C - Separate Chaining Hash Table - Output and Space Issues - c

Question

so basically I wrote a program to initialize, insert, and output the whole hash table. I thought I did pretty good, but there's many issues.
First issue being, some names are displayed with an additional weird character, why??
Second issue being, I can only input a size parameter (for initialize(size) function) of <8. Anything above 7 will output "Out of Space!" but why?? I thought I managed the space pretty well from what I was taught at uni:((
Please help!
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct list_node *node_ptr;
struct list_node
{
node_ptr next;
char *key;
char *value;
};
typedef node_ptr LIST;
typedef node_ptr position;
struct hash_table
{
LIST *list_ptr_arr;
unsigned int table_size;
};
typedef struct hash_table *HASHTABLE;
unsigned long long int
hash(const char *key, unsigned int hash_size)
{
unsigned long long int hash;
for(int i = 0; key[i]; i++)
{
hash = (hash<<32)+key[i];
}
return (hash%hash_size);
}
unsigned int
next_prime(int number)
{
int j;
for(int i = number; ; i++)
{
for(j = 2; j<i; j++)
{
if(i%j == 0){break;}
}
if(i==j){return j;}
}
}
HASHTABLE
initialize(unsigned int table_size)
{
HASHTABLE H;
H = (HASHTABLE) malloc(sizeof(struct hash_table));
if(H==NULL){printf("Out of Space!"); return 0;}
H->table_size = next_prime(table_size);
H->list_ptr_arr = (position*) malloc(sizeof(LIST)*H->table_size);
if(H->list_ptr_arr==NULL){printf("Out of Space!"); return 0;}
H->list_ptr_arr = (LIST*) malloc(sizeof(struct list_node)*H->table_size);
for(unsigned int i = 0; i<H->table_size; i++)
{
if(H->list_ptr_arr[i]==NULL){printf("Out of Space!"); return 0;}
H->list_ptr_arr[i]=NULL;
}
return H;
}
position
set(const char *key, const char *value)
{
position entry = (position) malloc(sizeof(struct list_node));
entry->value = (char*) malloc(strlen(value)+1);
entry->key = (char*) malloc(strlen(key)+1);
strncpy(entry->key,key,strlen(key));
strncpy(entry->value,value,strlen(value));
entry->next = NULL;
return entry;
}
void
insert(const char *key, const char *value, HASHTABLE H)
{
unsigned int slot = hash(key, H->table_size);
node_ptr entry = H->list_ptr_arr[slot];
node_ptr prev;
if(entry==NULL)
{
H->list_ptr_arr[slot] = set(key, value);
return;
}
while(entry!=NULL)
{
if(strcmp(entry->key, key)==0)
{
free(entry->value);
entry->value = malloc(strlen(value)+1);
strncpy(entry->value,value,strlen(value));
return;
}
prev = entry;
entry = prev->next;
}
prev->next = set(key, value);
}
void
dump(HASHTABLE H)
{
for(unsigned int i = 0; i<H->table_size; i++)
{
position entry = H->list_ptr_arr[i];
if(H->list_ptr_arr[i]==NULL){continue;}
printf("slot[%d]: ", i);
for(;;)
{
printf("%s|%s -> ", entry->key, entry->value);
if(entry->next == NULL)
{
printf("NULL");
break;
}
entry = entry->next;
}
printf("\n");
}
}
int main()
{
HASHTABLE H = initialize(7);
insert("name1", "David", H);
insert("name2", "Lara", H);
insert("name3", "Slavka", H);
insert("name4", "Ivo", H);
insert("name5", "Radka", H);
insert("name6", "Kvetka", H);
dump(H);
return 0;
}
Then I tried to change it up a bit:
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct list_node *node_ptr;
struct list_node
{
node_ptr next;
char *key;
char *value;
};
typedef node_ptr LIST;
typedef node_ptr position;
struct hash_table
{
LIST *list_ptr_arr;
unsigned int table_size;
};
typedef struct hash_table *HASHTABLE;
unsigned long long int
hash(const char *key, unsigned int hash_size)
{
unsigned long long int hash;
for(int i = 0; key[i]; i++)
{
hash = (hash<<32)+key[i];
}
return (hash%hash_size);
}
unsigned int
next_prime(int number)
{
int j;
for(int i = number; ; i++)
{
for(j = 2; j<i; j++)
{
if(i%j == 0){break;}
}
if(i==j){return j;}
}
}
HASHTABLE
initialize(unsigned int table_size)
{
HASHTABLE H;
H = (HASHTABLE) malloc(sizeof(struct hash_table));
if(H==NULL){printf("Out of Space!1"); return 0;}
H->table_size = next_prime(table_size);
H->list_ptr_arr = (position*) malloc(sizeof(LIST)*H->table_size);
if(H->list_ptr_arr==NULL){printf("Out of Space!2"); return 0;}
H->list_ptr_arr = (LIST*) malloc(sizeof(struct list_node)*H->table_size);
for(unsigned int i = 0; i<H->table_size; ++i)
{
if(H->list_ptr_arr[i]==NULL){printf("Out of Space!3"); return 0;}
H->list_ptr_arr[i]->value="HEAD";
H->list_ptr_arr[i]->next=NULL;
}
return H;
}
void
insert(const char *key, const char *value, HASHTABLE H)
{
unsigned int slot = hash(key, H->table_size);
LIST entry = H->list_ptr_arr[slot], newNode;
newNode = (position) malloc(sizeof(struct list_node));
if(newNode==NULL){printf("Out of Space4!"); return;}
newNode->next = entry->next;
strncpy(newNode->key,key,strlen(key));
strncpy(newNode->value,value,strlen(value));
entry->next = newNode;
}
void
dump(HASHTABLE H)
{
for(unsigned int i = 0; i<H->table_size; i++)
{
position entry = H->list_ptr_arr[i];
position p = entry->next;
if(p==NULL){continue;}
printf("slot[%d]: ", i);
for(;;)
{
printf("%s|%s -> ", p->key, p->value);
if(p->next == NULL)
{
printf("NULL");
break;
}
p = p->next;
}
printf("\n");
}
}
int main()
{
HASHTABLE H = initialize(4);
insert("name1", "David", H);
insert("name2", "Lara", H);
insert("name3", "Slavka", H);
insert("name4", "Ivo", H);
insert("name5", "Radka", H);
insert("name6", "Kvetka", H);
dump(H);
return 0;
}
Thank you!

Answer 1

I modified the second piece of code, it runs correctly on my computer.
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_SIZE 256
// typedefing struct list_node multiple times is confusing, so I remove these typedefs
struct list_node {
struct list_node *next;
// strings need storage space in the memory,
// declaring key and value as array here can save some calls to malloc()
char key[MAX_SIZE];
char value[MAX_SIZE];
};
struct hash_table {
struct list_node **list_ptr_arr;
unsigned int table_size;
};
// it's better not to hide pointer type using typedef
typedef struct hash_table HASHTABLE;
unsigned long long int hash(const char *key, unsigned int hash_size) {
// hash is not initialized originally (the value is choosed randomly)
unsigned long long int hash = 5;
for (int i = 0; key[i]; i++) {
hash = (hash << 32) + key[i];
}
return (hash%hash_size);
}
unsigned int next_prime(int number) {
int j;
for (int i = number; ; i++) {
for (j = 2; j < i; j++) {
if (i%j == 0) { break; }
}
if (i == j) { return j; }
}
}
HASHTABLE *initialize(unsigned int table_size) {
HASHTABLE *H;
// you don't need to type cast malloc() result in C
H = malloc(sizeof(*H));
H->table_size = next_prime(table_size);
// I suppose list_ptr_arr is a pointer to an array of struct list_node * object
H->list_ptr_arr = malloc(sizeof(*(H->list_ptr_arr)) * H->table_size);
for (unsigned int i = 0; i < H->table_size; ++i) {
// malloc() for H->list_ptr_arr only allocated area for struct list_node * array, the struct list_node pointed to is not allocated yet, so malloc() here
H->list_ptr_arr[i] = malloc(sizeof(*(H->list_ptr_arr[i])));
strcpy(H->list_ptr_arr[i]->value, "HEAD");
H->list_ptr_arr[i]->next = NULL;
}
return H;
}
void insert(const char *key, const char *value, HASHTABLE *H) {
unsigned int slot = hash(key, H->table_size);
struct list_node *entry = H->list_ptr_arr[slot], *newNode;
newNode = malloc(sizeof(*newNode));
newNode->next = entry->next;
// strlen() doesn't count the '\0', just use strcpy here
strcpy(newNode->key, key);
strcpy(newNode->value, value);
entry->next = newNode;
}
void dump(HASHTABLE *H) {
for (unsigned int i = 0; i < H->table_size; i++) {
struct list_node *entry = H->list_ptr_arr[i];
struct list_node *p = entry->next;
if (p == NULL) { continue; }
printf("slot[%d]: ", i);
for (;;) {
printf("%s|%s -> ", p->key, p->value);
if (p->next == NULL) {
printf("NULL");
break;
}
p = p->next;
}
printf("\n");
}
}
int main() {
HASHTABLE *H = initialize(4);
insert("name1", "David", H);
insert("name2", "Lara", H);
insert("name3", "Slavka", H);
insert("name4", "Ivo", H);
insert("name5", "Radka", H);
insert("name6", "Kvetka", H);
dump(H);
return 0;
}
P.S. Don't forget to free the hashtable.