/* ******************************************************************

 * huff0 huffman codec,

 * part of Finite State Entropy library

 * Copyright (c) Meta Platforms, Inc. and affiliates.

 *

 * You can contact the author at :

 * - Source repository : https://github.com/Cyan4973/FiniteStateEntropy

 *

 * 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 HUF_H_298734234

#define HUF_H_298734234

/* *** Dependencies *** */

#include "zstd_deps.h"    /* size_t */

#include "mem.h"          /* U32 */

#define FSE_STATIC_LINKING_ONLY

#include "fse.h"

/* ***   Tool functions *** */

#define HUF_BLOCKSIZE_MAX (128 * 1024)   /**< maximum input size for a single block compressed with HUF_compress */

size_t HUF_compressBound(size_t size);   /**< maximum compressed size (worst case) */

/* Error Management */

unsigned    HUF_isError(size_t code);       /**< tells if a return value is an error code */

const char* HUF_getErrorName(size_t code);  /**< provides error code string (useful for debugging) */

#define HUF_WORKSPACE_SIZE ((8 << 10) + 512 /* sorting scratch space */)

#define HUF_WORKSPACE_SIZE_U64 (HUF_WORKSPACE_SIZE / sizeof(U64))

/* *** Constants *** */

#define HUF_TABLELOG_MAX      12      /* max runtime value of tableLog (due to static allocation); can be modified up to HUF_TABLELOG_ABSOLUTEMAX */

#define HUF_TABLELOG_DEFAULT  11      /* default tableLog value when none specified */

#define HUF_SYMBOLVALUE_MAX  255

#define HUF_TABLELOG_ABSOLUTEMAX  12  /* absolute limit of HUF_MAX_TABLELOG. Beyond that value, code does not work */

#if (HUF_TABLELOG_MAX > HUF_TABLELOG_ABSOLUTEMAX)

#  error "HUF_TABLELOG_MAX is too large !"

#endif

/* ****************************************

*  Static allocation

******************************************/

/* HUF buffer bounds */

#define HUF_CTABLEBOUND 129

#define HUF_BLOCKBOUND(size) (size + (size>>8) + 8)   /* only true when incompressible is pre-filtered with fast heuristic */

#define HUF_COMPRESSBOUND(size) (HUF_CTABLEBOUND + HUF_BLOCKBOUND(size))   /* Macro version, useful for static allocation */

/* static allocation of HUF's Compression Table */

/* this is a private definition, just exposed for allocation and strict aliasing purpose. never EVER access its members directly */

typedef size_t HUF_CElt;   /* consider it an incomplete type */

#define HUF_CTABLE_SIZE_ST(maxSymbolValue)   ((maxSymbolValue)+2)   /* Use tables of size_t, for proper alignment */

#define HUF_CTABLE_SIZE(maxSymbolValue)       (HUF_CTABLE_SIZE_ST(maxSymbolValue) * sizeof(size_t))

#define HUF_CREATE_STATIC_CTABLE(name, maxSymbolValue) \

    HUF_CElt name[HUF_CTABLE_SIZE_ST(maxSymbolValue)] /* no final ; */

/* static allocation of HUF's DTable */

typedef U32 HUF_DTable;

#define HUF_DTABLE_SIZE(maxTableLog)   (1 + (1<<(maxTableLog)))

#define HUF_CREATE_STATIC_DTABLEX1(DTable, maxTableLog) \

        HUF_DTable DTable[HUF_DTABLE_SIZE((maxTableLog)-1)] = { ((U32)((maxTableLog)-1) * 0x01000001) }

#define HUF_CREATE_STATIC_DTABLEX2(DTable, maxTableLog) \

        HUF_DTable DTable[HUF_DTABLE_SIZE(maxTableLog)] = { ((U32)(maxTableLog) * 0x01000001) }

/* ****************************************

*  Advanced decompression functions

******************************************/

/**

 * Huffman flags bitset.

 * For all flags, 0 is the default value.

 */

typedef enum {

    /**

     * If compiled with DYNAMIC_BMI2: Set flag only if the CPU supports BMI2 at runtime.

     * Otherwise: Ignored.

     */

    HUF_flags_bmi2 = (1 << 0),

    /**

     * If set: Test possible table depths to find the one that produces the smallest header + encoded size.

     * If unset: Use heuristic to find the table depth.

     */

    HUF_flags_optimalDepth = (1 << 1),

    /**

     * If set: If the previous table can encode the input, always reuse the previous table.

     * If unset: If the previous table can encode the input, reuse the previous table if it results in a smaller output.

     */

    HUF_flags_preferRepeat = (1 << 2),

    /**

     * If set: Sample the input and check if the sample is uncompressible, if it is then don't attempt to compress.

     * If unset: Always histogram the entire input.

     */

    HUF_flags_suspectUncompressible = (1 << 3),

    /**

     * If set: Don't use assembly implementations

     * If unset: Allow using assembly implementations

     */

    HUF_flags_disableAsm = (1 << 4),

    /**

     * If set: Don't use the fast decoding loop, always use the fallback decoding loop.

     * If unset: Use the fast decoding loop when possible.

     */

    HUF_flags_disableFast = (1 << 5)

} HUF_flags_e;

/* ****************************************

 *  HUF detailed API

 * ****************************************/

#define HUF_OPTIMAL_DEPTH_THRESHOLD ZSTD_btultra

/*! HUF_compress() does the following:

 *  1. count symbol occurrence from source[] into table count[] using FSE_count() (exposed within "fse.h")

 *  2. (optional) refine tableLog using HUF_optimalTableLog()

 *  3. build Huffman table from count using HUF_buildCTable()

 *  4. save Huffman table to memory buffer using HUF_writeCTable()

 *  5. encode the data stream using HUF_compress4X_usingCTable()

 *

 *  The following API allows targeting specific sub-functions for advanced tasks.

 *  For example, it's possible to compress several blocks using the same 'CTable',

 *  or to save and regenerate 'CTable' using external methods.

 */

unsigned HUF_minTableLog(unsigned symbolCardinality);

unsigned HUF_cardinality(const unsigned* count, unsigned maxSymbolValue);

unsigned HUF_optimalTableLog(unsigned maxTableLog, size_t srcSize, unsigned maxSymbolValue, void* workSpace,

 size_t wkspSize, HUF_CElt* table, const unsigned* count, int flags); /* table is used as scratch space for building and testing tables, not a return value */

size_t HUF_writeCTable_wksp(void* dst, size_t maxDstSize, const HUF_CElt* CTable, unsigned maxSymbolValue, unsigned huffLog, void* workspace, size_t workspaceSize);

size_t HUF_compress4X_usingCTable(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable, int flags);

size_t HUF_estimateCompressedSize(const HUF_CElt* CTable, const unsigned* count, unsigned maxSymbolValue);

int HUF_validateCTable(const HUF_CElt* CTable, const unsigned* count, unsigned maxSymbolValue);

typedef enum {

   HUF_repeat_none,  /**< Cannot use the previous table */

   HUF_repeat_check, /**< Can use the previous table but it must be checked. Note : The previous table must have been constructed by HUF_compress{1, 4}X_repeat */

   HUF_repeat_valid  /**< Can use the previous table and it is assumed to be valid */

 } HUF_repeat;

/** HUF_compress4X_repeat() :

 *  Same as HUF_compress4X_wksp(), but considers using hufTable if *repeat != HUF_repeat_none.

 *  If it uses hufTable it does not modify hufTable or repeat.

 *  If it doesn't, it sets *repeat = HUF_repeat_none, and it sets hufTable to the table used.

 *  If preferRepeat then the old table will always be used if valid.

 *  If suspectUncompressible then some sampling checks will be run to potentially skip huffman coding */

size_t HUF_compress4X_repeat(void* dst, size_t dstSize,

                       const void* src, size_t srcSize,

                       unsigned maxSymbolValue, unsigned tableLog,

                       void* workSpace, size_t wkspSize,    /**< `workSpace` must be aligned on 4-bytes boundaries, `wkspSize` must be >= HUF_WORKSPACE_SIZE */

                       HUF_CElt* hufTable, HUF_repeat* repeat, int flags);

/** HUF_buildCTable_wksp() :

 *  Same as HUF_buildCTable(), but using externally allocated scratch buffer.

 * `workSpace` must be aligned on 4-bytes boundaries, and its size must be >= HUF_CTABLE_WORKSPACE_SIZE.

 */

#define HUF_CTABLE_WORKSPACE_SIZE_U32 ((4 * (HUF_SYMBOLVALUE_MAX + 1)) + 192)

#define HUF_CTABLE_WORKSPACE_SIZE (HUF_CTABLE_WORKSPACE_SIZE_U32 * sizeof(unsigned))

size_t HUF_buildCTable_wksp (HUF_CElt* tree,

                       const unsigned* count, U32 maxSymbolValue, U32 maxNbBits,

                             void* workSpace, size_t wkspSize);

/*! HUF_readStats() :

 *  Read compact Huffman tree, saved by HUF_writeCTable().

 * `huffWeight` is destination buffer.

 * @return : size read from `src` , or an error Code .

 *  Note : Needed by HUF_readCTable() and HUF_readDTableXn() . */

size_t HUF_readStats(BYTE* huffWeight, size_t hwSize,

                     U32* rankStats, U32* nbSymbolsPtr, U32* tableLogPtr,

                     const void* src, size_t srcSize);

/*! HUF_readStats_wksp() :

 * Same as HUF_readStats() but takes an external workspace which must be

 * 4-byte aligned and its size must be >= HUF_READ_STATS_WORKSPACE_SIZE.

 * If the CPU has BMI2 support, pass bmi2=1, otherwise pass bmi2=0.

 */

#define HUF_READ_STATS_WORKSPACE_SIZE_U32 FSE_DECOMPRESS_WKSP_SIZE_U32(6, HUF_TABLELOG_MAX-1)

#define HUF_READ_STATS_WORKSPACE_SIZE (HUF_READ_STATS_WORKSPACE_SIZE_U32 * sizeof(unsigned))

size_t HUF_readStats_wksp(BYTE* huffWeight, size_t hwSize,

                          U32* rankStats, U32* nbSymbolsPtr, U32* tableLogPtr,

                          const void* src, size_t srcSize,

                          void* workspace, size_t wkspSize,

                          int flags);

/** HUF_readCTable() :

 *  Loading a CTable saved with HUF_writeCTable() */

size_t HUF_readCTable (HUF_CElt* CTable, unsigned* maxSymbolValuePtr, const void* src, size_t srcSize, unsigned *hasZeroWeights);

/** HUF_getNbBitsFromCTable() :

 *  Read nbBits from CTable symbolTable, for symbol `symbolValue` presumed <= HUF_SYMBOLVALUE_MAX

 *  Note 1 : If symbolValue > HUF_readCTableHeader(symbolTable).maxSymbolValue, returns 0

 *  Note 2 : is not inlined, as HUF_CElt definition is private

 */

U32 HUF_getNbBitsFromCTable(const HUF_CElt* symbolTable, U32 symbolValue);

typedef struct {

    BYTE tableLog;

    BYTE maxSymbolValue;

    BYTE unused[sizeof(size_t) - 2];

} HUF_CTableHeader;

/** HUF_readCTableHeader() :

 *  @returns The header from the CTable specifying the tableLog and the maxSymbolValue.

 */

HUF_CTableHeader HUF_readCTableHeader(HUF_CElt const* ctable);

/*

 * HUF_decompress() does the following:

 * 1. select the decompression algorithm (X1, X2) based on pre-computed heuristics

 * 2. build Huffman table from save, using HUF_readDTableX?()

 * 3. decode 1 or 4 segments in parallel using HUF_decompress?X?_usingDTable()

 */

/** HUF_selectDecoder() :

 *  Tells which decoder is likely to decode faster,

 *  based on a set of pre-computed metrics.

 * @return : 0==HUF_decompress4X1, 1==HUF_decompress4X2 .

 *  Assumption : 0 < dstSize <= 128 KB */

U32 HUF_selectDecoder (size_t dstSize, size_t cSrcSize);

/**

 *  The minimum workspace size for the `workSpace` used in

 *  HUF_readDTableX1_wksp() and HUF_readDTableX2_wksp().

 *

 *  The space used depends on HUF_TABLELOG_MAX, ranging from ~1500 bytes when

 *  HUF_TABLE_LOG_MAX=12 to ~1850 bytes when HUF_TABLE_LOG_MAX=15.

 *  Buffer overflow errors may potentially occur if code modifications result in

 *  a required workspace size greater than that specified in the following

 *  macro.

 */

#define HUF_DECOMPRESS_WORKSPACE_SIZE ((2 << 10) + (1 << 9))

#define HUF_DECOMPRESS_WORKSPACE_SIZE_U32 (HUF_DECOMPRESS_WORKSPACE_SIZE / sizeof(U32))

/* ====================== */

/* single stream variants */

/* ====================== */

size_t HUF_compress1X_usingCTable(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable, int flags);

/** HUF_compress1X_repeat() :

 *  Same as HUF_compress1X_wksp(), but considers using hufTable if *repeat != HUF_repeat_none.

 *  If it uses hufTable it does not modify hufTable or repeat.

 *  If it doesn't, it sets *repeat = HUF_repeat_none, and it sets hufTable to the table used.

 *  If preferRepeat then the old table will always be used if valid.

 *  If suspectUncompressible then some sampling checks will be run to potentially skip huffman coding */

size_t HUF_compress1X_repeat(void* dst, size_t dstSize,

                       const void* src, size_t srcSize,

                       unsigned maxSymbolValue, unsigned tableLog,

                       void* workSpace, size_t wkspSize,   /**< `workSpace` must be aligned on 4-bytes boundaries, `wkspSize` must be >= HUF_WORKSPACE_SIZE */

                       HUF_CElt* hufTable, HUF_repeat* repeat, int flags);

size_t HUF_decompress1X_DCtx_wksp(HUF_DTable* dctx, void* dst, size_t dstSize, const void* cSrc, size_t cSrcSize, void* workSpace, size_t wkspSize, int flags);

#ifndef HUF_FORCE_DECOMPRESS_X1

size_t HUF_decompress1X2_DCtx_wksp(HUF_DTable* dctx, void* dst, size_t dstSize, const void* cSrc, size_t cSrcSize, void* workSpace, size_t wkspSize, int flags);   /**< double-symbols decoder */

#endif

/* BMI2 variants.

 * If the CPU has BMI2 support, pass bmi2=1, otherwise pass bmi2=0.

 */

size_t HUF_decompress1X_usingDTable(void* dst, size_t maxDstSize, const void* cSrc, size_t cSrcSize, const HUF_DTable* DTable, int flags);

#ifndef HUF_FORCE_DECOMPRESS_X2

size_t HUF_decompress1X1_DCtx_wksp(HUF_DTable* dctx, void* dst, size_t dstSize, const void* cSrc, size_t cSrcSize, void* workSpace, size_t wkspSize, int flags);

#endif

size_t HUF_decompress4X_usingDTable(void* dst, size_t maxDstSize, const void* cSrc, size_t cSrcSize, const HUF_DTable* DTable, int flags);

size_t HUF_decompress4X_hufOnly_wksp(HUF_DTable* dctx, void* dst, size_t dstSize, const void* cSrc, size_t cSrcSize, void* workSpace, size_t wkspSize, int flags);

#ifndef HUF_FORCE_DECOMPRESS_X2

size_t HUF_readDTableX1_wksp(HUF_DTable* DTable, const void* src, size_t srcSize, void* workSpace, size_t wkspSize, int flags);

#endif

#ifndef HUF_FORCE_DECOMPRESS_X1

size_t HUF_readDTableX2_wksp(HUF_DTable* DTable, const void* src, size_t srcSize, void* workSpace, size_t wkspSize, int flags);

#endif

#endif   /* HUF_H_298734234 */