45 lines
1.6 KiB
C
45 lines
1.6 KiB
C
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/* definitions for 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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#include <stdbool.h>
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#include "verify.h"
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enum { I_RING_SIZE = 4 };
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verify (1 <= I_RING_SIZE);
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/* When ir_empty is true, the ring is empty.
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Otherwise, ir_data[B..F] are defined, where B..F is the contiguous
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range of indices, modulo I_RING_SIZE, from back to front, inclusive.
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Undefined elements of ir_data are always set to ir_default_val.
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Popping from an empty ring aborts.
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Pushing onto a full ring returns the displaced value.
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An empty ring has F==B and ir_empty == true.
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A ring with one entry still has F==B, but now ir_empty == false. */
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struct I_ring
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{
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int ir_data[I_RING_SIZE];
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int ir_default_val;
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unsigned int ir_front;
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unsigned int ir_back;
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bool ir_empty;
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};
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typedef struct I_ring I_ring;
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void i_ring_init (I_ring *ir, int ir_default_val);
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int i_ring_push (I_ring *ir, int val);
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int i_ring_pop (I_ring *ir);
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bool i_ring_empty (I_ring const *ir) _GL_ATTRIBUTE_PURE;
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