queue.h

/*
 * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#ifndef _UTIL_QUEUE_H
#define _UTIL_QUEUE_H

#include "pico.h"
#include "hardware/sync.h"

/** \file queue.h
 * \defgroup queue queue
 * Multi-core and IRQ safe queue implementation.
 *
 * Note that this queue stores values of a specified size, and pushed values are copied into the queue
 * \ingroup pico_util
 */

#include "pico/lock_core.h"

typedef struct {
    lock_core_t core;
    uint8_t *data;
    uint16_t wptr;
    uint16_t rptr;
    uint16_t element_count;
} queue_t;

/*! \brief Initialise a queue with a specific spinlock for concurrency protection
 *  \ingroup queue
 *
 * \param q Pointer to a queue_t structure, used as a handle
 * \param element_count Maximum number of entries in the queue
 * \param spinlock_num The spin ID used to protect the queue
 */
void queue2_init_with_spinlock(queue_t *q, uint8_t *buf, uint element_count, uint spinlock_num);

/*! \brief Initialise a queue, allocating a (possibly shared) spinlock
 *  \ingroup queue
 *
 * \param q Pointer to a queue_t structure, used as a handle
 * \param element_count Maximum number of entries in the queue
 */
static inline void queue2_init(queue_t *q, uint8_t *buf, uint element_count) {
    return queue2_init_with_spinlock(q, buf, element_count, next_striped_spin_lock_num());
    //return queue2_init_with_spinlock(q, buf, element_count, spin_lock_claim_unused(true));
}

void queue_available_bytes(queue_t *q, uint16_t* cnt);
void queue_update_read_pointer(queue_t *q, uint16_t* cnt);
void queue_available_bytes_unsafe(queue_t *q, uint16_t* cnt);

/*! \brief Unsafe check of level of the specified queue.
 *  \ingroup queue
 *
 * \param q Pointer to a queue_t structure, used as a handle
 * \return Number of entries in the queue
 *
 * This does not use the spinlock, so may return incorrect results if the
 * spin lock is not externally locked
 */
/*static inline uint queue2_get_level_unsafe(queue_t *q) {
    int32_t rc = (int32_t)q->wptr - (int32_t)q->rptr;
    if (rc < 0) {
        rc += q->element_count + 1;
    }
    return (uint)rc;
}*/

/*! \brief Check of level of the specified queue.
 *  \ingroup queue
 *
 * \param q Pointer to a queue_t structure, used as a handle
 * \return Number of entries in the queue
 */
/*static inline uint queue2_get_level(queue_t *q) {
    uint32_t save = spin_lock_blocking(q->core.spin_lock);
    uint level = queue2_get_level_unsafe(q);
    spin_unlock(q->core.spin_lock, save);
    return level;
}*/

/*! \brief Check if queue is empty
 *  \ingroup queue
 *
 * \param q Pointer to a queue_t structure, used as a handle
 * \return true if queue is empty, false otherwise
 *
 * This function is interrupt and multicore safe.
 */
/*
static inline bool queue2_is_empty(queue_t *q) {
    return queue2_get_level(q) == 0;
}
*/

/*! \brief Check if queue is full
 *  \ingroup queue
 *
 * \param q Pointer to a queue_t structure, used as a handle
 * \return true if queue is full, false otherwise
 *
 * This function is interrupt and multicore safe.
 */
/*
static inline bool queue2_is_full(queue_t *q) {
    return queue2_get_level(q) == q->element_count;
}
*/

// nonblocking queue access functions:

/*! \brief Non-blocking add value queue if not full
 *  \ingroup queue
 *
 * \param q Pointer to a queue_t structure, used as a handle
 * \param data Pointer to value to be copied into the queue
 * \return true if the value was added
 *
 * If the queue is full this function will return immediately with false, otherwise
 * the data is copied into a new value added to the queue, and this function will return true.
 */
bool queue2_try_add(queue_t *q, const char *data);

/*! \brief Non-blocking removal of entry from the queue if non empty
 *  \ingroup queue
 *
 * \param q Pointer to a queue_t structure, used as a handle
 * \param data Pointer to the location to receive the removed value
 * \return true if a value was removed
 *
 * If the queue is not empty function will copy the removed value into the location provided and return
 * immediately with true, otherwise the function will return immediately with false.
 */
bool queue2_try_remove(queue_t *q, char *data);

/*! \brief Non-blocking peek at the next item to be removed from the queue
 *  \ingroup queue
 *
 * \param q Pointer to a queue_t structure, used as a handle
 * \param data Pointer to the location to receive the peeked value
 * \return true if there was a value to peek
 *
 * If the queue is not empty this function will return immediately with true with the peeked entry
 * copied into the location specified by the data parameter, otherwise the function will return false.
 */
bool queue2_try_peek(queue_t *q, char *data);

// blocking queue access functions:

/*! \brief Blocking add of value to queue
 *  \ingroup queue
 *
 * \param q Pointer to a queue_t structure, used as a handle
 * \param data Pointer to value to be copied into the queue
 *
 * If the queue is full this function will block, until a removal happens on the queue
 */
void queue2_add_blocking(queue_t *q, const char *data);

/*! \brief Blocking remove entry from queue
 *  \ingroup queue
 *
 * \param q Pointer to a queue_t structure, used as a handle
 * \param data Pointer to the location to receive the removed value
 *
 * If the queue is empty this function will block until a value is added.
 */
void queue2_remove_blocking(queue_t *q, char *data);

/*! \brief Blocking peek at next value to be removed from queue
 *  \ingroup queue
 *
 * \param q Pointer to a queue_t structure, used as a handle
 * \param data Pointer to the location to receive the peeked value
 *
 * If the queue is empty function will block until a value is added
 */
void queue2_peek_blocking(queue_t *q, char *data);


#endif