C dictionary implementation

//// // C Dictionary data structure ////////////

Struct NLIST {/* Table entry :*/

Struct NLIST * Next;/* next entry in chain */

Char * Name;/* defined name */

Char * defn;/* Replacement text */

};

# Define hashsize 101

Static struct NLIST * hashtab [hashsize];/* pointer table */

/* Hash: Form hash value for string S */

Unsigned Hash (char * s)

{

Unsigned hashval;

For (hashval = 0; * s! = '\ 0'; s ++)

Hashval = * s + 31 * hashval;

Return hashval % hashsize;

}

/* Lookup: Look for S in hashtab */

Struct NLIST * Lookup (char * s)

{

Struct NLIST * NP;

For (Np = hashtab [Hash (s)]; NP! = NULL; Np = NP-> next)

If (strcmp (S, NP-> name) = 0)

Return NP;/* found */

Return NULL;/* not found */

}

Char * strdup (char *);

/* Install: Put (name, defn) in hashtab */

Struct NLIST * install (char * Name, char * defn)

{

Struct NLIST * NP;

Unsigned hashval;

If (Np = Lookup (name) = NULL) {/* not found */

NP = (struct NLIST *) malloc (sizeof (* NP ));

If (Np = NULL | (NP-> name = strdup (name) = NULL)

Return NULL;

Hashval = hash (name );

NP-> next = hashtab [hashval];

Hashtab [hashval] = NP;

} Else/* already there */

Free (void *) NP-> defn);/* free previous defn */

If (NP-> defn = strdup (defn) = NULL)

Return NULL;

Return NP;

}

Char * strdup (char * s)/* make a duplicate of S */

{

Char * P;

P = (char *) malloc (strlen (s) + 1);/* + 1 for '\ 0 '*/

If (P! = NULL)

Strcpy (P, S );

Return P;

}

/* DIC opreation interface */

Void dic_put (char * Key, char * value)

{

Install (Key, value );

}

Char * dic_value_for_key (char * key)

{

Char * ret = "";

Struct NLIST * NP = Lookup (key );

If (NP! = NULL ){

Ret = NP-> defn;

}

Return ret;

}

//// // C Dictionary data structure end ////////////

=============== Call example ==============================

Dic_put ("1", "hello ");

Printf ("value ==>>% s \ n", dic_value_for_key ("1 "));

Output:

Value ==>> hello

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