/*
 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/* $Id: compress.h,v 1.6 2024/05/17 23:56:19 jsg Exp $ */

#ifndef DNS_COMPRESS_H
#define DNS_COMPRESS_H 1

#include <isc/region.h>

#include <dns/types.h>

#define DNS_COMPRESS_NONE               0x00    /*%< no compression */
#define DNS_COMPRESS_GLOBAL14           0x01    /*%< "normal" compression. */
#define DNS_COMPRESS_ALL                0x01    /*%< all compression. */
#define DNS_COMPRESS_CASESENSITIVE      0x02    /*%< case sensitive compression. */

/*! \file dns/compress.h
 *      Direct manipulation of the structures is strongly discouraged.
 */

#define DNS_COMPRESS_TABLESIZE 64
#define DNS_COMPRESS_INITIALNODES 16

typedef struct dns_compressnode dns_compressnode_t;

struct dns_compressnode {
        isc_region_t            r;
        uint16_t                offset;
        uint16_t                count;
        uint8_t         labels;
        dns_compressnode_t      *next;
};

struct dns_compress {
        unsigned int            allowed;        /*%< Allowed methods. */
        int                     edns;           /*%< Edns version or -1. */
        /*% Global compression table. */
        dns_compressnode_t      *table[DNS_COMPRESS_TABLESIZE];
        /*% Preallocated nodes for the table. */
        dns_compressnode_t      initialnodes[DNS_COMPRESS_INITIALNODES];
        uint16_t                count;          /*%< Number of nodes. */
};

typedef enum {
        DNS_DECOMPRESS_ANY,                     /*%< Any compression */
        DNS_DECOMPRESS_STRICT,                  /*%< Allowed compression */
        DNS_DECOMPRESS_NONE                     /*%< No compression */
} dns_decompresstype_t;

struct dns_decompress {
        unsigned int            allowed;        /*%< Allowed methods. */
        int                     edns;           /*%< Edns version or -1. */
        dns_decompresstype_t    type;           /*%< Strict checking */
};

isc_result_t
dns_compress_init(dns_compress_t *cctx, int edns);
/*%<
 *      Initialise the compression context structure pointed to by 'cctx'.
 *
 *      Requires:
 *      \li     'cctx' is a valid dns_compress_t structure.
 *      \li     'mctx' is an initialized memory context.
 *      Ensures:
 *      \li     cctx->global is initialized.
 *
 *      Returns:
 *      \li     #ISC_R_SUCCESS
 */

void
dns_compress_invalidate(dns_compress_t *cctx);

/*%<
 *      Invalidate the compression structure pointed to by cctx.
 *
 *      Requires:
 *\li           'cctx' to be initialized.
 */

void
dns_compress_setmethods(dns_compress_t *cctx, unsigned int allowed);

/*%<
 *      Sets allowed compression methods.
 *
 *      Requires:
 *\li           'cctx' to be initialized.
 */

unsigned int
dns_compress_getmethods(dns_compress_t *cctx);

/*%<
 *      Gets allowed compression methods.
 *
 *      Requires:
 *\li           'cctx' to be initialized.
 *
 *      Returns:
 *\li           allowed compression bitmap.
 */

int
dns_compress_findglobal(dns_compress_t *cctx, const dns_name_t *name,
                        dns_name_t *prefix, uint16_t *offset);
/*%<
 *      Finds longest possible match of 'name' in the global compression table.
 *
 *      Requires:
 *\li           'cctx' to be initialized.
 *\li           'name' to be a absolute name.
 *\li           'prefix' to be initialized.
 *\li           'offset' to point to an uint16_t.
 *
 *      Ensures:
 *\li           'prefix' and 'offset' are valid if 1 is         returned.
 *
 *      Returns:
 *\li           #1 / #0
 */

void
dns_compress_add(dns_compress_t *cctx, const dns_name_t *name,
                 const dns_name_t *prefix, uint16_t offset);
/*%<
 *      Add compression pointers for 'name' to the compression table,
 *      not replacing existing pointers.
 *
 *      Requires:
 *\li           'cctx' initialized
 *
 *\li           'name' must be initialized and absolute, and must remain
 *              valid until the message compression is complete.
 *
 *\li           'prefix' must be a prefix returned by
 *              dns_compress_findglobal(), or the same as 'name'.
 */

void
dns_compress_rollback(dns_compress_t *cctx, uint16_t offset);

/*%<
 *      Remove any compression pointers from global table >= offset.
 *
 *      Requires:
 *\li           'cctx' is initialized.
 */

void
dns_decompress_init(dns_decompress_t *dctx, int edns,
                    dns_decompresstype_t type);

/*%<
 *      Initializes 'dctx'.
 *      Records 'edns' and 'type' into the structure.
 *
 *      Requires:
 *\li           'dctx' to be a valid pointer.
 */

void
dns_decompress_setmethods(dns_decompress_t *dctx, unsigned int allowed);

/*%<
 *      Sets 'dctx->allowed' to 'allowed'.
 *
 *      Requires:
 *\li           'dctx' to be initialized
 */

#endif /* DNS_COMPRESS_H */