lib: bm_queue: a dynamic queue implementation

A dynamic queue implementation based on Zephyr's k_queue.
The library has a compatibility mode to export Zephyr's k_queue API,
but it also exposes its own bm_queue API set so that bare metal
libraries and application can avoid including zephyr/kernel.h
and using a k_ prefixed (kernel's) API.

Signed-off-by: Emanuele Di Santo <[email protected]>

Author: lemrey

include/bm_queue.h

@@ -0,0 +1,224 @@
+/*
+ * Copyright (c) 2016, Wind River Systems, Inc.
+ * Copyright (c) 2025, Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <zephyr/sys/slist.h>
+#include <zephyr/sys/sflist.h>
+
+/**
+ * @brief Queue.
+ */
+struct bm_queue {
+	sys_sflist_t data_q;
+};
+
+/**
+ * @brief Initialize a queue.
+ *
+ * This routine initializes a queue, prior to its first use.
+ *
+ * @param queue Queue.
+ */
+void bm_queue_init(struct bm_queue *queue);
+
+/**
+ * @brief Append an element to the end of a queue.
+ *
+ * This routine appends a data item to @a queue. A queue data item must be
+ * aligned on a word boundary, and the first word of the item is reserved
+ * for internal use. The data is not copied.
+ *
+ * @funcprops \isr_ok
+ *
+ * @param queue Queue.
+ * @param data Data item.
+ */
+void bm_queue_append(struct bm_queue *queue, void *data);
+
+/**
+ * @brief Allocate an element and append it to the queue.
+ *
+ * This routine appends a data item to @a queue. There is an implicit memory
+ * allocation on the system heap to create an additional temporary bookkeeping data structure,
+ * which is automatically freed when the item is removed. The data itself is not copied.
+ *
+ * @funcprops \isr_ok
+ *
+ * @param queue Queue.
+ * @param data Data item.
+ *
+ * @retval 0 on success
+ * @retval -ENOMEM if there isn't sufficient RAM in the system heap
+ */
+int32_t bm_queue_alloc_append(struct bm_queue *queue, void *data);
+
+/**
+ * @brief Prepend an element to the queue.
+ *
+ * This routine prepends a data item to @a queue. A queue data item must be
+ * aligned on a word boundary, and the first word of the item is reserved
+ * for internal use. The data is not copied.
+ *
+ * @funcprops \isr_ok
+ *
+ * @param queue Queue.
+ * @param data Data item.
+ */
+void bm_queue_prepend(struct bm_queue *queue, void *data);
+
+/**
+ * @brief Prepend an element to a queue.
+ *
+ * This routine prepends a data item to @a queue. There is an implicit memory
+ * allocation to create an additional temporary bookkeeping data structure from
+ * the system heap, which is automatically freed when the item is removed.
+ * The data itself is not copied.
+ *
+ * @funcprops \isr_ok
+ *
+ * @param queue Queue.
+ * @param data Data item.
+ *
+ * @retval 0 on success
+ * @retval -ENOMEM if there isn't sufficient RAM in the system heap.
+ */
+int32_t bm_queue_alloc_prepend(struct bm_queue *queue, void *data);
+
+/**
+ * @brief Insert an element at a given position in the queue.
+ *
+ * This routine inserts a data item to @a queue after previous item. A queue
+ * data item must be aligned on a word boundary, and the first word of
+ * the item is reserved for internal use.
+ *
+ * @funcprops \isr_ok
+ *
+ * @param queue Queue.
+ * @param prev Previous element.
+ * @param data Data item.
+ */
+void bm_queue_insert(struct bm_queue *queue, void *prev, void *data);
+
+/**
+ * @brief Atomically append a list of elements to a queue.
+ *
+ * This routine adds a list of data items to @a queue in one operation.
+ * The data items must be in a singly-linked list, with the first word
+ * in each data item pointing to the next data item; the list must be
+ * NULL-terminated.
+ *
+ * @funcprops \isr_ok
+ *
+ * @param queue Queue.
+ * @param head Pointer to first node in singly-linked list.
+ * @param tail Pointer to last node in singly-linked list.
+ *
+ * @retval 0 on success
+ * @retval -EINVAL on invalid supplied data
+ */
+int bm_queue_append_list(struct bm_queue *queue, void *head, void *tail);
+
+/**
+ * @brief Atomically add a list of elements to a queue.
+ *
+ * This routine adds a list of data items to @a queue in one operation.
+ * The data items must be in a singly-linked list implemented using a
+ * sys_slist_t object. Upon completion, the original list is empty.
+ *
+ * @funcprops \isr_ok
+ *
+ * @param queue Queue.
+ * @param list Pointer to sys_slist_t object.
+ *
+ * @retval 0 on success
+ * @retval -EINVAL on invalid data
+ */
+int bm_queue_merge_slist(struct bm_queue *queue, sys_slist_t *list);
+
+/**
+ * @brief Get an element from a queue.
+ *
+ * This routine removes first data item from @a queue. The first word of the
+ * data item is reserved for internal use.
+ *
+ * @funcprops \isr_ok
+ *
+ * @param queue Queue.
+ *
+ * @return Address of the data item if successful; NULL otherwise.
+ */
+void *bm_queue_get(struct bm_queue *queue);
+
+/**
+ * @brief Remove an element from a queue.
+ *
+ * This routine removes data item from @a queue. The first word of the
+ * data item is reserved for internal use. Removing elements from bm_queue
+ * rely on sys_slist_find_and_remove which is not a constant time operation.
+ *
+ * @funcprops \isr_ok
+ *
+ * @param queue Queue.
+ * @param data Data item.
+ *
+ * @return true if data item was removed
+ */
+bool bm_queue_remove(struct bm_queue *queue, void *data);
+
+/**
+ * @brief Append an element to a queue only if it's not present already.
+ *
+ * This routine appends data item to @a queue. The first word of the data
+ * item is reserved for internal use. Appending elements to bm_queue
+ * relies on sys_slist_is_node_in_list which is not a constant time operation.
+ *
+ * @funcprops \isr_ok
+ *
+ * @param queue Queue.
+ * @param data Data item.
+ *
+ * @return true if data item was added, false if not
+ */
+bool bm_queue_unique_append(struct bm_queue *queue, void *data);
+
+/**
+ * @brief Query a queue to see if it has data available.
+ *
+ * @funcprops \isr_ok
+ *
+ * @param queue Queue.
+ *
+ * @return Non-zero if the queue is empty.
+ * @return 0 if data is available.
+ */
+static inline bool bm_queue_is_empty(struct bm_queue *queue)
+{
+	return sys_sflist_is_empty(&queue->data_q);
+}
+
+/**
+ * @brief Peek element at the head of queue.
+ *
+ * Return element from the head of queue without removing it.
+ *
+ * @param queue Queue.
+ *
+ * @return Head element, or NULL if queue is empty.
+ */
+void *bm_queue_peek_head(struct bm_queue *queue);
+
+/**
+ * @brief Peek element at the tail of queue.
+ *
+ * Return element from the tail of queue without removing it.
+ *
+ * @param queue Queue.
+ *
+ * @return Tail element, or NULL if queue is empty.
+ */
+void *bm_queue_peek_tail(struct bm_queue *queue);

lib/CMakeLists.txt

@@ -11,6 +11,7 @@ add_subdirectory_ifdef(CONFIG_BLE_RACP ble_racp)
 add_subdirectory_ifdef(CONFIG_EVENT_SCHEDULER event_scheduler)
 add_subdirectory_ifdef(CONFIG_BM_BUTTONS bm_buttons)
 add_subdirectory_ifdef(CONFIG_BM_TIMER bm_timer)
+add_subdirectory_ifdef(CONFIG_BM_QUEUE bm_queue)
 add_subdirectory_ifdef(CONFIG_BLE_QWR ble_qwr)
 add_subdirectory_ifdef(CONFIG_SENSORSIM sensorsim)
 add_subdirectory_ifdef(CONFIG_NCS_BARE_METAL_BOOT_BANNER boot_banner)

lib/Kconfig

@@ -12,6 +12,7 @@ rsource "ble_racp/Kconfig"
 rsource "event_scheduler/Kconfig"
 rsource "bm_buttons/Kconfig"
 rsource "bm_timer/Kconfig"
+rsource "bm_queue/Kconfig"
 rsource "ble_qwr/Kconfig"
 rsource "sensorsim/Kconfig"
 rsource "boot_banner/Kconfig"

lib/bm_queue/CMakeLists.txt

@@ -0,0 +1,7 @@
+#
+# Copyright (c) 2025 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+zephyr_library()
+zephyr_library_sources(bm_queue.c)

lib/bm_queue/Kconfig

@@ -0,0 +1,24 @@
+#
+# Copyright (c) 2025 Nordic Semiconductor
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+menuconfig BM_QUEUE
+	bool "Queue library"
+	help
+	  A simple, dynamic queue using singly linked lists.
+
+if BM_QUEUE
+
+config BM_QUEUE_K_QUEUE_COMPAT
+	bool "Export k_queue compatible API"
+	depends on !MULTITHREADING
+	help
+	  Export a k_queue compatible API for compatibility with Zephyr subsystems.
+
+module=BM_QUEUE
+module-dep=LOG
+module-str=Queue library
+source "${ZEPHYR_BASE}/subsys/logging/Kconfig.template.log_config"
+
+endif