/*
 * Copyright (c) 2018-2019 Cisco and/or its affiliates.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/**
 * @file
 * @brief Unidirectional shared-memory multi-ring message queue
 */

#ifndef SRC_SVM_MESSAGE_QUEUE_H_
#define SRC_SVM_MESSAGE_QUEUE_H_

#include <vppinfra/clib.h>
#include <vppinfra/error.h>
#include <vppinfra/lock.h>
#include <svm/queue.h>

typedef struct svm_msg_q_shr_queue_
{
  pthread_mutex_t mutex;  /* 8 bytes */
  pthread_cond_t condvar; /* 8 bytes */
  u32 head;
  u32 tail;
  volatile u32 cursize;
  u32 maxsize;
  u32 elsize;
  u32 pad;
  u8 data[0];
} svm_msg_q_shared_queue_t;

typedef struct svm_msg_q_queue_
{
  svm_msg_q_shared_queue_t *shr; /**< pointer to shared queue */
  int evtfd;			 /**< producer/consumer eventfd */
  clib_spinlock_t lock;		 /**< private lock for multi-producer */
} svm_msg_q_queue_t;

typedef struct svm_msg_q_ring_shared_
{
  volatile u32 cursize;			/**< current size of the ring */
  u32 nitems;				/**< max size of the ring */
  volatile u32 head;			/**< current head (for dequeue) */
  volatile u32 tail;			/**< current tail (for enqueue) */
  u32 elsize;				/**< size of an element */
  u8 data[0];				/**< chunk of memory for msg data */
} svm_msg_q_ring_shared_t;

typedef struct svm_msg_q_ring_
{
  u32 nitems;			/**< max size of the ring */
  u32 elsize;			/**< size of an element */
  svm_msg_q_ring_shared_t *shr; /**< ring in shared memory */
} __clib_packed svm_msg_q_ring_t;

typedef struct svm_msg_q_shared_
{
  u32 n_rings;			 /**< number of rings after q */
  u32 pad;			 /**< 8 byte alignment for q */
  svm_msg_q_shared_queue_t q[0]; /**< queue for exchanging messages */
} __clib_packed svm_msg_q_shared_t;

typedef struct svm_msg_q_
{
  svm_msg_q_queue_t q;			/**< queue for exchanging messages */
  svm_msg_q_ring_t *rings;		/**< rings with message data*/
} __clib_packed svm_msg_q_t;

typedef struct svm_msg_q_ring_cfg_
{
  u32 nitems;
  u32 elsize;
  void *data;
} svm_msg_q_ring_cfg_t;

typedef struct svm_msg_q_cfg_
{
  int consumer_pid;			/**< pid of msg consumer */
  u32 q_nitems;				/**< msg queue size (not rings) */
  u32 n_rings;				/**< number of msg rings */
  svm_msg_q_ring_cfg_t *ring_cfgs;	/**< array of ring cfgs */
} svm_msg_q_cfg_t;

typedef union
{
  struct
  {
    u32 ring_index;			/**< ring index, could be u8 */
    u32 elt_index;			/**< index in ring */
  };
  u64 as_u64;
} svm_msg_q_msg_t;

#define SVM_MQ_INVALID_MSG { .as_u64 = ~0 }

typedef enum svm_msg_q_wait_type_
{
  SVM_MQ_WAIT_EMPTY,
  SVM_MQ_WAIT_FULL
} svm_msg_q_wait_type_t;

/**
 * Allocate message queue
 *
 * Allocates a message queue on the heap. Based on the configuration options,
 * apart from the message queue this also allocates (one or multiple)
 * shared-memory rings for the messages.
 *
 * @param cfg 		configuration options: queue len, consumer pid,
 * 			ring configs
 * @return		message queue
 */
svm_msg_q_shared_t *svm_msg_q_alloc (svm_msg_q_cfg_t *cfg);
svm_msg_q_shared_t *svm_msg_q_init (void *base, svm_msg_q_cfg_t *cfg);
uword svm_msg_q_size_to_alloc (svm_msg_q_cfg_t *cfg);

void svm_msg_q_attach (svm_msg_q_t *mq, void *smq_base);

/**
 * Cleanup mq's private data
 */
void svm_msg_q_cleanup (svm_msg_q_t *mq);

/**
 * Free message queue
 *
 * @param mq		message queue to be freed
 */
void svm_msg_q_free (svm_msg_q_t * mq);

/**
 * Allocate message buffer
 *
 * Message is allocated on the first available ring capable of holding
 * the requested number of bytes.
 *
 * @param mq		message queue
 * @param nbytes	number of bytes needed for message
 * @return		message structure pointing to the ring and position
 * 			allocated
 */
svm_msg_q_msg_t svm_msg_q_alloc_msg (svm_msg_q_t * mq, u32 nbytes);

/**
 * Allocate message buffer on ring
 *
 * Message is allocated, on requested ring. The caller MUST check that
 * the ring is not full.
 *
 * @param mq		message queue
 * @param ring_index	ring on which the allocation should occur
 * @return		message structure pointing to the ring and position
 * 			allocated
 */
svm_msg_q_msg_t svm_msg_q_alloc_msg_w_ring (svm_msg_q_t * mq, u32 ring_index);

/**
 * Lock message queue and allocate message buffer on ring
 *
 * This should be used when multiple writers/readers are expected to
 * compete for the rings/queue. Message should be enqueued by calling
 * @ref svm_msg_q_add_w_lock and the caller MUST unlock the queue once
 * the message in enqueued.
 *
 * @param mq		message queue
 * @param ring_index	ring on which the allocation should occur
 * @param noblock	flag that indicates if request should block
 * @param msg		pointer to message to be filled in
 * @return		0 on success, negative number otherwise
 */
int svm_msg_q_lock_and_alloc_msg_w_ring (svm_msg_q_t * mq, u32 ring_index,
					 u8 noblock, svm_msg_q_msg_t * msg);

/**
 * Free message buffer
 *
 * Marks message<style>
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