/*
  Copyright (c) 2008-2015 Red Hat, Inc. <http://www.redhat.com>
  This file is part of GlusterFS.

  This file is licensed to you under your choice of the GNU Lesser
  General Public License, version 3 or any later version (LGPLv3 or
  later), or the GNU General Public License, version 2 (GPLv2), in all
  cases as published by the Free Software Foundation.
*/

#ifndef __ROT_BUFFS_H
#define __ROT_BUFFS_H

#include "glusterfs/list.h"
#include "glusterfs/locking.h"

typedef struct rbuf_iovec {
    struct iovec iov;

    struct list_head list;
} rbuf_iovec_t;

#define RBUF_IOVEC_SIZE (sizeof(rbuf_iovec_t))

typedef struct rbuf_list {
    gf_lock_t c_lock;

    pthread_mutex_t b_lock; /* protects this structure */
    pthread_cond_t b_cond;  /* signal for writer completion */

    gf_boolean_t awaiting;

    unsigned long long pending;   /* pending writers */
    unsigned long long completed; /* completed writers */

    rbuf_iovec_t *rvec; /* currently used IO vector */

    struct list_head veclist; /* list of attached rbuf_iov */

    unsigned long long used;  /* consumable entries
                                  attached in ->veclist */
    unsigned long long total; /* total entries in ->veclist (used
                                 during deallocation) */

    unsigned long seq[2]; /* if interested, this whould store
                             the start sequence number and the
                             range */

    struct list_head list; /* attachment to rbuf_t */
} rbuf_list_t;

struct rlist_iter {
    struct list_head veclist;

    unsigned long long iter;
};

#define RLIST_ENTRY_COUNT(rlist) rlist->used

#define rlist_iter_init(riter, rlist)                                          \
    do {                                                                       \
        (riter)->iter = rlist->used;                                           \
        (riter)->veclist = rlist->veclist;                                     \
    } while (0)

#define rvec_for_each_entry(pos, riter)                                        \
    for (pos = list_entry((riter)->veclist.next, typeof(*pos), list);          \
         (riter)->iter > 0;                                                    \
         pos = list_entry(pos->list.next, typeof(*pos), list),                 \
        --((riter)->iter))

/**
 * Sequence number assignment routine is called during buffer
 * switch under rbuff ->lock.
 */
typedef void(sequence_fn)(rbuf_list_t *, void *);

#define RLIST_STORE_SEQ(rlist, start, range)                                   \
    do {                                                                       \
        rlist->seq[0] = start;                                                 \
        rlist->seq[1] = range;                                                 \
    } while (0)

#define RLIST_GET_SEQ(rlist, start, range)                                     \
    do {                                                                       \
        start = rlist->seq[0];                                                 \
        range = rlist->seq[1];                                                 \
    } while (0)

typedef struct rbuf {
    gf_lock_t lock; /* protects "current" rlist */

    rbuf_list_t *current; /* cached pointer to first free rlist */

    struct list_head freelist;
} rbuf_t;

typedef enum {
    RBUF_CONSUMABLE = 1,
    RBUF_BUSY,
    RBUF_EMPTY,
    RBUF_WOULD_STARVE,
} rlist_retval_t;

/* Initialization/Destruction */
rbuf_t *
rbuf_init(int);
void
rbuf_dtor(rbuf_t *);

/* Producer API */
char *
rbuf_reserve_write_area(rbuf_t *, size_t, void **);
int
rbuf_write_complete(void *);

/* Consumer API */
int
rbuf_get_buffer(rbuf_t *, void **, sequence_fn *, void *);
int
rbuf_wait_for_completion(rbuf_t *, void *, void (*)(rbuf_list_t *, void *),
                         void *);

#endif
