Merge tag 'zstd-for-linus-v5.16' of git://github.com/terrelln/linux

Pull zstd update from Nick Terrell:
 "Update to zstd-1.4.10.

  Add myself as the maintainer of zstd and update the zstd version in
  the kernel, which is now 4 years out of date, to a much more recent
  zstd release. This includes bug fixes, much more extensive fuzzing,
  and performance improvements. And generates the kernel zstd
  automatically from upstream zstd, so it is easier to keep the zstd
  verison up to date, and we don't fall so far out of date again.

  This includes 5 commits that update the zstd library version:

   - Adds a new kernel-style wrapper around zstd.

     This wrapper API is functionally equivalent to the subset of the
     current zstd API that is currently used. The wrapper API changes to
     be kernel style so that the symbols don't collide with zstd's
     symbols. The update to zstd-1.4.10 maintains the same API and
     preserves the semantics, so that none of the callers need to be
     updated. All callers are updated in the commit, because there are
     zero functional changes.

   - Adds an indirection for `lib/decompress_unzstd.c` so it doesn't
     depend on the layout of `lib/zstd/` to include every source file.
     This allows the next patch to be automatically generated.

   - Imports the zstd-1.4.10 source code. This commit is automatically
     generated from upstream zstd (https://github.com/facebook/zstd).

   - Adds me (terrelln@fb.com) as the maintainer of `lib/zstd`.

   - Fixes a newly added build warning for clang.

  The discussion around this patchset has been pretty long, so I've
  included a FAQ-style summary of the history of the patchset, and why
  we are taking this approach.

  Why do we need to update?
  -------------------------

  The zstd version in the kernel is based off of zstd-1.3.1, which is
  was released August 20, 2017. Since then zstd has seen many bug fixes
  and performance improvements. And, importantly, upstream zstd is
  continuously fuzzed by OSS-Fuzz, and bug fixes aren't backported to
  older versions. So the only way to sanely get these fixes is to keep
  up to date with upstream zstd.

  There are no known security issues that affect the kernel, but we need
  to be able to update in case there are. And while there are no known
  security issues, there are relevant bug fixes. For example the problem
  with large kernel decompression has been fixed upstream for over 2
  years [1]

  Additionally the performance improvements for kernel use cases are
  significant. Measured for x86_64 on my Intel i9-9900k @ 3.6 GHz:

   - BtrFS zstd compression at levels 1 and 3 is 5% faster

   - BtrFS zstd decompression+read is 15% faster

   - SquashFS zstd decompression+read is 15% faster

   - F2FS zstd compression+write at level 3 is 8% faster

   - F2FS zstd decompression+read is 20% faster

   - ZRAM decompression+read is 30% faster

   - Kernel zstd decompression is 35% faster

   - Initramfs zstd decompression+build is 5% faster

  On top of this, there are significant performance improvements coming
  down the line in the next zstd release, and the new automated update
  patch generation will allow us to pull them easily.

  How is the update patch generated?
  ----------------------------------

  The first two patches are preparation for updating the zstd version.
  Then the 3rd patch in the series imports upstream zstd into the
  kernel. This patch is automatically generated from upstream. A script
  makes the necessary changes and imports it into the kernel. The
  changes are:

   - Replace all libc dependencies with kernel replacements and rewrite
     includes.

   - Remove unncessary portability macros like: #if defined(_MSC_VER).

   - Use the kernel xxhash instead of bundling it.

  This automation gets tested every commit by upstream's continuous
  integration. When we cut a new zstd release, we will submit a patch to
  the kernel to update the zstd version in the kernel.

  The automated process makes it easy to keep the kernel version of zstd
  up to date. The current zstd in the kernel shares the guts of the
  code, but has a lot of API and minor changes to work in the kernel.
  This is because at the time upstream zstd was not ready to be used in
  the kernel envrionment as-is. But, since then upstream zstd has
  evolved to support being used in the kernel as-is.

  Why are we updating in one big patch?
  -------------------------------------

  The 3rd patch in the series is very large. This is because it is
  restructuring the code, so it both deletes the existing zstd, and
  re-adds the new structure. Future updates will be directly
  proportional to the changes in upstream zstd since the last import.
  They will admittidly be large, as zstd is an actively developed
  project, and has hundreds of commits between every release. However,
  there is no other great alternative.

  One option ruled out is to replay every upstream zstd commit. This is
  not feasible for several reasons:

   - There are over 3500 upstream commits since the zstd version in the
     kernel.

   - The automation to automatically generate the kernel update was only
     added recently, so older commits cannot easily be imported.

   - Not every upstream zstd commit builds.

   - Only zstd releases are "supported", and individual commits may have
     bugs that were fixed before a release.

  Another option to reduce the patch size would be to first reorganize
  to the new file structure, and then apply the patch. However, the
  current kernel zstd is formatted with clang-format to be more
  "kernel-like". But, the new method imports zstd as-is, without
  additional formatting, to allow for closer correlation with upstream,
  and easier debugging. So the patch wouldn't be any smaller.

  It also doesn't make sense to import upstream zstd commit by commit
  going forward. Upstream zstd doesn't support production use cases
  running of the development branch. We have a lot of post-commit
  fuzzing that catches many bugs, so indiviudal commits may be buggy,
  but fixed before a release. So going forward, I intend to import every
  (important) zstd release into the Kernel.

  So, while it isn't ideal, updating in one big patch is the only patch
  I see forward.

  Who is responsible for this code?
  ---------------------------------

  I am. This patchset adds me as the maintainer for zstd. Previously,
  there was no tree for zstd patches. Because of that, there were
  several patches that either got ignored, or took a long time to merge,
  since it wasn't clear which tree should pick them up. I'm officially
  stepping up as maintainer, and setting up my tree as the path through
  which zstd patches get merged. I'll make sure that patches to the
  kernel zstd get ported upstream, so they aren't erased when the next
  version update happens.

  How is this code tested?
  ------------------------

  I tested every caller of zstd on x86_64 (BtrFS, ZRAM, SquashFS, F2FS,
  Kernel, InitRAMFS). I also tested Kernel & InitRAMFS on i386 and
  aarch64. I checked both performance and correctness.

  Also, thanks to many people in the community who have tested these
  patches locally.

  Lastly, this code will bake in linux-next before being merged into
  v5.16.

  Why update to zstd-1.4.10 when zstd-1.5.0 has been released?
  ------------------------------------------------------------

  This patchset has been outstanding since 2020, and zstd-1.4.10 was the
  latest release when it was created. Since the update patch is
  automatically generated from upstream, I could generate it from
  zstd-1.5.0.

  However, there were some large stack usage regressions in zstd-1.5.0,
  and are only fixed in the latest development branch. And the latest
  development branch contains some new code that needs to bake in the
  fuzzer before I would feel comfortable releasing to the kernel.

  Once this patchset has been merged, and we've released zstd-1.5.1, we
  can update the kernel to zstd-1.5.1, and exercise the update process.

  You may notice that zstd-1.4.10 doesn't exist upstream. This release
  is an artifical release based off of zstd-1.4.9, with some fixes for
  the kernel backported from the development branch. I will tag the
  zstd-1.4.10 release after this patchset is merged, so the Linux Kernel
  is running a known version of zstd that can be debugged upstream.

  Why was a wrapper API added?
  ----------------------------

  The first versions of this patchset migrated the kernel to the
  upstream zstd API. It first added a shim API that supported the new
  upstream API with the old code, then updated callers to use the new
  shim API, then transitioned to the new code and deleted the shim API.
  However, Cristoph Hellwig suggested that we transition to a kernel
  style API, and hide zstd's upstream API behind that. This is because
  zstd's upstream API is supports many other use cases, and does not
  follow the kernel style guide, while the kernel API is focused on the
  kernel's use cases, and follows the kernel style guide.

  Where is the previous discussion?
  ---------------------------------

  Links for the discussions of the previous versions of the patch set
  below. The largest changes in the design of the patchset are driven by
  the discussions in v11, v5, and v1. Sorry for the mix of links, I
  couldn't find most of the the threads on lkml.org"

Link: https://lkml.org/lkml/2020/9/29/27 [1]
Link: https://www.spinics.net/lists/linux-crypto/msg58189.html [v12]
Link: https://lore.kernel.org/linux-btrfs/20210430013157.747152-1-nickrterrell@gmail.com/ [v11]
Link: https://lore.kernel.org/lkml/20210426234621.870684-2-nickrterrell@gmail.com/ [v10]
Link: https://lore.kernel.org/linux-btrfs/20210330225112.496213-1-nickrterrell@gmail.com/ [v9]
Link: https://lore.kernel.org/linux-f2fs-devel/20210326191859.1542272-1-nickrterrell@gmail.com/ [v8]
Link: https://lkml.org/lkml/2020/12/3/1195 [v7]
Link: https://lkml.org/lkml/2020/12/2/1245 [v6]
Link: https://lore.kernel.org/linux-btrfs/20200916034307.2092020-1-nickrterrell@gmail.com/ [v5]
Link: https://www.spinics.net/lists/linux-btrfs/msg105783.html [v4]
Link: https://lkml.org/lkml/2020/9/23/1074 [v3]
Link: https://www.spinics.net/lists/linux-btrfs/msg105505.html [v2]
Link: https://lore.kernel.org/linux-btrfs/20200916034307.2092020-1-nickrterrell@gmail.com/ [v1]
Signed-off-by: Nick Terrell <terrelln@fb.com>
Tested By: Paul Jones <paul@pauljones.id.au>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM/Clang v13.0.0 on x86-64
Tested-by: Jean-Denis Girard <jd.girard@sysnux.pf>

* tag 'zstd-for-linus-v5.16' of git://github.com/terrelln/linux:
  lib: zstd: Add cast to silence clang's -Wbitwise-instead-of-logical
  MAINTAINERS: Add maintainer entry for zstd
  lib: zstd: Upgrade to latest upstream zstd version 1.4.10
  lib: zstd: Add decompress_sources.h for decompress_unzstd
  lib: zstd: Add kernel-specific API

1 files changed, 0 insertions, 795 deletions

diff --git a/lib/zstd/fse_compress.c b/lib/zstd/fse_compress.c
deleted file mode 100644
index ef3d1741d532..000000000000
--- a/lib/zstd/fse_compress.c
+++ /dev/null
@@ -1,795 +0,0 @@
-/*
- * FSE : Finite State Entropy encoder
- * Copyright (C) 2013-2015, 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
- */
-
-/* **************************************************************
-*  Compiler specifics
-****************************************************************/
-#define FORCE_INLINE static __always_inline
-
-/* **************************************************************
-*  Includes
-****************************************************************/
-#include "bitstream.h"
-#include "fse.h"
-#include <linux/compiler.h>
-#include <linux/kernel.h>
-#include <linux/math64.h>
-#include <linux/string.h> /* memcpy, memset */
-
-/* **************************************************************
-*  Error Management
-****************************************************************/
-#define FSE_STATIC_ASSERT(c)                                   \
-	{                                                      \
-		enum { FSE_static_assert = 1 / (int)(!!(c)) }; \
-	} /* use only *after* variable declarations */
-
-/* **************************************************************
-*  Templates
-****************************************************************/
-/*
-  designed to be included
-  for type-specific functions (template emulation in C)
-  Objective is to write these functions only once, for improved maintenance
-*/
-
-/* safety checks */
-#ifndef FSE_FUNCTION_EXTENSION
-#error "FSE_FUNCTION_EXTENSION must be defined"
-#endif
-#ifndef FSE_FUNCTION_TYPE
-#error "FSE_FUNCTION_TYPE must be defined"
-#endif
-
-/* Function names */
-#define FSE_CAT(X, Y) X##Y
-#define FSE_FUNCTION_NAME(X, Y) FSE_CAT(X, Y)
-#define FSE_TYPE_NAME(X, Y) FSE_CAT(X, Y)
-
-/* Function templates */
-
-/* FSE_buildCTable_wksp() :
- * Same as FSE_buildCTable(), but using an externally allocated scratch buffer (`workSpace`).
- * wkspSize should be sized to handle worst case situation, which is `1<<max_tableLog * sizeof(FSE_FUNCTION_TYPE)`
- * workSpace must also be properly aligned with FSE_FUNCTION_TYPE requirements
- */
-size_t FSE_buildCTable_wksp(FSE_CTable *ct, const short *normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void *workspace, size_t workspaceSize)
-{
-	U32 const tableSize = 1 << tableLog;
-	U32 const tableMask = tableSize - 1;
-	void *const ptr = ct;
-	U16 *const tableU16 = ((U16 *)ptr) + 2;
-	void *const FSCT = ((U32 *)ptr) + 1 /* header */ + (tableLog ? tableSize >> 1 : 1);
-	FSE_symbolCompressionTransform *const symbolTT = (FSE_symbolCompressionTransform *)(FSCT);
-	U32 const step = FSE_TABLESTEP(tableSize);
-	U32 highThreshold = tableSize - 1;
-
-	U32 *cumul;
-	FSE_FUNCTION_TYPE *tableSymbol;
-	size_t spaceUsed32 = 0;
-
-	cumul = (U32 *)workspace + spaceUsed32;
-	spaceUsed32 += FSE_MAX_SYMBOL_VALUE + 2;
-	tableSymbol = (FSE_FUNCTION_TYPE *)((U32 *)workspace + spaceUsed32);
-	spaceUsed32 += ALIGN(sizeof(FSE_FUNCTION_TYPE) * ((size_t)1 << tableLog), sizeof(U32)) >> 2;
-
-	if ((spaceUsed32 << 2) > workspaceSize)
-		return ERROR(tableLog_tooLarge);
-	workspace = (U32 *)workspace + spaceUsed32;
-	workspaceSize -= (spaceUsed32 << 2);
-
-	/* CTable header */
-	tableU16[-2] = (U16)tableLog;
-	tableU16[-1] = (U16)maxSymbolValue;
-
-	/* For explanations on how to distribute symbol values over the table :
-	*  http://fastcompression.blogspot.fr/2014/02/fse-distributing-symbol-values.html */
-
-	/* symbol start positions */
-	{
-		U32 u;
-		cumul[0] = 0;
-		for (u = 1; u <= maxSymbolValue + 1; u++) {
-			if (normalizedCounter[u - 1] == -1) { /* Low proba symbol */
-				cumul[u] = cumul[u - 1] + 1;
-				tableSymbol[highThreshold--] = (FSE_FUNCTION_TYPE)(u - 1);
-			} else {
-				cumul[u] = cumul[u - 1] + normalizedCounter[u - 1];
-			}
-		}
-		cumul[maxSymbolValue + 1] = tableSize + 1;
-	}
-
-	/* Spread symbols */
-	{
-		U32 position = 0;
-		U32 symbol;
-		for (symbol = 0; symbol <= maxSymbolValue; symbol++) {
-			int nbOccurences;
-			for (nbOccurences = 0; nbOccurences < normalizedCounter[symbol]; nbOccurences++) {
-				tableSymbol[position] = (FSE_FUNCTION_TYPE)symbol;
-				position = (position + step) & tableMask;
-				while (position > highThreshold)
-					position = (position + step) & tableMask; /* Low proba area */
-			}
-		}
-
-		if (position != 0)
-			return ERROR(GENERIC); /* Must have gone through all positions */
-	}
-
-	/* Build table */
-	{
-		U32 u;
-		for (u = 0; u < tableSize; u++) {
-			FSE_FUNCTION_TYPE s = tableSymbol[u];	/* note : static analyzer may not understand tableSymbol is properly initialized */
-			tableU16[cumul[s]++] = (U16)(tableSize + u); /* TableU16 : sorted by symbol order; gives next state value */
-		}
-	}
-
-	/* Build Symbol Transformation Table */
-	{
-		unsigned total = 0;
-		unsigned s;
-		for (s = 0; s <= maxSymbolValue; s++) {
-			switch (normalizedCounter[s]) {
-			case 0: break;
-
-			case -1:
-			case 1:
-				symbolTT[s].deltaNbBits = (tableLog << 16) - (1 << tableLog);
-				symbolTT[s].deltaFindState = total - 1;
-				total++;
-				break;
-			default: {
-				U32 const maxBitsOut = tableLog - BIT_highbit32(normalizedCounter[s] - 1);
-				U32 const minStatePlus = normalizedCounter[s] << maxBitsOut;
-				symbolTT[s].deltaNbBits = (maxBitsOut << 16) - minStatePlus;
-				symbolTT[s].deltaFindState = total - normalizedCounter[s];
-				total += normalizedCounter[s];
-			}
-			}
-		}
-	}
-
-	return 0;
-}
-
-/*-**************************************************************
-*  FSE NCount encoding-decoding
-****************************************************************/
-size_t FSE_NCountWriteBound(unsigned maxSymbolValue, unsigned tableLog)
-{
-	size_t const maxHeaderSize = (((maxSymbolValue + 1) * tableLog) >> 3) + 3;
-	return maxSymbolValue ? maxHeaderSize : FSE_NCOUNTBOUND; /* maxSymbolValue==0 ? use default */
-}
-
-static size_t FSE_writeNCount_generic(void *header, size_t headerBufferSize, const short *normalizedCounter, unsigned maxSymbolValue, unsigned tableLog,
-				      unsigned writeIsSafe)
-{
-	BYTE *const ostart = (BYTE *)header;
-	BYTE *out = ostart;
-	BYTE *const oend = ostart + headerBufferSize;
-	int nbBits;
-	const int tableSize = 1 << tableLog;
-	int remaining;
-	int threshold;
-	U32 bitStream;
-	int bitCount;
-	unsigned charnum = 0;
-	int previous0 = 0;
-
-	bitStream = 0;
-	bitCount = 0;
-	/* Table Size */
-	bitStream += (tableLog - FSE_MIN_TABLELOG) << bitCount;
-	bitCount += 4;
-
-	/* Init */
-	remaining = tableSize + 1; /* +1 for extra accuracy */
-	threshold = tableSize;
-	nbBits = tableLog + 1;
-
-	while (remaining > 1) { /* stops at 1 */
-		if (previous0) {
-			unsigned start = charnum;
-			while (!normalizedCounter[charnum])
-				charnum++;
-			while (charnum >= start + 24) {
-				start += 24;
-				bitStream += 0xFFFFU << bitCount;
-				if ((!writeIsSafe) && (out > oend - 2))
-					return ERROR(dstSize_tooSmall); /* Buffer overflow */
-				out[0] = (BYTE)bitStream;
-				out[1] = (BYTE)(bitStream >> 8);
-				out += 2;
-				bitStream >>= 16;
-			}
-			while (charnum >= start + 3) {
-				start += 3;
-				bitStream += 3 << bitCount;
-				bitCount += 2;
-			}
-			bitStream += (charnum - start) << bitCount;
-			bitCount += 2;
-			if (bitCount > 16) {
-				if ((!writeIsSafe) && (out > oend - 2))
-					return ERROR(dstSize_tooSmall); /* Buffer overflow */
-				out[0] = (BYTE)bitStream;
-				out[1] = (BYTE)(bitStream >> 8);
-				out += 2;
-				bitStream >>= 16;
-				bitCount -= 16;
-			}
-		}
-		{
-			int count = normalizedCounter[charnum++];
-			int const max = (2 * threshold - 1) - remaining;
-			remaining -= count < 0 ? -count : count;
-			count++; /* +1 for extra accuracy */
-			if (count >= threshold)
-				count += max; /* [0..max[ [max..threshold[ (...) [threshold+max 2*threshold[ */
-			bitStream += count << bitCount;
-			bitCount += nbBits;
-			bitCount -= (count < max);
-			previous0 = (count == 1);
-			if (remaining < 1)
-				return ERROR(GENERIC);
-			while (remaining < threshold)
-				nbBits--, threshold >>= 1;
-		}
-		if (bitCount > 16) {
-			if ((!writeIsSafe) && (out > oend - 2))
-				return ERROR(dstSize_tooSmall); /* Buffer overflow */
-			out[0] = (BYTE)bitStream;
-			out[1] = (BYTE)(bitStream >> 8);
-			out += 2;
-			bitStream >>= 16;
-			bitCount -= 16;
-		}
-	}
-
-	/* flush remaining bitStream */
-	if ((!writeIsSafe) && (out > oend - 2))
-		return ERROR(dstSize_tooSmall); /* Buffer overflow */
-	out[0] = (BYTE)bitStream;
-	out[1] = (BYTE)(bitStream >> 8);
-	out += (bitCount + 7) / 8;
-
-	if (charnum > maxSymbolValue + 1)
-		return ERROR(GENERIC);
-
-	return (out - ostart);
-}
-
-size_t FSE_writeNCount(void *buffer, size_t bufferSize, const short *normalizedCounter, unsigned maxSymbolValue, unsigned tableLog)
-{
-	if (tableLog > FSE_MAX_TABLELOG)
-		return ERROR(tableLog_tooLarge); /* Unsupported */
-	if (tableLog < FSE_MIN_TABLELOG)
-		return ERROR(GENERIC); /* Unsupported */
-
-	if (bufferSize < FSE_NCountWriteBound(maxSymbolValue, tableLog))
-		return FSE_writeNCount_generic(buffer, bufferSize, normalizedCounter, maxSymbolValue, tableLog, 0);
-
-	return FSE_writeNCount_generic(buffer, bufferSize, normalizedCounter, maxSymbolValue, tableLog, 1);
-}
-
-/*-**************************************************************
-*  Counting histogram
-****************************************************************/
-/*! FSE_count_simple
-	This function counts byte values within `src`, and store the histogram into table `count`.
-	It doesn't use any additional memory.
-	But this function is unsafe : it doesn't check that all values within `src` can fit into `count`.
-	For this reason, prefer using a table `count` with 256 elements.
-	@return : count of most numerous element
-*/
-size_t FSE_count_simple(unsigned *count, unsigned *maxSymbolValuePtr, const void *src, size_t srcSize)
-{
-	const BYTE *ip = (const BYTE *)src;
-	const BYTE *const end = ip + srcSize;
-	unsigned maxSymbolValue = *maxSymbolValuePtr;
-	unsigned max = 0;
-
-	memset(count, 0, (maxSymbolValue + 1) * sizeof(*count));
-	if (srcSize == 0) {
-		*maxSymbolValuePtr = 0;
-		return 0;
-	}
-
-	while (ip < end)
-		count[*ip++]++;
-
-	while (!count[maxSymbolValue])
-		maxSymbolValue--;
-	*maxSymbolValuePtr = maxSymbolValue;
-
-	{
-		U32 s;
-		for (s = 0; s <= maxSymbolValue; s++)
-			if (count[s] > max)
-				max = count[s];
-	}
-
-	return (size_t)max;
-}
-
-/* FSE_count_parallel_wksp() :
- * Same as FSE_count_parallel(), but using an externally provided scratch buffer.
- * `workSpace` size must be a minimum of `1024 * sizeof(unsigned)`` */
-static size_t FSE_count_parallel_wksp(unsigned *count, unsigned *maxSymbolValuePtr, const void *source, size_t sourceSize, unsigned checkMax,
-				      unsigned *const workSpace)
-{
-	const BYTE *ip = (const BYTE *)source;
-	const BYTE *const iend = ip + sourceSize;
-	unsigned maxSymbolValue = *maxSymbolValuePtr;
-	unsigned max = 0;
-	U32 *const Counting1 = workSpace;
-	U32 *const Counting2 = Counting1 + 256;
-	U32 *const Counting3 = Counting2 + 256;
-	U32 *const Counting4 = Counting3 + 256;
-
-	memset(Counting1, 0, 4 * 256 * sizeof(unsigned));
-
-	/* safety checks */
-	if (!sourceSize) {
-		memset(count, 0, maxSymbolValue + 1);
-		*maxSymbolValuePtr = 0;
-		return 0;
-	}
-	if (!maxSymbolValue)
-		maxSymbolValue = 255; /* 0 == default */
-
-	/* by stripes of 16 bytes */
-	{
-		U32 cached = ZSTD_read32(ip);
-		ip += 4;
-		while (ip < iend - 15) {
-			U32 c = cached;
-			cached = ZSTD_read32(ip);
-			ip += 4;
-			Counting1[(BYTE)c]++;
-			Counting2[(BYTE)(c >> 8)]++;
-			Counting3[(BYTE)(c >> 16)]++;
-			Counting4[c >> 24]++;
-			c = cached;
-			cached = ZSTD_read32(ip);
-			ip += 4;
-			Counting1[(BYTE)c]++;
-			Counting2[(BYTE)(c >> 8)]++;
-			Counting3[(BYTE)(c >> 16)]++;
-			Counting4[c >> 24]++;
-			c = cached;
-			cached = ZSTD_read32(ip);
-			ip += 4;
-			Counting1[(BYTE)c]++;
-			Counting2[(BYTE)(c >> 8)]++;
-			Counting3[(BYTE)(c >> 16)]++;
-			Counting4[c >> 24]++;
-			c = cached;
-			cached = ZSTD_read32(ip);
-			ip += 4;
-			Counting1[(BYTE)c]++;
-			Counting2[(BYTE)(c >> 8)]++;
-			Counting3[(BYTE)(c >> 16)]++;
-			Counting4[c >> 24]++;
-		}
-		ip -= 4;
-	}
-
-	/* finish last symbols */
-	while (ip < iend)
-		Counting1[*ip++]++;
-
-	if (checkMax) { /* verify stats will fit into destination table */
-		U32 s;
-		for (s = 255; s > maxSymbolValue; s--) {
-			Counting1[s] += Counting2[s] + Counting3[s] + Counting4[s];
-			if (Counting1[s])
-				return ERROR(maxSymbolValue_tooSmall);
-		}
-	}
-
-	{
-		U32 s;
-		for (s = 0; s <= maxSymbolValue; s++) {
-			count[s] = Counting1[s] + Counting2[s] + Counting3[s] + Counting4[s];
-			if (count[s] > max)
-				max = count[s];
-		}
-	}
-
-	while (!count[maxSymbolValue])
-		maxSymbolValue--;
-	*maxSymbolValuePtr = maxSymbolValue;
-	return (size_t)max;
-}
-
-/* FSE_countFast_wksp() :
- * Same as FSE_countFast(), but using an externally provided scratch buffer.
- * `workSpace` size must be table of >= `1024` unsigned */
-size_t FSE_countFast_wksp(unsigned *count, unsigned *maxSymbolValuePtr, const void *source, size_t sourceSize, unsigned *workSpace)
-{
-	if (sourceSize < 1500)
-		return FSE_count_simple(count, maxSymbolValuePtr, source, sourceSize);
-	return FSE_count_parallel_wksp(count, maxSymbolValuePtr, source, sourceSize, 0, workSpace);
-}
-
-/* FSE_count_wksp() :
- * Same as FSE_count(), but using an externally provided scratch buffer.
- * `workSpace` size must be table of >= `1024` unsigned */
-size_t FSE_count_wksp(unsigned *count, unsigned *maxSymbolValuePtr, const void *source, size_t sourceSize, unsigned *workSpace)
-{
-	if (*maxSymbolValuePtr < 255)
-		return FSE_count_parallel_wksp(count, maxSymbolValuePtr, source, sourceSize, 1, workSpace);
-	*maxSymbolValuePtr = 255;
-	return FSE_countFast_wksp(count, maxSymbolValuePtr, source, sourceSize, workSpace);
-}
-
-/*-**************************************************************
-*  FSE Compression Code
-****************************************************************/
-/*! FSE_sizeof_CTable() :
-	FSE_CTable is a variable size structure which contains :
-	`U16 tableLog;`
-	`U16 maxSymbolValue;`
-	`U16 nextStateNumber[1 << tableLog];`                         // This size is variable
-	`FSE_symbolCompressionTransform symbolTT[maxSymbolValue+1];`  // This size is variable
-Allocation is manual (C standard does not support variable-size structures).
-*/
-size_t FSE_sizeof_CTable(unsigned maxSymbolValue, unsigned tableLog)
-{
-	if (tableLog > FSE_MAX_TABLELOG)
-		return ERROR(tableLog_tooLarge);
-	return FSE_CTABLE_SIZE_U32(tableLog, maxSymbolValue) * sizeof(U32);
-}
-
-/* provides the minimum logSize to safely represent a distribution */
-static unsigned FSE_minTableLog(size_t srcSize, unsigned maxSymbolValue)
-{
-	U32 minBitsSrc = BIT_highbit32((U32)(srcSize - 1)) + 1;
-	U32 minBitsSymbols = BIT_highbit32(maxSymbolValue) + 2;
-	U32 minBits = minBitsSrc < minBitsSymbols ? minBitsSrc : minBitsSymbols;
-	return minBits;
-}
-
-unsigned FSE_optimalTableLog_internal(unsigned maxTableLog, size_t srcSize, unsigned maxSymbolValue, unsigned minus)
-{
-	U32 maxBitsSrc = BIT_highbit32((U32)(srcSize - 1)) - minus;
-	U32 tableLog = maxTableLog;
-	U32 minBits = FSE_minTableLog(srcSize, maxSymbolValue);
-	if (tableLog == 0)
-		tableLog = FSE_DEFAULT_TABLELOG;
-	if (maxBitsSrc < tableLog)
-		tableLog = maxBitsSrc; /* Accuracy can be reduced */
-	if (minBits > tableLog)
-		tableLog = minBits; /* Need a minimum to safely represent all symbol values */
-	if (tableLog < FSE_MIN_TABLELOG)
-		tableLog = FSE_MIN_TABLELOG;
-	if (tableLog > FSE_MAX_TABLELOG)
-		tableLog = FSE_MAX_TABLELOG;
-	return tableLog;
-}
-
-unsigned FSE_optimalTableLog(unsigned maxTableLog, size_t srcSize, unsigned maxSymbolValue)
-{
-	return FSE_optimalTableLog_internal(maxTableLog, srcSize, maxSymbolValue, 2);
-}
-
-/* Secondary normalization method.
-   To be used when primary method fails. */
-
-static size_t FSE_normalizeM2(short *norm, U32 tableLog, const unsigned *count, size_t total, U32 maxSymbolValue)
-{
-	short const NOT_YET_ASSIGNED = -2;
-	U32 s;
-	U32 distributed = 0;
-	U32 ToDistribute;
-
-	/* Init */
-	U32 const lowThreshold = (U32)(total >> tableLog);
-	U32 lowOne = (U32)((total * 3) >> (tableLog + 1));
-
-	for (s = 0; s <= maxSymbolValue; s++) {
-		if (count[s] == 0) {
-			norm[s] = 0;
-			continue;
-		}
-		if (count[s] <= lowThreshold) {
-			norm[s] = -1;
-			distributed++;
-			total -= count[s];
-			continue;
-		}
-		if (count[s] <= lowOne) {
-			norm[s] = 1;
-			distributed++;
-			total -= count[s];
-			continue;
-		}
-
-		norm[s] = NOT_YET_ASSIGNED;
-	}
-	ToDistribute = (1 << tableLog) - distributed;
-
-	if ((total / ToDistribute) > lowOne) {
-		/* risk of rounding to zero */
-		lowOne = (U32)((total * 3) / (ToDistribute * 2));
-		for (s = 0; s <= maxSymbolValue; s++) {
-			if ((norm[s] == NOT_YET_ASSIGNED) && (count[s] <= lowOne)) {
-				norm[s] = 1;
-				distributed++;
-				total -= count[s];
-				continue;
-			}
-		}
-		ToDistribute = (1 << tableLog) - distributed;
-	}
-
-	if (distributed == maxSymbolValue + 1) {
-		/* all values are pretty poor;
-		   probably incompressible data (should have already been detected);
-		   find max, then give all remaining points to max */
-		U32 maxV = 0, maxC = 0;
-		for (s = 0; s <= maxSymbolValue; s++)
-			if (count[s] > maxC)
-				maxV = s, maxC = count[s];
-		norm[maxV] += (short)ToDistribute;
-		return 0;
-	}
-
-	if (total == 0) {
-		/* all of the symbols were low enough for the lowOne or lowThreshold */
-		for (s = 0; ToDistribute > 0; s = (s + 1) % (maxSymbolValue + 1))
-			if (norm[s] > 0)
-				ToDistribute--, norm[s]++;
-		return 0;
-	}
-
-	{
-		U64 const vStepLog = 62 - tableLog;
-		U64 const mid = (1ULL << (vStepLog - 1)) - 1;
-		U64 const rStep = div_u64((((U64)1 << vStepLog) * ToDistribute) + mid, (U32)total); /* scale on remaining */
-		U64 tmpTotal = mid;
-		for (s = 0; s <= maxSymbolValue; s++) {
-			if (norm[s] == NOT_YET_ASSIGNED) {
-				U64 const end = tmpTotal + (count[s] * rStep);
-				U32 const sStart = (U32)(tmpTotal >> vStepLog);
-				U32 const sEnd = (U32)(end >> vStepLog);
-				U32 const weight = sEnd - sStart;
-				if (weight < 1)
-					return ERROR(GENERIC);
-				norm[s] = (short)weight;
-				tmpTotal = end;
-			}
-		}
-	}
-
-	return 0;
-}
-
-size_t FSE_normalizeCount(short *normalizedCounter, unsigned tableLog, const unsigned *count, size_t total, unsigned maxSymbolValue)
-{
-	/* Sanity checks */
-	if (tableLog == 0)
-		tableLog = FSE_DEFAULT_TABLELOG;
-	if (tableLog < FSE_MIN_TABLELOG)
-		return ERROR(GENERIC); /* Unsupported size */
-	if (tableLog > FSE_MAX_TABLELOG)
-		return ERROR(tableLog_tooLarge); /* Unsupported size */
-	if (tableLog < FSE_minTableLog(total, maxSymbolValue))
-		return ERROR(GENERIC); /* Too small tableLog, compression potentially impossible */
-
-	{
-		U32 const rtbTable[] = {0, 473195, 504333, 520860, 550000, 700000, 750000, 830000};
-		U64 const scale = 62 - tableLog;
-		U64 const step = div_u64((U64)1 << 62, (U32)total); /* <== here, one division ! */
-		U64 const vStep = 1ULL << (scale - 20);
-		int stillToDistribute = 1 << tableLog;
-		unsigned s;
-		unsigned largest = 0;
-		short largestP = 0;
-		U32 lowThreshold = (U32)(total >> tableLog);
-
-		for (s = 0; s <= maxSymbolValue; s++) {
-			if (count[s] == total)
-				return 0; /* rle special case */
-			if (count[s] == 0) {
-				normalizedCounter[s] = 0;
-				continue;
-			}
-			if (count[s] <= lowThreshold) {
-				normalizedCounter[s] = -1;
-				stillToDistribute--;
-			} else {
-				short proba = (short)((count[s] * step) >> scale);
-				if (proba < 8) {
-					U64 restToBeat = vStep * rtbTable[proba];
-					proba += (count[s] * step) - ((U64)proba << scale) > restToBeat;
-				}
-				if (proba > largestP)
-					largestP = proba, largest = s;
-				normalizedCounter[s] = proba;
-				stillToDistribute -= proba;
-			}
-		}
-		if (-stillToDistribute >= (normalizedCounter[largest] >> 1)) {
-			/* corner case, need another normalization method */
-			size_t const errorCode = FSE_normalizeM2(normalizedCounter, tableLog, count, total, maxSymbolValue);
-			if (FSE_isError(errorCode))
-				return errorCode;
-		} else
-			normalizedCounter[largest] += (short)stillToDistribute;
-	}
-
-	return tableLog;
-}
-
-/* fake FSE_CTable, for raw (uncompressed) input */
-size_t FSE_buildCTable_raw(FSE_CTable *ct, unsigned nbBits)
-{
-	const unsigned tableSize = 1 << nbBits;
-	const unsigned tableMask = tableSize - 1;
-	const unsigned maxSymbolValue = tableMask;
-	void *const ptr = ct;
-	U16 *const tableU16 = ((U16 *)ptr) + 2;
-	void *const FSCT = ((U32 *)ptr) + 1 /* header */ + (tableSize >> 1); /* assumption : tableLog >= 1 */
-	FSE_symbolCompressionTransform *const symbolTT = (FSE_symbolCompressionTransform *)(FSCT);
-	unsigned s;
-
-	/* Sanity checks */
-	if (nbBits < 1)
-		return ERROR(GENERIC); /* min size */
-
-	/* header */
-	tableU16[-2] = (U16)nbBits;
-	tableU16[-1] = (U16)maxSymbolValue;
-
-	/* Build table */
-	for (s = 0; s < tableSize; s++)
-		tableU16[s] = (U16)(tableSize + s);
-
-	/* Build Symbol Transformation Table */
-	{
-		const U32 deltaNbBits = (nbBits << 16) - (1 << nbBits);
-		for (s = 0; s <= maxSymbolValue; s++) {
-			symbolTT[s].deltaNbBits = deltaNbBits;
-			symbolTT[s].deltaFindState = s - 1;
-		}
-	}
-
-	return 0;
-}
-
-/* fake FSE_CTable, for rle input (always same symbol) */
-size_t FSE_buildCTable_rle(FSE_CTable *ct, BYTE symbolValue)
-{
-	void *ptr = ct;
-	U16 *tableU16 = ((U16 *)ptr) + 2;
-	void *FSCTptr = (U32 *)ptr + 2;
-	FSE_symbolCompressionTransform *symbolTT = (FSE_symbolCompressionTransform *)FSCTptr;
-
-	/* header */
-	tableU16[-2] = (U16)0;
-	tableU16[-1] = (U16)symbolValue;
-
-	/* Build table */
-	tableU16[0] = 0;
-	tableU16[1] = 0; /* just in case */
-
-	/* Build Symbol Transformation Table */
-	symbolTT[symbolValue].deltaNbBits = 0;
-	symbolTT[symbolValue].deltaFindState = 0;
-
-	return 0;
-}
-
-static size_t FSE_compress_usingCTable_generic(void *dst, size_t dstSize, const void *src, size_t srcSize, const FSE_CTable *ct, const unsigned fast)
-{
-	const BYTE *const istart = (const BYTE *)src;
-	const BYTE *const iend = istart + srcSize;
-	const BYTE *ip = iend;
-
-	BIT_CStream_t bitC;
-	FSE_CState_t CState1, CState2;
-
-	/* init */
-	if (srcSize <= 2)
-		return 0;
-	{
-		size_t const initError = BIT_initCStream(&bitC, dst, dstSize);
-		if (FSE_isError(initError))
-			return 0; /* not enough space available to write a bitstream */
-	}
-
-#define FSE_FLUSHBITS(s) (fast ? BIT_flushBitsFast(s) : BIT_flushBits(s))
-
-	if (srcSize & 1) {
-		FSE_initCState2(&CState1, ct, *--ip);
-		FSE_initCState2(&CState2, ct, *--ip);
-		FSE_encodeSymbol(&bitC, &CState1, *--ip);
-		FSE_FLUSHBITS(&bitC);
-	} else {
-		FSE_initCState2(&CState2, ct, *--ip);
-		FSE_initCState2(&CState1, ct, *--ip);
-	}
-
-	/* join to mod 4 */
-	srcSize -= 2;
-	if ((sizeof(bitC.bitContainer) * 8 > FSE_MAX_TABLELOG * 4 + 7) && (srcSize & 2)) { /* test bit 2 */
-		FSE_encodeSymbol(&bitC, &CState2, *--ip);
-		FSE_encodeSymbol(&bitC, &CState1, *--ip);
-		FSE_FLUSHBITS(&bitC);
-	}
-
-	/* 2 or 4 encoding per loop */
-	while (ip > istart) {
-
-		FSE_encodeSymbol(&bitC, &CState2, *--ip);
-
-		if (sizeof(bitC.bitContainer) * 8 < FSE_MAX_TABLELOG * 2 + 7) /* this test must be static */
-			FSE_FLUSHBITS(&bitC);
-
-		FSE_encodeSymbol(&bitC, &CState1, *--ip);
-
-		if (sizeof(bitC.bitContainer) * 8 > FSE_MAX_TABLELOG * 4 + 7) { /* this test must be static */
-			FSE_encodeSymbol(&bitC, &CState2, *--ip);
-			FSE_encodeSymbol(&bitC, &CState1, *--ip);
-		}
-
-		FSE_FLUSHBITS(&bitC);
-	}
-
-	FSE_flushCState(&bitC, &CState2);
-	FSE_flushCState(&bitC, &CState1);
-	return BIT_closeCStream(&bitC);
-}
-
-size_t FSE_compress_usingCTable(void *dst, size_t dstSize, const void *src, size_t srcSize, const FSE_CTable *ct)
-{
-	unsigned const fast = (dstSize >= FSE_BLOCKBOUND(srcSize));
-
-	if (fast)
-		return FSE_compress_usingCTable_generic(dst, dstSize, src, srcSize, ct, 1);
-	else
-		return FSE_compress_usingCTable_generic(dst, dstSize, src, srcSize, ct, 0);
-}
-
-size_t FSE_compressBound(size_t size) { return FSE_COMPRESSBOUND(size); }