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