C语言实现的简单HashTable - jwHash
xpkdi
10年前
你可创建一个HashTable，然后往其添加字符串，long ints, doubles 和指针，keyed是strings或long ints。
然后通过get函数取得strings, long ints, doubles 和 pointers。
Data Structures
Hash Table
typedef struct jwHashTable jwHashTable; struct jwHashTable { jwHashEntry **bucket; // pointer to array of buckets size_t buckets; size_t bucketsinitial; // if we resize, may need to hash multiple times HASHRESULT lastError; #ifdef HASHTHREADED volatile int *locks; // array of locks volatile int lock; // lock for entire table #endif }; Hash Entry
typedef struct jwHashEntry jwHashEntry; struct jwHashEntry { union { char *strValue; double dblValue; int intValue; } key; HASHVALTAG valtag; union { char *strValue; double dblValue; int intValue; void *ptrValue; } value; jwHashEntry *next; }; API
Creating a Hash Table
jwHashTable *create_hash( size_t buckets ); void *delete_hash( jwHashTable *table ); // clean up all memory
Storing by String Key
HASHRESULT add_str_by_str( jwHashTable*, char *key, char *value ); HASHRESULT add_int_by_str( jwHashTable*, char *key, long int value ); HASHRESULT add_dbl_by_str( jwHashTable*, char *key, double value ); HASHRESULT add_ptr_by_str( jwHashTable*, char *key, void *value );
Deleting by String
HASHRESULT del_by_str( jwHashTable*, char *key );
Retrieving by String
HASHRESULT get_str_by_str( jwHashTable *table, char *key, char **value ); HASHRESULT get_int_by_str( jwHashTable *table, char *key, int *i ); HASHRESULT get_dbl_by_str( jwHashTable *table, char *key, double *val ); HASHRESULT get_ptr_by_str( jwHashTable *table, char *key, void **val );
[Similar for long int keys]
TODO
- Support multi-threading, -- this started, and implemented for the test
- Implement clean-up,
- Implement re-hashing to a larger hash table,
- Implement a callback to allow iterating through keys, values
Examples
Example 1 - Save and Retrieve Some Values
// Test hashing by string char * strv1 = "Jonathan"; char * strv2 = "Zevi"; char * strv3 = "Jude"; char * strv4 = "Voldemort"; add_str_by_str(table,"oldest",strv1); add_str_by_str(table,"2ndoldest",strv2); add_str_by_str(table,"3rdoldest",strv3); add_str_by_str(table,"4tholdest",strv4); char * sstrv1; get_str_by_str(table,"oldest",&sstrv1); char * sstrv2; get_str_by_str(table,"2ndoldest",&sstrv2); char * sstrv3; get_str_by_str(table,"3rdoldest",&sstrv3); char * sstrv4; get_str_by_str(table,"4tholdest",&sstrv4); printf("got strings:\noldest->%s \n2ndoldest->%s \n3rdoldest->%s \n4tholdest->%s\n", sstrv1,sstrv2,sstrv3,sstrv4); Example 2 - Write and Read Key Value Pairs on Multiple Threads
#define NUMTHREADS 8 #define HASHCOUNT 1000000 typedef struct threadinfo {jwHashTable *table; int start;} threadinfo; void * thread_func(void *arg) { threadinfo *info = arg; char buffer[512]; int i = info->start; jwHashTable *table = info->table; free(info); for(;i<HASHCOUNT;i+=NUMTHREADS) { sprintf(buffer,"%d",i); add_int_by_str(table,buffer,i); } } int thread_test() { // create jwHashTable * table = create_hash(HASHCOUNT>>2); // hash a million strings into various sizes of table struct timeval tval_before, tval_done1, tval_done2, tval_writehash, tval_readhash; gettimeofday(&tval_before, NULL); int t; pthread_t * threads[NUMTHREADS]; for(t=0;t<NUMTHREADS;++t) { pthread_t * pth = malloc(sizeof(pthread_t)); threads[t] = pth; threadinfo *info = (threadinfo*)malloc(sizeof(threadinfo)); info->table = table; info->start = t; pthread_create(pth,NULL,thread_func,info); } for(t=0;t<NUMTHREADS;++t) { pthread_join(*threads[t], NULL); } gettimeofday(&tval_done1, NULL); int i,j; int error = 0; char buffer[512]; for(i=0;i<HASHCOUNT;++i) { sprintf(buffer,"%d",i); get_int_by_str(table,buffer,&j); if(i!=j) { printf("Error: %d != %d\n",i,j); error = 1; } } if(!error) { printf("No errors.\n"); } gettimeofday(&tval_done2, NULL); timersub(&tval_done1, &tval_before, &tval_writehash); timersub(&tval_done2, &tval_done1, &tval_readhash); printf("\n%d threads.\n",NUMTHREADS); printf("Store %d ints by string: %ld.%06ld sec, read %d ints: %ld.%06ld sec\n",HASHCOUNT, (long int)tval_writehash.tv_sec, (long int)tval_writehash.tv_usec,HASHCOUNT, (long int)tval_readhash.tv_sec, (long int)tval_readhash.tv_usec); return 0; }