lib: add Zstandard decompression support

Add the zstd library from Linux kernel (only decompression support).
There are minimal changes to build with U-Boot, otherwise the files are
identical to Linux commit dc35da16 from March 2018, the files had not
been touched since in kernel. Also SPDX lincese tags were added.

Signed-off-by: Marek Behún <marek.behun@nic.cz>

1 files changed, 1147 insertions, 0 deletions

diff --git a/include/linux/zstd.h b/include/linux/zstd.h
new file mode 100644
index 0000000000..724f69350e
--- /dev/null
+++ b/include/linux/zstd.h
@@ -0,0 +1,1147 @@
+/* SPDX-License-Identifier: (GPL-2.0 or BSD-3-Clause-Clear) */
+/*
+ * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
+ * All rights reserved.
+ */
+
+#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 */