112 lines
2.7 KiB
C
112 lines
2.7 KiB
C
/**
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* @file mmedian.c
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* @note Copyright (C) 2013 Miroslav Lichvar <mlichvar@redhat.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <stdlib.h>
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#include <string.h>
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#include "mmedian.h"
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#include "filter_private.h"
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struct mmedian {
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struct filter filter;
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int cnt;
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int len;
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int index;
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/* Indices sorted by value. */
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int *order;
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/* Values stored in circular buffer. */
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tmv_t *samples;
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};
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static void mmedian_destroy(struct filter *filter)
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{
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struct mmedian *m = container_of(filter, struct mmedian, filter);
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free(m->order);
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free(m->samples);
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free(m);
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}
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static tmv_t mmedian_sample(struct filter *filter, tmv_t sample)
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{
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struct mmedian *m = container_of(filter, struct mmedian, filter);
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int i;
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m->samples[m->index] = sample;
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if (m->cnt < m->len) {
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m->cnt++;
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} else {
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/* Remove index of the replaced value from order. */
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for (i = 0; i < m->cnt; i++)
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if (m->order[i] == m->index)
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break;
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for (; i + 1 < m->cnt; i++)
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m->order[i] = m->order[i + 1];
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}
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/* Insert index of the new value to order. */
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for (i = m->cnt - 1; i > 0; i--) {
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if (tmv_cmp(m->samples[m->order[i - 1]],
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m->samples[m->index]) <= 0)
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break;
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m->order[i] = m->order[i - 1];
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}
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m->order[i] = m->index;
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m->index = (1 + m->index) % m->len;
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if (m->cnt % 2)
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return m->samples[m->order[m->cnt / 2]];
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else
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return tmv_div(tmv_add(m->samples[m->order[m->cnt / 2 - 1]],
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m->samples[m->order[m->cnt / 2]]), 2);
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}
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static void mmedian_reset(struct filter *filter)
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{
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struct mmedian *m = container_of(filter, struct mmedian, filter);
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m->cnt = 0;
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m->index = 0;
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}
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struct filter *mmedian_create(int length)
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{
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struct mmedian *m;
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if (length < 1)
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return NULL;
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m = calloc(1, sizeof(*m));
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if (!m)
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return NULL;
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m->filter.destroy = mmedian_destroy;
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m->filter.sample = mmedian_sample;
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m->filter.reset = mmedian_reset;
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m->order = calloc(1, length * sizeof(*m->order));
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if (!m->order) {
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free(m);
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return NULL;
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}
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m->samples = calloc(1, length * sizeof(*m->samples));
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if (!m->samples) {
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free(m->order);
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free(m);
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return NULL;
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}
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m->len = length;
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return &m->filter;
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}
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