uses
  zstd;

procedure SimpleCompressDecompress;
var
  Src, Compressed, Decompressed: TBytes;
  CompressedSize, DecompressedSize: TZSTDSize;
begin
  Src := TEncoding.UTF8.GetBytes('Hello world! This is a test of Zstandard compression.');

  // Compress
  SetLength(Compressed, ZSTD_compressBound(Length(Src)));
  CompressedSize := ZSTD_compress(@Compressed[0], Length(Compressed),
                                @Src[0], Length(Src), 3);
  if ZSTD_isError(CompressedSize) <> 0 then
    raise Exception.Create('Compression failed: ' + ZSTD_getErrorName(CompressedSize));
  SetLength(Compressed, CompressedSize);

  // Decompress
  SetLength(Decompressed, Length(Src)); // known original size
  DecompressedSize := ZSTD_decompress(@Decompressed[0], Length(Decompressed),
                                      @Compressed[0], Length(Compressed));
  if ZSTD_isError(DecompressedSize) <> 0 then
    raise Exception.Create('Decompression failed: ' + ZSTD_getErrorName(DecompressedSize));

  Writeln('Original size: ', Length(Src));
  Writeln('Compressed size: ', Length(Compressed));
  Writeln('Decompressed matches: ', CompareMem(@Src[0], @Decompressed[0], Length(Src)));
end;

uses
  Classes, zstdstreams;

procedure CompressFile(const InFile, OutFile: string);
var
  InStream, OutStream: TFileStream;
  ZStream: TZCompressionStream;
begin
  InStream := TFileStream.Create(InFile, fmOpenRead);
  try
    OutStream := TFileStream.Create(OutFile, fmCreate);
    try
      // Level 3, write content size, no checksum, owns OutStream
      ZStream := TZCompressionStream.Create(OutStream, 3, True, True, False);
      try
        ZStream.CopyFrom(InStream, 0); // copies everything
        // Destructor automatically calls Finish and flushes
      finally
        ZStream.Free;
      end;
    finally
      OutStream.Free;
    end;
  finally
    InStream.Free;
  end;
end;

uses
  Classes, zstdstreams;

procedure DecompressFile(const InFile, OutFile: string);
var
  InStream, OutStream: TFileStream;
  ZStream: TZDecompressionStream;
  Buffer: TBytes;
begin
  InStream := TFileStream.Create(InFile, fmOpenRead);
  try
    OutStream := TFileStream.Create(OutFile, fmCreate);
    try
      ZStream := TZDecompressionStream.Create(InStream); // does not own InStream
      try
        SetLength(Buffer, 64 * 1024);
        repeat
          Count := ZStream.Read(Buffer[0], Length(Buffer));
          if Count > 0 then
            OutStream.WriteBuffer(Buffer[0], Count);
        until Count = 0;
      finally
        ZStream.Free;
      end;
    finally
      OutStream.Free;
    end;
  finally
    InStream.Free;
  end;
end;

var
  CDict: PZSTD_CDict;
  DDict: PZSTD_DDict;
begin
  CDict := ZSTD_createCDict(DictBuffer, DictSize, CompressionLevel);
  try
    // Use with ZSTD_compress_usingCDict(...)
  finally
    ZSTD_freeCDict(CDict);
  end;

  DDict := ZSTD_createDDict(DictBuffer, DictSize);
  try
    // Use with ZSTD_decompress_usingDDict(...)
  finally
    ZSTD_freeDDict(DDict);
  end;
end;

MIT License

Copyright (c) 2026 Aleksandr Vorobev aka CynicRus, CynicRus@gmail.com

  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:

  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.