ppp-comp.h

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/*
 * ppp-comp.h - Definitions for doing PPP packet compression.
 *
 * Copyright 1994-1998 Paul Mackerras.
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  version 2 as published by the Free Software Foundation.
 */
#ifndef _NET_PPP_COMP_H
#define _NET_PPP_COMP_H

#include <uapi/linux/ppp-comp.h>


struct module;

/*
 * The following symbols control whether we include code for
 * various compression methods.
 */

#ifndef DO_BSD_COMPRESS
#define DO_BSD_COMPRESS 1   /* by default, include BSD-Compress */
#endif
#ifndef DO_DEFLATE
#define DO_DEFLATE  1   /* by default, include Deflate */
#endif
#define DO_PREDICTOR_1  0
#define DO_PREDICTOR_2  0

/*
 * Structure giving methods for compression/decompression.
 */

struct compressor {
    int compress_proto; /* CCP compression protocol number */

    /* Allocate space for a compressor (transmit side) */
    void    *(*comp_alloc) (unsigned char *options, int opt_len);

    /* Free space used by a compressor */
    void    (*comp_free) (void *state);

    /* Initialize a compressor */
    int (*comp_init) (void *state, unsigned char *options,
                  int opt_len, int unit, int opthdr, int debug);

    /* Reset a compressor */
    void    (*comp_reset) (void *state);

    /* Compress a packet */
    int     (*compress) (void *state, unsigned char *rptr,
                  unsigned char *obuf, int isize, int osize);

    /* Return compression statistics */
    void    (*comp_stat) (void *state, struct compstat *stats);

    /* Allocate space for a decompressor (receive side) */
    void    *(*decomp_alloc) (unsigned char *options, int opt_len);

    /* Free space used by a decompressor */
    void    (*decomp_free) (void *state);

    /* Initialize a decompressor */
    int (*decomp_init) (void *state, unsigned char *options,
                int opt_len, int unit, int opthdr, int mru,
                int debug);

    /* Reset a decompressor */
    void    (*decomp_reset) (void *state);

    /* Decompress a packet. */
    int (*decompress) (void *state, unsigned char *ibuf, int isize,
                unsigned char *obuf, int osize);

    /* Update state for an incompressible packet received */
    void    (*incomp) (void *state, unsigned char *ibuf, int icnt);

    /* Return decompression statistics */
    void    (*decomp_stat) (void *state, struct compstat *stats);

    /* Used in locking compressor modules */
    struct module *owner;
    /* Extra skb space needed by the compressor algorithm */
    unsigned int comp_extra;
};

/*
 * The return value from decompress routine is the length of the
 * decompressed packet if successful, otherwise DECOMP_ERROR
 * or DECOMP_FATALERROR if an error occurred.
 * 
 * We need to make this distinction so that we can disable certain
 * useful functionality, namely sending a CCP reset-request as a result
 * of an error detected after decompression.  This is to avoid infringing
 * a patent held by Motorola.
 * Don't you just lurve software patents.
 */

#define DECOMP_ERROR        -1  /* error detected before decomp. */
#define DECOMP_FATALERROR   -2  /* error detected after decomp. */

extern int ppp_register_compressor(struct compressor *);
extern void ppp_unregister_compressor(struct compressor *);
#endif /* _NET_PPP_COMP_H */