counter.c

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/*
 * Copyright (C) 2014  Internet Systems Consortium, Inc. ("ISC")
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/*! \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);
}

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