C23 find in sys/queue

find_in_list.h

#pragma once

#include <sys/queue.h>

#define find_in_slist(element, list_head, entry_name, comparator) \
    ({                                                            \
        typeof(element) ret = nullptr;                            \
        typeof(element) current_element = nullptr;                \
        SLIST_FOREACH(current_element, list_head, entry_name) {   \
            if (comparator(current_element, element)) {           \
                ret = current_element;                            \
                break;                                            \
            }                                                     \
        }                                                         \
        ret;                                                      \
    })

#define find_in_stailq(element, queue_head, entry_name, comparator) \
    ({                                                              \
        typeof(element) ret = nullptr;                              \
        typeof(element) current_element = nullptr;                  \
        STAILQ_FOREACH(current_element, queue_head, entry_name) {   \
            if (comparator(current_element, element)) {             \
                ret = current_element;                              \
                break;                                              \
            }                                                       \
        }                                                           \
        ret;                                                        \
    })

#define find_in_list(element, list_head, entry_name, comparator) \
    ({                                                           \
        typeof(element) ret = nullptr;                           \
        typeof(element) current_element = nullptr;               \
        LIST_FOREACH(current_element, list_head, entry_name) {   \
            if (comparator(current_element, element)) {          \
                ret = current_element;                           \
                break;                                           \
            }                                                    \
        }                                                        \
        ret;                                                     \
    })

#define find_in_tailq(element, queue_head, entry_name, comparator) \
    ({                                                             \
        typeof(element) ret = nullptr;                             \
        typeof(element) current_element = nullptr;                 \
        TAILQ_FOREACH(current_element, queue_head, entry_name) {   \
            if (comparator(current_element, element)) {            \
                ret = current_element;                             \
                break;                                             \
            }                                                      \
        }                                                          \
        ret;                                                       \
    })

usage.c

#include <stdio.h>
#include <string.h>
#include <sys/queue.h>

#include "find_in_list.h"

typedef struct my_list_element {
    char my_string[12];
    int my_number;
    TAILQ_ENTRY(my_list_element) entry;
} my_list_element_t;

bool my_list_element_comparator(
    my_list_element_t* element1, my_list_element_t* element2) {
    return strcmp(element1->my_string, element2->my_string) == 0;
}

TAILQ_HEAD(my_list, my_list_element);

int main(int argc, char* argv[]) {
    struct my_list my_list_head;
    TAILQ_INIT(&my_list_head);

    my_list_element_t element1 = { .my_string = "element1", .my_number = 1 };

    TAILQ_INSERT_TAIL(&my_list_head, &element1, entry);

    my_list_element_t element1_clone = { .my_string = "element1",
                                         .my_number = 1 };
    my_list_element_t element2 = { .my_string = "element2", .my_number = 2 };

    my_list_element_t* element_p = find_in_tailq(
        &element1_clone, &my_list_head, entry, my_list_element_comparator);
    if (element_p) {
        printf("element1_clone is in the list\n");
    } else {
        printf("element1_clone is not in the list\n");
    }

    element_p = find_in_tailq(
        &element2, &my_list_head, entry, my_list_element_comparator);
    if (element_p) {
        printf("element2 is in the list\n");
    } else {
        printf("element2 is not in the list\n");
    }

    return 0;
}