hash.c

   1 /* HASHING TABLE */
   2
   3 #include <stdlib.h>
   4 #include <string.h>
   5 #include <stdio.h>
   6
   7 #include "hash.h"
   8 #include "data.h"
   9 #include "error.h"
  10
  11 struct table_type table[TABLE_SIZE];
  12
  13
  14 /* hash function */
  15
  16 #define hash(id) (id&(TABLE_SIZE-1))
  17
  18
  19 /* adds item to hash table */
  20 void add_to_table(struct object_list *pointer)
  21 {
  22         int c;
  23         unsigned int a;
  24         a=hash(pointer->member.id);
  25         c=table[a].count;
  26         table[a].pointer=mem_realloc(table[a].pointer,(c+1)*sizeof(struct object *));
  27         if (!table[a].pointer){ERROR("Not enough memory.\n");EXIT(1);}
  28
  29         table[a].pointer[c]=pointer;
  30         table[a].count++;
  31 }
  32
  33
  34 /* removes object from table */
  35 /* returns pointer to the object */
  36 /* if there's not such an object returns null */
  37 struct object_list * remove_from_table(unsigned int id)
  38 {
  39         unsigned int a;
  40         int b;
  41         struct object_list *p;
  42
  43         a=hash(id);
  44         if (!table[a].count)return 0;
  45         for (b=0;b<table[a].count;b++)
  46                 if (table[a].pointer[b]->member.id==id)
  47                 {
  48                         p=table[a].pointer[b];
  49                         memmove(table[a].pointer+b,table[a].pointer+b+1,(table[a].count-b-1)*sizeof(struct object_list *));
  50                         table[a].count--;
  51                         table[a].pointer=mem_realloc(table[a].pointer,table[a].count*sizeof(struct object_list*));
  52                         return p;
  53                 }
  54         return 0;
  55 }
  56
  57
  58 /* tests if object number id is in table */
  59 /* if true returns pointer, otherwise returns null */
  60 struct object_list* find_in_table(unsigned int id)
  61 {
  62         unsigned int a;
  63         int b;
  64
  65         a=hash(id);
  66         if (!table[a].count)return 0;
  67         for (b=0;b<table[a].count;b++)
  68                 if (table[a].pointer[b]->member.id==id) return table[a].pointer[b];
  69         return 0;
  70 }
  71
  72
  73 /* initializes hash table */
  74 void hash_table_init(void)
  75 {
  76         int a;
  77
  78         for (a=0;a<TABLE_SIZE;a++)
  79         {
  80                 table[a].count=0;
  81                 table[a].pointer=DUMMY;
  82         }
  83 }
  84
  85
  86 /* removes hash table from memory */
  87 void free_hash_table(void)
  88 {
  89         int a,b;
  90
  91         for (a=0;a<TABLE_SIZE;a++)
  92         {
  93                 for (b=0;b<table[a].count;b++)
  94                         mem_free(table[a].pointer[b]);
  95                 mem_free(table[a].pointer);
  96         }
  97 }