src/common/pico_util/include/pico/util/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
 */

typedef struct {
    spin_lock_t *lock;
    uint8_t *data;
    uint16_t wptr;
    uint16_t rptr;
    uint16_t element_size;
    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_size Size of each value in the queue
 * \param element_count Maximum number of entries in the queue
 * \param spinlock_num The spin ID used to protect the queue
 */
void queue_init_with_spinlock(queue_t *q, uint element_size, 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_size Size of each value in the queue
 * \param element_count Maximum number of entries in the queue
 */
static inline void queue_init(queue_t *q, uint element_size, uint element_count) {
    return queue_init_with_spinlock(q, element_size, element_count, next_striped_spin_lock_num());
}

/*! \brief Destroy the specified queue.
 *  \ingroup queue
 *
 * \param q Pointer to a queue_t structure, used as a handle
 *
 * Does not deallocate the queue_t structure itself.
 */
void queue_free(queue_t *q);

/*! \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 queue_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 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 queue_get_level(queue_t *q) {
    uint32_t save = spin_lock_blocking(q->lock);
    uint level = queue_get_level_unsafe(q);
    spin_unlock(q->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 queue_is_empty(queue_t *q) {
    return queue_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 queue_is_full(queue_t *q) {
    return queue_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 queue_try_add(queue_t *q, void *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 queue_try_remove(queue_t *q, void *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 queue_try_peek(queue_t *q, void *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 queue_add_blocking(queue_t *q, void *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 queue_remove_blocking(queue_t *q, void *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 queue_peek_blocking(queue_t *q, void *data);

#endif