zstd/lib/dictBuilder/zdict.h

/**
 * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

#ifndef DICTBUILDER_H_001
#define DICTBUILDER_H_001

#if defined (__cplusplus)
extern "C" {
#endif


/*======  Dependencies  ======*/
#include <stddef.h>  /* size_t */


/* =====   ZDICTLIB_API : control library symbols visibility   ===== */
#if defined(__GNUC__) && (__GNUC__ >= 4)
#  define ZDICTLIB_VISIBILITY __attribute__ ((visibility ("default")))
#else
#  define ZDICTLIB_VISIBILITY
#endif
#if defined(ZSTD_DLL_EXPORT) && (ZSTD_DLL_EXPORT==1)
#  define ZDICTLIB_API __declspec(dllexport) ZDICTLIB_VISIBILITY
#elif defined(ZSTD_DLL_IMPORT) && (ZSTD_DLL_IMPORT==1)
#  define ZDICTLIB_API __declspec(dllimport) ZDICTLIB_VISIBILITY /* It isn't required but allows to generate better code, saving a function pointer load from the IAT and an indirect jump.*/
#else
#  define ZDICTLIB_API ZDICTLIB_VISIBILITY
#endif


/*! ZDICT_trainFromBuffer() :
    Train a dictionary from an array of samples.
    Samples must be stored concatenated in a single flat buffer `samplesBuffer`,
    supplied with an array of sizes `samplesSizes`, providing the size of each sample, in order.
    The resulting dictionary will be saved into `dictBuffer`.
    @return : size of dictionary stored into `dictBuffer` (<= `dictBufferCapacity`)
              or an error code, which can be tested with ZDICT_isError().
    Tips : In general, a reasonable dictionary has a size of ~ 100 KB.
           It's obviously possible to target smaller or larger ones, just by specifying different `dictBufferCapacity`.
           In general, it's recommended to provide a few thousands samples, but this can vary a lot.
           It's recommended that total size of all samples be about ~x100 times the target size of dictionary.
*/
ZDICTLIB_API size_t ZDICT_trainFromBuffer(void* dictBuffer, size_t dictBufferCapacity,
                       const void* samplesBuffer, const size_t* samplesSizes, unsigned nbSamples);


/*======   Helper functions   ======*/
ZDICTLIB_API unsigned ZDICT_getDictID(const void* dictBuffer, size_t dictSize);  /**< extracts dictID; @return zero if error (not a valid dictionary) */
ZDICTLIB_API unsigned ZDICT_isError(size_t errorCode);
ZDICTLIB_API const char* ZDICT_getErrorName(size_t errorCode);



#ifdef ZDICT_STATIC_LINKING_ONLY

/* ====================================================================================
 * The definitions in this section are considered experimental.
 * They should never be used with a dynamic library, as they may change in the future.
 * They are provided for advanced usages.
 * Use them only in association with static linking.
 * ==================================================================================== */

typedef struct {
    unsigned selectivityLevel;   /* 0 means default; larger => select more => larger dictionary */
    int      compressionLevel;   /* 0 means default; target a specific zstd compression level */
    unsigned notificationLevel;  /* Write to stderr; 0 = none (default); 1 = errors; 2 = progression; 3 = details; 4 = debug; */
    unsigned dictID;             /* 0 means auto mode (32-bits random value); other : force dictID value */
    unsigned reserved[2];        /* reserved space for future parameters */
} ZDICT_params_t;


/*! ZDICT_trainFromBuffer_advanced() :
    Same as ZDICT_trainFromBuffer() with control over more parameters.
    `parameters` is optional and can be provided with values set to 0 to mean "default".
    @return : size of dictionary stored into `dictBuffer` (<= `dictBufferSize`),
              or an error code, which can be tested by ZDICT_isError().
    note : ZDICT_trainFromBuffer_advanced() will send notifications into stderr if instructed to, using notificationLevel>0.
*/
ZDICTLIB_API size_t ZDICT_trainFromBuffer_advanced(void* dictBuffer, size_t dictBufferCapacity,
                                const void* samplesBuffer, const size_t* samplesSizes, unsigned nbSamples,
                                ZDICT_params_t parameters);

/*! COVER_params_t :
    For all values 0 means default.
    k and d are the only required parameters.
*/
typedef struct {
    unsigned k;                  /* Segment size : constraint: 0 < k : Reasonable range [16, 2048+] */
    unsigned d;                  /* dmer size : constraint: 0 < d <= k : Reasonable range [6, 16] */
    unsigned steps;              /* Number of steps : Only used for optimization : 0 means default (32) : Higher means more parameters checked */

    unsigned nbThreads;          /* Number of threads : constraint: 0 < nbThreads : 1 means single-threaded : Only used for optimization : Ignored if ZSTD_MULTITHREAD is not defined */
    unsigned notificationLevel;  /* Write to stderr; 0 = none (default); 1 = errors; 2 = progression; 3 = details; 4 = debug; */
    unsigned dictID;             /* 0 means auto mode (32-bits random value); other : force dictID value */
    int      compressionLevel;   /* 0 means default; target a specific zstd compression level */
} COVER_params_t;


/*! COVER_trainFromBuffer() :
    Train a dictionary from an array of samples using the COVER algorithm.
    Samples must be stored concatenated in a single flat buffer `samplesBuffer`,
    supplied with an array of sizes `samplesSizes`, providing the size of each sample, in order.
    The resulting dictionary will be saved into `dictBuffer`.
    @return : size of dictionary stored into `dictBuffer` (<= `dictBufferCapacity`)
              or an error code, which can be tested with ZDICT_isError().
    Note : COVER_trainFromBuffer() requires about 9 bytes of memory for each input byte.
    Tips : In general, a reasonable dictionary has a size of ~ 100 KB.
           It's obviously possible to target smaller or larger ones, just by specifying different `dictBufferCapacity`.
           In general, it's recommended to provide a few thousands samples, but this can vary a lot.
           It's recommended that total size of all samples be about ~x100 times the target size of dictionary.
*/
ZDICTLIB_API size_t COVER_trainFromBuffer(void* dictBuffer, size_t dictBufferCapacity,
                              const void* samplesBuffer, const size_t* samplesSizes, unsigned nbSamples,
                              COVER_params_t parameters);

/*! COVER_optimizeTrainFromBuffer() :
    The same requirements as above hold for all the parameters except `parameters`.
    This function tries many parameter combinations and picks the best parameters.
    `*parameters` is filled with the best parameters found, and the dictionary
    constructed with those parameters is stored in `dictBuffer`.

    All of the parameters d, k, steps are optional.
    If d is non-zero then we don't check multiple values of d, otherwise we check d = {6, 8, 10, 12, 14, 16}.
    if steps is zero it defaults to its default value.
    If k is non-zero then we don't check multiple values of k, otherwise we check steps values in [16, 2048].

    @return : size of dictionary stored into `dictBuffer` (<= `dictBufferCapacity`)
              or an error code, which can be tested with ZDICT_isError().
              On success `*parameters` contains the parameters selected.
    Note : COVER_optimizeTrainFromBuffer() requires about 8 bytes of memory for each input byte and additionally another 5 bytes of memory for each byte of memory for each thread.
*/
ZDICTLIB_API size_t COVER_optimizeTrainFromBuffer(void* dictBuffer, size_t dictBufferCapacity,
                                     const void* samplesBuffer, const size_t *samplesSizes, unsigned nbSamples,
                                     COVER_params_t *parameters);

/*! ZDICT_finalizeDictionary() :

    Given a custom content as a basis for dictionary, and a set of samples,
    finalize dictionary by adding headers and statistics.

    Samples must be stored concatenated in a flat buffer `samplesBuffer`,
    supplied with an array of sizes `samplesSizes`, providing the size of each sample in order.

    dictContentSize must be >= ZDICT_CONTENTSIZE_MIN bytes.
    maxDictSize must be >= dictContentSize, and must be >= ZDICT_DICTSIZE_MIN bytes.

    @return : size of dictionary stored into `dictBuffer` (<= `dictBufferCapacity`),
              or an error code, which can be tested by ZDICT_isError().
    note : ZDICT_finalizeDictionary() will push notifications into stderr if instructed to, using notificationLevel>0.
    note 2 : dictBuffer and dictContent can overlap
*/
#define ZDICT_CONTENTSIZE_MIN 128
#define ZDICT_DICTSIZE_MIN    256
ZDICTLIB_API size_t ZDICT_finalizeDictionary(void* dictBuffer, size_t dictBufferCapacity,
                                const void* dictContent, size_t dictContentSize,
                                const void* samplesBuffer, const size_t* samplesSizes, unsigned nbSamples,
                                ZDICT_params_t parameters);



/* Deprecation warnings */
/* It is generally possible to disable deprecation warnings from compiler,
   for example with -Wno-deprecated-declarations for gcc
   or _CRT_SECURE_NO_WARNINGS in Visual.
   Otherwise, it's also possible to manually define ZDICT_DISABLE_DEPRECATE_WARNINGS */
#ifdef ZDICT_DISABLE_DEPRECATE_WARNINGS
#  define ZDICT_DEPRECATED(message) ZDICTLIB_API   /* disable deprecation warnings */
#else
#  define ZDICT_GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
#  if defined (__cplusplus) && (__cplusplus >= 201402) /* C++14 or greater */
#    define ZDICT_DEPRECATED(message) [[deprecated(message)]] ZDICTLIB_API
#  elif (ZDICT_GCC_VERSION >= 405) || defined(__clang__)
#    define ZDICT_DEPRECATED(message) ZDICTLIB_API __attribute__((deprecated(message)))
#  elif (ZDICT_GCC_VERSION >= 301)
#    define ZDICT_DEPRECATED(message) ZDICTLIB_API __attribute__((deprecated))
#  elif defined(_MSC_VER)
#    define ZDICT_DEPRECATED(message) ZDICTLIB_API __declspec(deprecated(message))
#  else
#    pragma message("WARNING: You need to implement ZDICT_DEPRECATED for this compiler")
#    define ZDICT_DEPRECATED(message) ZDICTLIB_API
#  endif
#endif /* ZDICT_DISABLE_DEPRECATE_WARNINGS */

ZDICT_DEPRECATED("use ZDICT_finalizeDictionary() instead")
size_t ZDICT_addEntropyTablesFromBuffer(void* dictBuffer, size_t dictContentSize, size_t dictBufferCapacity,
                                  const void* samplesBuffer, const size_t* samplesSizes, unsigned nbSamples);


#endif   /* ZDICT_STATIC_LINKING_ONLY */

#if defined (__cplusplus)
}
#endif

#endif   /* DICTBUILDER_H_001 */