contrib/linux-kernel/lib/zstd/huf_compress.c

/*
 * Huffman encoder, part of New Generation Entropy library
 * Copyright (C) 2013-2016, Yann Collet.
 *
 * BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *   * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License version 2 as published by the
 * Free Software Foundation. This program is dual-licensed; you may select
 * either version 2 of the GNU General Public License ("GPL") or BSD license
 * ("BSD").
 *
 * You can contact the author at :
 * - Source repository : https://github.com/Cyan4973/FiniteStateEntropy
 */


/* **************************************************************
*  Includes
****************************************************************/
#include <linux/string.h>     /* memcpy, memset */
#include "bitstream.h"
#include "fse.h"        /* header compression */
#include "huf.h"


/* **************************************************************
*  Error Management
****************************************************************/
#define HUF_STATIC_ASSERT(c) { enum { HUF_static_assert = 1/(int)(!!(c)) }; }   /* use only *after* variable declarations */
#define CHECK_V_F(e, f) size_t const e = f; if (ERR_isError(e)) return f
#define CHECK_F(f)   { CHECK_V_F(_var_err__, f); }


/* **************************************************************
*  Utils
****************************************************************/
unsigned HUF_optimalTableLog(unsigned maxTableLog, size_t srcSize, unsigned maxSymbolValue)
{
	return FSE_optimalTableLog_internal(maxTableLog, srcSize, maxSymbolValue, 1);
}


/* *******************************************************
*  HUF : Huffman block compression
*********************************************************/
/* HUF_compressWeights() :
 * Same as FSE_compress(), but dedicated to huff0's weights compression.
 * The use case needs much less stack memory.
 * Note : all elements within weightTable are supposed to be <= HUF_TABLELOG_MAX.
 */
#define MAX_FSE_TABLELOG_FOR_HUFF_HEADER 6
size_t HUF_compressWeights (void* dst, size_t dstSize, const void* weightTable, size_t wtSize)
{
	BYTE* const ostart = (BYTE*) dst;
	BYTE* op = ostart;
	BYTE* const oend = ostart + dstSize;

	U32 maxSymbolValue = HUF_TABLELOG_MAX;
	U32 tableLog = MAX_FSE_TABLELOG_FOR_HUFF_HEADER;

	FSE_CTable CTable[FSE_CTABLE_SIZE_U32(MAX_FSE_TABLELOG_FOR_HUFF_HEADER, HUF_TABLELOG_MAX)];
	BYTE scratchBuffer[1<<MAX_FSE_TABLELOG_FOR_HUFF_HEADER];

	U32 count[HUF_TABLELOG_MAX+1];
	S16 norm[HUF_TABLELOG_MAX+1];

	/* init conditions */
	if (wtSize <= 1) return 0;  /* Not compressible */

	/* Scan input and build symbol stats */
	{	CHECK_V_F(maxCount, FSE_count_simple(count, &maxSymbolValue, weightTable, wtSize) );
		if (maxCount == wtSize) return 1;   /* only a single symbol in src : rle */
		if (maxCount == 1) return 0;         /* each symbol present maximum once => not compressible */
	}

	tableLog = FSE_optimalTableLog(tableLog, wtSize, maxSymbolValue);
	CHECK_F( FSE_normalizeCount(norm, tableLog, count, wtSize, maxSymbolValue) );

	/* Write table description header */
	{	CHECK_V_F(hSize, FSE_writeNCount(op, oend-op, norm, maxSymbolValue, tableLog) );
		op += hSize;
	}

	/* Compress */
	CHECK_F( FSE_buildCTable_wksp(CTable, norm, maxSymbolValue, tableLog, scratchBuffer, sizeof(scratchBuffer)) );
	{	CHECK_V_F(cSize, FSE_compress_usingCTable(op, oend - op, weightTable, wtSize, CTable) );
		if (cSize == 0) return 0;   /* not enough space for compressed data */
		op += cSize;
	}

	return op-ostart;
}


struct HUF_CElt_s {
  U16  val;
  BYTE nbBits;
};   /* typedef'd to HUF_CElt within "huf.h" */

/*! HUF_writeCTable() :
	`CTable` : Huffman tree to save, using huf representation.
	@return : size of saved CTable */
size_t HUF_writeCTable (void* dst, size_t maxDstSize,
						const HUF_CElt* CTable, U32 maxSymbolValue, U32 huffLog)
{
	BYTE bitsToWeight[HUF_TABLELOG_MAX + 1];   /* precomputed conversion table */
	BYTE huffWeight[HUF_SYMBOLVALUE_MAX];
	BYTE* op = (BYTE*)dst;
	U32 n;

	 /* check conditions */
	if (maxSymbolValue > HUF_SYMBOLVALUE_MAX) return ERROR(maxSymbolValue_tooLarge);

	/* convert to weight */
	bitsToWeight[0] = 0;
	for (n=1; n<huffLog+1; n++)
		bitsToWeight[n] = (BYTE)(huffLog + 1 - n);
	for (n=0; n<maxSymbolValue; n++)
		huffWeight[n] = bitsToWeight[CTable[n].nbBits];

	/* attempt weights compression by FSE */
	{	CHECK_V_F(hSize, HUF_compressWeights(op+1, maxDstSize-1, huffWeight, maxSymbolValue) );
		if ((hSize>1) & (hSize < maxSymbolValue/2)) {   /* FSE compressed */
			op[0] = (BYTE)hSize;
			return hSize+1;
	}   }

	/* write raw values as 4-bits (max : 15) */
	if (maxSymbolValue > (256-128)) return ERROR(GENERIC);   /* should not happen : likely means source cannot be compressed */
	if (((maxSymbolValue+1)/2) + 1 > maxDstSize) return ERROR(dstSize_tooSmall);   /* not enough space within dst buffer */
	op[0] = (BYTE)(128 /*special case*/ + (maxSymbolValue-1));
	huffWeight[maxSymbolValue] = 0;   /* to be sure it doesn't cause msan issue in final combination */
	for (n=0; n<maxSymbolValue; n+=2)
		op[(n/2)+1] = (BYTE)((huffWeight[n] << 4) + huffWeight[n+1]);
	return ((maxSymbolValue+1)/2) + 1;
}


size_t HUF_readCTable (HUF_CElt* CTable, U32 maxSymbolValue, const void* src, size_t srcSize)
{
	BYTE huffWeight[HUF_SYMBOLVALUE_MAX + 1];   /* init not required, even though some static analyzer may complain */
	U32 rankVal[HUF_TABLELOG_ABSOLUTEMAX + 1];   /* large enough for values from 0 to 16 */
	U32 tableLog = 0;
	U32 nbSymbols = 0;

	/* get symbol weights */
	CHECK_V_F(readSize, HUF_readStats(huffWeight, HUF_SYMBOLVALUE_MAX+1, rankVal, &nbSymbols, &tableLog, src, srcSize));

	/* check result */
	if (tableLog > HUF_TABLELOG_MAX) return ERROR(tableLog_tooLarge);
	if (nbSymbols > maxSymbolValue+1) return ERROR(maxSymbolValue_tooSmall);

	/* Prepare base value per rank */
	{	U32 n, nextRankStart = 0;
		for (n=1; n<=tableLog; n++) {
			U32 curr = nextRankStart;
			nextRankStart += (rankVal[n] << (n-1));
			rankVal[n] = curr;
	}   }

	/* fill nbBits */
	{	U32 n; for (n=0; n<nbSymbols; n++) {
			const U32 w = huffWeight[n];
			CTable[n].nbBits = (BYTE)(tableLog + 1 - w);
	}   }

	/* fill val */
	{	U16 nbPerRank[HUF_TABLELOG_MAX+2]  = {0};  /* support w=0=>n=tableLog+1 */
		U16 valPerRank[HUF_TABLELOG_MAX+2] = {0};
		{ U32 n; for (n=0; n<nbSymbols; n++) nbPerRank[CTable[n].nbBits]++; }
		/* determine stating value per rank */
		valPerRank[tableLog+1] = 0;   /* for w==0 */
		{	U16 min = 0;
			U32 n; for (n=tableLog; n>0; n--) {  /* start at n=tablelog <-> w=1 */
				valPerRank[n] = min;     /* get starting value within each rank */
				min += nbPerRank[n];
				min >>= 1;
		}   }
		/* assign value within rank, symbol order */
		{ U32 n; for (n=0; n<=maxSymbolValue; n++) CTable[n].val = valPerRank[CTable[n].nbBits]++; }
	}

	return readSize;
}


typedef struct nodeElt_s {
	U32 count;
	U16 parent;
	BYTE byte;
	BYTE nbBits;
} nodeElt;

static U32 HUF_setMaxHeight(nodeElt* huffNode, U32 lastNonNull, U32 maxNbBits)
{
	const U32 largestBits = huffNode[lastNonNull].nbBits;
	if (largestBits <= maxNbBits) return largestBits;   /* early exit : no elt > maxNbBits */

	/* there are several too large elements (at least >= 2) */
	{	int totalCost = 0;
		const U32 baseCost = 1 << (largestBits - maxNbBits);
		U32 n = lastNonNull;

		while (huffNode[n].nbBits > maxNbBits) {
			totalCost += baseCost - (1 << (largestBits - huffNode[n].nbBits));
			huffNode[n].nbBits = (BYTE)maxNbBits;
			n --;
		}  /* n stops at huffNode[n].nbBits <= maxNbBits */
		while (huffNode[n].nbBits == maxNbBits) n--;   /* n end at index of smallest symbol using < maxNbBits */

		/* renorm totalCost */
		totalCost >>= (largestBits - maxNbBits);  /* note : totalCost is necessarily a multiple of baseCost */

		/* repay normalized cost */
		{	U32 const noSymbol = 0xF0F0F0F0;
			U32 rankLast[HUF_TABLELOG_MAX+2];
			int pos;

			/* Get pos of last (smallest) symbol per rank */
			memset(rankLast, 0xF0, sizeof(rankLast));
			{	U32 currNbBits = maxNbBits;
				for (pos=n ; pos >= 0; pos--) {
					if (huffNode[pos].nbBits >= currNbBits) continue;
					currNbBits = huffNode[pos].nbBits;   /* < maxNbBits */
					rankLast[maxNbBits-currNbBits] = pos;
			}   }

			while (totalCost > 0) {
				U32 nBitsToDecrease = BIT_highbit32(totalCost) + 1;
				for ( ; nBitsToDecrease > 1; nBitsToDecrease--) {
					U32 highPos = rankLast[nBitsToDecrease];
					U32 lowPos = rankLast[nBitsToDecrease-1];
					if (highPos == noSymbol) continue;
					if (lowPos == noSymbol) break;
					{	U32 const highTotal = huffNode[highPos].count;
						U32 const lowTotal = 2 * huffNode[lowPos].count;
						if (highTotal <= lowTotal) break;
				}   }
				/* only triggered when no more rank 1 symbol left => find closest one (note : there is necessarily at least one !) */
				while ((nBitsToDecrease<=HUF_TABLELOG_MAX) && (rankLast[nBitsToDecrease] == noSymbol))  /* HUF_MAX_TABLELOG test just to please gcc 5+; but it should not be necessary */
					nBitsToDecrease ++;
				totalCost -= 1 << (nBitsToDecrease-1);
				if (rankLast[nBitsToDecrease-1] == noSymbol)
					rankLast[nBitsToDecrease-1] = rankLast[nBitsToDecrease];   /* this rank is no longer empty */
				huffNode[rankLast[nBitsToDecrease]].nbBits ++;
				if (rankLast[nBitsToDecrease] == 0)    /* special case, reached largest symbol */
					rankLast[nBitsToDecrease] = noSymbol;
				else {
					rankLast[nBitsToDecrease]--;
					if (huffNode[rankLast[nBitsToDecrease]].nbBits != maxNbBits-nBitsToDecrease)
						rankLast[nBitsToDecrease] = noSymbol;   /* this rank is now empty */
			}   }   /* while (totalCost > 0) */

			while (totalCost < 0) {  /* Sometimes, cost correction overshoot */
				if (rankLast[1] == noSymbol) {  /* special case : no rank 1 symbol (using maxNbBits-1); let's create one from largest rank 0 (using maxNbBits) */
					while (huffNode[n].nbBits == maxNbBits) n--;
					huffNode[n+1].nbBits--;
					rankLast[1] = n+1;
					totalCost++;
					continue;
				}
				huffNode[ rankLast[1] + 1 ].nbBits--;
				rankLast[1]++;
				totalCost ++;
	}   }   }   /* there are several too large elements (at least >= 2) */

	return maxNbBits;
}


typedef struct {
	U32 base;
	U32 curr;
} rankPos;

static void HUF_sort(nodeElt* huffNode, const U32* count, U32 maxSymbolValue)
{
	rankPos rank[32];
	U32 n;

	memset(rank, 0, sizeof(rank));
	for (n=0; n<=maxSymbolValue; n++) {
		U32 r = BIT_highbit32(count[n] + 1);
		rank[r].base ++;
	}
	for (n=30; n>0; n--) rank[n-1].base += rank[n].base;
	for (n=0; n<32; n++) rank[n].curr = rank[n].base;
	for (n=0; n<=maxSymbolValue; n++) {
		U32 const c = count[n];
		U32 const r = BIT_highbit32(c+1) + 1;
		U32 pos = rank[r].curr++;
		while ((pos > rank[r].base) && (c > huffNode[pos-1].count)) huffNode[pos]=huffNode[pos-1], pos--;
		huffNode[pos].count = c;
		huffNode[pos].byte  = (BYTE)n;
	}
}


/** HUF_buildCTable_wksp() :
 *  Same as HUF_buildCTable(), but using externally allocated scratch buffer.
 *  `workSpace` must be aligned on 4-bytes boundaries, and be at least as large as a table of 1024 unsigned.
 */
#define STARTNODE (HUF_SYMBOLVALUE_MAX+1)
typedef nodeElt huffNodeTable[2*HUF_SYMBOLVALUE_MAX+1 +1];
size_t HUF_buildCTable_wksp (HUF_CElt* tree, const U32* count, U32 maxSymbolValue, U32 maxNbBits, void* workSpace, size_t wkspSize)
{
	nodeElt* const huffNode0 = (nodeElt*)workSpace;
	nodeElt* const huffNode = huffNode0+1;
	U32 n, nonNullRank;
	int lowS, lowN;
	U16 nodeNb = STARTNODE;
	U32 nodeRoot;

	/* safety checks */
	if (wkspSize < sizeof(huffNodeTable)) return ERROR(GENERIC);   /* workSpace is not large enough */
	if (maxNbBits == 0) maxNbBits = HUF_TABLELOG_DEFAULT;
	if (maxSymbolValue > HUF_SYMBOLVALUE_MAX) return ERROR(GENERIC);
	memset(huffNode0, 0, sizeof(huffNodeTable));

	/* sort, decreasing order */
	HUF_sort(huffNode, count, maxSymbolValue);

	/* init for parents */
	nonNullRank = maxSymbolValue;
	while(huffNode[nonNullRank].count == 0) nonNullRank--;
	lowS = nonNullRank; nodeRoot = nodeNb + lowS - 1; lowN = nodeNb;
	huffNode[nodeNb].count = huffNode[lowS].count + huffNode[lowS-1].count;
	huffNode[lowS].parent = huffNode[lowS-1].parent = nodeNb;
	nodeNb++; lowS-=2;
	for (n=nodeNb; n<=nodeRoot; n++) huffNode[n].count = (U32)(1U<<30);
	huffNode0[0].count = (U32)(1U<<31);  /* fake entry, strong barrier */

	/* create parents */
	while (nodeNb <= nodeRoot) {
		U32 n1 = (huffNode[lowS].count < huffNode[lowN].count) ? lowS-- : lowN++;
		U32 n2 = (huffNode[lowS].count < huffNode[lowN].count) ? lowS-- : lowN++;
		huffNode[nodeNb].count = huffNode[n1].count + huffNode[n2].count;
		huffNode[n1].parent = huffNode[n2].parent = nodeNb;
		nodeNb++;
	}

	/* distribute weights (unlimited tree height) */
	huffNode[nodeRoot].nbBits = 0;
	for (n=nodeRoot-1; n>=STARTNODE; n--)
		huffNode[n].nbBits = huffNode[ huffNode[n].parent ].nbBits + 1;
	for (n=0; n<=nonNullRank; n++)
		huffNode[n].nbBits = huffNode[ huffNode[n].parent ].nbBits + 1;

	/* enforce maxTableLog */
	maxNbBits = HUF_setMaxHeight(huffNode, nonNullRank, maxNbBits);

	/* fill result into tree (val, nbBits) */
	{	U16 nbPerRank[HUF_TABLELOG_MAX+1] = {0};
		U16 valPerRank[HUF_TABLELOG_MAX+1] = {0};
		if (maxNbBits > HUF_TABLELOG_MAX) return ERROR(GENERIC);   /* check fit into table */
		for (n=0; n<=nonNullRank; n++)
			nbPerRank[huffNode[n].nbBits]++;
		/* determine stating value per rank */
		{	U16 min = 0;
			for (n=maxNbBits; n>0; n--) {
				valPerRank[n] = min;      /* get starting value within each rank */
				min += nbPerRank[n];
				min >>= 1;
		}   }
		for (n=0; n<=maxSymbolValue; n++)
			tree[huffNode[n].byte].nbBits = huffNode[n].nbBits;   /* push nbBits per symbol, symbol order */
		for (n=0; n<=maxSymbolValue; n++)
			tree[n].val = valPerRank[tree[n].nbBits]++;   /* assign value within rank, symbol order */
	}

	return maxNbBits;
}

static size_t HUF_estimateCompressedSize(HUF_CElt* CTable, const unsigned* count, unsigned maxSymbolValue)
{
	size_t nbBits = 0;
	int s;
	for (s = 0; s <= (int)maxSymbolValue; ++s) {
		nbBits += CTable[s].nbBits * count[s];
	}
	return nbBits >> 3;
}

static int HUF_validateCTable(const HUF_CElt* CTable, const unsigned* count, unsigned maxSymbolValue) {
  int bad = 0;
  int s;
  for (s = 0; s <= (int)maxSymbolValue; ++s) {
	bad |= (count[s] != 0) & (CTable[s].nbBits == 0);
  }
  return !bad;
}

static void HUF_encodeSymbol(BIT_CStream_t* bitCPtr, U32 symbol, const HUF_CElt* CTable)
{
	BIT_addBitsFast(bitCPtr, CTable[symbol].val, CTable[symbol].nbBits);
}

size_t HUF_compressBound(size_t size) { return HUF_COMPRESSBOUND(size); }

#define HUF_FLUSHBITS(s)  (fast ? BIT_flushBitsFast(s) : BIT_flushBits(s))

#define HUF_FLUSHBITS_1(stream) \
	if (sizeof((stream)->bitContainer)*8 < HUF_TABLELOG_MAX*2+7) HUF_FLUSHBITS(stream)

#define HUF_FLUSHBITS_2(stream) \
	if (sizeof((stream)->bitContainer)*8 < HUF_TABLELOG_MAX*4+7) HUF_FLUSHBITS(stream)

size_t HUF_compress1X_usingCTable(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable)
{
	const BYTE* ip = (const BYTE*) src;
	BYTE* const ostart = (BYTE*)dst;
	BYTE* const oend = ostart + dstSize;
	BYTE* op = ostart;
	size_t n;
	const unsigned fast = (dstSize >= HUF_BLOCKBOUND(srcSize));
	BIT_CStream_t bitC;

	/* init */
	if (dstSize < 8) return 0;   /* not enough space to compress */
	{ size_t const initErr = BIT_initCStream(&bitC, op, oend-op);
	  if (HUF_isError(initErr)) return 0; }

	n = srcSize & ~3;  /* join to mod 4 */
	switch (srcSize & 3)
	{
		case 3 : HUF_encodeSymbol(&bitC, ip[n+ 2], CTable);
				 HUF_FLUSHBITS_2(&bitC);
		case 2 : HUF_encodeSymbol(&bitC, ip[n+ 1], CTable);
				 HUF_FLUSHBITS_1(&bitC);
		case 1 : HUF_encodeSymbol(&bitC, ip[n+ 0], CTable);
				 HUF_FLUSHBITS(&bitC);
		case 0 :
		default: ;
	}

	for (; n>0; n-=4) {  /* note : n&3==0 at this stage */
		HUF_encodeSymbol(&bitC, ip[n- 1], CTable);
		HUF_FLUSHBITS_1(&bitC);
		HUF_encodeSymbol(&bitC, ip[n- 2], CTable);
		HUF_FLUSHBITS_2(&bitC);
		HUF_encodeSymbol(&bitC, ip[n- 3], CTable);
		HUF_FLUSHBITS_1(&bitC);
		HUF_encodeSymbol(&bitC, ip[n- 4], CTable);
		HUF_FLUSHBITS(&bitC);
	}

	return BIT_closeCStream(&bitC);
}


size_t HUF_compress4X_usingCTable(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable)
{
	size_t const segmentSize = (srcSize+3)/4;   /* first 3 segments */
	const BYTE* ip = (const BYTE*) src;
	const BYTE* const iend = ip + srcSize;
	BYTE* const ostart = (BYTE*) dst;
	BYTE* const oend = ostart + dstSize;
	BYTE* op = ostart;

	if (dstSize < 6 + 1 + 1 + 1 + 8) return 0;   /* minimum space to compress successfully */
	if (srcSize < 12) return 0;   /* no saving possible : too small input */
	op += 6;   /* jumpTable */

	{	CHECK_V_F(cSize, HUF_compress1X_usingCTable(op, oend-op, ip, segmentSize, CTable) );
		if (cSize==0) return 0;
		ZSTD_writeLE16(ostart, (U16)cSize);
		op += cSize;
	}

	ip += segmentSize;
	{	CHECK_V_F(cSize, HUF_compress1X_usingCTable(op, oend-op, ip, segmentSize, CTable) );
		if (cSize==0) return 0;
		ZSTD_writeLE16(ostart+2, (U16)cSize);
		op += cSize;
	}

	ip += segmentSize;
	{	CHECK_V_F(cSize, HUF_compress1X_usingCTable(op, oend-op, ip, segmentSize, CTable) );
		if (cSize==0) return 0;
		ZSTD_writeLE16(ostart+4, (U16)cSize);
		op += cSize;
	}

	ip += segmentSize;
	{	CHECK_V_F(cSize, HUF_compress1X_usingCTable(op, oend-op, ip, iend-ip, CTable) );
		if (cSize==0) return 0;
		op += cSize;
	}

	return op-ostart;
}


static size_t HUF_compressCTable_internal(
				BYTE* const ostart, BYTE* op, BYTE* const oend,
				const void* src, size_t srcSize,
				unsigned singleStream, const HUF_CElt* CTable)
{
	size_t const cSize = singleStream ?
						 HUF_compress1X_usingCTable(op, oend - op, src, srcSize, CTable) :
						 HUF_compress4X_usingCTable(op, oend - op, src, srcSize, CTable);
	if (HUF_isError(cSize)) { return cSize; }
	if (cSize==0) { return 0; }   /* uncompressible */
	op += cSize;
	/* check compressibility */
	if ((size_t)(op-ostart) >= srcSize-1) { return 0; }
	return op-ostart;
}


/* `workSpace` must a table of at least 1024 unsigned */
static size_t HUF_compress_internal (
				void* dst, size_t dstSize,
				const void* src, size_t srcSize,
				unsigned maxSymbolValue, unsigned huffLog,
				unsigned singleStream,
				void* workSpace, size_t wkspSize,
				HUF_CElt* oldHufTable, HUF_repeat* repeat, int preferRepeat)
{
	BYTE* const ostart = (BYTE*)dst;
	BYTE* const oend = ostart + dstSize;
	BYTE* op = ostart;

	U32* count;
	size_t const countSize = sizeof(U32) * (HUF_SYMBOLVALUE_MAX + 1);
	HUF_CElt* CTable;
	size_t const CTableSize = sizeof(HUF_CElt) * (HUF_SYMBOLVALUE_MAX + 1);

	/* checks & inits */
	if (wkspSize < sizeof(huffNodeTable) + countSize + CTableSize) return ERROR(GENERIC);
	if (!srcSize) return 0;  /* Uncompressed (note : 1 means rle, so first byte must be correct) */
	if (!dstSize) return 0;  /* cannot fit within dst budget */
	if (srcSize > HUF_BLOCKSIZE_MAX) return ERROR(srcSize_wrong);   /* curr block size limit */
	if (huffLog > HUF_TABLELOG_MAX) return ERROR(tableLog_tooLarge);
	if (!maxSymbolValue) maxSymbolValue = HUF_SYMBOLVALUE_MAX;
	if (!huffLog) huffLog = HUF_TABLELOG_DEFAULT;

	count = (U32*)workSpace;
	workSpace = (BYTE*)workSpace + countSize;
	wkspSize -= countSize;
	CTable = (HUF_CElt*)workSpace;
	workSpace = (BYTE*)workSpace + CTableSize;
	wkspSize -= CTableSize;

	/* Heuristic : If we don't need to check the validity of the old table use the old table for small inputs */
	if (preferRepeat && repeat && *repeat == HUF_repeat_valid) {
		return HUF_compressCTable_internal(ostart, op, oend, src, srcSize, singleStream, oldHufTable);
	}

	/* Scan input and build symbol stats */
	{	CHECK_V_F(largest, FSE_count_wksp (count, &maxSymbolValue, (const BYTE*)src, srcSize, (U32*)workSpace) );
		if (largest == srcSize) { *ostart = ((const BYTE*)src)[0]; return 1; }   /* single symbol, rle */
		if (largest <= (srcSize >> 7)+1) return 0;   /* Fast heuristic : not compressible enough */
	}

	/* Check validity of previous table */
	if (repeat && *repeat == HUF_repeat_check && !HUF_validateCTable(oldHufTable, count, maxSymbolValue)) {
		*repeat = HUF_repeat_none;
	}
	/* Heuristic : use existing table for small inputs */
	if (preferRepeat && repeat && *repeat != HUF_repeat_none) {
		return HUF_compressCTable_internal(ostart, op, oend, src, srcSize, singleStream, oldHufTable);
	}

	/* Build Huffman Tree */
	huffLog = HUF_optimalTableLog(huffLog, srcSize, maxSymbolValue);
	{	CHECK_V_F(maxBits, HUF_buildCTable_wksp (CTable, count, maxSymbolValue, huffLog, workSpace, wkspSize) );
		huffLog = (U32)maxBits;
		/* Zero the unused symbols so we can check it for validity */
		memset(CTable + maxSymbolValue + 1, 0, CTableSize - (maxSymbolValue + 1) * sizeof(HUF_CElt));
	}

	/* Write table description header */
	{	CHECK_V_F(hSize, HUF_writeCTable (op, dstSize, CTable, maxSymbolValue, huffLog) );
		/* Check if using the previous table will be beneficial */
		if (repeat && *repeat != HUF_repeat_none) {
			size_t const oldSize = HUF_estimateCompressedSize(oldHufTable, count, maxSymbolValue);
			size_t const newSize = HUF_estimateCompressedSize(CTable, count, maxSymbolValue);
			if (oldSize <= hSize + newSize || hSize + 12 >= srcSize) {
				return HUF_compressCTable_internal(ostart, op, oend, src, srcSize, singleStream, oldHufTable);
			}
		}
		/* Use the new table */
		if (hSize + 12ul >= srcSize) { return 0; }
		op += hSize;
		if (repeat) { *repeat = HUF_repeat_none; }
		if (oldHufTable) { memcpy(oldHufTable, CTable, CTableSize); } /* Save the new table */
	}
	return HUF_compressCTable_internal(ostart, op, oend, src, srcSize, singleStream, CTable);
}


size_t HUF_compress1X_wksp (void* dst, size_t dstSize,
					  const void* src, size_t srcSize,
					  unsigned maxSymbolValue, unsigned huffLog,
					  void* workSpace, size_t wkspSize)
{
	return HUF_compress_internal(dst, dstSize, src, srcSize, maxSymbolValue, huffLog, 1 /* single stream */, workSpace, wkspSize, NULL, NULL, 0);
}

size_t HUF_compress1X_repeat (void* dst, size_t dstSize,
					  const void* src, size_t srcSize,
					  unsigned maxSymbolValue, unsigned huffLog,
					  void* workSpace, size_t wkspSize,
					  HUF_CElt* hufTable, HUF_repeat* repeat, int preferRepeat)
{
	return HUF_compress_internal(dst, dstSize, src, srcSize, maxSymbolValue, huffLog, 1 /* single stream */, workSpace, wkspSize, hufTable, repeat, preferRepeat);
}

size_t HUF_compress4X_wksp (void* dst, size_t dstSize,
					  const void* src, size_t srcSize,
					  unsigned maxSymbolValue, unsigned huffLog,
					  void* workSpace, size_t wkspSize)
{
	return HUF_compress_internal(dst, dstSize, src, srcSize, maxSymbolValue, huffLog, 0 /* 4 streams */, workSpace, wkspSize, NULL, NULL, 0);
}

size_t HUF_compress4X_repeat (void* dst, size_t dstSize,
					  const void* src, size_t srcSize,
					  unsigned maxSymbolValue, unsigned huffLog,
					  void* workSpace, size_t wkspSize,
					  HUF_CElt* hufTable, HUF_repeat* repeat, int preferRepeat)
{
	return HUF_compress_internal(dst, dstSize, src, srcSize, maxSymbolValue, huffLog, 0 /* 4 streams */, workSpace, wkspSize, hufTable, repeat, preferRepeat);
}