lib/isc/counter.c

	counter.c revision 0c27b3fe77ac1d5094ba3521e8142d9e7973133f
/*
 * Copyright (C) 2014, 2016  Internet Systems Consortium, Inc. ("ISC")
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

/*! \file */

#include <config.h>

#include <stddef.h>

#include <isc/counter.h>
#include <isc/magic.h>
#include <isc/mem.h>
#include <isc/util.h>

#define COUNTER_MAGIC           ISC_MAGIC('C', 'n', 't', 'r')
#define VALID_COUNTER(r)        ISC_MAGIC_VALID(r, COUNTER_MAGIC)

struct isc_counter {
    unsigned int    magic;
    isc_mem_t   *mctx;
    isc_mutex_t lock;
    unsigned int    references;
    unsigned int    limit;
    unsigned int    used;
};

isc_result_t
isc_counter_create(isc_mem_t *mctx, int limit, isc_counter_t **counterp) {
    isc_result_t result;
    isc_counter_t *counter;

    REQUIRE(counterp != NULL && *counterp == NULL);

    counter = isc_mem_get(mctx, sizeof(*counter));
    if (counter == NULL)
        return (ISC_R_NOMEMORY);

    result = isc_mutex_init(&counter->lock);
    if (result != ISC_R_SUCCESS) {
        isc_mem_put(mctx, counter, sizeof(*counter));
        return (result);
    }

    counter->mctx = NULL;
    isc_mem_attach(mctx, &counter->mctx);

    counter->references = 1;
    counter->limit = limit;
    counter->used = 0;

    counter->magic = COUNTER_MAGIC;
    *counterp = counter;
    return (ISC_R_SUCCESS);
}

isc_result_t
isc_counter_increment(isc_counter_t *counter) {
    isc_result_t result = ISC_R_SUCCESS;

    LOCK(&counter->lock);
    counter->used++;
    if (counter->limit != 0 && counter->used >= counter->limit)
        result = ISC_R_QUOTA;
    UNLOCK(&counter->lock);

    return (result);
}

unsigned int
isc_counter_used(isc_counter_t *counter) {
    REQUIRE(VALID_COUNTER(counter));

    return (counter->used);
}

void
isc_counter_setlimit(isc_counter_t *counter, int limit) {
    REQUIRE(VALID_COUNTER(counter));

    LOCK(&counter->lock);
    counter->limit = limit;
    UNLOCK(&counter->lock);
}

void
isc_counter_attach(isc_counter_t *source, isc_counter_t **targetp) {
    REQUIRE(VALID_COUNTER(source));
    REQUIRE(targetp != NULL && *targetp == NULL);

    LOCK(&source->lock);
    source->references++;
    INSIST(source->references > 0);
    UNLOCK(&source->lock);

    *targetp = source;
}

static void
destroy(isc_counter_t *counter) {
    counter->magic = 0;
    isc_mutex_destroy(&counter->lock);
    isc_mem_putanddetach(&counter->mctx, counter, sizeof(*counter));
}

void
isc_counter_detach(isc_counter_t **counterp) {
    isc_counter_t *counter;
    isc_boolean_t want_destroy = ISC_FALSE;

    REQUIRE(counterp != NULL && *counterp != NULL);
    counter = *counterp;
    REQUIRE(VALID_COUNTER(counter));

    *counterp = NULL;

    LOCK(&counter->lock);
    INSIST(counter->references > 0);
    counter->references--;
    if (counter->references == 0)
        want_destroy = ISC_TRUE;
    UNLOCK(&counter->lock);

    if (want_destroy)
        destroy(counter);
}