pstack.c

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

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

struct pstack {
    unsigned short  top;
    unsigned short  max_nr_entries;
    void        *entries[0];
};

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__pop(struct pstack *pstack)
{
    void *ret;

    if (pstack->top == 0) {
        pr_err("%s: underflow!\n", __func__);
        return NULL;
    }

    ret = pstack->entries[--pstack->top];
    pstack->entries[pstack->top] = NULL;
    return ret;
}

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