86 lines
2.7 KiB
C
86 lines
2.7 KiB
C
/*
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* Copyright 2018 Robert C. Curtis. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials
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* provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY ROBERT C. CURTIS ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL ROBERT C. CURTIS OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
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* USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
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* DAMAGE.
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*
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* The views and conclusions contained in the software and documentation
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* are those of the authors and should not be interpreted as representing
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* official policies, either expressed or implied, of Robert C. Curtis.
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*/
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/** @file util/queue.h
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* Static queue primitives.
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*
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* This file contains a set of static queue primitives that are common among
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* all of the low level queue implementations. The primitives are inline
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* functions, and will be optimal if size is a constant power of 2.
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*/
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#ifndef I__QUEUE_H__
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#define I__QUEUE_H__
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/** Increment a queue index.
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* @param[in] idx Queue index
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* @param[in] size Queue size
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* @returns The new queue index value
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*/
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static inline size_t qinc(size_t idx, size_t size)
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{
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return ((idx + 1) % size);
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}
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/** Decrement a queue index.
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* @param[in] idx Queue index
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* @param[in] size Queue size
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* @returns The new queue index value
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*/
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static inline size_t qdec(size_t idx, size_t size)
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{
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return ((idx - 1) % size);
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}
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/** Tests if a queue is full.
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* @param[in] head Head index
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* @param[in] tail Tail index
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* @param[in] size Queue size
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*/
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static inline int qfull(size_t head, size_t tail, size_t size)
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{
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size_t next_head = qinc(head, size);
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return (next_head == tail);
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}
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/** Tests if a queue is empty.
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* @param[in] head Head index
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* @param[in] tail Tail index
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*/
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static inline int qempty(size_t head, size_t tail)
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{
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return (head == tail);
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}
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#endif /* I__QUEUE_H__ */
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