/*      $NetBSD: kfifo.h,v 1.3 2018/08/27 14:41:53 riastradh Exp $      */

/*-
 * Copyright (c) 2018 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Taylor R. Campbell.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef _LINUX_KFIFO_H_
#define _LINUX_KFIFO_H_

#include <sys/types.h>
#include <sys/errno.h>
#include <sys/lock.h>

#include <linux/gfp.h>
#include <linux/slab.h>

struct kfifo_meta {
        struct lock     kfm_lock;
        size_t          kfm_head;
        size_t          kfm_tail;
        size_t          kfm_nbytes;
};

#define _KFIFO_PTR_TYPE(TAG, TYPE)                                            \
        struct TAG {                                                          \
                struct kfifo_meta       kf_meta;                              \
                TYPE                    *kf_buf;                              \
        }

#define DECLARE_KFIFO_PTR(FIFO, TYPE)   _KFIFO_PTR_TYPE(, TYPE) FIFO

_KFIFO_PTR_TYPE(kfifo, void);

#define kfifo_alloc(FIFO, SIZE, GFP)                                          \
        _kfifo_alloc(&(FIFO)->kf_meta, &(FIFO)->kf_buf, (SIZE), (GFP))

static inline int
_kfifo_alloc(struct kfifo_meta *meta, void *bufp, size_t nbytes, gfp_t gfp)
{
        void *buf;

        buf = kmalloc(nbytes, M_DRM, gfp);
        if (buf == NULL)
                return -ENOMEM;

        /* Type pun!  Hope void * == struct whatever *.  */
        memcpy(bufp, &buf, sizeof(void *));

        lockinit(&meta->kfm_lock, "lkfl", 0, LK_CANRECURSE);
        meta->kfm_head = 0;
        meta->kfm_tail = 0;
        meta->kfm_nbytes = nbytes;

        return 0;
}

#define kfifo_free(FIFO)                                                      \
        _kfifo_free(&(FIFO)->kf_meta, &(FIFO)->kf_buf)

static inline void
_kfifo_free(struct kfifo_meta *meta, void *bufp)
{
        void *buf;

        mutex_destroy(&meta->kfm_lock);

        memcpy(&buf, bufp, sizeof(void *));
        kfree(buf);

        /* Paranoia.  */
        buf = NULL;
        memcpy(bufp, &buf, sizeof(void *));
}

#define kfifo_is_empty(FIFO)    (kfifo_len(FIFO) == 0)
#define kfifo_len(FIFO)         _kfifo_len(&(FIFO)->kf_meta)

static inline size_t
_kfifo_len(struct kfifo_meta *meta)
{
        const size_t head = meta->kfm_head;
        const size_t tail = meta->kfm_tail;
        const size_t nbytes = meta->kfm_nbytes;

        return (head <= tail ? tail - head : nbytes + tail - head);
}

#define kfifo_out_peek(FIFO, PTR, SIZE)                                       \
        _kfifo_out_peek(&(FIFO)->kf_meta, (FIFO)->kf_buf, (PTR), (SIZE))

static inline size_t
_kfifo_out_peek(struct kfifo_meta *meta, void *buf, void *ptr, size_t size)
{
        const char *src = buf;
        char *dst = ptr;
        size_t copied = 0;

        lockmgr(&meta->kfm_lock, LK_EXCLUSIVE);
        const size_t head = meta->kfm_head;
        const size_t tail = meta->kfm_tail;
        const size_t nbytes = meta->kfm_nbytes;
        if (head <= tail) {
                if (size <= tail - head) {
                        memcpy(dst, src + head, size);
                        copied = size;
                }
        } else {
                if (size <= nbytes - head) {
                        memcpy(dst, src + head, size);
                        copied = size;
                } else if (size <= nbytes + tail - head) {
                        memcpy(dst, src + head, nbytes - head);
                        memcpy(dst + nbytes - head, src,
                            size - (nbytes - head));
                        copied = size;
                }
        }
        lockmgr(&meta->kfm_lock, LK_RELEASE);

        return copied;
}

#define kfifo_out(FIFO, PTR, SIZE)                                            \
        _kfifo_out(&(FIFO)->kf_meta, (FIFO)->kf_buf, (PTR), (SIZE))

static inline size_t
_kfifo_out(struct kfifo_meta *meta, const void *buf, void *ptr, size_t size)
{
        const char *src = buf;
        char *dst = ptr;
        size_t copied = 0;

        lockmgr(&meta->kfm_lock, LK_EXCLUSIVE);
        const size_t head = meta->kfm_head;
        const size_t tail = meta->kfm_tail;
        const size_t nbytes = meta->kfm_nbytes;
        if (head <= tail) {
                if (size <= tail - head) {
                        memcpy(dst, src + head, size);
                        meta->kfm_head = head + size;
                        copied = size;
                }
        } else {
                if (size <= nbytes - head) {
                        memcpy(dst, src + head, size);
                        meta->kfm_head = head + size;
                        copied = size;
                } else if (size <= nbytes + tail - head) {
                        memcpy(dst, src + head, nbytes - head);
                        memcpy(dst + nbytes - head, src,
                            size - (nbytes - head));
                        meta->kfm_head = size - (nbytes - head);
                        copied = size;
                }
        }
        lockmgr(&meta->kfm_lock, LK_RELEASE);

        return copied;
}

#define kfifo_in(FIFO, PTR, SIZE)                                             \
        _kfifo_in(&(FIFO)->kf_meta, (FIFO)->kf_buf, (PTR), (SIZE))

static inline size_t
_kfifo_in(struct kfifo_meta *meta, void *buf, const void *ptr, size_t size)
{
        const char *src = ptr;
        char *dst = buf;
        size_t copied = 0;

        lockmgr(&meta->kfm_lock, LK_EXCLUSIVE);
        const size_t head = meta->kfm_head;
        const size_t tail = meta->kfm_tail;
        const size_t nbytes = meta->kfm_nbytes;
        if (tail <= head) {
                if (size <= head - tail) {
                        memcpy(dst + tail, src, size);
                        meta->kfm_tail = tail + size;
                        copied = size;
                }
        } else {
                if (size <= nbytes - tail) {
                        memcpy(dst + tail, src, size);
                        meta->kfm_tail = tail + size;
                } else if (size <= nbytes + tail - head) {
                        memcpy(dst + tail, src, nbytes - tail);
                        memcpy(dst, src + nbytes - tail,
                            size - (nbytes - tail));
                        meta->kfm_tail = size - (nbytes - tail);
                        copied = size;
                }
        }
        lockmgr(&meta->kfm_lock, LK_RELEASE);

        return copied;
}

struct __kfifo {
        unsigned int    in;
        unsigned int    out;
        unsigned int    mask;
        unsigned int    esize;
        void            *data;
};

#define __STRUCT_KFIFO_COMMON(datatype, recsize, ptrtype) \
        union { \
                struct __kfifo  kfifo; \
                datatype        *type; \
                const datatype  *const_type; \
                char            (*rectype)[recsize]; \
                ptrtype         *ptr; \
                ptrtype const   *ptr_const; \
        }

#define __STRUCT_KFIFO(type, size, recsize, ptrtype) \
{ \
        __STRUCT_KFIFO_COMMON(type, recsize, ptrtype); \
        type            buf[((size < 2) || (size & (size - 1))) ? -1 : size]; \
}

#define _KFIFO_TYPE(TYPE, SIZE) \
        struct __STRUCT_KFIFO(TYPE, SIZE, 0, TYPE)
/**
 * DECLARE_KFIFO - macro to declare a fifo object
 * @fifo: name of the declared fifo
 * @type: type of the fifo elements
 * @size: the number of elements in the fifo, this must be a power of 2
 */
#define DECLARE_KFIFO(FIFO, TYPE, SIZE) _KFIFO_TYPE(TYPE, SIZE) FIFO 

#endif  /* _LINUX_KFIFO_H_ */