comp_wlsb.h

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/*
 * Copyright 2011,2012,2013 Didier Barvaux
 * Copyright 2007,2009,2010 Viveris Technologies
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

/**
 * @file   schemes/comp_wlsb.h
 * @brief  Window-based Least Significant Bits (W-LSB) encoding
 * @author Didier Barvaux <didier.barvaux@toulouse.viveris.com>
 * @author David Moreau from TAS
 */

#ifndef ROHC_COMP_SCHEMES_WLSB_H
#define ROHC_COMP_SCHEMES_WLSB_H

#include "interval.h" /* for rohc_lsb_shift_t */

#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>


/*
 * Public structures and types
 */

/**
 * @brief One W-LSB window entry
 */
struct c_window
{
        bool used;       /**< Whether the window entry is used or not */
        uint32_t sn;     /**< The Sequence Number (SN) associated with the entry
                              (used to acknowledge the entry) */
        uint32_t value;  /**< The value stored in the window entry */
};


/**
 * @brief One W-LSB encoding object
 */
struct c_wlsb
{
        /** The width of the window */
        size_t window_width; /* TODO: R-mode needs a non-fixed window width */

        /** A pointer on the oldest entry in the window (change on acknowledgement) */
        size_t oldest;
        /** A pointer on the current entry in the window  (change on add and ack) */
        size_t next;

        /** The count of entries in the window */
        size_t count;

        /** The maximal number of bits for representing the value */
        size_t bits;
        /** The shift parameter (see 4.5.2 in the RFC 3095) */
        rohc_lsb_shift_t p;

        /** The window in which previous values of the encoded value are stored */
        struct c_window window[ROHC_WLSB_WIDTH_MAX];
};


/*
 * Public function prototypes:
 */

void wlsb_init(struct c_wlsb *const wlsb,
               const size_t bits,
               const size_t window_width,
               const rohc_lsb_shift_t p)
        __attribute__((nonnull(1)));

void c_add_wlsb(struct c_wlsb *const wlsb,
                const uint32_t sn,
                const uint32_t value)
        __attribute__((nonnull(1)));

size_t wlsb_get_k_8bits(const struct c_wlsb *const wlsb,
                        const uint8_t value)
        __attribute__((warn_unused_result, nonnull(1)));
size_t wlsb_get_kp_8bits(const struct c_wlsb *const wlsb,
                         const uint8_t value,
                         const rohc_lsb_shift_t p)
        __attribute__((warn_unused_result, nonnull(1)));

size_t wlsb_get_k_16bits(const struct c_wlsb *const wlsb,
                         const uint16_t value)
        __attribute__((warn_unused_result, nonnull(1)));
size_t wlsb_get_mink_16bits(const struct c_wlsb *const wlsb,
                            const uint16_t value,
                            const size_t min_k)
        __attribute__((warn_unused_result, nonnull(1)));
size_t wlsb_get_kp_16bits(const struct c_wlsb *const wlsb,
                          const uint16_t value,
                          const rohc_lsb_shift_t p)
        __attribute__((warn_unused_result, nonnull(1)));
size_t wlsb_get_minkp_16bits(const struct c_wlsb *const wlsb,
                             const uint16_t value,
                             const size_t min_k,
                             const rohc_lsb_shift_t p)
        __attribute__((warn_unused_result, nonnull(1)));

size_t wlsb_get_k_32bits(const struct c_wlsb *const wlsb,
                         const uint32_t value)
        __attribute__((warn_unused_result, nonnull(1)));
size_t wlsb_get_mink_32bits(const struct c_wlsb *const wlsb,
                            const uint32_t value,
                            const size_t min_k)
        __attribute__((warn_unused_result, nonnull(1)));
size_t wlsb_get_kp_32bits(const struct c_wlsb *const wlsb,
                          const uint32_t value,
                          const rohc_lsb_shift_t p)
        __attribute__((warn_unused_result, nonnull(1)));

size_t wlsb_ack(struct c_wlsb *const wlsb,
                const uint32_t sn_bits,
                const size_t sn_bits_nr)
        __attribute__((warn_unused_result, nonnull(1)));

bool wlsb_is_sn_present(struct c_wlsb *const wlsb, const uint32_t sn)
        __attribute__((warn_unused_result, nonnull(1)));

#endif