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   1 #include <string.h>
   2
   3 /**
   4  * hashtable - hash table routines
   5  *
   6  * A hash table is an efficient structure for looking up keys.  This version
   7  * grows with usage and allows efficient deletion.
   8  *
   9  * Caveat: pointers placed into the hash must be aligned to 64 bits.
  10  * ie. from malloc or because the structure they point to is aligned.
  11  * An assert will be raised if this isn't true.
  12  *
  13  * Example:
  14  *      #include <ccan/hashtable/hashtable.h>
  15  *      #include <ccan/hash/hash.h>
  16  *      #include <stdio.h>
  17  *      #include <err.h>
  18  *      #include <string.h>
  19  *
  20  *      struct name_to_digit {
  21  *              const char *name;
  22  *              unsigned int val;
  23  *      };
  24  *
  25  *      static struct name_to_digit map[] = {
  26  *              { "zero", 0},
  27  *              { "one", 1 },
  28  *              { "two", 2 },
  29  *              { "three", 3 },
  30  *              { "four", 4 },
  31  *              { "five", 5 },
  32  *              { "six", 6 },
  33  *              { "seven", 7 },
  34  *              { "eight", 8 },
  35  *              { "nine", 9 }
  36  *      };
  37  *
  38  *      // Wrapper for rehash function pointer.
  39  *      static unsigned long rehash(const void *e, void *unused)
  40  *      {
  41  *              return hash_string(((struct name_to_digit *)e)->name);
  42  *      }
  43  *
  44  *      // Comparison function.
  45  *      static bool streq(const void *e, void *string)
  46  *      {
  47  *              return strcmp(((struct name_to_digit *)e)->name, string) == 0;
  48  *      }
  49  *
  50  *      // We let them add their own aliases, eg. --alias=v=5
  51  *      static void add_alias(struct hashtable *ht, const char *alias)
  52  *      {
  53  *              char *eq;
  54  *              struct name_to_digit *n;
  55  *
  56  *              n = malloc(sizeof(*n));
  57  *              n->name = strdup(alias);
  58  *
  59  *              eq = strchr(n->name, '=');
  60  *              if (!eq || ((n->val = atoi(eq+1)) == 0 && !strcmp(eq+1, "0")))
  61  *                      errx(1, "Usage: --alias=<name>=<value>");
  62  *              *eq = '\0';
  63  *              hashtable_add(ht, hash_string(n->name), n);
  64  *      }
  65  *
  66  *      int main(int argc, char *argv[])
  67  *      {
  68  *              struct hashtable *ht;
  69  *              unsigned int i;
  70  *              unsigned long val;
  71  *
  72  *              if (argc < 2)
  73  *                      errx(1, "Usage: %s [--alias=<name>=<val>]... <str>...",
  74  *                           argv[0]);
  75  *
  76  *              // Create and populate hash table.
  77  *              ht = hashtable_new(rehash, NULL);
  78  *              for (i = 0; i < sizeof(map)/sizeof(map[0]); i++)
  79  *                      hashtable_add(ht, hash_string(map[i].name), &map[i]);
  80  *
  81  *              // Add any aliases to the hash table.
  82  *              for (i = 1; i < argc; i++) {
  83  *                      if (!strncmp(argv[i], "--alias=", strlen("--alias=")))
  84  *                              add_alias(ht, argv[i] + strlen("--alias="));
  85  *                      else
  86  *                              break;
  87  *              }
  88  *
  89  *              // Find the other args in the hash table.
  90  *              for (val = 0; i < argc; i++) {
  91  *                      struct name_to_digit *n;
  92  *                      n = hashtable_find(ht, hash_string(argv[i]),
  93  *                                         streq, argv[i]);
  94  *                      if (!n)
  95  *                              errx(1, "Invalid digit name %s", argv[i]);
  96  *                      // Append it to the value we are building up.
  97  *                      val *= 10;
  98  *                      val += n->val;
  99  *              }
 100  *              printf("%lu\n", val);
 101  *              return 0;
 102  *      }
 103  *
 104  * License: GPLv2 (or later)
 105  * Author: Rusty Russell <rusty@rustcorp.com.au>
 106  */
 107 int main(int argc, char *argv[])
 108 {
 109         if (argc != 2)
 110                 return 1;
 111
 112         if (strcmp(argv[1], "depends") == 0) {
 113                 return 0;
 114         }
 115
 116         return 1;
 117 }