mariadb/storage/tokudb/PerconaFT/util/queue.cc

/* -*- mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
// vim: ft=cpp:expandtab:ts=8:sw=4:softtabstop=4:
#ident "$Id$"
/*======
This file is part of PerconaFT.


Copyright (c) 2006, 2015, Percona and/or its affiliates. All rights reserved.

    PerconaFT is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License, version 2,
    as published by the Free Software Foundation.

    PerconaFT is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with PerconaFT.  If not, see <http://www.gnu.org/licenses/>.

----------------------------------------

    PerconaFT is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License, version 3,
    as published by the Free Software Foundation.

    PerconaFT is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with PerconaFT.  If not, see <http://www.gnu.org/licenses/>.
======= */

#ident "Copyright (c) 2006, 2015, Percona and/or its affiliates. All rights reserved."

#include <toku_portability.h>
#include "toku_os.h"
#include <errno.h>
#include <toku_assert.h>
#include "queue.h"
#include "memory.h"
#include <toku_pthread.h>

struct qitem;

struct qitem {
    void *item;
    struct qitem *next;
    uint64_t weight;
};

struct queue {
    uint64_t contents_weight; // how much stuff is in there?
    uint64_t weight_limit;    // Block enqueueing when the contents gets to be bigger than the weight.
    struct qitem *head, *tail;

    bool eof;

    toku_mutex_t mutex;
    toku_cond_t  cond;
};

// Representation invariant:
//   q->contents_weight is the sum of the weights of everything in the queue.
//   q->weight_limit    is the limit on the weight before we block.
//   q->head is the oldest thing in the queue.  q->tail is the newest.  (If nothing is in the queue then both are NULL)
//   If q->head is not null:
//    q->head->item is the oldest item.
//    q->head->weight is the weight of that item.
//    q->head->next is the next youngest thing.
//   q->eof indicates that the producer has said "that's all".
//   q->mutex and q->cond are used as condition variables.


int toku_queue_create (QUEUE *q, uint64_t weight_limit)
{
    QUEUE CALLOC(result);
    if (result==NULL) return get_error_errno();
    result->contents_weight = 0;
    result->weight_limit    = weight_limit;
    result->head            = NULL;
    result->tail            = NULL;
    result->eof             = false;
    toku_mutex_init(&result->mutex, NULL);
    toku_cond_init(&result->cond, NULL);
    *q = result;
    return 0;
}

int toku_queue_destroy (QUEUE q)
{
    if (q->head) return EINVAL;
    assert(q->contents_weight==0);
    toku_mutex_destroy(&q->mutex);
    toku_cond_destroy(&q->cond);
    toku_free(q);
    return 0;
}

int toku_queue_enq (QUEUE q, void *item, uint64_t weight, uint64_t *total_weight_after_enq)
{
    toku_mutex_lock(&q->mutex);
    assert(!q->eof);
    // Go ahead and put it in, even if it's too much.
    struct qitem *MALLOC(qi);
    if (qi==NULL) {
	int r = get_error_errno();
	toku_mutex_unlock(&q->mutex);
	return r;
    }
    q->contents_weight += weight;
    qi->item = item;
    qi->weight = weight;
    qi->next   = NULL;
    if (q->tail) {
	q->tail->next = qi;
    } else {
	assert(q->head==NULL);
	q->head = qi;
    }
    q->tail = qi;
    // Wake up the consumer.
    toku_cond_signal(&q->cond);
    // Now block if there's too much stuff in there.
    while (q->weight_limit < q->contents_weight) {
	toku_cond_wait(&q->cond, &q->mutex);
    }
    // we are allowed to return.
    if (total_weight_after_enq) {
	*total_weight_after_enq = q->contents_weight;
    }
    toku_mutex_unlock(&q->mutex);
    return 0;
}

int toku_queue_eof (QUEUE q)
{
    toku_mutex_lock(&q->mutex);
    assert(!q->eof);
    q->eof = true;
    toku_cond_signal(&q->cond);
    toku_mutex_unlock(&q->mutex);
    return 0;
}

int toku_queue_deq (QUEUE q, void **item, uint64_t *weight, uint64_t *total_weight_after_deq)
{
    toku_mutex_lock(&q->mutex);
    int result;
    while (q->head==NULL && !q->eof) {
	toku_cond_wait(&q->cond, &q->mutex);
    }
    if (q->head==NULL) {
	assert(q->eof);
	result = EOF;
    } else {
	struct qitem *head = q->head;
	q->contents_weight -= head->weight;
	*item   = head->item;
	if (weight)
	    *weight = head->weight;
	if (total_weight_after_deq)
	    *total_weight_after_deq = q->contents_weight;
	q->head = head->next;
	toku_free(head);
	if (q->head==NULL) {
	    q->tail = NULL;
	}
	// wake up the producer, since we decreased the contents_weight.
	toku_cond_signal(&q->cond);
	// Successful result.
	result = 0;
    }
    toku_mutex_unlock(&q->mutex);
    return result;
}