hash.h

linuxFedure4环境下串口编程后台运行状态机

#ifndef HASH_H
#define HASH_H

/**
 * hash.h -- a simple hash table implementation inspired by list.h
 * in the linux kernel
 * author: donald<[e-mail]>
 * everyone is permitted to use and modify this file freely
 */

/**
 * list.h modified based on <linux/list.h>, for more info. read any
 * linux source code analysis book 
 */
#include"list.h"

#define MAX_KEY_LEN 40

struct hash_table{
	/**
	 * the hash table data struct is nothing but a bunch of
	 * buckets, which are simply linked lists 
	 */
	struct list_head *buckets;
	/** 
	 * we store all entries in the hash table in the list 'all',
	 * so that we can easily release them in a single iteration
	 */
	struct list_head all;
	unsigned int n; /* number of buckets */
};

/* 
 * every hash table entry must include this struct as a member, see
 * struct list_head to comprend the mechanism better 
 */
struct hash_table_entry{
	/**/
	unsigned char key[MAX_KEY_LEN];
	/* list of hash table entries in the same bucket */
	struct list_head bucket;
	/* list of all hash table entries in the same hash table */
	struct list_head all;
};

/* create an empty hash_table with specified number of buckets */
struct hash_table *
hash_table_create(int bucket_num);

/* add an entry into existing hash table */
void 
hash_table_add(struct hash_table *table, struct hash_table_entry* entry);

/* retrieve an entry with specified key from existing hash table */
struct hash_table_entry *
hash_table_get(struct hash_table *table, const unsigned char *key);

/* release an hash table, note that entries must be released manually */
void
hash_table_free(struct hash_table *table);

/* to comprehend how this works, refer to list_entry in list.h */
#define hash_entry(ptr, type, member) \
	((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))

/* to comprehend how this works, refer to list_for_each in list.h */
#define hash_for_each(pos, hash_table) \
	for(pos=list_entry((hash_table)->all.next, struct hash_table_entry, all);\
	    pos!=list_entry(&(hash_table)->all, struct hash_table_entry, all);\
	    pos=list_entry(pos->all.next, struct hash_table_entry, all))

#endif /* #ifndef HASH_H */