src/include/lib/qunique.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * qunique.h
   4  *              inline array unique functions
   5  * Portions Copyright (c) 2019-2021, PostgreSQL Global Development Group
   6  *
   7  * IDENTIFICATION
   8  *              src/include/lib/qunique.h
   9  *-------------------------------------------------------------------------
  10  */
  11
  12 #ifndef QUNIQUE_H
  13 #define QUNIQUE_H
  14
  15 /*
  16  * Remove duplicates from a pre-sorted array, according to a user-supplied
  17  * comparator.  Usually the array should have been sorted with qsort() using
  18  * the same arguments.  Return the new size.
  19  */
  20 static inline size_t
  21 qunique(void *array, size_t elements, size_t width,
  22                 int (*compare) (const void *, const void *))
  23 {
  24         char       *bytes = (char *) array;
  25         size_t          i,
  26                                 j;
  27
  28         if (elements <= 1)
  29                 return elements;
  30
  31         for (i = 1, j = 0; i < elements; ++i)
  32         {
  33                 if (compare(bytes + i * width, bytes + j * width) != 0 &&
  34                         ++j != i)
  35                         memcpy(bytes + j * width, bytes + i * width, width);
  36         }
  37
  38         return j + 1;
  39 }
  40
  41 /*
  42  * Like qunique(), but takes a comparator with an extra user data argument
  43  * which is passed through, for compatibility with qsort_arg().
  44  */
  45 static inline size_t
  46 qunique_arg(void *array, size_t elements, size_t width,
  47                         int (*compare) (const void *, const void *, void *),
  48                         void *arg)
  49 {
  50         char       *bytes = (char *) array;
  51         size_t          i,
  52                                 j;
  53
  54         if (elements <= 1)
  55                 return elements;
  56
  57         for (i = 1, j = 0; i < elements; ++i)
  58         {
  59                 if (compare(bytes + i * width, bytes + j * width, arg) != 0 &&
  60                         ++j != i)
  61                         memcpy(bytes + j * width, bytes + i * width, width);
  62         }
  63
  64         return j + 1;
  65 }
  66
  67 #endif                                                  /* QUNIQUE_H */