a6f9df16ac
In a ringbuffer implementation with only two begin/end pointers, it's impossible to distinguish between an empty and a full ringbuffer. The correct interpretation mode needs to be specified by the user.
103 lines
2.3 KiB
C
103 lines
2.3 KiB
C
/*
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* libdivecomputer
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*
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* Copyright (C) 2008 Jef Driesen
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library 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 GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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* MA 02110-1301 USA
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*/
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#include <assert.h>
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#include "ringbuffer.h"
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static unsigned int
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normalize (unsigned int a, unsigned int size)
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{
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return a % size;
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}
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static unsigned int
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distance (unsigned int a, unsigned int b, int mode, unsigned int size)
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{
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if (a < b) {
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return (b - a) % size;
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} else if (a > b) {
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return size - (a - b) % size;
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} else {
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return (mode == 0 ? 0 : size);
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}
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}
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static unsigned int
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increment (unsigned int a, unsigned int delta, unsigned int size)
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{
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return (a + delta) % size;
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}
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static unsigned int
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decrement (unsigned int a, unsigned int delta, unsigned int size)
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{
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if (delta <= a) {
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return (a - delta) % size;
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} else {
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return size - (delta - a) % size;
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}
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}
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unsigned int
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ringbuffer_normalize (unsigned int a, unsigned int begin, unsigned int end)
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{
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assert (end >= begin);
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assert (a >= begin);
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return normalize (a, end - begin);
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}
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unsigned int
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ringbuffer_distance (unsigned int a, unsigned int b, int mode, unsigned int begin, unsigned int end)
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{
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assert (end >= begin);
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assert (a >= begin);
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return distance (a, b, mode, end - begin);
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}
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unsigned int
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ringbuffer_increment (unsigned int a, unsigned int delta, unsigned int begin, unsigned int end)
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{
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assert (end >= begin);
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assert (a >= begin);
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return increment (a - begin, delta, end - begin) + begin;
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}
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unsigned int
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ringbuffer_decrement (unsigned int a, unsigned int delta, unsigned int begin, unsigned int end)
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{
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assert (end >= begin);
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assert (a >= begin);
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return decrement (a - begin, delta, end - begin) + begin;
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}
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