CIRCLEQ_LOOP_PREV - Linux
Overview
CIRCLEQ_LOOP_PREV iterates through a circular queue in reverse order, beginning from a specified element. It’s commonly used in data structures and kernel code for managing and traversing circular queues.
Syntax
#include <sys/queue.h>
void *CIRCLEQ_LOOP_PREV(void *element, offsetof(struct circle_entry, next));
Parameters
- element: The current element in the circular queue where the reverse iteration starts.
- offsetof(struct circle_entry, next): The offset of the next pointer within the
struct circle_entry
.
Options/Flags
None
Examples
struct circle_entry *prev_element;
for (prev_element = CIRCLEQ_LOOP_PREV(current_element, offsetof(struct circle_entry, next));
prev_element != current_element;
prev_element = CIRCLEQ_LOOP_PREV(prev_element, offsetof(struct circle_entry, next))) {
// Perform some operation on the previous element
}
Common Issues
- Ensure that current_element is a valid element within the circular queue. Iterating from an invalid element may lead to undefined behavior.
- Be cautious when modifying the circular queue while iterating in reverse. Changes may affect the iteration order or cause inconsistencies.
Integration
CIRCLEQ_LOOP_PREV is often used in conjunction with other circular queue operations such as CIRCLEQ_INSERT, CIRCLEQ_REMOVE, and CIRCLEQ_FIRST.
Related Commands
- CIRCLEQ_FIRST: Retrieves the first element in the circular queue.
- CIRCLEQ_INSERT: Inserts an element into a circular queue.
- CIRCLEQ_LOOP: Iterates through a circular queue in the forward direction.