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/******************************************************************************
* The MIT License
*
* Copyright (c) 2011 LeafLabs, LLC.
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy,
* modify, merge, publish, distribute, sublicense, and/or sell copies
* of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*****************************************************************************/
/**
* @file ring_buffer.h
* @brief Simple circular buffer
*
* This implementation is not thread-safe. In particular, none of
* these functions are guaranteed re-entrant.
*/
#ifndef _RING_BUFFER_H_
#define _RING_BUFFER_H_
#ifdef __cplusplus
extern "C"{
#endif
/**
* Ring buffer type.
*
* The buffer is empty when head == tail.
*
* The buffer is full when the head is one byte in front of the tail,
* modulo buffer length.
*
* One byte is left free to distinguish empty from full. */
typedef struct ring_buffer {
volatile uint8 *buf; /**< Buffer items are stored into */
uint16 head; /**< Index of the next item to remove */
uint16 tail; /**< Index where the next item will get inserted */
uint16 size; /**< Buffer capacity minus one */
} ring_buffer;
/**
* Initialise a ring buffer.
*
* @param rb Instance to initialise
*
* @param size Number of items in buf. The ring buffer will always
* leave one element unoccupied, so the maximum number of
* elements it can store will be size - 1. Thus, size
* must be at least 2.
*
* @param buf Buffer to store items into
*/
static inline void rb_init(ring_buffer *rb, uint16 size, uint8 *buf) {
rb->head = 0;
rb->tail = 0;
rb->size = size - 1;
rb->buf = buf;
}
/**
* @brief Return the number of elements stored in the ring buffer.
* @param rb Buffer whose elements to count.
*/
static inline uint16 rb_full_count(ring_buffer *rb) {
volatile ring_buffer *arb = rb;
int32 size = arb->tail - arb->head;
if (arb->tail < arb->head) {
size += arb->size + 1;
}
return (uint16)size;
}
/**
* @brief Returns true if and only if the ring buffer is full.
* @brief rb Buffer to test.
*/
static inline int rb_is_full(ring_buffer *rb) {
return (rb->tail + 1 == rb->head) ||
(rb->tail == rb->size && rb->head == 0);
}
/**
* @brief Returns true if and only if the ring buffer is empty.
* @param rb Buffer to test.
*/
static inline int rb_is_empty(ring_buffer *rb) {
return rb->head == rb->tail;
}
/**
* Append element onto the end of a ring buffer.
* @param rb Buffer to append onto.
* @param element Value to append.
*/
static inline void rb_insert(ring_buffer *rb, uint8 element) {
rb->buf[rb->tail] = element;
rb->tail = (rb->tail == rb->size) ? 0 : rb->tail + 1;
}
/**
* @brief Remove and return the first item from a ring buffer.
* @param rb Buffer to remove from, must contain at least one element.
*/
static inline uint8 rb_remove(ring_buffer *rb) {
uint8 ch = rb->buf[rb->head];
rb->head = (rb->head == rb->size) ? 0 : rb->head + 1;
return ch;
}
/**
* @brief Attempt to remove the first item from a ring buffer.
*
* If the ring buffer is nonempty, removes and returns its first item.
* If it is empty, does nothing and returns a negative value.
*
* @param rb Buffer to attempt to remove from.
*/
static inline int16 rb_safe_remove(ring_buffer *rb) {
return rb_is_empty(rb) ? -1 : rb_remove(rb);
}
/**
* @brief Attempt to insert an element into a ring buffer.
*
* @brief rb Buffer to insert into.
* @brief element Value to insert into rb.
* @sideeffect If rb is not full, appends element onto buffer.
* @return If element was appended, then true; otherwise, false. */
static inline int rb_safe_insert(ring_buffer *rb, uint8 element) {
if (rb_is_full(rb)) {
return 0;
}
rb_insert(rb, element);
return 1;
}
/**
* @brief Append an item onto the end of a non-full ring buffer.
*
* If the buffer is full, removes its first item, then inserts the new
* element at the end.
*
* @param rb Ring buffer to insert into.
* @param element Value to insert into ring buffer.
* @return On success, returns -1. If an element was popped, returns
* the popped value.
*/
static inline int rb_push_insert(ring_buffer *rb, uint8 element) {
int ret = -1;
if (rb_is_full(rb)) {
ret = rb_remove(rb);
}
rb_insert(rb, element);
return ret;
}
/**
* @brief Discard all items from a ring buffer.
* @param rb Ring buffer to discard all items from.
*/
static inline void rb_reset(ring_buffer *rb) {
rb->tail = rb->head;
}
#ifdef __cplusplus
} // extern "C"
#endif
#endif
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