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/* a simple ring buffer
Copyright (C) 2006, 2009-2021 Free Software Foundation, Inc.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 3 of the
License, or (at your option) any later version.
This file is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* written by Jim Meyering */
#include <config.h>
#include "i-ring.h"
#include <stdlib.h>
void
i_ring_init (I_ring *ir, int default_val)
{
int i;
ir->ir_empty = true;
ir->ir_front = 0;
ir->ir_back = 0;
for (i = 0; i < I_RING_SIZE; i++)
ir->ir_data[i] = default_val;
ir->ir_default_val = default_val;
}
bool
i_ring_empty (I_ring const *ir)
{
return ir->ir_empty;
}
int
i_ring_push (I_ring *ir, int val)
{
unsigned int dest_idx = (ir->ir_front + !ir->ir_empty) % I_RING_SIZE;
int old_val = ir->ir_data[dest_idx];
ir->ir_data[dest_idx] = val;
ir->ir_front = dest_idx;
if (dest_idx == ir->ir_back)
ir->ir_back = (ir->ir_back + !ir->ir_empty) % I_RING_SIZE;
ir->ir_empty = false;
return old_val;
}
int
i_ring_pop (I_ring *ir)
{
int top_val;
if (i_ring_empty (ir))
abort ();
top_val = ir->ir_data[ir->ir_front];
ir->ir_data[ir->ir_front] = ir->ir_default_val;
if (ir->ir_front == ir->ir_back)
ir->ir_empty = true;
else
ir->ir_front = ((ir->ir_front + I_RING_SIZE - 1) % I_RING_SIZE);
return top_val;
}
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