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

// キーの長さの最大値
#define MAX_KEY_SIZE (128)

// ハッシュの領域の大きさ
#define MAX_HASH_SIZE (4)

struct Hash{
	char key[MAX_KEY_SIZE];
	void *val;
};


unsigned int calcHash(const unsigned char *key){
	unsigned int calc = 0;
	while(*key) calc += (calc<<5) + *key++;
	return ((calc >> 5) + calc) % MAX_HASH_SIZE;
}

unsigned int rehash(unsigned int calc){
	return (calc+1) % MAX_HASH_SIZE;
}

void clearHash(struct Hash *hash){
	hash->key[0] = '\0';
	hash->val = 0;
}

void initHash(struct Hash *hash){
	int i=0;
	while(i++<MAX_HASH_SIZE) clearHash(hash+i);
}


void setHash(struct Hash *hash, const char *key, void *val){
	int i=1;
	unsigned int calc = calcHash(key);
	
	if(*key == '\0'){ puts("NULL KEY error(set)"); exit(0); }
	
	do{
		if(strncmp(hash[calc].key, key, MAX_KEY_SIZE) == 0 || hash[calc].key[0] == '\0') break;
		calc = rehash(calc);
	}while(i++ < MAX_HASH_SIZE);
	
	if(i>=MAX_HASH_SIZE){
		puts("error"); exit(0);
	}
	
	strncpy(hash[calc].key, key, MAX_KEY_SIZE);
	hash[calc].val = val;
}

void * getHash(struct Hash *hash, const char *key){
	int i=1;
	unsigned int calc = calcHash(key);
	
	if(*key == '\0'){ puts("NULL KEY error(get)"); exit(0); }
	
	do{
		if(strncmp(hash[calc].key, key, MAX_KEY_SIZE) == 0) break;
		calc = rehash(calc);
	}while(i++ < MAX_HASH_SIZE);
	
	if(i>=MAX_HASH_SIZE){
		printf("'%s' is not entry.\n", key); return 0;
	}
	
	return hash[calc].val;
}


#define HV(V) ((void *)(V))

int main(int argc, char **argv){
	struct Hash hash[MAX_HASH_SIZE];
	
	initHash(hash);
	
	setHash(hash, "a", HV(100));
	printf("a: %d\n", getHash(hash, "a")); // 100
	
	setHash(hash, "a", HV(200)); // 値を変えてみる
	printf("a: %d\n", getHash(hash, "a"));
	
	setHash(hash, "string", HV("string string")); // 文字列もいけます
	printf("string: %s\n", getHash(hash, "string"));
	
	return 0;
}

a: 100
a: 200
string: string string