;
    new->val      = val;

    // insert node at beginning of list
    if (h->vals[hash]) {
        new->next = h->vals[hash];
    }
    h->vals[hash] = new;

    ++(h->size);
}

void ht_delete(ht_t *h, char *key)
{
    unsigned int hash = djb2_hash(key) % h->max_size;

    if (!h->vals[hash])
        return; // exit if the hash is not found

    // remove the key from the front of the list if it's there
    if (strcmp(key, h->vals[hash]->key) == 0) {
        struct node *temp = h->vals[hash];
        h->vals[hash]     = h->vals[hash]->next;
        free(temp->key);
        free(temp);
    } else {
        // iterate through list and remove once a match is found
        struct node *prev = h->vals[hash];
        struct node *curr = h->vals[hash]->next;
        while (curr) {
            if (strcmp(key, curr->key) == 0) {
                prev->next = curr->next;
                free(curr->key);
                free(curr);
                return;
            }

            prev = curr;
            curr = curr->next;
        }
    }
}

int ht_size(ht_t *h)
{
    return h->size;
}

void ht_iter_init(ht_t *h)
{
    h->curr_index = 0;
    h->curr_node  = h->vals[0];
}

void *ht_iter_next(ht_t *h)
{
    // return NULL if we've reached the end
    if (!h->curr_node && h->curr_index >= h->max_size)
        return NULL;

    if (!h->curr_node) {
        // look for next index with node if current node is NULL
        while (!h->curr_node) {
            h->curr_node = h->vals[h->curr_index++];
            if (h->curr_index >= h->max_size)
                return NULL;
        }
        return h->curr_node->val;
    } else {
        // move to the next node
        h->curr_node = h->curr_node->next;
        if (h->curr_node)
            return h->curr_node->val;

        // look for next index with node if necessary
        while (!h->curr_node) {
            h->curr_node = h->vals[h->curr_index++];
            if (h->curr_index >= h->max_size)
                return NULL;
        }
        return h->curr_node->val;
    }
}