lib: Add zstd modules

Add zstd compression and decompression kernel modules.
zstd offers a wide varity of compression speed and quality trade-offs.
It can compress at speeds approaching lz4, and quality approaching lzma.
zstd decompressions at speeds more than twice as fast as zlib, and
decompression speed remains roughly the same across all compression levels.

The code was ported from the upstream zstd source repository. The
`linux/zstd.h` header was modified to match linux kernel style.
The cross-platform and allocation code was stripped out. Instead zstd
requires the caller to pass a preallocated workspace. The source files
were clang-formatted [1] to match the Linux Kernel style as much as
possible. Otherwise, the code was unmodified. We would like to avoid
as much further manual modification to the source code as possible, so it
will be easier to keep the kernel zstd up to date.

I benchmarked zstd compression as a special character device. I ran zstd
and zlib compression at several levels, as well as performing no
compression, which measure the time spent copying the data to kernel space.
Data is passed to the compresser 4096 B at a time. The benchmark file is
located in the upstream zstd source repository under
`contrib/linux-kernel/zstd_compress_test.c` [2].

I ran the benchmarks on a Ubuntu 14.04 VM with 2 cores and 4 GiB of RAM.
The VM is running on a MacBook Pro with a 3.1 GHz Intel Core i7 processor,
16 GB of RAM, and a SSD. I benchmarked using `silesia.tar` [3], which is
211,988,480 B large. Run the following commands for the benchmark:

    sudo modprobe zstd_compress_test
    sudo mknod zstd_compress_test c 245 0
    sudo cp silesia.tar zstd_compress_test

The time is reported by the time of the userland `cp`.
The MB/s is computed with

    1,536,217,008 B / time(buffer size, hash)

which includes the time to copy from userland.
The Adjusted MB/s is computed with

    1,536,217,088 B / (time(buffer size, hash) - time(buffer size, none)).

The memory reported is the amount of memory the compressor requests.

| Method   | Size (B) | Time (s) | Ratio | MB/s    | Adj MB/s | Mem (MB) |
|----------|----------|----------|-------|---------|----------|----------|
| none     | 11988480 |    0.100 |     1 | 2119.88 |        - |        - |
| zstd -1  | 73645762 |    1.044 | 2.878 |  203.05 |   224.56 |     1.23 |
| zstd -3  | 66988878 |    1.761 | 3.165 |  120.38 |   127.63 |     2.47 |
| zstd -5  | 65001259 |    2.563 | 3.261 |   82.71 |    86.07 |     2.86 |
| zstd -10 | 60165346 |   13.242 | 3.523 |   16.01 |    16.13 |    13.22 |
| zstd -15 | 58009756 |   47.601 | 3.654 |    4.45 |     4.46 |    21.61 |
| zstd -19 | 54014593 |  102.835 | 3.925 |    2.06 |     2.06 |    60.15 |
| zlib -1  | 77260026 |    2.895 | 2.744 |   73.23 |    75.85 |     0.27 |
| zlib -3  | 72972206 |    4.116 | 2.905 |   51.50 |    52.79 |     0.27 |
| zlib -6  | 68190360 |    9.633 | 3.109 |   22.01 |    22.24 |     0.27 |
| zlib -9  | 67613382 |   22.554 | 3.135 |    9.40 |     9.44 |     0.27 |

I benchmarked zstd decompression using the same method on the same machine.
The benchmark file is located in the upstream zstd repo under
`contrib/linux-kernel/zstd_decompress_test.c` [4]. The memory reported is
the amount of memory required to decompress data compressed with the given
compression level. If you know the maximum size of your input, you can
reduce the memory usage of decompression irrespective of the compression
level.

| Method   | Time (s) | MB/s    | Adjusted MB/s | Memory (MB) |
|----------|----------|---------|---------------|-------------|
| none     |    0.025 | 8479.54 |             - |           - |
| zstd -1  |    0.358 |  592.15 |        636.60 |        0.84 |
| zstd -3  |    0.396 |  535.32 |        571.40 |        1.46 |
| zstd -5  |    0.396 |  535.32 |        571.40 |        1.46 |
| zstd -10 |    0.374 |  566.81 |        607.42 |        2.51 |
| zstd -15 |    0.379 |  559.34 |        598.84 |        4.61 |
| zstd -19 |    0.412 |  514.54 |        547.77 |        8.80 |
| zlib -1  |    0.940 |  225.52 |        231.68 |        0.04 |
| zlib -3  |    0.883 |  240.08 |        247.07 |        0.04 |
| zlib -6  |    0.844 |  251.17 |        258.84 |        0.04 |
| zlib -9  |    0.837 |  253.27 |        287.64 |        0.04 |

Tested in userland using the test-suite in the zstd repo under
`contrib/linux-kernel/test/UserlandTest.cpp` [5] by mocking the kernel
functions. Fuzz tested using libfuzzer [6] with the fuzz harnesses under
`contrib/linux-kernel/test/{RoundTripCrash.c,DecompressCrash.c}` [7] [8]
with ASAN, UBSAN, and MSAN. Additionaly, it was tested while testing the
BtrFS and SquashFS patches coming next.

[1] https://clang.llvm.org/docs/ClangFormat.html
[2] https://github.com/facebook/zstd/blob/dev/contrib/linux-kernel/zstd_compress_test.c
[3] http://sun.aei.polsl.pl/~sdeor/index.php?page=silesia
[4] https://github.com/facebook/zstd/blob/dev/contrib/linux-kernel/zstd_decompress_test.c
[5] https://github.com/facebook/zstd/blob/dev/contrib/linux-kernel/test/UserlandTest.cpp
[6] http://llvm.org/docs/LibFuzzer.html
[7] https://github.com/facebook/zstd/blob/dev/contrib/linux-kernel/test/RoundTripCrash.c
[8] https://github.com/facebook/zstd/blob/dev/contrib/linux-kernel/test/DecompressCrash.c

zstd source repository: https://github.com/facebook/zstd

Signed-off-by: Nick Terrell <terrelln@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 1157 insertions, 0 deletions

diff --git a/include/linux/zstd.h b/include/linux/zstd.h
new file mode 100644
index 000000000000..249575e2485f
--- /dev/null
+++ b/include/linux/zstd.h
@@ -0,0 +1,1157 @@
+/*
+ * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of https://github.com/facebook/zstd.
+ * An additional grant of patent rights can be found in the PATENTS file in the
+ * same directory.
+ *
+ * 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").
+ */
+
+#ifndef ZSTD_H
+#define ZSTD_H
+
+/* ======   Dependency   ======*/
+#include <linux/types.h>   /* size_t */
+
+
+/*-*****************************************************************************
+ * Introduction
+ *
+ * zstd, short for Zstandard, is a fast lossless compression algorithm,
+ * targeting real-time compression scenarios at zlib-level and better
+ * compression ratios. The zstd compression library provides in-memory
+ * compression and decompression functions. The library supports compression
+ * levels from 1 up to ZSTD_maxCLevel() which is 22. Levels >= 20, labeled
+ * ultra, should be used with caution, as they require more memory.
+ * Compression can be done in:
+ *  - a single step, reusing a context (described as Explicit memory management)
+ *  - unbounded multiple steps (described as Streaming compression)
+ * The compression ratio achievable on small data can be highly improved using
+ * compression with a dictionary in:
+ *  - a single step (described as Simple dictionary API)
+ *  - a single step, reusing a dictionary (described as Fast dictionary API)
+ ******************************************************************************/
+
+/*======  Helper functions  ======*/
+
+/**
+ * enum ZSTD_ErrorCode - zstd error codes
+ *
+ * Functions that return size_t can be checked for errors using ZSTD_isError()
+ * and the ZSTD_ErrorCode can be extracted using ZSTD_getErrorCode().
+ */
+typedef enum {
+	ZSTD_error_no_error,
+	ZSTD_error_GENERIC,
+	ZSTD_error_prefix_unknown,
+	ZSTD_error_version_unsupported,
+	ZSTD_error_parameter_unknown,
+	ZSTD_error_frameParameter_unsupported,
+	ZSTD_error_frameParameter_unsupportedBy32bits,
+	ZSTD_error_frameParameter_windowTooLarge,
+	ZSTD_error_compressionParameter_unsupported,
+	ZSTD_error_init_missing,
+	ZSTD_error_memory_allocation,
+	ZSTD_error_stage_wrong,
+	ZSTD_error_dstSize_tooSmall,
+	ZSTD_error_srcSize_wrong,
+	ZSTD_error_corruption_detected,
+	ZSTD_error_checksum_wrong,
+	ZSTD_error_tableLog_tooLarge,
+	ZSTD_error_maxSymbolValue_tooLarge,
+	ZSTD_error_maxSymbolValue_tooSmall,
+	ZSTD_error_dictionary_corrupted,
+	ZSTD_error_dictionary_wrong,
+	ZSTD_error_dictionaryCreation_failed,
+	ZSTD_error_maxCode
+} ZSTD_ErrorCode;
+
+/**
+ * ZSTD_maxCLevel() - maximum compression level available
+ *
+ * Return: Maximum compression level available.
+ */
+int ZSTD_maxCLevel(void);
+/**
+ * ZSTD_compressBound() - maximum compressed size in worst case scenario
+ * @srcSize: The size of the data to compress.
+ *
+ * Return:   The maximum compressed size in the worst case scenario.
+ */
+size_t ZSTD_compressBound(size_t srcSize);
+/**
+ * ZSTD_isError() - tells if a size_t function result is an error code
+ * @code:  The function result to check for error.
+ *
+ * Return: Non-zero iff the code is an error.
+ */
+static __attribute__((unused)) unsigned int ZSTD_isError(size_t code)
+{
+	return code > (size_t)-ZSTD_error_maxCode;
+}
+/**
+ * ZSTD_getErrorCode() - translates an error function result to a ZSTD_ErrorCode
+ * @functionResult: The result of a function for which ZSTD_isError() is true.
+ *
+ * Return:          The ZSTD_ErrorCode corresponding to the functionResult or 0
+ *                  if the functionResult isn't an error.
+ */
+static __attribute__((unused)) ZSTD_ErrorCode ZSTD_getErrorCode(
+	size_t functionResult)
+{
+	if (!ZSTD_isError(functionResult))
+		return (ZSTD_ErrorCode)0;
+	return (ZSTD_ErrorCode)(0 - functionResult);
+}
+
+/**
+ * enum ZSTD_strategy - zstd compression search strategy
+ *
+ * From faster to stronger.
+ */
+typedef enum {
+	ZSTD_fast,
+	ZSTD_dfast,
+	ZSTD_greedy,
+	ZSTD_lazy,
+	ZSTD_lazy2,
+	ZSTD_btlazy2,
+	ZSTD_btopt,
+	ZSTD_btopt2
+} ZSTD_strategy;
+
+/**
+ * struct ZSTD_compressionParameters - zstd compression parameters
+ * @windowLog:    Log of the largest match distance. Larger means more
+ *                compression, and more memory needed during decompression.
+ * @chainLog:     Fully searched segment. Larger means more compression, slower,
+ *                and more memory (useless for fast).
+ * @hashLog:      Dispatch table. Larger means more compression,
+ *                slower, and more memory.
+ * @searchLog:    Number of searches. Larger means more compression and slower.
+ * @searchLength: Match length searched. Larger means faster decompression,
+ *                sometimes less compression.
+ * @targetLength: Acceptable match size for optimal parser (only). Larger means
+ *                more compression, and slower.
+ * @strategy:     The zstd compression strategy.
+ */
+typedef struct {
+	unsigned int windowLog;
+	unsigned int chainLog;
+	unsigned int hashLog;
+	unsigned int searchLog;
+	unsigned int searchLength;
+	unsigned int targetLength;
+	ZSTD_strategy strategy;
+} ZSTD_compressionParameters;
+
+/**
+ * struct ZSTD_frameParameters - zstd frame parameters
+ * @contentSizeFlag: Controls whether content size will be present in the frame
+ *                   header (when known).
+ * @checksumFlag:    Controls whether a 32-bit checksum is generated at the end
+ *                   of the frame for error detection.
+ * @noDictIDFlag:    Controls whether dictID will be saved into the frame header
+ *                   when using dictionary compression.
+ *
+ * The default value is all fields set to 0.
+ */
+typedef struct {
+	unsigned int contentSizeFlag;
+	unsigned int checksumFlag;
+	unsigned int noDictIDFlag;
+} ZSTD_frameParameters;
+
+/**
+ * struct ZSTD_parameters - zstd parameters
+ * @cParams: The compression parameters.
+ * @fParams: The frame parameters.
+ */
+typedef struct {
+	ZSTD_compressionParameters cParams;
+	ZSTD_frameParameters fParams;
+} ZSTD_parameters;
+
+/**
+ * ZSTD_getCParams() - returns ZSTD_compressionParameters for selected level
+ * @compressionLevel: The compression level from 1 to ZSTD_maxCLevel().
+ * @estimatedSrcSize: The estimated source size to compress or 0 if unknown.
+ * @dictSize:         The dictionary size or 0 if a dictionary isn't being used.
+ *
+ * Return:            The selected ZSTD_compressionParameters.
+ */
+ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel,
+	unsigned long long estimatedSrcSize, size_t dictSize);
+
+/**
+ * ZSTD_getParams() - returns ZSTD_parameters for selected level
+ * @compressionLevel: The compression level from 1 to ZSTD_maxCLevel().
+ * @estimatedSrcSize: The estimated source size to compress or 0 if unknown.
+ * @dictSize:         The dictionary size or 0 if a dictionary isn't being used.
+ *
+ * The same as ZSTD_getCParams() except also selects the default frame
+ * parameters (all zero).
+ *
+ * Return:            The selected ZSTD_parameters.
+ */
+ZSTD_parameters ZSTD_getParams(int compressionLevel,
+	unsigned long long estimatedSrcSize, size_t dictSize);
+
+/*-*************************************
+ * Explicit memory management
+ **************************************/
+
+/**
+ * ZSTD_CCtxWorkspaceBound() - amount of memory needed to initialize a ZSTD_CCtx
+ * @cParams: The compression parameters to be used for compression.
+ *
+ * If multiple compression parameters might be used, the caller must call
+ * ZSTD_CCtxWorkspaceBound() for each set of parameters and use the maximum
+ * size.
+ *
+ * Return:   A lower bound on the size of the workspace that is passed to
+ *           ZSTD_initCCtx().
+ */
+size_t ZSTD_CCtxWorkspaceBound(ZSTD_compressionParameters cParams);
+
+/**
+ * struct ZSTD_CCtx - the zstd compression context
+ *
+ * When compressing many times it is recommended to allocate a context just once
+ * and reuse it for each successive compression operation.
+ */
+typedef struct ZSTD_CCtx_s ZSTD_CCtx;
+/**
+ * ZSTD_initCCtx() - initialize a zstd compression context
+ * @workspace:     The workspace to emplace the context into. It must outlive
+ *                 the returned context.
+ * @workspaceSize: The size of workspace. Use ZSTD_CCtxWorkspaceBound() to
+ *                 determine how large the workspace must be.
+ *
+ * Return:         A compression context emplaced into workspace.
+ */
+ZSTD_CCtx *ZSTD_initCCtx(void *workspace, size_t workspaceSize);
+
+/**
+ * ZSTD_compressCCtx() - compress src into dst
+ * @ctx:         The context. Must have been initialized with a workspace at
+ *               least as large as ZSTD_CCtxWorkspaceBound(params.cParams).
+ * @dst:         The buffer to compress src into.
+ * @dstCapacity: The size of the destination buffer. May be any size, but
+ *               ZSTD_compressBound(srcSize) is guaranteed to be large enough.
+ * @src:         The data to compress.
+ * @srcSize:     The size of the data to compress.
+ * @params:      The parameters to use for compression. See ZSTD_getParams().
+ *
+ * Return:       The compressed size or an error, which can be checked using
+ *               ZSTD_isError().
+ */
+size_t ZSTD_compressCCtx(ZSTD_CCtx *ctx, void *dst, size_t dstCapacity,
+	const void *src, size_t srcSize, ZSTD_parameters params);
+
+/**
+ * ZSTD_DCtxWorkspaceBound() - amount of memory needed to initialize a ZSTD_DCtx
+ *
+ * Return: A lower bound on the size of the workspace that is passed to
+ *         ZSTD_initDCtx().
+ */
+size_t ZSTD_DCtxWorkspaceBound(void);
+
+/**
+ * struct ZSTD_DCtx - the zstd decompression context
+ *
+ * When decompressing many times it is recommended to allocate a context just
+ * once and reuse it for each successive decompression operation.
+ */
+typedef struct ZSTD_DCtx_s ZSTD_DCtx;
+/**
+ * ZSTD_initDCtx() - initialize a zstd decompression context
+ * @workspace:     The workspace to emplace the context into. It must outlive
+ *                 the returned context.
+ * @workspaceSize: The size of workspace. Use ZSTD_DCtxWorkspaceBound() to
+ *                 determine how large the workspace must be.
+ *
+ * Return:         A decompression context emplaced into workspace.
+ */
+ZSTD_DCtx *ZSTD_initDCtx(void *workspace, size_t workspaceSize);
+
+/**
+ * ZSTD_decompressDCtx() - decompress zstd compressed src into dst
+ * @ctx:         The decompression context.
+ * @dst:         The buffer to decompress src into.
+ * @dstCapacity: The size of the destination buffer. Must be at least as large
+ *               as the decompressed size. If the caller cannot upper bound the
+ *               decompressed size, then it's better to use the streaming API.
+ * @src:         The zstd compressed data to decompress. Multiple concatenated
+ *               frames and skippable frames are allowed.
+ * @srcSize:     The exact size of the data to decompress.
+ *
+ * Return:       The decompressed size or an error, which can be checked using
+ *               ZSTD_isError().
+ */
+size_t ZSTD_decompressDCtx(ZSTD_DCtx *ctx, void *dst, size_t dstCapacity,
+	const void *src, size_t srcSize);
+
+/*-************************
+ * Simple dictionary API
+ **************************/
+
+/**
+ * ZSTD_compress_usingDict() - compress src into dst using a dictionary
+ * @ctx:         The context. Must have been initialized with a workspace at
+ *               least as large as ZSTD_CCtxWorkspaceBound(params.cParams).
+ * @dst:         The buffer to compress src into.
+ * @dstCapacity: The size of the destination buffer. May be any size, but
+ *               ZSTD_compressBound(srcSize) is guaranteed to be large enough.
+ * @src:         The data to compress.
+ * @srcSize:     The size of the data to compress.
+ * @dict:        The dictionary to use for compression.
+ * @dictSize:    The size of the dictionary.
+ * @params:      The parameters to use for compression. See ZSTD_getParams().
+ *
+ * Compression using a predefined dictionary. The same dictionary must be used
+ * during decompression.
+ *
+ * Return:       The compressed size or an error, which can be checked using
+ *               ZSTD_isError().
+ */
+size_t ZSTD_compress_usingDict(ZSTD_CCtx *ctx, void *dst, size_t dstCapacity,
+	const void *src, size_t srcSize, const void *dict, size_t dictSize,
+	ZSTD_parameters params);
+
+/**
+ * ZSTD_decompress_usingDict() - decompress src into dst using a dictionary
+ * @ctx:         The decompression context.
+ * @dst:         The buffer to decompress src into.
+ * @dstCapacity: The size of the destination buffer. Must be at least as large
+ *               as the decompressed size. If the caller cannot upper bound the
+ *               decompressed size, then it's better to use the streaming API.
+ * @src:         The zstd compressed data to decompress. Multiple concatenated
+ *               frames and skippable frames are allowed.
+ * @srcSize:     The exact size of the data to decompress.
+ * @dict:        The dictionary to use for decompression. The same dictionary
+ *               must've been used to compress the data.
+ * @dictSize:    The size of the dictionary.
+ *
+ * Return:       The decompressed size or an error, which can be checked using
+ *               ZSTD_isError().
+ */
+size_t ZSTD_decompress_usingDict(ZSTD_DCtx *ctx, void *dst, size_t dstCapacity,
+	const void *src, size_t srcSize, const void *dict, size_t dictSize);
+
+/*-**************************
+ * Fast dictionary API
+ ***************************/
+
+/**
+ * ZSTD_CDictWorkspaceBound() - memory needed to initialize a ZSTD_CDict
+ * @cParams: The compression parameters to be used for compression.
+ *
+ * Return:   A lower bound on the size of the workspace that is passed to
+ *           ZSTD_initCDict().
+ */
+size_t ZSTD_CDictWorkspaceBound(ZSTD_compressionParameters cParams);
+
+/**
+ * struct ZSTD_CDict - a digested dictionary to be used for compression
+ */
+typedef struct ZSTD_CDict_s ZSTD_CDict;
+
+/**
+ * ZSTD_initCDict() - initialize a digested dictionary for compression
+ * @dictBuffer:    The dictionary to digest. The buffer is referenced by the
+ *                 ZSTD_CDict so it must outlive the returned ZSTD_CDict.
+ * @dictSize:      The size of the dictionary.
+ * @params:        The parameters to use for compression. See ZSTD_getParams().
+ * @workspace:     The workspace. It must outlive the returned ZSTD_CDict.
+ * @workspaceSize: The workspace size. Must be at least
+ *                 ZSTD_CDictWorkspaceBound(params.cParams).
+ *
+ * When compressing multiple messages / blocks with the same dictionary it is
+ * recommended to load it just once. The ZSTD_CDict merely references the
+ * dictBuffer, so it must outlive the returned ZSTD_CDict.
+ *
+ * Return:         The digested dictionary emplaced into workspace.
+ */
+ZSTD_CDict *ZSTD_initCDict(const void *dictBuffer, size_t dictSize,
+	ZSTD_parameters params, void *workspace, size_t workspaceSize);
+
+/**
+ * ZSTD_compress_usingCDict() - compress src into dst using a ZSTD_CDict
+ * @ctx:         The context. Must have been initialized with a workspace at
+ *               least as large as ZSTD_CCtxWorkspaceBound(cParams) where
+ *               cParams are the compression parameters used to initialize the
+ *               cdict.
+ * @dst:         The buffer to compress src into.
+ * @dstCapacity: The size of the destination buffer. May be any size, but
+ *               ZSTD_compressBound(srcSize) is guaranteed to be large enough.
+ * @src:         The data to compress.
+ * @srcSize:     The size of the data to compress.
+ * @cdict:       The digested dictionary to use for compression.
+ * @params:      The parameters to use for compression. See ZSTD_getParams().
+ *
+ * Compression using a digested dictionary. The same dictionary must be used
+ * during decompression.
+ *
+ * Return:       The compressed size or an error, which can be checked using
+ *               ZSTD_isError().
+ */
+size_t ZSTD_compress_usingCDict(ZSTD_CCtx *cctx, void *dst, size_t dstCapacity,
+	const void *src, size_t srcSize, const ZSTD_CDict *cdict);
+
+
+/**
+ * ZSTD_DDictWorkspaceBound() - memory needed to initialize a ZSTD_DDict
+ *
+ * Return:  A lower bound on the size of the workspace that is passed to
+ *          ZSTD_initDDict().
+ */
+size_t ZSTD_DDictWorkspaceBound(void);
+
+/**
+ * struct ZSTD_DDict - a digested dictionary to be used for decompression
+ */
+typedef struct ZSTD_DDict_s ZSTD_DDict;
+
+/**
+ * ZSTD_initDDict() - initialize a digested dictionary for decompression
+ * @dictBuffer:    The dictionary to digest. The buffer is referenced by the
+ *                 ZSTD_DDict so it must outlive the returned ZSTD_DDict.
+ * @dictSize:      The size of the dictionary.
+ * @workspace:     The workspace. It must outlive the returned ZSTD_DDict.
+ * @workspaceSize: The workspace size. Must be at least
+ *                 ZSTD_DDictWorkspaceBound().
+ *
+ * When decompressing multiple messages / blocks with the same dictionary it is
+ * recommended to load it just once. The ZSTD_DDict merely references the
+ * dictBuffer, so it must outlive the returned ZSTD_DDict.
+ *
+ * Return:         The digested dictionary emplaced into workspace.
+ */
+ZSTD_DDict *ZSTD_initDDict(const void *dictBuffer, size_t dictSize,
+	void *workspace, size_t workspaceSize);
+
+/**
+ * ZSTD_decompress_usingDDict() - decompress src into dst using a ZSTD_DDict
+ * @ctx:         The decompression context.
+ * @dst:         The buffer to decompress src into.
+ * @dstCapacity: The size of the destination buffer. Must be at least as large
+ *               as the decompressed size. If the caller cannot upper bound the
+ *               decompressed size, then it's better to use the streaming API.
+ * @src:         The zstd compressed data to decompress. Multiple concatenated
+ *               frames and skippable frames are allowed.
+ * @srcSize:     The exact size of the data to decompress.
+ * @ddict:       The digested dictionary to use for decompression. The same
+ *               dictionary must've been used to compress the data.
+ *
+ * Return:       The decompressed size or an error, which can be checked using
+ *               ZSTD_isError().
+ */
+size_t ZSTD_decompress_usingDDict(ZSTD_DCtx *dctx, void *dst,
+	size_t dstCapacity, const void *src, size_t srcSize,
+	const ZSTD_DDict *ddict);
+
+
+/*-**************************
+ * Streaming
+ ***************************/
+
+/**
+ * struct ZSTD_inBuffer - input buffer for streaming
+ * @src:  Start of the input buffer.
+ * @size: Size of the input buffer.
+ * @pos:  Position where reading stopped. Will be updated.
+ *        Necessarily 0 <= pos <= size.
+ */
+typedef struct ZSTD_inBuffer_s {
+	const void *src;
+	size_t size;
+	size_t pos;
+} ZSTD_inBuffer;
+
+/**
+ * struct ZSTD_outBuffer - output buffer for streaming
+ * @dst:  Start of the output buffer.
+ * @size: Size of the output buffer.
+ * @pos:  Position where writing stopped. Will be updated.
+ *        Necessarily 0 <= pos <= size.
+ */
+typedef struct ZSTD_outBuffer_s {
+	void *dst;
+	size_t size;
+	size_t pos;
+} ZSTD_outBuffer;
+
+
+
+/*-*****************************************************************************
+ * Streaming compression - HowTo
+ *
+ * A ZSTD_CStream object is required to track streaming operation.
+ * Use ZSTD_initCStream() to initialize a ZSTD_CStream object.
+ * ZSTD_CStream objects can be reused multiple times on consecutive compression
+ * operations. It is recommended to re-use ZSTD_CStream in situations where many
+ * streaming operations will be achieved consecutively. Use one separate
+ * ZSTD_CStream per thread for parallel execution.
+ *
+ * Use ZSTD_compressStream() repetitively to consume input stream.
+ * The function will automatically update both `pos` fields.
+ * Note that it may not consume the entire input, in which case `pos < size`,
+ * and it's up to the caller to present again remaining data.
+ * It returns a hint for the preferred number of bytes to use as an input for
+ * the next function call.
+ *
+ * At any moment, it's possible to flush whatever data remains within internal
+ * buffer, using ZSTD_flushStream(). `output->pos` will be updated. There might
+ * still be some content left within the internal buffer if `output->size` is
+ * too small. It returns the number of bytes left in the internal buffer and
+ * must be called until it returns 0.
+ *
+ * ZSTD_endStream() instructs to finish a frame. It will perform a flush and
+ * write frame epilogue. The epilogue is required for decoders to consider a
+ * frame completed. Similar to ZSTD_flushStream(), it may not be able to flush
+ * the full content if `output->size` is too small. In which case, call again
+ * ZSTD_endStream() to complete the flush. It returns the number of bytes left
+ * in the internal buffer and must be called until it returns 0.
+ ******************************************************************************/
+
+/**
+ * ZSTD_CStreamWorkspaceBound() - memory needed to initialize a ZSTD_CStream
+ * @cParams: The compression parameters to be used for compression.
+ *
+ * Return:   A lower bound on the size of the workspace that is passed to
+ *           ZSTD_initCStream() and ZSTD_initCStream_usingCDict().
+ */
+size_t ZSTD_CStreamWorkspaceBound(ZSTD_compressionParameters cParams);
+
+/**
+ * struct ZSTD_CStream - the zstd streaming compression context
+ */
+typedef struct ZSTD_CStream_s ZSTD_CStream;
+
+/*===== ZSTD_CStream management functions =====*/
+/**
+ * ZSTD_initCStream() - initialize a zstd streaming compression context
+ * @params:         The zstd compression parameters.
+ * @pledgedSrcSize: If params.fParams.contentSizeFlag == 1 then the caller must
+ *                  pass the source size (zero means empty source). Otherwise,
+ *                  the caller may optionally pass the source size, or zero if
+ *                  unknown.
+ * @workspace:      The workspace to emplace the context into. It must outlive
+ *                  the returned context.
+ * @workspaceSize:  The size of workspace.
+ *                  Use ZSTD_CStreamWorkspaceBound(params.cParams) to determine
+ *                  how large the workspace must be.
+ *
+ * Return:          The zstd streaming compression context.
+ */
+ZSTD_CStream *ZSTD_initCStream(ZSTD_parameters params,
+	unsigned long long pledgedSrcSize, void *workspace,
+	size_t workspaceSize);
+
+/**
+ * ZSTD_initCStream_usingCDict() - initialize a streaming compression context
+ * @cdict:          The digested dictionary to use for compression.
+ * @pledgedSrcSize: Optionally the source size, or zero if unknown.
+ * @workspace:      The workspace to emplace the context into. It must outlive
+ *                  the returned context.
+ * @workspaceSize:  The size of workspace. Call ZSTD_CStreamWorkspaceBound()
+ *                  with the cParams used to initialize the cdict to determine
+ *                  how large the workspace must be.
+ *
+ * Return:          The zstd streaming compression context.
+ */
+ZSTD_CStream *ZSTD_initCStream_usingCDict(const ZSTD_CDict *cdict,
+	unsigned long long pledgedSrcSize, void *workspace,
+	size_t workspaceSize);
+
+/*===== Streaming compression functions =====*/
+/**
+ * ZSTD_resetCStream() - reset the context using parameters from creation
+ * @zcs:            The zstd streaming compression context to reset.
+ * @pledgedSrcSize: Optionally the source size, or zero if unknown.
+ *
+ * Resets the context using the parameters from creation. Skips dictionary
+ * loading, since it can be reused. If `pledgedSrcSize` is non-zero the frame
+ * content size is always written into the frame header.
+ *
+ * Return:          Zero or an error, which can be checked using ZSTD_isError().
+ */
+size_t ZSTD_resetCStream(ZSTD_CStream *zcs, unsigned long long pledgedSrcSize);
+/**
+ * ZSTD_compressStream() - streaming compress some of input into output
+ * @zcs:    The zstd streaming compression context.
+ * @output: Destination buffer. `output->pos` is updated to indicate how much
+ *          compressed data was written.
+ * @input:  Source buffer. `input->pos` is updated to indicate how much data was
+ *          read. Note that it may not consume the entire input, in which case
+ *          `input->pos < input->size`, and it's up to the caller to present
+ *          remaining data again.
+ *
+ * The `input` and `output` buffers may be any size. Guaranteed to make some
+ * forward progress if `input` and `output` are not empty.
+ *
+ * Return:  A hint for the number of bytes to use as the input for the next
+ *          function call or an error, which can be checked using
+ *          ZSTD_isError().
+ */
+size_t ZSTD_compressStream(ZSTD_CStream *zcs, ZSTD_outBuffer *output,
+	ZSTD_inBuffer *input);
+/**
+ * ZSTD_flushStream() - flush internal buffers into output
+ * @zcs:    The zstd streaming compression context.
+ * @output: Destination buffer. `output->pos` is updated to indicate how much
+ *          compressed data was written.
+ *
+ * ZSTD_flushStream() must be called until it returns 0, meaning all the data
+ * has been flushed. Since ZSTD_flushStream() causes a block to be ended,
+ * calling it too often will degrade the compression ratio.
+ *
+ * Return:  The number of bytes still present within internal buffers or an
+ *          error, which can be checked using ZSTD_isError().
+ */
+size_t ZSTD_flushStream(ZSTD_CStream *zcs, ZSTD_outBuffer *output);
+/**
+ * ZSTD_endStream() - flush internal buffers into output and end the frame
+ * @zcs:    The zstd streaming compression context.
+ * @output: Destination buffer. `output->pos` is updated to indicate how much
+ *          compressed data was written.
+ *
+ * ZSTD_endStream() must be called until it returns 0, meaning all the data has
+ * been flushed and the frame epilogue has been written.
+ *
+ * Return:  The number of bytes still present within internal buffers or an
+ *          error, which can be checked using ZSTD_isError().
+ */
+size_t ZSTD_endStream(ZSTD_CStream *zcs, ZSTD_outBuffer *output);
+
+/**
+ * ZSTD_CStreamInSize() - recommended size for the input buffer
+ *
+ * Return: The recommended size for the input buffer.
+ */
+size_t ZSTD_CStreamInSize(void);
+/**
+ * ZSTD_CStreamOutSize() - recommended size for the output buffer
+ *
+ * When the output buffer is at least this large, it is guaranteed to be large
+ * enough to flush at least one complete compressed block.
+ *
+ * Return: The recommended size for the output buffer.
+ */
+size_t ZSTD_CStreamOutSize(void);
+
+
+
+/*-*****************************************************************************
+ * Streaming decompression - HowTo
+ *
+ * A ZSTD_DStream object is required to track streaming operations.
+ * Use ZSTD_initDStream() to initialize a ZSTD_DStream object.
+ * ZSTD_DStream objects can be re-used multiple times.
+ *
+ * Use ZSTD_decompressStream() repetitively to consume your input.
+ * The function will update both `pos` fields.
+ * If `input->pos < input->size`, some input has not been consumed.
+ * It's up to the caller to present again remaining data.
+ * If `output->pos < output->size`, decoder has flushed everything it could.
+ * Returns 0 iff a frame is completely decoded and fully flushed.
+ * Otherwise it returns a suggested next input size that will never load more
+ * than the current frame.
+ ******************************************************************************/
+
+/**
+ * ZSTD_DStreamWorkspaceBound() - memory needed to initialize a ZSTD_DStream
+ * @maxWindowSize: The maximum window size allowed for compressed frames.
+ *
+ * Return:         A lower bound on the size of the workspace that is passed to
+ *                 ZSTD_initDStream() and ZSTD_initDStream_usingDDict().
+ */
+size_t ZSTD_DStreamWorkspaceBound(size_t maxWindowSize);
+
+/**
+ * struct ZSTD_DStream - the zstd streaming decompression context
+ */
+typedef struct ZSTD_DStream_s ZSTD_DStream;
+/*===== ZSTD_DStream management functions =====*/
+/**
+ * ZSTD_initDStream() - initialize a zstd streaming decompression context
+ * @maxWindowSize: The maximum window size allowed for compressed frames.
+ * @workspace:     The workspace to emplace the context into. It must outlive
+ *                 the returned context.
+ * @workspaceSize: The size of workspace.
+ *                 Use ZSTD_DStreamWorkspaceBound(maxWindowSize) to determine
+ *                 how large the workspace must be.
+ *
+ * Return:         The zstd streaming decompression context.
+ */
+ZSTD_DStream *ZSTD_initDStream(size_t maxWindowSize, void *workspace,
+	size_t workspaceSize);
+/**
+ * ZSTD_initDStream_usingDDict() - initialize streaming decompression context
+ * @maxWindowSize: The maximum window size allowed for compressed frames.
+ * @ddict:         The digested dictionary to use for decompression.
+ * @workspace:     The workspace to emplace the context into. It must outlive
+ *                 the returned context.
+ * @workspaceSize: The size of workspace.
+ *                 Use ZSTD_DStreamWorkspaceBound(maxWindowSize) to determine
+ *                 how large the workspace must be.
+ *
+ * Return:         The zstd streaming decompression context.
+ */
+ZSTD_DStream *ZSTD_initDStream_usingDDict(size_t maxWindowSize,
+	const ZSTD_DDict *ddict, void *workspace, size_t workspaceSize);
+
+/*===== Streaming decompression functions =====*/
+/**
+ * ZSTD_resetDStream() - reset the context using parameters from creation
+ * @zds:   The zstd streaming decompression context to reset.
+ *
+ * Resets the context using the parameters from creation. Skips dictionary
+ * loading, since it can be reused.
+ *
+ * Return: Zero or an error, which can be checked using ZSTD_isError().
+ */
+size_t ZSTD_resetDStream(ZSTD_DStream *zds);
+/**
+ * ZSTD_decompressStream() - streaming decompress some of input into output
+ * @zds:    The zstd streaming decompression context.
+ * @output: Destination buffer. `output.pos` is updated to indicate how much
+ *          decompressed data was written.
+ * @input:  Source buffer. `input.pos` is updated to indicate how much data was
+ *          read. Note that it may not consume the entire input, in which case
+ *          `input.pos < input.size`, and it's up to the caller to present
+ *          remaining data again.
+ *
+ * The `input` and `output` buffers may be any size. Guaranteed to make some
+ * forward progress if `input` and `output` are not empty.
+ * ZSTD_decompressStream() will not consume the last byte of the frame until
+ * the entire frame is flushed.
+ *
+ * Return:  Returns 0 iff a frame is completely decoded and fully flushed.
+ *          Otherwise returns a hint for the number of bytes to use as the input
+ *          for the next function call or an error, which can be checked using
+ *          ZSTD_isError(). The size hint will never load more than the frame.
+ */
+size_t ZSTD_decompressStream(ZSTD_DStream *zds, ZSTD_outBuffer *output,
+	ZSTD_inBuffer *input);
+
+/**
+ * ZSTD_DStreamInSize() - recommended size for the input buffer
+ *
+ * Return: The recommended size for the input buffer.
+ */
+size_t ZSTD_DStreamInSize(void);
+/**
+ * ZSTD_DStreamOutSize() - recommended size for the output buffer
+ *
+ * When the output buffer is at least this large, it is guaranteed to be large
+ * enough to flush at least one complete decompressed block.
+ *
+ * Return: The recommended size for the output buffer.
+ */
+size_t ZSTD_DStreamOutSize(void);
+
+
+/* --- Constants ---*/
+#define ZSTD_MAGICNUMBER            0xFD2FB528   /* >= v0.8.0 */
+#define ZSTD_MAGIC_SKIPPABLE_START  0x184D2A50U
+
+#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1)
+#define ZSTD_CONTENTSIZE_ERROR   (0ULL - 2)
+
+#define ZSTD_WINDOWLOG_MAX_32  27
+#define ZSTD_WINDOWLOG_MAX_64  27
+#define ZSTD_WINDOWLOG_MAX \
+	((unsigned int)(sizeof(size_t) == 4 \
+		? ZSTD_WINDOWLOG_MAX_32 \
+		: ZSTD_WINDOWLOG_MAX_64))
+#define ZSTD_WINDOWLOG_MIN 10
+#define ZSTD_HASHLOG_MAX ZSTD_WINDOWLOG_MAX
+#define ZSTD_HASHLOG_MIN        6
+#define ZSTD_CHAINLOG_MAX     (ZSTD_WINDOWLOG_MAX+1)
+#define ZSTD_CHAINLOG_MIN      ZSTD_HASHLOG_MIN
+#define ZSTD_HASHLOG3_MAX      17
+#define ZSTD_SEARCHLOG_MAX    (ZSTD_WINDOWLOG_MAX-1)
+#define ZSTD_SEARCHLOG_MIN      1
+/* only for ZSTD_fast, other strategies are limited to 6 */
+#define ZSTD_SEARCHLENGTH_MAX   7
+/* only for ZSTD_btopt, other strategies are limited to 4 */
+#define ZSTD_SEARCHLENGTH_MIN   3
+#define ZSTD_TARGETLENGTH_MIN   4
+#define ZSTD_TARGETLENGTH_MAX 999
+
+/* for static allocation */
+#define ZSTD_FRAMEHEADERSIZE_MAX 18
+#define ZSTD_FRAMEHEADERSIZE_MIN  6
+static const size_t ZSTD_frameHeaderSize_prefix = 5;
+static const size_t ZSTD_frameHeaderSize_min = ZSTD_FRAMEHEADERSIZE_MIN;
+static const size_t ZSTD_frameHeaderSize_max = ZSTD_FRAMEHEADERSIZE_MAX;
+/* magic number + skippable frame length */
+static const size_t ZSTD_skippableHeaderSize = 8;
+
+
+/*-*************************************
+ * Compressed size functions
+ **************************************/
+
+/**
+ * ZSTD_findFrameCompressedSize() - returns the size of a compressed frame
+ * @src:     Source buffer. It should point to the start of a zstd encoded frame
+ *           or a skippable frame.
+ * @srcSize: The size of the source buffer. It must be at least as large as the
+ *           size of the frame.
+ *
+ * Return:   The compressed size of the frame pointed to by `src` or an error,
+ *           which can be check with ZSTD_isError().
+ *           Suitable to pass to ZSTD_decompress() or similar functions.
+ */
+size_t ZSTD_findFrameCompressedSize(const void *src, size_t srcSize);
+
+/*-*************************************
+ * Decompressed size functions
+ **************************************/
+/**
+ * ZSTD_getFrameContentSize() - returns the content size in a zstd frame header
+ * @src:     It should point to the start of a zstd encoded frame.
+ * @srcSize: The size of the source buffer. It must be at least as large as the
+ *           frame header. `ZSTD_frameHeaderSize_max` is always large enough.
+ *
+ * Return:   The frame content size stored in the frame header if known.
+ *           `ZSTD_CONTENTSIZE_UNKNOWN` if the content size isn't stored in the
+ *           frame header. `ZSTD_CONTENTSIZE_ERROR` on invalid input.
+ */
+unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);
+
+/**
+ * ZSTD_findDecompressedSize() - returns decompressed size of a series of frames
+ * @src:     It should point to the start of a series of zstd encoded and/or
+ *           skippable frames.
+ * @srcSize: The exact size of the series of frames.
+ *
+ * If any zstd encoded frame in the series doesn't have the frame content size
+ * set, `ZSTD_CONTENTSIZE_UNKNOWN` is returned. But frame content size is always
+ * set when using ZSTD_compress(). The decompressed size can be very large.
+ * If the source is untrusted, the decompressed size could be wrong or
+ * intentionally modified. Always ensure the result fits within the
+ * application's authorized limits. ZSTD_findDecompressedSize() handles multiple
+ * frames, and so it must traverse the input to read each frame header. This is
+ * efficient as most of the data is skipped, however it does mean that all frame
+ * data must be present and valid.
+ *
+ * Return:   Decompressed size of all the data contained in the frames if known.
+ *           `ZSTD_CONTENTSIZE_UNKNOWN` if the decompressed size is unknown.
+ *           `ZSTD_CONTENTSIZE_ERROR` if an error occurred.
+ */
+unsigned long long ZSTD_findDecompressedSize(const void *src, size_t srcSize);
+
+/*-*************************************
+ * Advanced compression functions
+ **************************************/
+/**
+ * ZSTD_checkCParams() - ensure parameter values remain within authorized range
+ * @cParams: The zstd compression parameters.
+ *
+ * Return:   Zero or an error, which can be checked using ZSTD_isError().
+ */
+size_t ZSTD_checkCParams(ZSTD_compressionParameters cParams);
+
+/**
+ * ZSTD_adjustCParams() - optimize parameters for a given srcSize and dictSize
+ * @srcSize:  Optionally the estimated source size, or zero if unknown.
+ * @dictSize: Optionally the estimated dictionary size, or zero if unknown.
+ *
+ * Return:    The optimized parameters.
+ */
+ZSTD_compressionParameters ZSTD_adjustCParams(
+	ZSTD_compressionParameters cParams, unsigned long long srcSize,
+	size_t dictSize);
+
+/*--- Advanced decompression functions ---*/
+
+/**
+ * ZSTD_isFrame() - returns true iff the buffer starts with a valid frame
+ * @buffer: The source buffer to check.
+ * @size:   The size of the source buffer, must be at least 4 bytes.
+ *
+ * Return: True iff the buffer starts with a zstd or skippable frame identifier.
+ */
+unsigned int ZSTD_isFrame(const void *buffer, size_t size);
+
+/**
+ * ZSTD_getDictID_fromDict() - returns the dictionary id stored in a dictionary
+ * @dict:     The dictionary buffer.
+ * @dictSize: The size of the dictionary buffer.
+ *
+ * Return:    The dictionary id stored within the dictionary or 0 if the
+ *            dictionary is not a zstd dictionary. If it returns 0 the
+ *            dictionary can still be loaded as a content-only dictionary.
+ */
+unsigned int ZSTD_getDictID_fromDict(const void *dict, size_t dictSize);
+
+/**
+ * ZSTD_getDictID_fromDDict() - returns the dictionary id stored in a ZSTD_DDict
+ * @ddict: The ddict to find the id of.
+ *
+ * Return: The dictionary id stored within `ddict` or 0 if the dictionary is not
+ *         a zstd dictionary. If it returns 0 `ddict` will be loaded as a
+ *         content-only dictionary.
+ */
+unsigned int ZSTD_getDictID_fromDDict(const ZSTD_DDict *ddict);
+
+/**
+ * ZSTD_getDictID_fromFrame() - returns the dictionary id stored in a zstd frame
+ * @src:     Source buffer. It must be a zstd encoded frame.
+ * @srcSize: The size of the source buffer. It must be at least as large as the
+ *           frame header. `ZSTD_frameHeaderSize_max` is always large enough.
+ *
+ * Return:   The dictionary id required to decompress the frame stored within
+ *           `src` or 0 if the dictionary id could not be decoded. It can return
+ *           0 if the frame does not require a dictionary, the dictionary id
+ *           wasn't stored in the frame, `src` is not a zstd frame, or `srcSize`
+ *           is too small.
+ */
+unsigned int ZSTD_getDictID_fromFrame(const void *src, size_t srcSize);
+
+/**
+ * struct ZSTD_frameParams - zstd frame parameters stored in the frame header
+ * @frameContentSize: The frame content size, or 0 if not present.
+ * @windowSize:       The window size, or 0 if the frame is a skippable frame.
+ * @dictID:           The dictionary id, or 0 if not present.
+ * @checksumFlag:     Whether a checksum was used.
+ */
+typedef struct {
+	unsigned long long frameContentSize;
+	unsigned int windowSize;
+	unsigned int dictID;
+	unsigned int checksumFlag;
+} ZSTD_frameParams;
+
+/**
+ * ZSTD_getFrameParams() - extracts parameters from a zstd or skippable frame
+ * @fparamsPtr: On success the frame parameters are written here.
+ * @src:        The source buffer. It must point to a zstd or skippable frame.
+ * @srcSize:    The size of the source buffer. `ZSTD_frameHeaderSize_max` is
+ *              always large enough to succeed.
+ *
+ * Return:      0 on success. If more data is required it returns how many bytes
+ *              must be provided to make forward progress. Otherwise it returns
+ *              an error, which can be checked using ZSTD_isError().
+ */
+size_t ZSTD_getFrameParams(ZSTD_frameParams *fparamsPtr, const void *src,
+	size_t srcSize);
+
+/*-*****************************************************************************
+ * Buffer-less and synchronous inner streaming functions
+ *
+ * This is an advanced API, giving full control over buffer management, for
+ * users which need direct control over memory.
+ * But it's also a complex one, with many restrictions (documented below).
+ * Prefer using normal streaming API for an easier experience
+ ******************************************************************************/
+
+/*-*****************************************************************************
+ * Buffer-less streaming compression (synchronous mode)
+ *
+ * A ZSTD_CCtx object is required to track streaming operations.
+ * Use ZSTD_initCCtx() to initialize a context.
+ * ZSTD_CCtx object can be re-used multiple times within successive compression
+ * operations.
+ *
+ * Start by initializing a context.
+ * Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary
+ * compression,
+ * or ZSTD_compressBegin_advanced(), for finer parameter control.
+ * It's also possible to duplicate a reference context which has already been
+ * initialized, using ZSTD_copyCCtx()
+ *
+ * Then, consume your input using ZSTD_compressContinue().
+ * There are some important considerations to keep in mind when using this
+ * advanced function :
+ * - ZSTD_compressContinue() has no internal buffer. It uses externally provided
+ *   buffer only.
+ * - Interface is synchronous : input is consumed entirely and produce 1+
+ *   (or more) compressed blocks.
+ * - Caller must ensure there is enough space in `dst` to store compressed data
+ *   under worst case scenario. Worst case evaluation is provided by
+ *   ZSTD_compressBound().
+ *   ZSTD_compressContinue() doesn't guarantee recover after a failed
+ *   compression.
+ * - ZSTD_compressContinue() presumes prior input ***is still accessible and
+ *   unmodified*** (up to maximum distance size, see WindowLog).
+ *   It remembers all previous contiguous blocks, plus one separated memory
+ *   segment (which can itself consists of multiple contiguous blocks)
+ * - ZSTD_compressContinue() detects that prior input has been overwritten when
+ *   `src` buffer overlaps. In which case, it will "discard" the relevant memory
+ *   section from its history.
+ *
+ * Finish a frame with ZSTD_compressEnd(), which will write the last block(s)
+ * and optional checksum. It's possible to use srcSize==0, in which case, it
+ * will write a final empty block to end the frame. Without last block mark,
+ * frames will be considered unfinished (corrupted) by decoders.
+ *
+ * `ZSTD_CCtx` object can be re-used (ZSTD_compressBegin()) to compress some new
+ * frame.
+ ******************************************************************************/
+
+/*=====   Buffer-less streaming compression functions  =====*/
+size_t ZSTD_compressBegin(ZSTD_CCtx *cctx, int compressionLevel);
+size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx *cctx, const void *dict,
+	size_t dictSize, int compressionLevel);
+size_t ZSTD_compressBegin_advanced(ZSTD_CCtx *cctx, const void *dict,
+	size_t dictSize, ZSTD_parameters params,
+	unsigned long long pledgedSrcSize);
+size_t ZSTD_copyCCtx(ZSTD_CCtx *cctx, const ZSTD_CCtx *preparedCCtx,
+	unsigned long long pledgedSrcSize);
+size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx *cctx, const ZSTD_CDict *cdict,
+	unsigned long long pledgedSrcSize);
+size_t ZSTD_compressContinue(ZSTD_CCtx *cctx, void *dst, size_t dstCapacity,
+	const void *src, size_t srcSize);
+size_t ZSTD_compressEnd(ZSTD_CCtx *cctx, void *dst, size_t dstCapacity,
+	const void *src, size_t srcSize);
+
+
+
+/*-*****************************************************************************
+ * Buffer-less streaming decompression (synchronous mode)
+ *
+ * A ZSTD_DCtx object is required to track streaming operations.
+ * Use ZSTD_initDCtx() to initialize a context.
+ * A ZSTD_DCtx object can be re-used multiple times.
+ *
+ * First typical operation is to retrieve frame parameters, using
+ * ZSTD_getFrameParams(). It fills a ZSTD_frameParams structure which provide
+ * important information to correctly decode the frame, such as the minimum
+ * rolling buffer size to allocate to decompress data (`windowSize`), and the
+ * dictionary ID used.
+ * Note: content size is optional, it may not be present. 0 means unknown.
+ * Note that these values could be wrong, either because of data malformation,
+ * or because an attacker is spoofing deliberate false information. As a
+ * consequence, check that values remain within valid application range,
+ * especially `windowSize`, before allocation. Each application can set its own
+ * limit, depending on local restrictions. For extended interoperability, it is
+ * recommended to support at least 8 MB.
+ * Frame parameters are extracted from the beginning of the compressed frame.
+ * Data fragment must be large enough to ensure successful decoding, typically
+ * `ZSTD_frameHeaderSize_max` bytes.
+ * Result: 0: successful decoding, the `ZSTD_frameParams` structure is filled.
+ *        >0: `srcSize` is too small, provide at least this many bytes.
+ *        errorCode, which can be tested using ZSTD_isError().
+ *
+ * Start decompression, with ZSTD_decompressBegin() or
+ * ZSTD_decompressBegin_usingDict(). Alternatively, you can copy a prepared
+ * context, using ZSTD_copyDCtx().
+ *
+ * Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue()
+ * alternatively.
+ * ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize'
+ * to ZSTD_decompressContinue().
+ * ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will
+ * fail.
+ *
+ * The result of ZSTD_decompressContinue() is the number of bytes regenerated
+ * within 'dst' (necessarily <= dstCapacity). It can be zero, which is not an
+ * error; it just means ZSTD_decompressContinue() has decoded some metadata
+ * item. It can also be an error code, which can be tested with ZSTD_isError().
+ *
+ * ZSTD_decompressContinue() needs previous data blocks during decompression, up
+ * to `windowSize`. They should preferably be located contiguously, prior to
+ * current block. Alternatively, a round buffer of sufficient size is also
+ * possible. Sufficient size is determined by frame parameters.
+ * ZSTD_decompressContinue() is very sensitive to contiguity, if 2 blocks don't
+ * follow each other, make sure that either the compressor breaks contiguity at
+ * the same place, or that previous contiguous segment is large enough to
+ * properly handle maximum back-reference.
+ *
+ * A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
+ * Context can then be reset to start a new decompression.
+ *
+ * Note: it's possible to know if next input to present is a header or a block,
+ * using ZSTD_nextInputType(). This information is not required to properly
+ * decode a frame.
+ *
+ * == Special case: skippable frames ==
+ *
+ * Skippable frames allow integration of user-defined data into a flow of
+ * concatenated frames. Skippable frames will be ignored (skipped) by a
+ * decompressor. The format of skippable frames is as follows:
+ * a) Skippable frame ID - 4 Bytes, Little endian format, any value from
+ *    0x184D2A50 to 0x184D2A5F
+ * b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
+ * c) Frame Content - any content (User Data) of length equal to Frame Size
+ * For skippable frames ZSTD_decompressContinue() always returns 0.
+ * For skippable frames ZSTD_getFrameParams() returns fparamsPtr->windowLog==0
+ * what means that a frame is skippable.
+ * Note: If fparamsPtr->frameContentSize==0, it is ambiguous: the frame might
+ *       actually be a zstd encoded frame with no content. For purposes of
+ *       decompression, it is valid in both cases to skip the frame using
+ *       ZSTD_findFrameCompressedSize() to find its size in bytes.
+ * It also returns frame size as fparamsPtr->frameContentSize.
+ ******************************************************************************/
+
+/*=====   Buffer-less streaming decompression functions  =====*/
+size_t ZSTD_decompressBegin(ZSTD_DCtx *dctx);
+size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx *dctx, const void *dict,
+	size_t dictSize);
+void   ZSTD_copyDCtx(ZSTD_DCtx *dctx, const ZSTD_DCtx *preparedDCtx);
+size_t ZSTD_nextSrcSizeToDecompress(ZSTD_DCtx *dctx);
+size_t ZSTD_decompressContinue(ZSTD_DCtx *dctx, void *dst, size_t dstCapacity,
+	const void *src, size_t srcSize);
+typedef enum {
+	ZSTDnit_frameHeader,
+	ZSTDnit_blockHeader,
+	ZSTDnit_block,
+	ZSTDnit_lastBlock,
+	ZSTDnit_checksum,
+	ZSTDnit_skippableFrame
+} ZSTD_nextInputType_e;
+ZSTD_nextInputType_e ZSTD_nextInputType(ZSTD_DCtx *dctx);
+
+/*-*****************************************************************************
+ * Block functions
+ *
+ * Block functions produce and decode raw zstd blocks, without frame metadata.
+ * Frame metadata cost is typically ~18 bytes, which can be non-negligible for
+ * very small blocks (< 100 bytes). User will have to take in charge required
+ * information to regenerate data, such as compressed and content sizes.
+ *
+ * A few rules to respect:
+ * - Compressing and decompressing require a context structure
+ *   + Use ZSTD_initCCtx() and ZSTD_initDCtx()
+ * - It is necessary to init context before starting
+ *   + compression : ZSTD_compressBegin()
+ *   + decompression : ZSTD_decompressBegin()
+ *   + variants _usingDict() are also allowed
+ *   + copyCCtx() and copyDCtx() work too
+ * - Block size is limited, it must be <= ZSTD_getBlockSizeMax()
+ *   + If you need to compress more, cut data into multiple blocks
+ *   + Consider using the regular ZSTD_compress() instead, as frame metadata
+ *     costs become negligible when source size is large.
+ * - When a block is considered not compressible enough, ZSTD_compressBlock()
+ *   result will be zero. In which case, nothing is produced into `dst`.
+ *   + User must test for such outcome and deal directly with uncompressed data
+ *   + ZSTD_decompressBlock() doesn't accept uncompressed data as input!!!
+ *   + In case of multiple successive blocks, decoder must be informed of
+ *     uncompressed block existence to follow proper history. Use
+ *     ZSTD_insertBlock() in such a case.
+ ******************************************************************************/
+
+/* Define for static allocation */
+#define ZSTD_BLOCKSIZE_ABSOLUTEMAX (128 * 1024)
+/*=====   Raw zstd block functions  =====*/
+size_t ZSTD_getBlockSizeMax(ZSTD_CCtx *cctx);
+size_t ZSTD_compressBlock(ZSTD_CCtx *cctx, void *dst, size_t dstCapacity,
+	const void *src, size_t srcSize);
+size_t ZSTD_decompressBlock(ZSTD_DCtx *dctx, void *dst, size_t dstCapacity,
+	const void *src, size_t srcSize);
+size_t ZSTD_insertBlock(ZSTD_DCtx *dctx, const void *blockStart,
+	size_t blockSize);
+
+#endif  /* ZSTD_H */