lib/zstd/common/entropy_common.c - linux - Git at Google

 /* ******************************************************************
  * Common functions of New Generation Entropy library
  * Copyright (c) Yann Collet, Facebook, Inc.
  *
  *  You can contact the author at :
  *  - FSE+HUF source repository : https://github.com/Cyan4973/FiniteStateEntropy
  *  - Public forum : https://groups.google.com/forum/#!forum/lz4c
  *
  * 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.
 ****************************************************************** */

 /* *************************************
 *  Dependencies
 ***************************************/
 #include <linux/module.h>
 #include "mem.h"
 #include "error_private.h"       /* ERR_*, ERROR */
 #define FSE_STATIC_LINKING_ONLY  /* FSE_MIN_TABLELOG */
 #include "fse.h"
 #define HUF_STATIC_LINKING_ONLY  /* HUF_TABLELOG_ABSOLUTEMAX */
 #include "huf.h"


 /*===   Version   ===*/
 unsigned FSE_versionNumber(void) { return FSE_VERSION_NUMBER; }


 /*===   Error Management   ===*/
 unsigned FSE_isError(size_t code) { return ERR_isError(code); }
 const char* FSE_getErrorName(size_t code) { return ERR_getErrorName(code); }

 unsigned HUF_isError(size_t code) { return ERR_isError(code); }
 const char* HUF_getErrorName(size_t code) { return ERR_getErrorName(code); }


 /*-**************************************************************
 *  FSE NCount encoding-decoding
 ****************************************************************/
 static U32 FSE_ctz(U32 val)
 {
     assert(val != 0);
     {
 #   if (__GNUC__ >= 3)   /* GCC Intrinsic */
         return __builtin_ctz(val);
 #   else   /* Software version */
         U32 count = 0;
         while ((val & 1) == 0) {
             val >>= 1;
             ++count;
         }
         return count;
 #   endif
     }
 }

 FORCE_INLINE_TEMPLATE
 size_t FSE_readNCount_body(short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
                            const void* headerBuffer, size_t hbSize)
 {
     const BYTE* const istart = (const BYTE*) headerBuffer;
     const BYTE* const iend = istart + hbSize;
     const BYTE* ip = istart;
     int nbBits;
     int remaining;
     int threshold;
     U32 bitStream;
     int bitCount;
     unsigned charnum = 0;
     unsigned const maxSV1 = *maxSVPtr + 1;
     int previous0 = 0;

     if (hbSize < 8) {
         /* This function only works when hbSize >= 8 */
         char buffer[8] = {0};
         ZSTD_memcpy(buffer, headerBuffer, hbSize);
         {   size_t const countSize = FSE_readNCount(normalizedCounter, maxSVPtr, tableLogPtr,
                                                     buffer, sizeof(buffer));
             if (FSE_isError(countSize)) return countSize;
             if (countSize > hbSize) return ERROR(corruption_detected);
             return countSize;
     }   }
     assert(hbSize >= 8);

     /* init */
     ZSTD_memset(normalizedCounter, 0, (*maxSVPtr+1) * sizeof(normalizedCounter[0]));   /* all symbols not present in NCount have a frequency of 0 */
     bitStream = MEM_readLE32(ip);
     nbBits = (bitStream & 0xF) + FSE_MIN_TABLELOG;   /* extract tableLog */
     if (nbBits > FSE_TABLELOG_ABSOLUTE_MAX) return ERROR(tableLog_tooLarge);
     bitStream >>= 4;
     bitCount = 4;
     *tableLogPtr = nbBits;
     remaining = (1<<nbBits)+1;
     threshold = 1<<nbBits;
     nbBits++;

     for (;;) {
         if (previous0) {
             /* Count the number of repeats. Each time the
              * 2-bit repeat code is 0b11 there is another
              * repeat.
              * Avoid UB by setting the high bit to 1.
              */
             int repeats = FSE_ctz(~bitStream | 0x80000000) >> 1;
             while (repeats >= 12) {
                 charnum += 3 * 12;
                 if (LIKELY(ip <= iend-7)) {
                     ip += 3;
                 } else {
                     bitCount -= (int)(8 * (iend - 7 - ip));
                     bitCount &= 31;
                     ip = iend - 4;
                 }
                 bitStream = MEM_readLE32(ip) >> bitCount;
                 repeats = FSE_ctz(~bitStream | 0x80000000) >> 1;
             }
             charnum += 3 * repeats;
             bitStream >>= 2 * repeats;
             bitCount += 2 * repeats;

             /* Add the final repeat which isn't 0b11. */
             assert((bitStream & 3) < 3);
             charnum += bitStream & 3;
             bitCount += 2;

             /* This is an error, but break and return an error
              * at the end, because returning out of a loop makes
              * it harder for the compiler to optimize.
              */
             if (charnum >= maxSV1) break;

             /* We don't need to set the normalized count to 0
              * because we already memset the whole buffer to 0.
              */

             if (LIKELY(ip <= iend-7) || (ip + (bitCount>>3) <= iend-4)) {
                 assert((bitCount >> 3) <= 3); /* For first condition to work */
                 ip += bitCount>>3;
                 bitCount &= 7;
             } else {
                 bitCount -= (int)(8 * (iend - 4 - ip));
                 bitCount &= 31;
                 ip = iend - 4;
             }
             bitStream = MEM_readLE32(ip) >> bitCount;
         }
         {
             int const max = (2*threshold-1) - remaining;
             int count;

             if ((bitStream & (threshold-1)) < (U32)max) {
                 count = bitStream & (threshold-1);
                 bitCount += nbBits-1;
             } else {
                 count = bitStream & (2*threshold-1);
                 if (count >= threshold) count -= max;
                 bitCount += nbBits;
             }

             count--;   /* extra accuracy */
             /* When it matters (small blocks), this is a
              * predictable branch, because we don't use -1.
              */
             if (count >= 0) {
                 remaining -= count;
             } else {
                 assert(count == -1);
                 remaining += count;
             }
             normalizedCounter[charnum++] = (short)count;
             previous0 = !count;

             assert(threshold > 1);
             if (remaining < threshold) {
                 /* This branch can be folded into the
                  * threshold update condition because we
                  * know that threshold > 1.
                  */
                 if (remaining <= 1) break;
                 nbBits = BIT_highbit32(remaining) + 1;
                 threshold = 1 << (nbBits - 1);
             }
             if (charnum >= maxSV1) break;

             if (LIKELY(ip <= iend-7) || (ip + (bitCount>>3) <= iend-4)) {
                 ip += bitCount>>3;
                 bitCount &= 7;
             } else {
                 bitCount -= (int)(8 * (iend - 4 - ip));
                 bitCount &= 31;
                 ip = iend - 4;
             }
             bitStream = MEM_readLE32(ip) >> bitCount;
     }   }
     if (remaining != 1) return ERROR(corruption_detected);
     /* Only possible when there are too many zeros. */
     if (charnum > maxSV1) return ERROR(maxSymbolValue_tooSmall);
     if (bitCount > 32) return ERROR(corruption_detected);
     *maxSVPtr = charnum-1;

     ip += (bitCount+7)>>3;
     return ip-istart;
 }

 /* Avoids the FORCE_INLINE of the _body() function. */
 static size_t FSE_readNCount_body_default(
         short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
         const void* headerBuffer, size_t hbSize)
 {
     return FSE_readNCount_body(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
 }

 #if DYNAMIC_BMI2
 TARGET_ATTRIBUTE("bmi2") static size_t FSE_readNCount_body_bmi2(
         short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
         const void* headerBuffer, size_t hbSize)
 {
     return FSE_readNCount_body(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
 }
 #endif

 size_t FSE_readNCount_bmi2(
         short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
         const void* headerBuffer, size_t hbSize, int bmi2)
 {
 #if DYNAMIC_BMI2
     if (bmi2) {
         return FSE_readNCount_body_bmi2(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
     }
 #endif
     (void)bmi2;
     return FSE_readNCount_body_default(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
 }

 size_t FSE_readNCount(
         short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
         const void* headerBuffer, size_t hbSize)
 {
     return FSE_readNCount_bmi2(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize, /* bmi2 */ 0);
 }
 EXPORT_SYMBOL_GPL(FSE_readNCount);

 /*! HUF_readStats() :
     Read compact Huffman tree, saved by HUF_writeCTable().
     `huffWeight` is destination buffer.
     `rankStats` is assumed to be a table of at least HUF_TABLELOG_MAX U32.
     @return : size read from `src` , or an error Code .
     Note : Needed by HUF_readCTable() and HUF_readDTableX?() .
 */
 size_t HUF_readStats(BYTE* huffWeight, size_t hwSize, U32* rankStats,
                      U32* nbSymbolsPtr, U32* tableLogPtr,
                      const void* src, size_t srcSize)
 {
     U32 wksp[HUF_READ_STATS_WORKSPACE_SIZE_U32];
     return HUF_readStats_wksp(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, wksp, sizeof(wksp), /* bmi2 */ 0);
 }
 EXPORT_SYMBOL_GPL(HUF_readStats);

 FORCE_INLINE_TEMPLATE size_t
 HUF_readStats_body(BYTE* huffWeight, size_t hwSize, U32* rankStats,
                    U32* nbSymbolsPtr, U32* tableLogPtr,
                    const void* src, size_t srcSize,
                    void* workSpace, size_t wkspSize,
                    int bmi2)
 {
     U32 weightTotal;
     const BYTE* ip = (const BYTE*) src;
     size_t iSize;
     size_t oSize;

     if (!srcSize) return ERROR(srcSize_wrong);
     iSize = ip[0];
     /* ZSTD_memset(huffWeight, 0, hwSize);   *//* is not necessary, even though some analyzer complain ... */

     if (iSize >= 128) {  /* special header */
         oSize = iSize - 127;
         iSize = ((oSize+1)/2);
         if (iSize+1 > srcSize) return ERROR(srcSize_wrong);
         if (oSize >= hwSize) return ERROR(corruption_detected);
         ip += 1;
         {   U32 n;
             for (n=0; n<oSize; n+=2) {
                 huffWeight[n]   = ip[n/2] >> 4;
                 huffWeight[n+1] = ip[n/2] & 15;
     }   }   }
     else  {   /* header compressed with FSE (normal case) */
         if (iSize+1 > srcSize) return ERROR(srcSize_wrong);
         /* max (hwSize-1) values decoded, as last one is implied */
         oSize = FSE_decompress_wksp_bmi2(huffWeight, hwSize-1, ip+1, iSize, 6, workSpace, wkspSize, bmi2);
         if (FSE_isError(oSize)) return oSize;
     }

     /* collect weight stats */
     ZSTD_memset(rankStats, 0, (HUF_TABLELOG_MAX + 1) * sizeof(U32));
     weightTotal = 0;
     {   U32 n; for (n=0; n<oSize; n++) {
             if (huffWeight[n] >= HUF_TABLELOG_MAX) return ERROR(corruption_detected);
             rankStats[huffWeight[n]]++;
             weightTotal += (1 << huffWeight[n]) >> 1;
     }   }
     if (weightTotal == 0) return ERROR(corruption_detected);

     /* get last non-null symbol weight (implied, total must be 2^n) */
     {   U32 const tableLog = BIT_highbit32(weightTotal) + 1;
         if (tableLog > HUF_TABLELOG_MAX) return ERROR(corruption_detected);
         *tableLogPtr = tableLog;
         /* determine last weight */
         {   U32 const total = 1 << tableLog;
             U32 const rest = total - weightTotal;
             U32 const verif = 1 << BIT_highbit32(rest);
             U32 const lastWeight = BIT_highbit32(rest) + 1;
             if (verif != rest) return ERROR(corruption_detected);    /* last value must be a clean power of 2 */
             huffWeight[oSize] = (BYTE)lastWeight;
             rankStats[lastWeight]++;
     }   }

     /* check tree construction validity */
     if ((rankStats[1] < 2) || (rankStats[1] & 1)) return ERROR(corruption_detected);   /* by construction : at least 2 elts of rank 1, must be even */

     /* results */
     *nbSymbolsPtr = (U32)(oSize+1);
     return iSize+1;
 }

 /* Avoids the FORCE_INLINE of the _body() function. */
 static size_t HUF_readStats_body_default(BYTE* huffWeight, size_t hwSize, U32* rankStats,
                      U32* nbSymbolsPtr, U32* tableLogPtr,
                      const void* src, size_t srcSize,
                      void* workSpace, size_t wkspSize)
 {
     return HUF_readStats_body(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize, 0);
 }

 #if DYNAMIC_BMI2
 static TARGET_ATTRIBUTE("bmi2") size_t HUF_readStats_body_bmi2(BYTE* huffWeight, size_t hwSize, U32* rankStats,
                      U32* nbSymbolsPtr, U32* tableLogPtr,
                      const void* src, size_t srcSize,
                      void* workSpace, size_t wkspSize)
 {
     return HUF_readStats_body(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize, 1);
 }
 #endif

 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 bmi2)
 {
 #if DYNAMIC_BMI2
     if (bmi2) {
         return HUF_readStats_body_bmi2(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize);
     }
 #endif
     (void)bmi2;
     return HUF_readStats_body_default(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize);
 }
 EXPORT_SYMBOL_GPL(HUF_readStats_wksp);
	/* ******************************************************************
	* Common functions of New Generation Entropy library
	* Copyright (c) Yann Collet, Facebook, Inc.
	*
	* You can contact the author at :
	* - FSE+HUF source repository : https://github.com/Cyan4973/FiniteStateEntropy
	* - Public forum : https://groups.google.com/forum/#!forum/lz4c
	*
	* 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.
	****************************************************************** */

	/* *************************************
	* Dependencies
	***************************************/
	#include <linux/module.h>
	#include "mem.h"
	#include "error_private.h" /* ERR_, ERROR /
	#define FSE_STATIC_LINKING_ONLY /* FSE_MIN_TABLELOG */
	#include "fse.h"
	#define HUF_STATIC_LINKING_ONLY /* HUF_TABLELOG_ABSOLUTEMAX */
	#include "huf.h"


	/=== Version ===/
	unsigned FSE_versionNumber(void) { return FSE_VERSION_NUMBER; }


	/=== Error Management ===/
	unsigned FSE_isError(size_t code) { return ERR_isError(code); }
	const char* FSE_getErrorName(size_t code) { return ERR_getErrorName(code); }

	unsigned HUF_isError(size_t code) { return ERR_isError(code); }
	const char* HUF_getErrorName(size_t code) { return ERR_getErrorName(code); }


	/-*************************************************************
	* FSE NCount encoding-decoding
	****************************************************************/
	static U32 FSE_ctz(U32 val)
	{
	assert(val != 0);
	{
	# if (__GNUC__ >= 3) /* GCC Intrinsic */
	return __builtin_ctz(val);
	# else /* Software version */
	U32 count = 0;
	while ((val & 1) == 0) {
	val >>= 1;
	++count;
	}
	return count;
	# endif
	}
	}

	FORCE_INLINE_TEMPLATE
	size_t FSE_readNCount_body(short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
	const void* headerBuffer, size_t hbSize)
	{
	const BYTE* const istart = (const BYTE*) headerBuffer;
	const BYTE* const iend = istart + hbSize;
	const BYTE* ip = istart;
	int nbBits;
	int remaining;
	int threshold;
	U32 bitStream;
	int bitCount;
	unsigned charnum = 0;
	unsigned const maxSV1 = *maxSVPtr + 1;
	int previous0 = 0;

	if (hbSize < 8) {
	/* This function only works when hbSize >= 8 */
	char buffer[8] = {0};
	ZSTD_memcpy(buffer, headerBuffer, hbSize);
	{ size_t const countSize = FSE_readNCount(normalizedCounter, maxSVPtr, tableLogPtr,
	buffer, sizeof(buffer));
	if (FSE_isError(countSize)) return countSize;
	if (countSize > hbSize) return ERROR(corruption_detected);
	return countSize;
	} }
	assert(hbSize >= 8);

	/* init */
	ZSTD_memset(normalizedCounter, 0, (maxSVPtr+1) sizeof(normalizedCounter[0])); /* all symbols not present in NCount have a frequency of 0 */
	bitStream = MEM_readLE32(ip);
	nbBits = (bitStream & 0xF) + FSE_MIN_TABLELOG; /* extract tableLog */
	if (nbBits > FSE_TABLELOG_ABSOLUTE_MAX) return ERROR(tableLog_tooLarge);
	bitStream >>= 4;
	bitCount = 4;
	*tableLogPtr = nbBits;
	remaining = (1<<nbBits)+1;
	threshold = 1<<nbBits;
	nbBits++;

	for (;;) {
	if (previous0) {
	/* Count the number of repeats. Each time the
	* 2-bit repeat code is 0b11 there is another
	* repeat.
	* Avoid UB by setting the high bit to 1.
	*/
	int repeats = FSE_ctz(~bitStream \| 0x80000000) >> 1;
	while (repeats >= 12) {
	charnum += 3 * 12;
	if (LIKELY(ip <= iend-7)) {
	ip += 3;
	} else {
	bitCount -= (int)(8 * (iend - 7 - ip));
	bitCount &= 31;
	ip = iend - 4;
	}
	bitStream = MEM_readLE32(ip) >> bitCount;
	repeats = FSE_ctz(~bitStream \| 0x80000000) >> 1;
	}
	charnum += 3 * repeats;
	bitStream >>= 2 * repeats;
	bitCount += 2 * repeats;

	/* Add the final repeat which isn't 0b11. */
	assert((bitStream & 3) < 3);
	charnum += bitStream & 3;
	bitCount += 2;

	/* This is an error, but break and return an error
	* at the end, because returning out of a loop makes
	* it harder for the compiler to optimize.
	*/
	if (charnum >= maxSV1) break;

	/* We don't need to set the normalized count to 0
	* because we already memset the whole buffer to 0.
	*/

	if (LIKELY(ip <= iend-7) \|\| (ip + (bitCount>>3) <= iend-4)) {
	assert((bitCount >> 3) <= 3); /* For first condition to work */
	ip += bitCount>>3;
	bitCount &= 7;
	} else {
	bitCount -= (int)(8 * (iend - 4 - ip));
	bitCount &= 31;
	ip = iend - 4;
	}
	bitStream = MEM_readLE32(ip) >> bitCount;
	}
	{
	int const max = (2*threshold-1) - remaining;
	int count;

	if ((bitStream & (threshold-1)) < (U32)max) {
	count = bitStream & (threshold-1);
	bitCount += nbBits-1;
	} else {
	count = bitStream & (2*threshold-1);
	if (count >= threshold) count -= max;
	bitCount += nbBits;
	}

	count--; /* extra accuracy */
	/* When it matters (small blocks), this is a
	* predictable branch, because we don't use -1.
	*/
	if (count >= 0) {
	remaining -= count;
	} else {
	assert(count == -1);
	remaining += count;
	}
	normalizedCounter[charnum++] = (short)count;
	previous0 = !count;

	assert(threshold > 1);
	if (remaining < threshold) {
	/* This branch can be folded into the
	* threshold update condition because we
	* know that threshold > 1.
	*/
	if (remaining <= 1) break;
	nbBits = BIT_highbit32(remaining) + 1;
	threshold = 1 << (nbBits - 1);
	}
	if (charnum >= maxSV1) break;

	if (LIKELY(ip <= iend-7) \|\| (ip + (bitCount>>3) <= iend-4)) {
	ip += bitCount>>3;
	bitCount &= 7;
	} else {
	bitCount -= (int)(8 * (iend - 4 - ip));
	bitCount &= 31;
	ip = iend - 4;
	}
	bitStream = MEM_readLE32(ip) >> bitCount;
	} }
	if (remaining != 1) return ERROR(corruption_detected);
	/* Only possible when there are too many zeros. */
	if (charnum > maxSV1) return ERROR(maxSymbolValue_tooSmall);
	if (bitCount > 32) return ERROR(corruption_detected);
	*maxSVPtr = charnum-1;

	ip += (bitCount+7)>>3;
	return ip-istart;
	}

	/* Avoids the FORCE_INLINE of the _body() function. */
	static size_t FSE_readNCount_body_default(
	short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
	const void* headerBuffer, size_t hbSize)
	{
	return FSE_readNCount_body(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
	}

	#if DYNAMIC_BMI2
	TARGET_ATTRIBUTE("bmi2") static size_t FSE_readNCount_body_bmi2(
	short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
	const void* headerBuffer, size_t hbSize)
	{
	return FSE_readNCount_body(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
	}
	#endif

	size_t FSE_readNCount_bmi2(
	short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
	const void* headerBuffer, size_t hbSize, int bmi2)
	{
	#if DYNAMIC_BMI2
	if (bmi2) {
	return FSE_readNCount_body_bmi2(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
	}
	#endif
	(void)bmi2;
	return FSE_readNCount_body_default(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
	}

	size_t FSE_readNCount(
	short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
	const void* headerBuffer, size_t hbSize)
	{
	return FSE_readNCount_bmi2(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize, /* bmi2 */ 0);
	}
	EXPORT_SYMBOL_GPL(FSE_readNCount);

	/*! HUF_readStats() :
	Read compact Huffman tree, saved by HUF_writeCTable().
	`huffWeight` is destination buffer.
	`rankStats` is assumed to be a table of at least HUF_TABLELOG_MAX U32.
	@return : size read from `src` , or an error Code .
	Note : Needed by HUF_readCTable() and HUF_readDTableX?() .
	*/
	size_t HUF_readStats(BYTE* huffWeight, size_t hwSize, U32* rankStats,
	U32* nbSymbolsPtr, U32* tableLogPtr,
	const void* src, size_t srcSize)
	{
	U32 wksp[HUF_READ_STATS_WORKSPACE_SIZE_U32];
	return HUF_readStats_wksp(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, wksp, sizeof(wksp), /* bmi2 */ 0);
	}
	EXPORT_SYMBOL_GPL(HUF_readStats);

	FORCE_INLINE_TEMPLATE size_t
	HUF_readStats_body(BYTE* huffWeight, size_t hwSize, U32* rankStats,
	U32* nbSymbolsPtr, U32* tableLogPtr,
	const void* src, size_t srcSize,
	void* workSpace, size_t wkspSize,
	int bmi2)
	{
	U32 weightTotal;
	const BYTE* ip = (const BYTE*) src;
	size_t iSize;
	size_t oSize;

	if (!srcSize) return ERROR(srcSize_wrong);
	iSize = ip[0];
	/* ZSTD_memset(huffWeight, 0, hwSize); // is not necessary, even though some analyzer complain ... */

	if (iSize >= 128) { /* special header */
	oSize = iSize - 127;
	iSize = ((oSize+1)/2);
	if (iSize+1 > srcSize) return ERROR(srcSize_wrong);
	if (oSize >= hwSize) return ERROR(corruption_detected);
	ip += 1;
	{ U32 n;
	for (n=0; n<oSize; n+=2) {
	huffWeight[n] = ip[n/2] >> 4;
	huffWeight[n+1] = ip[n/2] & 15;
	} } }
	else { /* header compressed with FSE (normal case) */
	if (iSize+1 > srcSize) return ERROR(srcSize_wrong);
	/* max (hwSize-1) values decoded, as last one is implied */
	oSize = FSE_decompress_wksp_bmi2(huffWeight, hwSize-1, ip+1, iSize, 6, workSpace, wkspSize, bmi2);
	if (FSE_isError(oSize)) return oSize;
	}

	/* collect weight stats */
	ZSTD_memset(rankStats, 0, (HUF_TABLELOG_MAX + 1) * sizeof(U32));
	weightTotal = 0;
	{ U32 n; for (n=0; n<oSize; n++) {
	if (huffWeight[n] >= HUF_TABLELOG_MAX) return ERROR(corruption_detected);
	rankStats[huffWeight[n]]++;
	weightTotal += (1 << huffWeight[n]) >> 1;
	} }
	if (weightTotal == 0) return ERROR(corruption_detected);

	/* get last non-null symbol weight (implied, total must be 2^n) */
	{ U32 const tableLog = BIT_highbit32(weightTotal) + 1;
	if (tableLog > HUF_TABLELOG_MAX) return ERROR(corruption_detected);
	*tableLogPtr = tableLog;
	/* determine last weight */
	{ U32 const total = 1 << tableLog;
	U32 const rest = total - weightTotal;
	U32 const verif = 1 << BIT_highbit32(rest);
	U32 const lastWeight = BIT_highbit32(rest) + 1;
	if (verif != rest) return ERROR(corruption_detected); /* last value must be a clean power of 2 */
	huffWeight[oSize] = (BYTE)lastWeight;
	rankStats[lastWeight]++;
	} }

	/* check tree construction validity */
	if ((rankStats[1] < 2) \|\| (rankStats[1] & 1)) return ERROR(corruption_detected); /* by construction : at least 2 elts of rank 1, must be even */

	/* results */
	*nbSymbolsPtr = (U32)(oSize+1);
	return iSize+1;
	}

	/* Avoids the FORCE_INLINE of the _body() function. */
	static size_t HUF_readStats_body_default(BYTE* huffWeight, size_t hwSize, U32* rankStats,
	U32* nbSymbolsPtr, U32* tableLogPtr,
	const void* src, size_t srcSize,
	void* workSpace, size_t wkspSize)
	{
	return HUF_readStats_body(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize, 0);
	}

	#if DYNAMIC_BMI2
	static TARGET_ATTRIBUTE("bmi2") size_t HUF_readStats_body_bmi2(BYTE* huffWeight, size_t hwSize, U32* rankStats,
	U32* nbSymbolsPtr, U32* tableLogPtr,
	const void* src, size_t srcSize,
	void* workSpace, size_t wkspSize)
	{
	return HUF_readStats_body(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize, 1);
	}
	#endif

	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 bmi2)
	{
	#if DYNAMIC_BMI2
	if (bmi2) {
	return HUF_readStats_body_bmi2(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize);
	}
	#endif
	(void)bmi2;
	return HUF_readStats_body_default(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize);
	}
	EXPORT_SYMBOL_GPL(HUF_readStats_wksp);