C language: hashtable

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

typedef int (*Func)(int, int);

// Zipper method 
// List nodes , Save string in data field 
typedef struct Node{
	Func func;
	struct Node *next;
}Node;

typedef struct
{
	char *funcName;
	Func func;
}funcTable;

int add(int a, int b)
{
	printf("add\n");
	return a+b;
}

int sub(int a, int b)
{
	printf("sub\n");
	return a-b;
}

// The order sheet （ Header , size ）
typedef struct HashTable{
	// List header address , It is the sequence table of the chain header nodes , Because the header node is Node *, Sequential representation Node **
	Node **data;
	int size;
}HashTable;

// Initialize linked list , The first interpolation , Of the new node next =  Incoming node 
Node *init_node(Func func, Node *head){
	Node *p = (Node *)malloc(sizeof(Node));
	p->func = func;
	p->next = head;
	return p;// Virtual head node 
}

HashTable *init_hashtable(int n){
	HashTable *h = (HashTable *)malloc(sizeof(HashTable));
	//h->size = n << 1;// To make hash table storage more efficient , Double the storage space ？？
	h->size = n;	
	h->data = (Node **)calloc(h->size, sizeof(Node *));
	return h;
}

void clear_node(Node *node){
	if (node == NULL) return;
	Node *p = node, *q;
	while(p){
		q = p->next;
		free(p);
		p = q;
	}
	free(q);//?
	return;
}

void clear_hashtable(HashTable *h){
	if (h == NULL) return;
	for (int i = 0; i < h->size; i++){
		clear_node(h->data[i]);
	}
	free(h->data);
	free(h);
	return;
}

int BKDRHash(char *str){
	int seed = 31, hash = 0;
	for (int i = 0; str[i]; i++) hash = hash * seed + str[i];
	// Ensure positive numbers 
	return hash & 0x7fffffff;
}

int insert(HashTable *h, char *str, Func func){
	int hash = BKDRHash(str);
	int ind = hash % h->size;
	printf("ind:%d\n", ind);
	h->data[ind] = init_node(func, h->data[ind]);
	return 1;
}

Func search(HashTable *h, char *str){
	int hash = BKDRHash(str);
	int ind = hash % h->size;
	Node *p = h->data[ind];
	//while (p && strcmp(str, p->str)) p = p->next;
	if (p != NULL)
	{
		return p->func;
	}	
	return NULL;
}

static funcTable gfuncTable[] = {
	{"func_add", add},
	{"test1", NULL},
	{"test2", NULL},
	{"test3", NULL},
	{"func_sub", sub},
	{"test4", NULL},
	{"test5", NULL},
	{"test6", NULL},
};
 
int main(){
	
	HashTable *h = init_hashtable(sizeof(gfuncTable)/sizeof(funcTable));
	for (int i = 0; i < sizeof(gfuncTable)/sizeof(funcTable); i++)
	{
		insert(h, gfuncTable[i].funcName, gfuncTable[i].func);
	}
	
	Func funcAdd = search(h, "func_add");
	printf("add:%d\n", funcAdd(1, 2));
	
	Func funcSub = search(h, "func_sub");
	printf("sub:%d\n", funcSub(7, 2));
	
	return 0;
}

Reference link ：https://blog.csdn.net/one_chow_chow/article/details/109561575