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utils-lists 4.0.2
The µOS++ Intrusive Lists
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utils-lists 4.0.2
The µOS++ Intrusive Lists
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A class for the core of a statically allocated doubly linked list (pointers to neighbours). More...
#include <micro-os-plus/utils/lists.h>
Inheritance diagram for micro_os_plus::utils::static_double_list_links:Public Types | |
| using | is_statically_allocated = std::true_type |
| Type indicating that the links node is statically allocated. | |
Public Member Functions | |
| constexpr | static_double_list_links () |
| Construct a statically allocated list node (BSS initialised). | |
| static_double_list_links (const static_double_list_links &)=delete | |
| Deleted copy constructor. | |
| static_double_list_links (static_double_list_links &&)=delete | |
| Deleted move constructor. | |
| constexpr | ~static_double_list_links () |
| Destruct the node. | |
| constexpr void | initialize (void) |
| Initialise the node links. | |
| void | initialize_once (void) |
| Initialise the node links only if not already initialised. | |
| void | link_next (double_list_links_base *node) |
| Link the new node as next. | |
| void | link_previous (double_list_links_base *node) |
| Link the new node as previous. | |
| bool | linked (void) const |
| Check if the node is linked to a doubly linked list. | |
| constexpr double_list_links_base * | next (void) const |
| Get the link to the next node. | |
| void | nullify (void) |
Reset the two pointers to nullptr. | |
| static_double_list_links & | operator= (const static_double_list_links &)=delete |
| Deleted copy assignment operator. | |
| static_double_list_links & | operator= (static_double_list_links &&)=delete |
| Deleted move assignment operator. | |
| constexpr double_list_links_base * | previous (void) const |
| Get the link to the previous node. | |
| bool | uninitialized (void) const |
| Check if the node is uninitialised. | |
| void | unlink (void) |
| Remove this node from the list. | |
Protected Attributes | |
| double_list_links_base * | next_ |
| Pointer to the next node. | |
| double_list_links_base * | previous_ |
| Pointer to the previous node. | |
A class for the core of a statically allocated doubly linked list (pointers to neighbours).
The static_double_list_links class inherits a pair of uninitialised pointers to the next and previous list elements, as well as methods to access and manipulate these pointers, from its base class.
Instances of this class are intended to be statically allocated in the BSS section and automatically cleared (set to zero) during startup. This design enables reliable initialisation before any static constructors are executed, which is essential because the order of static initialisation is not defined by the C++ standard.
Statically allocated lists are commonly used by registrar objects to automate the self-registration of other statically allocated objects, such as drivers, threads, and similar components. By leveraging BSS initialisation, the registrar is guaranteed to be ready before any static objects attempt to register themselves.
As a consequence, list initialisation cannot be performed in the constructor, but must be done manually before invoking any method that adds elements to the list. This approach ensures robust and predictable behaviour in embedded and system-level applications where static object registration is required.
| using micro_os_plus::utils::static_double_list_links::is_statically_allocated = std::true_type |
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constexpr |
Construct a statically allocated list node (BSS initialised).
This constructor is intended for statically allocated list link nodes. It must be empty and must not modify the member pointers, leaving them unchanged. For statically allocated objects, the entire memory region is zero-initialised at startup (via BSS initialisation), so both previous_ and next_ pointers are set to nullptr, representing an uninitialised state.
This approach ensures that statically allocated lists are in a known, safe state before any constructors run, and avoids unnecessary writes or side effects during construction.
previous_ was not initialized in constructornext_ was not initialized in constructor These warnings are expected and can be safely ignored in this context.Definition at line 189 of file lists-inlines.h.
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delete |
Deleted copy constructor.
Copying of statically allocated list node objects is explicitly disallowed to prevent accidental duplication, which could compromise the integrity of the list structure.
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delete |
Deleted move constructor.
Moving of statically allocated list node objects is explicitly disallowed to avoid invalid or inconsistent links within the list that could result from moving nodes.
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constexpr |
Destruct the node.
The destructor for static_double_list_links is intentionally left empty to avoid modifying the member pointers. The goal is to revert the content to a state similar to the statically initialised state (BSS zero), but recent versions of GCC may optimize out any code that attempts to clear the pointers (dead store elimination).
As a result, explicit pointer clearing in the destructor is not reliable. If pointer reset is required, use the nullify() method explicitly, or clear the memory before invoking the placement new constructor again.
__attribute__((optimize("no-lifetime-dse,no-dse,no-inline"))) did not help. The workaround is to use nullify() explicitly, or, even better, to clear the memory before invoking the placement new constructor again. Definition at line 220 of file lists-inlines.h.
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constexprinherited |
Initialise the node links.
Sets both the previous_ and next_ pointers to point to this node itself, marking the node as unlinked. This state is used to indicate that the node is not currently part of any list.
This method is called during initialisation and after a node is unlinked from a list, ensuring the node is in a safe, standalone state and cannot be traversed as part of a list.
Definition at line 113 of file lists-inlines.h.
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inherited |
Initialise the node links only if not already initialised.
If the statically allocated list is still in the initial uninitialised state (with both pointers nullptr), this method initialises the list to the empty state, with both pointers pointing to itself.
For non-statically initialised lists, this method is ineffective, since the node is always initialised at construct time.
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inherited |
Link the new node as next.
| [in] | node | Pointer to the node to be linked as next. |
Insert the new node between the next pointer and the node pointed by it. This operation is used by lists to link new nodes to the list head. The new node's previous_ pointer is set to the current node, and its next_ pointer is set to the current node's next_. The neighbouring nodes are updated to point to the new node, maintaining the integrity of the double-linked list.
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inherited |
Link the new node as previous.
| [in] | node | Pointer to the node to be linked as previous. |
Insert the new node between the previous pointer and the node pointed by it. Used by lists to link new nodes to the list tail. The new node's next_ pointer is set to the current node, and its previous_ pointer is set to the current node's previous_. The neighbouring nodes are updated to point to the new node, maintaining the integrity of the double-linked list.
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inherited |
Check if the node is linked to a doubly linked list.
| true | The node is linked with both pointers. |
| false | The node is not linked. |
To be linked, both pointers must point to different nodes than itself (double list requirement). If either next_ or previous_ points to this, the node is considered unlinked (empty state). This method checks the node's linkage status for safe list operations.
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constexprinherited |
Get the link to the next node.
| Pointer | to the next node. |
Returns a pointer to the next node in the list. If this node is the last in the list, the returned pointer may refer back to the list's sentinel node (for example, the links node in the list container) or to itself if the list is empty.
double_list_links_base* and may need to be cast to the appropriate derived type by the caller. Definition at line 137 of file lists-inlines.h.
| void micro_os_plus::utils::static_double_list_links::nullify | ( | void | ) |
Reset the two pointers to nullptr.
Sets both the next_ and previous_ pointers to nullptr, marking the node as uninitialized. This is typically used for statically allocated nodes to explicitly place them in an uninitialized state.
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delete |
Deleted copy assignment operator.
Copy assignment is explicitly disallowed to prevent accidental overwriting of list node objects, which could lead to corruption of the list structure.
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delete |
Deleted move assignment operator.
Move assignment is explicitly disallowed to avoid invalid or inconsistent links within the list that could result from moving nodes.
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constexprinherited |
Get the link to the previous node.
| Pointer | to the previous node. |
Returns a pointer to the previous node in the list. If this node is the first in the list, the returned pointer may refer back to the list's sentinel node (such as the links node in the list container) or to itself if the list is empty.
double_list_links_base* and may need to be cast to the appropriate derived type by the caller. Definition at line 154 of file lists-inlines.h.
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inherited |
Check if the node is uninitialised.
| true | The links are not initialised. |
| false | The links are initialised. |
An uninitialized node is a node with its pointers set to nullptr. Only statically allocated nodes in their initial state are considered uninitialized. Regular (dynamically or automatically allocated) nodes are always initialized during construction, so this method will only return true for statically allocated nodes that have not yet been initialized.
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inherited |
Remove this node from the list.
Update both neighbours to point to each other, effectively removing the node from the list. The node is then returned to the initial state (empty), with both pointers pointing to itself. This operation is safe to call even if the node is already unlinked.
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protectedinherited |
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protectedinherited |
1.13.2