1. hash_db.h
1 #ifndef _HASH_DB_H
2 #define _HASH_DB_H
3
4 #include "slist.h"
5
6 typedef unsigned int (*hash_func_t) (const void *key); //哈希函数类型，返回值为整数，参数为关键字
7 struct _hash_db
8 {
9 slist_head_t *p_head; //指向数组首地址
10 unsigned int size; //数组成员数
11 unsigned int value_len; //一条记录的长度
12 unsigned int key_len; //关键字的长度
13 hash_func_t pfn_hash; //哈希函数
14 };
15 typedef struct _hash_db hash_db_t; //指向哈希表对象的指针类型
16
17 int hash_db_init(hash_db_t *p_hash, //哈希表初始化
18 unsigned int size,
19 unsigned int key_len,
20 unsigned int value_len,
21 hash_func_t pfn_hash);
22
23 int hash_db_add(hash_db_t *p_hash, const void *key,const void *value); //添加记录
24 int hash_db_del(hash_db_t *p_hash, const void *key); //删除记录
25 int hash_db_search(hash_db_t *p_hash, const void *key, void *value); //查找记录
26 int hash_db_deinit(hash_db_t *p_hash); //解初始化
27
28 #endif2. hash_db.c
1 #include "hash_db.h"
2 #include <stdlib.h>
3 #include <string.h>
4
5 /* 寻找结点的上下文，仅内部使用 */
6 struct _node_find_ctx
7 {
8 const void *key; //查找关键字
9 unsigned int key_len; //关键字长度
10 slist_node_t *p_result; //用于存储查找到的结点
11 };
12
13 /**
14 * @brief 遍历链表的回调函数，查找指定结点
15 */
16 static int __hash_db_node_find (void *p_arg, slist_node_t *p_node)
17 {
18 struct _node_find_ctx *p_info = (struct _node_find_ctx *)p_arg; //用户参数为寻找结点的上下文
19 char *p_mem = (char *)p_node + sizeof(slist_node_t); //关键字存储在结点之后
20
21 if (memcmp(p_mem, p_info->key, p_info->key_len) == 0)
22 {
23 p_info->p_result = p_node;
24 return -1; //找到该结点，终止遍历
25 }
26 return 0;
27 }
28
29
30 /**
31 * @brief 哈希表初始化
32 */
33 int hash_db_init(hash_db_t *p_hash,
34 unsigned int size,
35 unsigned int key_len,
36 unsigned int value_len,
37 hash_func_t pfn_hash)
38 {
39 int i;
40 if ((p_hash == NULL) || (pfn_hash == NULL))
41 {
42 return -1;
43 }
44 p_hash->p_head = (slist_head_t *)malloc(size * sizeof(slist_head_t));
45 if (p_hash->p_head == NULL)
46 {
47 return -1;
48 }
49 for (i = 0; i < size; i++)
50 {
51 slist_init(&p_hash->p_head[i]);
52 }
53 p_hash->size = size;
54 p_hash->key_len = key_len;
55 p_hash->value_len = value_len;
56 p_hash->pfn_hash = pfn_hash;
57 return 0;
58 }
59
60 int hash_db_add(hash_db_t *p_hash, const void *key, const void *value)
61 {
62 int idx = p_hash -> pfn_hash(key); //使用哈希函数通过关键字得到哈希值
63 /* 分配内存，存储链表结点+关键字+记录 */
64 char *p_mem = (char *)malloc(sizeof(slist_node_t) + p_hash -> key_len + p_hash -> value_len);
65 if (p_mem == NULL)
66 {
67 return -1;
68 }
69 memcpy(p_mem + sizeof(slist_node_t), key, p_hash -> key_len); //存储关键字
70 memcpy(p_mem + sizeof(slist_node_t) + p_hash->key_len, value, p_hash->value_len); //存储记录
71 return slist_add_head(&p_hash -> p_head[idx], (slist_node_t *)p_mem); //将结点加入链表
72 }
73
74 int hash_db_del(hash_db_t *p_hash, const void *key)
75 {
76 int idx = p_hash->pfn_hash(key); //得到关键字对应哈希表的索引
77 struct _node_find_ctx info = {key, p_hash->key_len, NULL}; //设置遍历链表的上下文信息
78 slist_foreach(&p_hash->p_head[idx], __hash_db_node_find, &info); //遍历，寻找关键字对应的结点
79 if (info.p_result != NULL)
80 {
81 slist_del(&p_hash->p_head[idx], info.p_result); //从链表中删除该结点
82 free(info.p_result); //释放结点空间
83 return 0;
84 }
85 return -1;
86 }
87
88 int hash_db_search(hash_db_t *p_hash, const void *key, void *value)
89 {
90 int idx = p_hash->pfn_hash(key); ////得到关键字对应哈希表的索引
91 struct _node_find_ctx info = {key, p_hash->key_len, NULL}; //设置遍历链表的上下文信息
92 slist_foreach(&p_hash->p_head[idx], __hash_db_node_find, &info); //遍历，寻找关键字对应的结点
93
94 if (info.p_result != NULL)
95 { //找到对应结点，将存储的记录值拷贝到用户提供的空间中
96 memcpy(value, (char *)info.p_result+sizeof(slist_node_t)+p_hash->key_len, p_hash->value_len);
97 return 0;
98 }
99 return -1;
100 }
101
102 int hash_db_deinit(hash_db_t *p_hash)
103 {
104 int i;
105 slist_node_t *p_node;
106 for (i = 0; i < p_hash->size; i++)
107 { //释放哈希表中各个表项中存储的所有结点
108
109 while (slist_begin_get(&p_hash->p_head[i]) != slist_end_get(&p_hash->p_head[i]))
110 {
111 p_node = slist_begin_get(&p_hash->p_head[i]);
112 slist_del(&p_hash->p_head[i], p_node); //释放第一个结点
113 free(p_node);
114 }
115 }
116 free(p_hash->p_head); //释放链表头结点数组空间
117 return 0;
118 }3. demo
1 #include <stdio.h>
2 #include <stdlib.h>
3 #include "hash_db.h"
4
5 typedef struct _student
6 {
7 char name[10];
8 char sex;
9 float height, weight;
10 } student_t;
11
12 int db_id_to_idx(unsigned char id[6]) //通过ID得到数组索引
13 {
14 int i;
15 int sum = 0;
16 for (i = 0; i < 6; i++)
17 {
18 sum += id[0];
19 }
20 return sum % 250;
21 }
22
23 int student_info_generate(unsigned char *p_id, student_t *p_student)
24 {
25 int i;
26 for (i = 0; i < 6; i++)
27 { //随机产生一个学号
28 p_id[i] = rand();
29 }
30 for (i = 0; i < 9; i++)
31 {
32 p_student->name[i] = (rand() % ('z' - 'a')) + 'a';
33 }
34 p_student->name[i]= '\0';
35 p_student->sex = (rand() & 0x01) ? 'F' : 'M';
36 p_student->height = (float)rand() / rand();
37 p_student->weight = (float)rand() / rand();
38 return 0;
39 }
40
41 int main(void)
42 {
43 student_t stu;
44 unsigned char id[6];
45 int i;
46 hash_db_t hash_students;
47
48 hash_db_init(&hash_students, 250, 6, sizeof(student_t), (hash_func_t)db_id_to_idx);
49
50 for(i = 0; i < 100; i++)
51 { //添加100个学生信息
52 student_info_generate(id, &stu); //设置学生的信息，当前一随机数作为测试
53 if (hash_db_search(&hash_students, id, &stu) == 0)
54 { //查找到该ID已存在的学生记录
55 printf("该ID的记录已存在！\n");
56 continue;
57 }
58 printf("增加记录：ID : %02x%02x%02x%02x%02x%02x ",id[0],id[1],id[2],id[3],id[4],id[5]);
59 printf("ؑ信息：%s %c %.2f %.2f\n", stu.name, stu.sex, stu.height, stu.weight);
60 if (hash_db_add(&hash_students, id, &stu) != 0)
61 {
62 printf("添加失败");
63 }
64 }
65 printf("查找ID为：%02x%02x%02x%02x%02x%02x的信息\n",id[0],id[1],id[2],id[3],id[4],id[5]);
66 if (hash_db_search(&hash_students, id, &stu) == 0)
67 {
68 printf("学生信息：%s %c %.2f %.2f\n", stu.name, stu.sex, stu.height, stu.weight);
69 }
70 else
71 {
72 printf("未找到该ID的记录\n");
73 }
74 hash_db_deinit(&hash_students);
75 return 0;
76 }
来源：oschina
链接：https://my.oschina.net/u/4386395/blog/3234770