CIRCLEQ_INSERT_BEFORE - Linux

Overview

CIRCLEQ_INSERT_BEFORE is a command used within Linux Kernel space programming to insert a node before another node in a circular doubly linked list. It is particularly useful when implementing data structures that require maintaining sequential relationships between elements.

Syntax

void CIRCLEQ_INSERT_BEFORE(CIRCLEQ_HEAD(name) *head, CIRCLEQ_ENTRY *listelm, CIRCLEQ_ENTRY *elm);

Options/Flags

No options or flags are available for this command.

Examples

Consider a circular doubly linked list of structures called node and a list head named head.

To insert a node new_node before an existing node existing_node, use the following syntax:

CIRCLEQ_INSERT_BEFORE(&head, existing_node, new_node);

Common Issues

  • Incorrect Node Types: Ensure that the listelm and elm parameters are valid nodes of the correct type.
  • Empty List: If the list is empty (i.e., head->cqh_first is NULL), the insertion will fail.
  • Invalid Insertion Point: The listelm parameter must be a valid node in the list. Attempting to insert before a non-existing node will result in undefined behavior.

Integration

CIRCLEQ_INSERT_BEFORE can be used in conjunction with other Linux Kernel list manipulation commands such as:

  • CIRCLEQ_REMOVE: Remove a node from the list.
  • CIRCLEQ_INIT: Initialize a circular doubly linked list head.
  • CIRCLEQ_FIRST: Get the first node in the list.

Related Commands

  • CIRCLEQ_INSERT_TAIL
  • LIST_INSERT_BEFORE
  • TAILQ_INSERT_BEFORE