// SPDX-License-Identifier: GPL-2.0
/*
 * Simple pointer stack
 *
 * (c) 2010 Arnaldo Carvalho de Melo <acme@redhat.com>
 */

#include "pstack.h"
#include "debug.h"
#include <linux/kernel.h>
#include <linux/zalloc.h>
#include <stdlib.h>
#include <string.h>

struct pstack {
        unsigned short  top;
        unsigned short  max_nr_entries;
        void            *entries[];
};

struct pstack *pstack__new(unsigned short max_nr_entries)
{
        struct pstack *pstack = zalloc((sizeof(*pstack) +
                                       max_nr_entries * sizeof(void *)));
        if (pstack != NULL)
                pstack->max_nr_entries = max_nr_entries;
        return pstack;
}

void pstack__delete(struct pstack *pstack)
{
        free(pstack);
}

bool pstack__empty(const struct pstack *pstack)
{
        return pstack->top == 0;
}

void pstack__remove(struct pstack *pstack, void *key)
{
        unsigned short i = pstack->top, last_index = pstack->top - 1;

        while (i-- != 0) {
                if (pstack->entries[i] == key) {
                        if (i < last_index)
                                memmove(pstack->entries + i,
                                        pstack->entries + i + 1,
                                        (last_index - i) * sizeof(void *));
                        --pstack->top;
                        return;
                }
        }
        pr_err("%s: %p not on the pstack!\n", __func__, key);
}

void pstack__push(struct pstack *pstack, void *key)
{
        if (pstack->top == pstack->max_nr_entries) {
                pr_err("%s: top=%d, overflow!\n", __func__, pstack->top);
                return;
        }
        pstack->entries[pstack->top++] = key;
}

void *pstack__peek(struct pstack *pstack)
{
        if (pstack->top == 0)
                return NULL;
        return pstack->entries[pstack->top - 1];
}