nt-lite/code/public/ntlite/ddk/list.h

// Public nt-lite DDK intrusive list declarations.

#pragma once

#include <stddef.h>

// Doubly-linked intrusive list node.
typedef struct LIST_ENTRY {
    struct LIST_ENTRY* Fwd;
    struct LIST_ENTRY* Bwd;
} LIST_ENTRY;

#define LIST_INIT(head)     ((head)->Fwd = (head)->Bwd = (head))
#define LIST_IS_EMPTY(head) ((head)->Fwd == (head))

// Recover the containing struct pointer from an embedded list node.
#define CONTAINING_RECORD(ptr, type, member) \
    ((type*)((char*)(ptr) - offsetof(type, member)))

// Inserts a node at the tail of a list.
static inline void ListInsertTail(LIST_ENTRY* head, LIST_ENTRY* node) {
    node->Bwd      = head->Bwd;
    node->Fwd      = head;
    head->Bwd->Fwd = node;
    head->Bwd      = node;
}

// Inserts a node at the head of a list.
static inline void ListInsertHead(LIST_ENTRY* head, LIST_ENTRY* node) {
    node->Fwd      = head->Fwd;
    node->Bwd      = head;
    head->Fwd->Bwd = node;
    head->Fwd      = node;
}

// Removes a node from its current list.
static inline void ListRemove(LIST_ENTRY* node) {
    node->Bwd->Fwd = node->Fwd;
    node->Fwd->Bwd = node->Bwd;
    node->Fwd = node->Bwd = node;
}

// Removes and returns the first node in a list, or NULL when empty.
static inline LIST_ENTRY* ListPopHead(LIST_ENTRY* head) {
    if (LIST_IS_EMPTY(head))
        return (LIST_ENTRY*)0;

    LIST_ENTRY* node = head->Fwd;
    ListRemove(node);
    return node;
}