spamsum.h

/*
 * This file is part of the Aaru Data Preservation Suite.
 * Copyright (c) 2019-2026 Natalia Portillo.
 *
 * 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, see <http://www.gnu.org/licenses/>.
 */

#ifndef AARU_CHECKSUMS_NATIVE_SPAMSUM_H
#define AARU_CHECKSUMS_NATIVE_SPAMSUM_H

#define SPAMSUM_LENGTH   64
#define NUM_BLOCKHASHES  31
#define ROLLING_WINDOW   7
#define HASH_INIT        0x28021967
#define HASH_PRIME       0x01000193
#define MIN_BLOCKSIZE    3
#define FUZZY_MAX_RESULT ((2 * SPAMSUM_LENGTH) + 20)

typedef struct
{
    uint32_t h;
    uint32_t half_h;
    uint8_t  digest[SPAMSUM_LENGTH];
    uint8_t  half_digest;
    uint32_t d_len;
} blockhash_ctx;

typedef struct
{
    uint8_t  window[ROLLING_WINDOW];
    uint32_t h1;
    uint32_t h2;
    uint32_t h3;
    uint32_t n;
} roll_state;

typedef struct
{
    uint32_t      bh_start;
    uint32_t      bh_end;
    blockhash_ctx bh[NUM_BLOCKHASHES];
    uint64_t      total_size;
    roll_state    roll;
} spamsum_ctx;

AARU_EXPORT spamsum_ctx *AARU_CALL spamsum_init(void);
AARU_EXPORT int AARU_CALL          spamsum_update(spamsum_ctx *ctx, const uint8_t *data, uint32_t len);
AARU_EXPORT int AARU_CALL          spamsum_final(spamsum_ctx *ctx, uint8_t *result);
AARU_EXPORT void AARU_CALL         spamsum_free(spamsum_ctx *ctx);

FORCE_INLINE void fuzzy_engine_step(spamsum_ctx *ctx, uint8_t c);

FORCE_INLINE void roll_hash(spamsum_ctx *ctx, uint8_t c);

FORCE_INLINE void fuzzy_try_reduce_blockhash(spamsum_ctx *ctx);

FORCE_INLINE void fuzzy_try_fork_blockhash(spamsum_ctx *ctx);

#endif  // AARU_CHECKSUMS_NATIVE_SPAMSUM_H