qunique.h

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/*-------------------------------------------------------------------------
 *
 * qunique.h
 *      inline array unique functions
 * Portions Copyright (c) 2019-2024, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *      src/include/lib/qunique.h
 *-------------------------------------------------------------------------
 */
 
#ifndef QUNIQUE_H
#define QUNIQUE_H
 
/*
 * Remove duplicates from a pre-sorted array, according to a user-supplied
 * comparator.  Usually the array should have been sorted with qsort() using
 * the same arguments.  Return the new size.
 */
static inline size_t
qunique(void *array, size_t elements, size_t width,
        int (*compare) (const void *, const void *))
{
    char       *bytes = (char *) array;
    size_t      i,
                j;
 
    if (elements <= 1)
        return elements;
 
    for (i = 1, j = 0; i < elements; ++i)
    {
        if (compare(bytes + i * width, bytes + j * width) != 0 &&
            ++j != i)
            memcpy(bytes + j * width, bytes + i * width, width);
    }
 
    return j + 1;
}
 
/*
 * Like qunique(), but takes a comparator with an extra user data argument
 * which is passed through, for compatibility with qsort_arg().
 */
static inline size_t
qunique_arg(void *array, size_t elements, size_t width,
            int (*compare) (const void *, const void *, void *),
            void *arg)
{
    char       *bytes = (char *) array;
    size_t      i,
                j;
 
    if (elements <= 1)
        return elements;
 
    for (i = 1, j = 0; i < elements; ++i)
    {
        if (compare(bytes + i * width, bytes + j * width, arg) != 0 &&
            ++j != i)
            memcpy(bytes + j * width, bytes + i * width, width);
    }
 
    return j + 1;
}
 
#endif                          /* QUNIQUE_H */