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Hashtable + shared memory

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# 8  
Old 01-04-2011
I've given you concrete examples and working library implementations. I can't give you any further detail until you give me anything to work with. You're going to have to explain your data structures and modes of access.

This is what an answer in detail might look like:

Code:
char *key="databasename";

struct database
{
  members;
  members;
  more_members;
  stuff_of_potentially_varying_size;
};

struct hash_table
{
  struct
  {
    struct database *d;
    char *key;
  } table[1024];
};


my_variable = get_hash_entry(my_table, my_key);
add_hash_entry(my_table, my_key, my_database);

This is what a monosyllabic nonanswer might look like:

Quote:
one key and data
Please, I'm trying to help you.
This User Gave Thanks to Corona688 For This Post:
andrew.paul
# 9  
Old 01-04-2011
Please post some code. As corona says, 'my crystal ball is broken today'. Otherwise you are wasting your time.
# 10  
Old 01-05-2011
Databse
Last edited by andrew.paul; 01-05-2011 at 11:45 PM..
# 11  
Old 01-05-2011
Since you refuse to tell us anything about your code, I can't help you any more than I have. Sorry. It's like trying to find the right part for a car when you don't know what the car is, and whenever I ask, you tell me is "it's green!"
Last edited by Corona688; 01-05-2011 at 11:52 AM..
# 12  
Old 01-10-2011
Hi,

how to implement a hashtable whose KEYs are strings and VLAUEs are
again hashtables.
ie key - is a string and value -is another hashtable .????

Thanks in advance...
# 13  
Old 01-11-2011
Hi crona,,

Here i am attaching my code that handle single hashtable operation.I need to modify this program that should handle nested hashtable.The hashtable whose KEYs are strings and Values are again hashtables.

Code:
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
typedef size_t hash_size;
 struct hashnode_s {
        char *key;
        void *data;
        struct hashnode_s *next;
};
typedef struct hashtbl {
        hash_size size;
        struct hashnode_s **nodes;
        hash_size (*hashfunc)(const char *);
} HASHTBL;
static char *mystrdup(const char *s)
{
    char *b;
    if(!(b=malloc(strlen(s)+1))) return NULL;
    strcpy(b, s);
    return b;
}
static hash_size def_hashfunc(const char *key)
{
    hash_size hash=0;
    while(*key) hash+=(unsigned char)*key++;
    return hash;
}
HASHTBL *hashtbl_create(hash_size size, hash_size(*hashfunc)(const char *))
{
    HASHTBL *hashtbl;
    if(!(hashtbl=malloc(sizeof(HASHTBL)))) return NULL;      if(!(hashtbl->nodes=calloc(size, sizeof(struct hashnode_s*)))) {
        free(hashtbl);
        return NULL;
    }
    hashtbl->size=size;
    if(hashfunc) hashtbl->hashfunc=hashfunc;
    else hashtbl->hashfunc=def_hashfunc;
    return hashtbl;
}

int hashtbl_insert(HASHTBL *hashtbl, const char *key, void *data)
{
    struct hashnode_s *node;
    hash_size hash=hashtbl->hashfunc(key)%hashtbl->size;    
    node=hashtbl->nodes[hash];
    while(node) {
        if(!strcmp(node->key, key)) {
            node->data=data;
            return 0;
        }
        node=node->next;
                  }
    if(!(node=malloc(sizeof(struct hashnode_s)))) return -1;
    if(!(node->key=mystrdup(key))) {
        free(node);
        return -1;
    }
    node->data=data;      /*this data should point to the another hash table*/
    node->next=hashtbl->nodes[hash];
    hashtbl->nodes[hash]=node; 
    return 0;
}
void *hashtbl_get(HASHTBL *hashtbl, const char *key)
{
    struct hashnode_s *node;
    hash_size hash=hashtbl->hashfunc(key)%hashtbl->size;
    node=hashtbl->nodes[hash];
    while(node) {
        if(!strcmp(node->key, key)) return node->data;
        node=node->next;
    }
       return NULL;
}

int main()
{

HASHTBL *hashtbl;
    if(!(hashtbl=hashtbl_create(16, NULL))) {
                fprintf(stderr, "ERROR: hashtbl_create() failed\n");
                exit(EXIT_FAILURE);
        }
 hashtbl_insert(hashtbl, "Sports", "cricket");
 printf("After insert:%s\n",hashtbl_get(hashtbl, "Sports"));
return 0;
}

Now i am trying to implement h(sports)=>hashtable,ie it should contain hash table that should contain records of cricket,football,tennis etc.....
Code:
H=>
key           data

Sports              H1
Animals           H2
H1=>
cricket               ....
football            ....
H2=> 
cat                          ......
dog                        ......

Thanks in advance
Last edited by Franklin52; 01-13-2011 at 02:53 PM.. Reason: Code tags
# 14  
Old 01-13-2011
Code:
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
typedef size_t hash_size;
 struct hashnode_s {
        char *key;
        void *data;
        struct hashnode_s *next;
};
typedef struct hashtbl {
        hash_size size;
        struct hashnode_s **nodes;
        hash_size (*hashfunc)(const char *);
} HASHTBL;
static char *mystrdup(const char *s)
{
    char *b;
    if(!(b=malloc(strlen(s)+1))) return NULL;
    strcpy(b, s);
    return b;
}
static hash_size def_hashfunc(const char *key)
{
    hash_size hash=0;
    while(*key) hash+=(unsigned char)*key++;
    return hash;
}
HASHTBL *hashtbl_create(hash_size size, hash_size(*hashfunc)(const char *))
{
    HASHTBL *hashtbl;
    if(!(hashtbl=malloc(sizeof(HASHTBL)))) return NULL;      if(!(hashtbl->nodes=calloc(size, sizeof(struct hashnode_s*)))) {
        free(hashtbl);
        return NULL;
    }
    hashtbl->size=size;
    if(hashfunc) hashtbl->hashfunc=hashfunc;
    else hashtbl->hashfunc=def_hashfunc;
    return hashtbl;
}

int hashtbl_insert(HASHTBL *hashtbl, const char *key, void *data)
{
    struct hashnode_s *node;
    hash_size hash=hashtbl->hashfunc(key)%hashtbl->size;    
    node=hashtbl->nodes[hash];
    while(node) {
        if(!strcmp(node->key, key)) {
            node->data=data;
            return 0;
        }
        node=node->next;
                  }
    if(!(node=malloc(sizeof(struct hashnode_s)))) return -1;
    if(!(node->key=mystrdup(key))) {
        free(node);
        return -1;
    }
    node->data=data;      /*this data should point to the another hash table*/
    node->next=hashtbl->nodes[hash];
    hashtbl->nodes[hash]=node; 
    return 0;
}
void *hashtbl_get(HASHTBL *hashtbl, const char *key)
{
    struct hashnode_s *node;
    hash_size hash=hashtbl->hashfunc(key)%hashtbl->size;
    node=hashtbl->nodes[hash];
    while(node) {
        if(!strcmp(node->key, key)) return node->data;
        node=node->next;
    }
       return NULL;
}

int main()
{

HASHTBL *hashtbl;
    if(!(hashtbl=hashtbl_create(16, NULL))) {
                fprintf(stderr, "ERROR: hashtbl_create() failed\n");
                exit(EXIT_FAILURE);
        }
 hashtbl_insert(hashtbl, "Sports", "cricket");
 printf("After insert:%s\n",hashtbl_get(hashtbl, "Sports"));
return 0;
}

I've put it in code tags for you to make it legible.

You don't need to modify your hash table at all to make it store hash tables. It's already capable of storing any kind of pointer.

Code:
int main()
{
    HASHTBL *outer=hashtbl_create(16, NULL);
    HASHTBL *inner=hashtbl_create(16, NULL);
    hashtbl_insert(inner, "sports", "cricket");
    hashtbl_insert(outer, "sports_table", inner);

    {
      HASHTBL *inner=hashtbl_get(outer, "sports_table");
      const char *str=hashtbl_get(inner, "sports");

      printf("got %s\n", str);
    }
}

This User Gave Thanks to Corona688 For This Post:
Scott
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