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Filename : ipc_ring.h
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/*
   Copyright (C) 2009 Red Hat, Inc.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are
   met:

       * Redistributions of source code must retain the above copyright
         notice, this list of conditions and the following disclaimer.
       * 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.
       * Neither the name of the copyright holder nor the names of its
         contributors may be used to endorse or promote products derived
         from this software without specific prior written permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER 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 COPYRIGHT
   HOLDER 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 _H_SPICE_RING
#define _H_SPICE_RING

#include <spice/types.h>

#define _SPICE_MSB_MASK4(x)        \
    (((x) & 0x8) ? 0x8 :    \
     ((x) & 0x4) ? 0x4 :    \
     ((x) & 0x2) ? 0x2 :    \
     ((x) & 0x1) ? 0x1 : 0)

#define _SPICE_MSB_MASK8(x) \
    (((x) & 0xf0) ? _SPICE_MSB_MASK4((x) >> 4) << 4 : _SPICE_MSB_MASK4(x))

#define _SPICE_MSB_MASK16(x) \
    (((x) & 0xff00) ? _SPICE_MSB_MASK8((x) >> 8) << 8 : _SPICE_MSB_MASK8(x))

#define _SPICE_MSB_MASK(x) \
    (((x) & 0xffff0000) ? _SPICE_MSB_MASK16((x) >> 16) << 16 : _SPICE_MSB_MASK16(x))

#define _SPICE_POWER2_ALIGN(x) _SPICE_MSB_MASK((x) * 2 - 1)


#define _SPICE_TOSHIFT_4(x)      \
    (((x) & 0x8) ? 3 :     \
     ((x) & 0x4) ? 2 :     \
     ((x) & 0x2) ? 1 : 0)

#define _SPICE_TOSHIFT_8(x) \
    (((x) & 0xf0) ? _SPICE_TOSHIFT_4((x) >> 4) + 4 : _SPICE_TOSHIFT_4(x))

#define _SPICE_TOSHIFT_16(x) \
    (((x) & 0xff00) ? _SPICE_TOSHIFT_8((x) >> 8) + 8 : _SPICE_TOSHIFT_8(x))

#define _SPICE_POWER2_TO_SHIFT(x) \
    (((x) & 0xffff0000) ? _SPICE_TOSHIFT_16((x) >> 16) + 16 : _SPICE_TOSHIFT_16(x))



#define SPICE_RING_DECLARE(name, el_type, size)               \
typedef struct SPICE_ATTR_PACKED name##_ring_el {       \
    union {                                             \
        el_type el;                                     \
        uint8_t data[_SPICE_POWER2_ALIGN(sizeof(el_type))];      \
    } ;                                                 \
} name##_ring_el;                                       \
                                                        \
typedef struct SPICE_ATTR_PACKED name {                   \
    uint32_t num_items;                                   \
    uint32_t prod;                                        \
    uint32_t notify_on_prod;                              \
    uint32_t cons;                                        \
    uint32_t notify_on_cons;                              \
    name##_ring_el items[_SPICE_POWER2_ALIGN(size)];           \
} name;


#define SPICE_RING_INIT(r)                                                \
    (r)->num_items = sizeof((r)->items) >>                          \
                        _SPICE_POWER2_TO_SHIFT(sizeof((r)->items[0]));     \
    (r)->prod = (r)->cons = 0;                                      \
    (r)->notify_on_prod = 1;                                        \
    (r)->notify_on_cons = 0;


#define SPICE_RING_INDEX_MASK(r) ((r)->num_items - 1)

#define SPICE_RING_IS_PACKED(r) (sizeof((r)->items[0]) == sizeof((r)->items[0]).el)

#define SPICE_RING_IS_EMPTY(r) ((r)->cons == (r)->prod)

#define SPICE_RING_IS_FULL(r) (((r)->prod - (r)->cons) == (r)->num_items)

#define SPICE_RING_PROD_ITEM(r) (&(r)->items[(r)->prod & SPICE_RING_INDEX_MASK(r)].el)

#define SPICE_RING_PROD_WAIT(r, wait)                 \
    if (((wait) = SPICE_RING_IS_FULL(r))) {           \
        (r)->notify_on_cons = (r)->cons + 1;    \
        spice_mb();	                        \
        (wait) = SPICE_RING_IS_FULL(r);               \
    }

#define SPICE_RING_PUSH(r, notify)                    \
    (r)->prod++;                                \
    spice_mb();                                 \
    (notify) = (r)->prod == (r)->notify_on_prod;


#define SPICE_RING_CONS_ITEM(r) (&(r)->items[(r)->cons & SPICE_RING_INDEX_MASK(r)].el)

#define SPICE_RING_CONS_WAIT(r, wait)                 \
    if (((wait) = SPICE_RING_IS_EMPTY(r))) {          \
        (r)->notify_on_prod = (r)->prod + 1;    \
        spice_mb();                             \
        (wait) = SPICE_RING_IS_EMPTY(r);              \
    }

#define SPICE_RING_POP(r, notify)                         \
    (r)->cons++;                                    \
    spice_mb();                                     \
    (notify) = (r)->cons == (r)->notify_on_cons;



#endif /* _H_SPICE_RING */