// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.

//  This source code is licensed under both the GPLv2 (found in the

//  COPYING file in the root directory) and Apache 2.0 License

//  (found in the LICENSE.Apache file in the root directory).

//

// Copyright (c) 2011 The LevelDB Authors. All rights reserved.

// Use of this source code is governed by a BSD-style license that can be

// found in the LICENSE file. See the AUTHORS file for names of contributors.

//

#pragma once

#include <algorithm>

#include "memory/memory_allocator_impl.h"

#include "rocksdb/advanced_compression.h"

#include "rocksdb/options.h"

#include "table/block_based/block_type.h"

#include "util/aligned_buffer.h"

#include "util/coding.h"

#include "util/compression_context_cache.h"

#ifdef ZSTD

#include <zstd.h>

#include <zstd_errors.h>

// ZSTD_Compress2(), ZSTD_compressStream2() and frame parameters all belong to

// advanced APIs and require v1.4.0+, which is from April 2019.

// https://github.com/facebook/zstd/blob/eb9f881eb810f2242f1ef36b3f3e7014eecb8fa6/lib/zstd.h#L297C40-L297C45

// To avoid a rat's nest of #ifdefs, we now require v1.4.0+ for ZSTD support.

#if ZSTD_VERSION_NUMBER < 10400

#error "ZSTD support requires version >= 1.4.0 (libzstd-devel)"

#endif  // ZSTD_VERSION_NUMBER

// The above release also includes digested dictionary support, but some

// required functions (ZSTD_createDDict_byReference) are still only exported

// with ZSTD_STATIC_LINKING_ONLY defined.

#if defined(ZSTD_STATIC_LINKING_ONLY)

#define ROCKSDB_ZSTD_DDICT

#endif  // defined(ZSTD_STATIC_LINKING_ONLY)

//  For ZDICT_* functions

#include <zdict.h>

// ZDICT_finalizeDictionary API is exported and stable since v1.4.5

#if ZSTD_VERSION_NUMBER >= 10405

#define ROCKSDB_ZDICT_FINALIZE

#endif  // ZSTD_VERSION_NUMBER >= 10405

#endif  // ZSTD

namespace ROCKSDB_NAMESPACE {

// Need this for the context allocation override

// On windows we need to do this explicitly

#if defined(ZSTD) && defined(ROCKSDB_JEMALLOC) && defined(OS_WIN) && \

    defined(ZSTD_STATIC_LINKING_ONLY)

#define ROCKSDB_ZSTD_CUSTOM_MEM

namespace port {

ZSTD_customMem GetJeZstdAllocationOverrides();

}  // namespace port

#endif  // defined(ZSTD) && defined(ROCKSDB_JEMALLOC) && defined(OS_WIN) &&

        // defined(ZSTD_STATIC_LINKING_ONLY)

#ifdef ZSTD

// Translates a configured compression_opts.level into the effective ZSTD

// compression level. Besides resolving the "use default" sentinel, this

// removes a discontinuity at level 0: ZSTD itself treats a requested level of

// 0 as "use the default level" (historically 3), which would make level 0

// more aggressive than levels 1 and 2. Mapping 0 to -1 keeps the level spectrum

// monotonic, which is friendlier to auto-tuning.

inline int SanitizeZSTDCompressionLevel(int level) {

  if (level == CompressionOptions::kDefaultCompressionLevel) {

    // NB: ZSTD_CLEVEL_DEFAULT is historically == 3

    return ZSTD_CLEVEL_DEFAULT;

  } else if (level == 0) {

    // Avoid library's discontinuity at level 0

    return -1;

  } else {

    return level;

  }

}

#endif  // ZSTD

// Cached data represents a portion that can be re-used

// If, in the future we have more than one native context to

// cache we can arrange this as a tuple

class ZSTDUncompressCachedData {

 public:

#if defined(ZSTD)

  using ZSTDNativeContext = ZSTD_DCtx*;

#else

  using ZSTDNativeContext = void*;

#endif  // ZSTD

  ZSTDUncompressCachedData() {}

  // Init from cache

  ZSTDUncompressCachedData(const ZSTDUncompressCachedData& o) = delete;

  ZSTDUncompressCachedData& operator=(const ZSTDUncompressCachedData&) = delete;

  ZSTDUncompressCachedData(ZSTDUncompressCachedData&& o) noexcept

      : ZSTDUncompressCachedData() {

    *this = std::move(o);

  }

  ZSTDUncompressCachedData& operator=(ZSTDUncompressCachedData&& o) noexcept {

    assert(zstd_ctx_ == nullptr);

    std::swap(zstd_ctx_, o.zstd_ctx_);

    std::swap(cache_idx_, o.cache_idx_);

    return *this;

  }

  ZSTDNativeContext Get() const { return zstd_ctx_; }

  int64_t GetCacheIndex() const { return cache_idx_; }

  void CreateIfNeeded() {

    if (zstd_ctx_ == nullptr) {

#if !defined(ZSTD)

      zstd_ctx_ = nullptr;

#elif defined(ROCKSDB_ZSTD_CUSTOM_MEM)

      zstd_ctx_ =

          ZSTD_createDCtx_advanced(port::GetJeZstdAllocationOverrides());

#else  // ZSTD && !ROCKSDB_ZSTD_CUSTOM_MEM

      zstd_ctx_ = ZSTD_createDCtx();

#endif

      cache_idx_ = -1;

    }

  }

  void InitFromCache(const ZSTDUncompressCachedData& o, int64_t idx) {

    zstd_ctx_ = o.zstd_ctx_;

    cache_idx_ = idx;

  }

  ~ZSTDUncompressCachedData() {

#if defined(ZSTD)

    if (zstd_ctx_ != nullptr && cache_idx_ == -1) {

      ZSTD_freeDCtx(zstd_ctx_);

    }

#endif  // ZSTD

  }

 private:

  ZSTDNativeContext zstd_ctx_ = nullptr;

  int64_t cache_idx_ = -1;  // -1 means this instance owns the context

};

}  // namespace ROCKSDB_NAMESPACE

#if defined(XPRESS)

#include "port/xpress.h"

#endif

namespace ROCKSDB_NAMESPACE {

class FailureDecompressor : public Decompressor {

 public:

  explicit FailureDecompressor(Status&& status) : status_(std::move(status)) {

    assert(!status_.ok());

  }

  ~FailureDecompressor() override { status_.PermitUncheckedError(); }

  const char* Name() const override { return "FailureDecompressor"; }

  Status ExtractUncompressedSize(Args& /*args*/) override { return status_; }

  Status DecompressBlock(const Args& /*args*/,

                         char* /*uncompressed_output*/) override {

    return status_;

  }

 protected:

  Status status_;

};

// Owns a decompression dictionary, and associated Decompressor, for storing

// in the block cache.

//

// Justification: for a "processed" dictionary to be saved in block cache, we

// also need a reference to the decompressor that processed it, to ensure it

// is recognized properly. At that point, we might as well have the dictionary

// part of the decompressor identity and track an associated decompressor along

// with a decompression dictionary in the block cache, and the decompressor

// hides potential details of processing the dictionary.

struct DecompressorDict {

  // Block containing the data for the compression dictionary in case the

  // constructor that takes a string parameter is used.

  std::string dict_str_;

  // Block containing the data for the compression dictionary in case the

  // constructor that takes a Slice parameter is used and the passed in

  // CacheAllocationPtr is not nullptr.

  CacheAllocationPtr dict_allocation_;

  // A Decompressor referencing and using the dictionary owned by this.

  std::unique_ptr<Decompressor> decompressor_;

  // Approximate owned memory usage

  size_t memory_usage_;

  DecompressorDict(std::string&& dict, Decompressor& from_decompressor)

      : dict_str_(std::move(dict)) {

    Populate(from_decompressor, dict_str_);

  }

  DecompressorDict(Slice slice, CacheAllocationPtr&& allocation,

                   Decompressor& from_decompressor)

      : dict_allocation_(std::move(allocation)) {

    Populate(from_decompressor, slice);

  }

  DecompressorDict(DecompressorDict&& rhs) noexcept

      : dict_str_(std::move(rhs.dict_str_)),

        dict_allocation_(std::move(rhs.dict_allocation_)),

        decompressor_(std::move(rhs.decompressor_)),

        memory_usage_(std::move(rhs.memory_usage_)) {}

  DecompressorDict& operator=(DecompressorDict&& rhs) noexcept {

    if (this == &rhs) {

      return *this;

    }

    dict_str_ = std::move(rhs.dict_str_);

    dict_allocation_ = std::move(rhs.dict_allocation_);

    decompressor_ = std::move(rhs.decompressor_);

    return *this;

  }

  // Disable copy

  DecompressorDict(const DecompressorDict&) = delete;

  DecompressorDict& operator=(const DecompressorDict&) = delete;

  // The object is self-contained if the string constructor is used, or the

  // Slice constructor is invoked with a non-null allocation. Otherwise, it

  // is the caller's responsibility to ensure that the underlying storage

  // outlives this object.

  bool own_bytes() const { return !dict_str_.empty() || dict_allocation_; }

  const Slice& GetRawDict() const { return decompressor_->GetSerializedDict(); }

  // For TypedCacheInterface

  const Slice& ContentSlice() const { return GetRawDict(); }

  static constexpr CacheEntryRole kCacheEntryRole = CacheEntryRole::kOtherBlock;

  static constexpr BlockType kBlockType = BlockType::kCompressionDictionary;

  size_t ApproximateMemoryUsage() const { return memory_usage_; }

 private:

  void Populate(Decompressor& from_decompressor, Slice dict);

};

// Holds dictionary and related data, like ZSTD's digested compression

// dictionary.

struct CompressionDict {

#ifdef ZSTD

  ZSTD_CDict* zstd_cdict_ = nullptr;

#endif  // ZSTD

  std::string dict_;

 public:

  CompressionDict() = default;

  CompressionDict(std::string&& dict, CompressionType type, int level) {

    dict_ = std::move(dict);

#ifdef ZSTD

    zstd_cdict_ = nullptr;

    if (!dict_.empty() && type == kZSTD) {

      level = SanitizeZSTDCompressionLevel(level);

      // Should be safe (but slower) if below call fails as we'll use the

      // raw dictionary to compress.

      zstd_cdict_ = ZSTD_createCDict(dict_.data(), dict_.size(), level);

      assert(zstd_cdict_ != nullptr);

    }

#else

    (void)type;

    (void)level;

#endif  // ZSTD

  }

  CompressionDict(CompressionDict&& other) {

#ifdef ZSTD

    zstd_cdict_ = other.zstd_cdict_;

    other.zstd_cdict_ = nullptr;

#endif  // ZSTD

    dict_ = std::move(other.dict_);

  }

  CompressionDict& operator=(CompressionDict&& other) {

    if (this == &other) {

      return *this;

    }

#ifdef ZSTD

    zstd_cdict_ = other.zstd_cdict_;

    other.zstd_cdict_ = nullptr;

#endif  // ZSTD

    dict_ = std::move(other.dict_);

    return *this;

  }

  ~CompressionDict() {

#ifdef ZSTD

    size_t res = 0;

    if (zstd_cdict_ != nullptr) {

      res = ZSTD_freeCDict(zstd_cdict_);

    }

    assert(res == 0);  // Last I checked they can't fail

    (void)res;         // prevent unused var warning

#endif                 // ZSTD

  }

#ifdef ZSTD

  const ZSTD_CDict* GetDigestedZstdCDict() const { return zstd_cdict_; }

#endif  // ZSTD

  Slice GetRawDict() const { return dict_; }

  bool empty() const { return dict_.empty(); }

  static const CompressionDict& GetEmptyDict() {

    static CompressionDict empty_dict{};

    return empty_dict;

  }

  // Disable copy

  CompressionDict(const CompressionDict&) = delete;

  CompressionDict& operator=(const CompressionDict&) = delete;

};

class CompressionContext : public Compressor::WorkingArea {

 private:

#ifdef ZSTD

  ZSTD_CCtx* zstd_ctx_ = nullptr;

  ZSTD_CCtx* CreateZSTDContext() {

#ifdef ROCKSDB_ZSTD_CUSTOM_MEM

    return ZSTD_createCCtx_advanced(port::GetJeZstdAllocationOverrides());

#else   // ROCKSDB_ZSTD_CUSTOM_MEM

    return ZSTD_createCCtx();

#endif  // ROCKSDB_ZSTD_CUSTOM_MEM

  }

 public:

  // callable inside ZSTD_Compress

  ZSTD_CCtx* ZSTDPreallocCtx() const {

    assert(zstd_ctx_ != nullptr);

    return zstd_ctx_;

  }

 private:

#endif  // ZSTD

  void CreateNativeContext(CompressionType type, int level, bool checksum) {

#ifdef ZSTD

    if (type == kZSTD) {

      zstd_ctx_ = CreateZSTDContext();

      level = SanitizeZSTDCompressionLevel(level);

      size_t err =

          ZSTD_CCtx_setParameter(zstd_ctx_, ZSTD_c_compressionLevel, level);

      if (ZSTD_isError(err)) {

        assert(false);

        ZSTD_freeCCtx(zstd_ctx_);

        zstd_ctx_ = CreateZSTDContext();

      }

      if (checksum) {

        err = ZSTD_CCtx_setParameter(zstd_ctx_, ZSTD_c_checksumFlag, 1);

        if (ZSTD_isError(err)) {

          assert(false);

          ZSTD_freeCCtx(zstd_ctx_);

          zstd_ctx_ = CreateZSTDContext();

        }

      }

    }

#else

    (void)type;

    (void)level;

    (void)checksum;

#endif  // ZSTD

  }

  void DestroyNativeContext() {

#ifdef ZSTD

    if (zstd_ctx_ != nullptr) {

      ZSTD_freeCCtx(zstd_ctx_);

    }

#endif  // ZSTD

  }

 public:

  explicit CompressionContext(CompressionType type,

                              const CompressionOptions& options) {

    CreateNativeContext(type, options.level, options.checksum);

  }

  ~CompressionContext() { DestroyNativeContext(); }

  CompressionContext(const CompressionContext&) = delete;

  CompressionContext& operator=(const CompressionContext&) = delete;

};

// This is like a working area, reusable for different dicts, etc.

// TODO: refactor / consolidate

class UncompressionContext : public Decompressor::WorkingArea {

 private:

  CompressionContextCache* ctx_cache_ = nullptr;

  ZSTDUncompressCachedData uncomp_cached_data_;

 public:

  explicit UncompressionContext(CompressionType type) {

    if (type == kZSTD) {

      ctx_cache_ = CompressionContextCache::Instance();

      uncomp_cached_data_ = ctx_cache_->GetCachedZSTDUncompressData();

    }

  }

  ~UncompressionContext() {

    if (uncomp_cached_data_.GetCacheIndex() != -1) {

      assert(ctx_cache_ != nullptr);

      ctx_cache_->ReturnCachedZSTDUncompressData(

          uncomp_cached_data_.GetCacheIndex());

    }

  }

  UncompressionContext(const UncompressionContext&) = delete;

  UncompressionContext& operator=(const UncompressionContext&) = delete;

  ZSTDUncompressCachedData::ZSTDNativeContext GetZSTDContext() const {

    return uncomp_cached_data_.Get();

  }

};

inline bool Snappy_Supported() {

#ifdef SNAPPY

  return true;

#else

  return false;

#endif

}

inline bool Zlib_Supported() {

#ifdef ZLIB

  return true;

#else

  return false;

#endif

}

inline bool BZip2_Supported() {

#ifdef BZIP2

  return true;

#else

  return false;

#endif

}

inline bool LZ4_Supported() {

#ifdef LZ4

  return true;

#else

  return false;

#endif

}

inline CompressionType GetDefaultCompressionType() {

  return LZ4_Supported()

             ? kLZ4Compression

             : (Snappy_Supported() ? kSnappyCompression : kNoCompression);

}

inline bool XPRESS_Supported() {

#ifdef XPRESS

  return true;

#else

  return false;

#endif

}

inline bool ZSTD_Supported() {

#ifdef ZSTD

  // NB: ZSTD format is finalized since version 0.8.0. See ZSTD_VERSION_NUMBER

  // check above.

  return true;

#else

  return false;

#endif

}

inline bool ZSTD_Streaming_Supported() {

#if defined(ZSTD)

  return true;

#else

  return false;

#endif

}

inline bool StreamingCompressionTypeSupported(

    CompressionType compression_type) {

  switch (compression_type) {

    case kNoCompression:

      return true;

    case kZSTD:

      return ZSTD_Streaming_Supported();

    default:

      return false;

  }

}

inline bool CompressionTypeSupported(CompressionType compression_type) {

  switch (compression_type) {

    case kNoCompression:

      return true;

    case kSnappyCompression:

      return Snappy_Supported();

    case kZlibCompression:

      return Zlib_Supported();

    case kBZip2Compression:

      return BZip2_Supported();

    case kLZ4Compression:

      return LZ4_Supported();

    case kLZ4HCCompression:

      return LZ4_Supported();

    case kXpressCompression:

      return XPRESS_Supported();

    case kZSTD:

      return ZSTD_Supported();

    default:  // Including custom compression types

      return false;

  }

}

inline bool DictCompressionTypeSupported(CompressionType compression_type) {

  switch (compression_type) {

    case kNoCompression:

      return false;

    case kSnappyCompression:

      return false;

    case kZlibCompression:

      return Zlib_Supported();

    case kBZip2Compression:

      return false;

    case kLZ4Compression:

    case kLZ4HCCompression:

#if LZ4_VERSION_NUMBER >= 10400  // r124+

      return LZ4_Supported();

#else

      return false;

#endif

    case kXpressCompression:

      return false;

    case kZSTD:

      // NB: dictionary supported since 0.5.0. See ZSTD_VERSION_NUMBER check

      // above.

      return ZSTD_Supported();

    default:  // Including custom compression types

      return false;

  }

}

// WART: does not match OptionsHelper::compression_type_string_map

std::string CompressionTypeToString(CompressionType compression_type);

// WART: does not match OptionsHelper::compression_type_string_map

CompressionType CompressionTypeFromString(std::string compression_type_str);

std::string CompressionOptionsToString(

    const CompressionOptions& compression_options);

inline bool ZSTD_TrainDictionarySupported() {

#ifdef ZSTD

  // NB: Dictionary trainer is available since v0.6.1 for static linking, but

  // not available for dynamic linking until v1.1.3. See ZSTD_VERSION_NUMBER

  // check above.

  return true;

#else

  return false;

#endif

}

inline bool ZSTD_FinalizeDictionarySupported() {

#ifdef ROCKSDB_ZDICT_FINALIZE

  return true;

#else

  return false;

#endif

}

// Use to check whether compression types are related or unrelated

inline CompressionType CanonicalCompressionType(CompressionType type) {

  switch (type) {

    // Configuring LZ4 or LZ4HC can result in using the other, depending on

    // compression level.

    case kLZ4HCCompression:

      return kLZ4Compression;

    default:

      return type;

  }

}

// The new compression APIs intentionally make it difficult to generate

// compressed data larger than the original. (It is better to store the

// uncompressed version in that case.) For legacy cases that must store

// compressed data even when larger than the uncompressed, this is a convenient

// wrapper to support that, with a compressor from BuiltinCompressionManager and

// a GrowableBuffer.

Status LegacyForceBuiltinCompression(

    Compressor& builtin_compressor,

    Compressor::ManagedWorkingArea* working_area, Slice from,

    GrowableBuffer* to);

// Records the compression type for subsequent WAL records.

class CompressionTypeRecord {

 public:

  explicit CompressionTypeRecord(CompressionType compression_type)

      : compression_type_(compression_type) {}

  CompressionType GetCompressionType() const { return compression_type_; }

  inline void EncodeTo(std::string* dst) const {

    assert(dst != nullptr);

    PutFixed32(dst, compression_type_);

  }

  inline Status DecodeFrom(Slice* src) {

    constexpr char class_name[] = "CompressionTypeRecord";

    uint32_t val;

    if (!GetFixed32(src, &val)) {

      return Status::Corruption(class_name,

                                "Error decoding WAL compression type");

    }

    CompressionType compression_type = static_cast<CompressionType>(val);

    if (!StreamingCompressionTypeSupported(compression_type)) {

      return Status::Corruption(class_name,

                                "WAL compression type not supported");

    }

    compression_type_ = compression_type;

    return Status::OK();

  }

  inline std::string DebugString() const {

    return "compression_type: " + CompressionTypeToString(compression_type_);

  }

 private:

  CompressionType compression_type_;

};

// Base class to implement compression for a stream of buffers.

// Instantiate an implementation of the class using Create() with the

// compression type and use Compress() repeatedly.

// The output buffer needs to be at least max_output_len.

// Call Reset() in between frame boundaries or in case of an error.

// NOTE: This class is not thread safe.

class StreamingCompress {

 public:

  StreamingCompress(CompressionType compression_type,

                    const CompressionOptions& opts,

                    uint32_t compress_format_version, size_t max_output_len)

      : compression_type_(compression_type),

        opts_(opts),

        compress_format_version_(compress_format_version),

        max_output_len_(max_output_len) {}

  virtual ~StreamingCompress() = default;

  // compress should be called repeatedly with the same input till the method

  // returns 0

  // Parameters:

  // input - buffer to compress

  // input_size - size of input buffer

  // output - compressed buffer allocated by caller, should be at least

  // max_output_len

  // output_size - size of the output buffer

  // Returns -1 for errors, the remaining size of the input buffer that needs

  // to be compressed

  virtual int Compress(const char* input, size_t input_size, char* output,

                       size_t* output_pos) = 0;

  // static method to create object of a class inherited from

  // StreamingCompress based on the actual compression type.

  static std::unique_ptr<StreamingCompress> Create(

      CompressionType compression_type, const CompressionOptions& opts,

      uint32_t compress_format_version, size_t max_output_len);

  virtual void Reset() = 0;

 protected:

  const CompressionType compression_type_;

  const CompressionOptions opts_;

  const uint32_t compress_format_version_;

  const size_t max_output_len_;

};

// Base class to uncompress a stream of compressed buffers.

// Instantiate an implementation of the class using Create() with the

// compression type and use Uncompress() repeatedly.

// The output buffer needs to be at least max_output_len.

// Call Reset() in between frame boundaries or in case of an error.

// NOTE: This class is not thread safe.

class StreamingUncompress {

 public:

  StreamingUncompress(CompressionType compression_type,

                      uint32_t compress_format_version, size_t max_output_len)

      : compression_type_(compression_type),

        compress_format_version_(compress_format_version),

        max_output_len_(max_output_len) {}

  virtual ~StreamingUncompress() = default;

  // Uncompress can be called repeatedly to progressively process the same

  // input buffer, or can be called with a new input buffer. When the input

  // buffer is not fully consumed, the return value is > 0 or output_size

  // == max_output_len. When calling uncompress to continue processing the

  // same input buffer, the input argument should be nullptr.

  // Parameters:

  // input - buffer to uncompress

  // input_size - size of input buffer

  // output - uncompressed buffer allocated by caller, should be at least

  // max_output_len

  // output_size - size of the output buffer

  // Returns -1 for errors, remaining input to be processed otherwise.

  virtual int Uncompress(const char* input, size_t input_size, char* output,

                         size_t* output_pos) = 0;

  static std::unique_ptr<StreamingUncompress> Create(

      CompressionType compression_type, uint32_t compress_format_version,

      size_t max_output_len);

  virtual void Reset() = 0;

 protected:

  CompressionType compression_type_;

  uint32_t compress_format_version_;

  size_t max_output_len_;

};

class ZSTDStreamingCompress final : public StreamingCompress {

 public:

  explicit ZSTDStreamingCompress(const CompressionOptions& opts,

                                 uint32_t compress_format_version,

                                 size_t max_output_len)

      : StreamingCompress(kZSTD, opts, compress_format_version,

                          max_output_len) {

#ifdef ZSTD

    cctx_ = ZSTD_createCCtx();

    // Each compressed frame will have a checksum

    ZSTD_CCtx_setParameter(cctx_, ZSTD_c_checksumFlag, 1);

    assert(cctx_ != nullptr);

    input_buffer_ = {/*src=*/nullptr, /*size=*/0, /*pos=*/0};

#endif

  }

  ~ZSTDStreamingCompress() override {

#ifdef ZSTD

    ZSTD_freeCCtx(cctx_);

#endif

  }

  int Compress(const char* input, size_t input_size, char* output,

               size_t* output_pos) override;

  void Reset() override;

#ifdef ZSTD

  ZSTD_CCtx* cctx_;

  ZSTD_inBuffer input_buffer_;

#endif

};

class ZSTDStreamingUncompress final : public StreamingUncompress {

 public:

  explicit ZSTDStreamingUncompress(uint32_t compress_format_version,

                                   size_t max_output_len)

      : StreamingUncompress(kZSTD, compress_format_version, max_output_len) {

#ifdef ZSTD

    dctx_ = ZSTD_createDCtx();

    assert(dctx_ != nullptr);

    input_buffer_ = {/*src=*/nullptr, /*size=*/0, /*pos=*/0};

#endif

  }

  ~ZSTDStreamingUncompress() override {

#ifdef ZSTD

    ZSTD_freeDCtx(dctx_);

#endif

  }

  int Uncompress(const char* input, size_t input_size, char* output,

                 size_t* output_size) override;

  void Reset() override;

 private:

#ifdef ZSTD

  ZSTD_DCtx* dctx_;

  ZSTD_inBuffer input_buffer_;

#endif

};

}  // namespace ROCKSDB_NAMESPACE