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Title A hashtable in C
Author Sourav Datta
Author Email soura_jagat [at] yahoo.com
Description A hashtable that stores name, value pairs as strings
Category C » Data Structures
Hits 453508
Code Select and Copy the Code
#include <string.h> #include <stdio.h> #include <stdlib.h> typedef struct _node{ char *name; char *desc; struct _node *next; }node; #define HASHSIZE 101 static node* hashtab[HASHSIZE]; void inithashtab(){ int i; for(i=0;i<HASHSIZE;i++) hashtab[i]=NULL; } unsigned int hash(char *s){ unsigned int h=0; for(;*s;s++) h=*s+h*31; return h%HASHSIZE; } node* lookup(char *n){ unsigned int hi=hash(n); node* np=hashtab[hi]; for(;np!=NULL;np=np->next){ if(!strcmp(np->name,n)) return np; } return NULL; } char* m_strdup(char *o){ int l=strlen(o)+1; char *ns=(char*)malloc(l*sizeof(char)); strcpy(ns,o); if(ns==NULL) return NULL; else return ns; } char* get(char* name){ node* n=lookup(name); if(n==NULL) return NULL; else return n->desc; } int install(char* name,char* desc){ unsigned int hi; node* np; if((np=lookup(name))==NULL){ hi=hash(name); np=(node*)malloc(sizeof(node)); if(np==NULL) return 0; np->name=m_strdup(name); if(np->name==NULL) return 0; np->next=hashtab[hi]; hashtab[hi]=np; } else free(np->desc); np->desc=m_strdup(desc); if(np->desc==NULL) return 0; return 1; } /* A pretty useless but good debugging function, which simply displays the hashtable in (key.value) pairs */ void displaytable(){ int i; node *t; for(i=0;i<HASHSIZE;i++){ if(hashtab[i]==NULL) printf("() "); else{ t=hashtab[i]; printf("("); for(;t!=NULL;t=t->next) printf("(%s.%s) ",t->name,t->desc); printf(") "); } } } void cleanup(){ int i; node *np,*t; for(i=0;i<HASHSIZE;i++){ if(hashtab[i]!=NULL){ np=hashtab[i]; while(np!=NULL){ t=np->next; free(np->name); free(np->desc); free(np); np=t; } } } } main(){ int i; char* names[]={"name","address","phone","k101","k110"}; char* descs[]={"Sourav","Sinagor","26300788","Value1","Value2"}; inithashtab(); for(i=0;i<5;i++) install(names[i],descs[i]); printf("Done "); printf("If we didnt do anything wrong.." "we should see %s ",get("k110")); install("phone","9433120451"); printf("Again if we go right, we have %s and %s ",get("k101"),get("phone")); /*displaytable();*/ cleanup(); return 0; }

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