pstack.c

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/*
 * Simple pointer stack
 *
 * (c) 2010 Arnaldo Carvalho de Melo <[email protected]>
 */

#include "util.h"
#include "pstack.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 *self = zalloc((sizeof(*self) +
                     max_nr_entries * sizeof(void *)));
    if (self != NULL)
        self->max_nr_entries = max_nr_entries;
    return self;
}

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

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

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

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

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

void *pstack__pop(struct pstack *self)
{
    void *ret;

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

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