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/* Copyright (c) 2003-2004, Roger Dingledine
* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
* Copyright (c) 2007-2019, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file order.c
* \brief Functions for finding the n'th element of an array.
**/
#include <stdlib.h>
#include "lib/container/order.h"
#include "lib/log/util_bug.h"
/** Declare a function called <b>funcname</b> that acts as a find_nth_FOO
* function for an array of type <b>elt_t</b>*.
*
* NOTE: The implementation kind of sucks: It's O(n log n), whereas finding
* the kth element of an n-element list can be done in O(n). Then again, this
* implementation is not in critical path, and it is obviously correct. */
#define IMPLEMENT_ORDER_FUNC(funcname, elt_t) \
static int \
_cmp_ ## elt_t(const void *_a, const void *_b) \
{ \
const elt_t *a = _a, *b = _b; \
if (*a<*b) \
return -1; \
else if (*a>*b) \
return 1; \
else \
return 0; \
} \
elt_t \
funcname(elt_t *array, int n_elements, int nth) \
{ \
tor_assert(nth >= 0); \
tor_assert(nth < n_elements); \
qsort(array, n_elements, sizeof(elt_t), _cmp_ ##elt_t); \
return array[nth]; \
}
IMPLEMENT_ORDER_FUNC(find_nth_int, int)
IMPLEMENT_ORDER_FUNC(find_nth_time, time_t)
IMPLEMENT_ORDER_FUNC(find_nth_double, double)
IMPLEMENT_ORDER_FUNC(find_nth_uint32, uint32_t)
IMPLEMENT_ORDER_FUNC(find_nth_int32, int32_t)
IMPLEMENT_ORDER_FUNC(find_nth_long, long)
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