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/* definitions for a simple ring buffer
Copyright (C) 2006, 2009-2025 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/>. */
/* This file uses _GL_ATTRIBUTE_PURE. */
#if !_GL_CONFIG_H_INCLUDED
#error "Please include config.h first."
#endif
#ifdef __cplusplus
extern "C" {
#endif
enum { I_RING_SIZE = 4 };
static_assert (1 <= I_RING_SIZE);
/* When ir_empty is true, the ring is empty.
Otherwise, ir_data[B..F] are defined, where B..F is the contiguous
range of indices, modulo I_RING_SIZE, from back to front, inclusive.
Undefined elements of ir_data are always set to ir_default_val.
Popping from an empty ring aborts.
Pushing onto a full ring returns the displaced value.
An empty ring has F==B and ir_empty == true.
A ring with one entry still has F==B, but now ir_empty == false. */
struct I_ring
{
int ir_data[I_RING_SIZE];
int ir_default_val;
unsigned int ir_front;
unsigned int ir_back;
bool ir_empty;
};
typedef struct I_ring I_ring;
void i_ring_init (I_ring *ir, int ir_default_val);
int i_ring_push (I_ring *ir, int val);
int i_ring_pop (I_ring *ir);
bool i_ring_empty (I_ring const *ir) _GL_ATTRIBUTE_PURE;
#ifdef __cplusplus
}
#endif
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