/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
* All rights reserved.
*
* This source code is licensed under both the BSD-style license (found in the
* LICENSE file in the root directory of this source tree) and the GPLv2 (found
* in the COPYING file in the root directory of this source tree).
* You may select, at your option, one of the above-listed licenses.
*/

#ifndef SEQGEN_H
#define SEQGEN_H

#define XXH_STATIC_LINKING_ONLY

#include "xxhash.h"
#include <stddef.h>   /* size_t */

typedef enum {
   SEQ_gen_ml = 0,
   SEQ_gen_ll,
   SEQ_gen_of,
   SEQ_gen_max /* Must be the last value */
} SEQ_gen_type;

/* Internal state, do not use */
typedef struct {
   XXH64_state_t xxh; /* xxh state for all the data produced so far (seed=0) */
   unsigned seed;
   int state; /* enum to control state machine (clean=0) */
   unsigned saved;
   size_t bytesLeft;
} SEQ_stream;

SEQ_stream SEQ_initStream(unsigned seed);

typedef struct {
   void* dst;
   size_t size;
   size_t pos;
} SEQ_outBuffer;

/* Returns non-zero until the current type/value has been generated.
* Must pass the same type/value until it returns 0.
*
* Recommended to pick a value in the middle of the range you want, since there
* may be some noise that causes actual results to be slightly different.
* We try to be more accurate for smaller values.
*
* NOTE: Very small values don't work well (< 6).
*/
size_t SEQ_gen(SEQ_stream* stream, SEQ_gen_type type, unsigned value,
              SEQ_outBuffer* out);

/* Returns the xxhash of the data produced so far */
XXH64_hash_t SEQ_digest(SEQ_stream const* stream);

#endif /* SEQGEN_H */