69 lines
1.8 KiB
C
69 lines
1.8 KiB
C
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/* a simple ring buffer
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Copyright (C) 2006, 2009-2020 Free Software Foundation, Inc.
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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 3 of the License, or
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(at your option) any later version.
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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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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* written by Jim Meyering */
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#include <config.h>
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#include "i-ring.h"
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#include <stdlib.h>
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void
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i_ring_init (I_ring *ir, int default_val)
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{
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int i;
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ir->ir_empty = true;
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ir->ir_front = 0;
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ir->ir_back = 0;
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for (i = 0; i < I_RING_SIZE; i++)
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ir->ir_data[i] = default_val;
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ir->ir_default_val = default_val;
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}
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bool
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i_ring_empty (I_ring const *ir)
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{
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return ir->ir_empty;
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}
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int
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i_ring_push (I_ring *ir, int val)
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{
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unsigned int dest_idx = (ir->ir_front + !ir->ir_empty) % I_RING_SIZE;
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int old_val = ir->ir_data[dest_idx];
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ir->ir_data[dest_idx] = val;
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ir->ir_front = dest_idx;
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if (dest_idx == ir->ir_back)
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ir->ir_back = (ir->ir_back + !ir->ir_empty) % I_RING_SIZE;
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ir->ir_empty = false;
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return old_val;
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}
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int
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i_ring_pop (I_ring *ir)
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{
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int top_val;
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if (i_ring_empty (ir))
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abort ();
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top_val = ir->ir_data[ir->ir_front];
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ir->ir_data[ir->ir_front] = ir->ir_default_val;
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if (ir->ir_front == ir->ir_back)
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ir->ir_empty = true;
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else
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ir->ir_front = ((ir->ir_front + I_RING_SIZE - 1) % I_RING_SIZE);
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return top_val;
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}
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