myxce/src/lib/hook.c

#include <errno.h>
#include <stdatomic.h>
#include <stdlib.h>
#include <string.h>

#include "hook.h"
#include "utils.h"

int xce_hook_init(hooksys_t* s, int maxtypes)
{
    int i;
    if ((s == NULL) || (maxtypes <= 0)) {
        return -EINVAL;
    }

    s->maxtypes = 0;
    s->hooks    = (xlist_t*)calloc(maxtypes, sizeof(xlist_t));
    if (s->hooks == NULL) {
        return -ENOMEM;
    }

    s->maxtypes = maxtypes;
    for (i = 0; i < s->maxtypes; i++) {
        xlist_init(&(s->hooks[i]), 8);
    }
    return 0;
}

int xce_add_hook(hooksys_t* s, int typ, hook_fn_t fn, void* data)
{
    hook_item_t* it;

    if (s == NULL) {
        return -EINVAL;
    }

    if (fn == NULL) {
        return -EINVAL;
    }

    if ((typ < 0) || (typ >= s->maxtypes)) {
        return -EINVAL;
    }

    /* Scan for a disabled (NULL-fn) slot of the same type to reuse */
    {
        xlist_t* l = &s->hooks[typ];
        int      i;
        for (i = 0; i < l->count; i++) {
            hook_item_t* slot = (hook_item_t*)l->data[i];
            if (!slot) continue;
            hook_fn_t cur =
                atomic_load_explicit(&slot->fn, memory_order_acquire);
            if (cur == NULL) {
                slot->data = data;
                atomic_store_explicit(&slot->fn, fn, memory_order_release);
                return 0;
            }
        }
    }

    /* No reusable slot — allocate new */
    it = (hook_item_t*)calloc(1, sizeof(*it));
    if (it == NULL) {
        return -ENOMEM;
    }

    it->data = data;
    atomic_store_explicit(&it->fn, fn, memory_order_release);

    xlist_store(&(s->hooks[typ]), it);

    return 0;
}

int xce_disable_hook(hooksys_t* s, int typ, hook_fn_t fn)
{
    xlist_t* l;
    int      i;

    if (!s || !fn || typ < 0 || typ >= s->maxtypes) {
        return -EINVAL;
    }

    l = &s->hooks[typ];
    for (i = 0; i < l->count; i++) {
        hook_item_t* it = (hook_item_t*)l->data[i];
        if (!it) continue;
        hook_fn_t cur = atomic_load_explicit(&it->fn, memory_order_acquire);
        if (cur == fn) {
            atomic_store_explicit(&it->fn, (hook_fn_t)NULL,
                                  memory_order_release);
            return 0;
        }
    }
    return -ENOENT;
}

/* HOOK_BEFORE_EVENT returns
 * negative value will cause
 * fail
 */
int xce_run_hooks(hooksys_t* s, int type, int situation, int detail, ...)
{
    xlist_t* l;
    int      i;
    int      rc = 0;

    if (s == NULL) {
        return -EINVAL;
    }

    if ((type < 0) || (type >= s->maxtypes)) {
        return -EINVAL;
    }

    l = &(s->hooks[type]);

    for (i = 0; i < l->count; i++) {
        hook_item_t* it = l->data[i];
        hook_fn_t    local_fn;
        va_list      ap;

        if (it == NULL) {
            continue;
        }

        local_fn = atomic_load_explicit(&it->fn, memory_order_acquire);
        if (!local_fn) {
            continue; /* disabled slot */
        }

        va_start(ap, detail);
        rc = local_fn(type, situation, detail, it->data, ap);
        va_end(ap);

        if ((situation == HOOK_BEFORE_EVENT) && (rc < 0)) {
            break;
        }
    }

    return rc;
}

static int free_hook_item(void* data1, void* data2)
{
    if (data1 == NULL) {
        return -EINVAL;
    }

    free(data1);
    return 0;
}

void xce_hook_fini(hooksys_t* s)
{
    int i;

    if (s == NULL) {
        return;
    }

    if (s->hooks == NULL) {
        return;
    }

    for (i = 0; i < s->maxtypes; i++) {
        xlist_iter(&(s->hooks[i]), (xlist_iter_fn_t)free_hook_item, NULL);
        xlist_fini(&(s->hooks[i]));
    }

    FREEUP(s->hooks);
}