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/*

 * SpanDSP - a series of DSP components for telephony

 *

 * v42bis.h

 *

 * Written by Steve Underwood <steveu@coppice.org>

 *

 * Copyright (C) 2005 Steve Underwood

 *

 * All rights reserved.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU Lesser General Public License version 2.1,

 * as published by the Free Software Foundation.

 *

 * This program 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 program; if not, write to the Free Software

 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

 *

 * $Id: v42bis.h,v 1.27 2009/04/11 18:11:19 steveu Exp $

 */

/*! \page v42bis_page V.42bis modem data compression

\section v42bis_page_sec_1 What does it do?

The v.42bis specification defines a data compression scheme, to work in

conjunction with the error correction scheme defined in V.42.

\section v42bis_page_sec_2 How does it work?

*/

#ifndef V42BIS_H

#define V42BIS_H

#define V42BIS_MAX_BITS         12

#define V42BIS_MAX_CODEWORDS    4096    /* 2^V42BIS_MAX_BITS */

#define V42BIS_TABLE_SIZE       5021    /* This should be a prime >(2^V42BIS_MAX_BITS) */

#define V42BIS_MAX_STRING_SIZE  250

#define TRUE 1

#define FALSE 0

enum

{

    V42BIS_P0_NEITHER_DIRECTION = 0,

    V42BIS_P0_INITIATOR_RESPONDER,

    V42BIS_P0_RESPONDER_INITIATOR,

    V42BIS_P0_BOTH_DIRECTIONS

};

enum

{

    V42BIS_COMPRESSION_MODE_DYNAMIC = 0,

    V42BIS_COMPRESSION_MODE_ALWAYS,

    V42BIS_COMPRESSION_MODE_NEVER

};

typedef void (*v42bis_frame_handler_t)(void *user_data, const uint8_t *pkt, int len);

typedef void (*v42bis_data_handler_t)(void *user_data, const uint8_t *buf, int len);

/*!

    V.42bis dictionary node.

*/

typedef struct

{

    /*! \brief The prior code for each defined code. */

    uint16_t parent_code;

    /*! \brief The number of leaf nodes this node has */

    int16_t leaves;

    /*! \brief This leaf octet for each defined code. */

    uint8_t node_octet;

    /*! \brief Bit map of the children which exist */

    uint32_t children[8];

} v42bis_dict_node_t;

/*!

    V.42bis compression. This defines the working state for a single instance

    of V.42bis compression.

*/

typedef struct

{

    /*! \brief Compression mode. */

    int compression_mode;

    /*! \brief Callback function to handle received frames. */

    v42bis_frame_handler_t handler;

    /*! \brief An opaque pointer passed in calls to frame_handler. */

    void *user_data;

    /*! \brief The maximum frame length allowed */

    int max_len;

    uint32_t string_code;

    uint32_t latest_code;

    int string_length;

    uint32_t output_bit_buffer;

    int output_bit_count;

    int output_octet_count;

    uint8_t output_buf[1024];

    v42bis_dict_node_t dict[V42BIS_MAX_CODEWORDS];

    /*! \brief TRUE if we are in transparent (i.e. uncompressable) mode */

    int transparent;

    int change_transparency;

    /*! \brief IIR filter state, used in assessing compressibility. */

    int compressibility_filter;

    int compressibility_persistence;

    /*! \brief Next empty dictionary entry */

    uint32_t v42bis_parm_c1;

    /*! \brief Current codeword size */

    int v42bis_parm_c2;

    /*! \brief Threshold for codeword size change */

    uint32_t v42bis_parm_c3;

    /*! \brief Mark that this is the first octet/code to be processed */

    int first;

    uint8_t escape_code;

} v42bis_compress_state_t;

/*!

    V.42bis decompression. This defines the working state for a single instance

    of V.42bis decompression.

*/

typedef struct

{

    /*! \brief Callback function to handle decompressed data. */

    v42bis_data_handler_t handler;

    /*! \brief An opaque pointer passed in calls to data_handler. */

    void *user_data;

    /*! \brief The maximum decompressed data block length allowed */

    int max_len;

    uint32_t old_code;

    uint32_t last_old_code;

    uint32_t input_bit_buffer;

    int input_bit_count;

    int octet;

    int last_length;

    int output_octet_count;

    uint8_t output_buf[1024];

    v42bis_dict_node_t dict[V42BIS_MAX_CODEWORDS];

    /*! \brief TRUE if we are in transparent (i.e. uncompressable) mode */

    int transparent;

    int last_extra_octet;

    /*! \brief Next empty dictionary entry */

    uint32_t v42bis_parm_c1;

    /*! \brief Current codeword size */

    int v42bis_parm_c2;

    /*! \brief Threshold for codeword size change */

    uint32_t v42bis_parm_c3;

    /*! \brief Mark that this is the first octet/code to be processed */

    int first;

    uint8_t escape_code;

    int escaped;

} v42bis_decompress_state_t;

/*!

    V.42bis compression/decompression descriptor. This defines the working state for a

    single instance of V.42bis compress/decompression.

*/

struct v42bis_state_s

{

    /*! \brief V.42bis data compression directions. */

    int v42bis_parm_p0;

    /*! \brief Compression state. */

    v42bis_compress_state_t compress;

    /*! \brief Decompression state. */

    v42bis_decompress_state_t decompress;

    /*! \brief Maximum codeword size (bits) */

    int v42bis_parm_n1;

    /*! \brief Total number of codewords */

    uint32_t v42bis_parm_n2;

    /*! \brief Maximum string length */

    int v42bis_parm_n7;

};

/*!

    V.42bis compression/decompression descriptor. This defines the working state for a

    single instance of V.42bis compress/decompression.

*/

typedef struct v42bis_state_s v42bis_state_t;

/*! Compress a block of octets.

    \param s The V.42bis context.

    \param buf The data to be compressed.

    \param len The length of the data buffer.

    \return 0 */

int v42bis_compress(v42bis_state_t *s, const uint8_t *buf, int len);

/*! Flush out any data remaining in a compression buffer.

    \param s The V.42bis context.

    \return 0 */

int v42bis_compress_flush(v42bis_state_t *s);

/*! Decompress a block of octets.

    \param s The V.42bis context.

    \param buf The data to be decompressed.

    \param len The length of the data buffer.

    \return 0 */

int v42bis_decompress(v42bis_state_t *s, const uint8_t *buf, int len);

/*! Flush out any data remaining in the decompression buffer.

    \param s The V.42bis context.

    \return 0 */

int v42bis_decompress_flush(v42bis_state_t *s);

/*! Set the compression mode.

    \param s The V.42bis context.

    \param mode One of the V.42bis compression modes -

            V42BIS_COMPRESSION_MODE_DYNAMIC,

            V42BIS_COMPRESSION_MODE_ALWAYS,

            V42BIS_COMPRESSION_MODE_NEVER */

void v42bis_compression_control(v42bis_state_t *s, int mode);

/*! Initialise a V.42bis context.

    \param s The V.42bis context.

    \param negotiated_p0 The negotiated P0 parameter, from the V.42bis spec.

    \param negotiated_p1 The negotiated P1 parameter, from the V.42bis spec.

    \param negotiated_p2 The negotiated P2 parameter, from the V.42bis spec.

    \param frame_handler Frame callback handler.

    \param frame_user_data An opaque pointer passed to the frame callback handler.

    \param max_frame_len The maximum length that should be passed to the frame handler.

    \param data_handler data callback handler.

    \param data_user_data An opaque pointer passed to the data callback handler.

    \param max_data_len The maximum length that should be passed to the data handler.

    \return The V.42bis context. */

v42bis_state_t *v42bis_init(v42bis_state_t *s,

                                           int negotiated_p0,

                                           int negotiated_p1,

                                           int negotiated_p2,

                                           v42bis_frame_handler_t frame_handler,

                                           void *frame_user_data,

                                           int max_frame_len,

                                           v42bis_data_handler_t data_handler,

                                           void *data_user_data,

                                           int max_data_len);

/*! Release a V.42bis context.

    \param s The V.42bis context.

    \return 0 if OK */

int v42bis_release(v42bis_state_t *s);

/*! Free a V.42bis context.

    \param s The V.42bis context.

    \return 0 if OK */

int v42bis_free(v42bis_state_t *s);

#endif

/*- End of file ------------------------------------------------------------*/