Overview

zstd wraps Facebook's Zstandard library — the modern compression algorithm that achieves bzip2-level ratios at near-LZ4 speeds. It is the compression standard for Linux kernels, databases (RocksDB, MySQL), and container formats. Levels range from 1 (ultra-fast) to 22 (maximum ratio), plus a unique dictionary mode for compressing many small similar buffers.

Quick Start

uses zstd;

var data := ReadFile('/data/events.json');
var compressed := Compress(data);          // default level 3
var restored   := Decompress(compressed);

WriteLn('Original:   ', Length(data));
WriteLn('Compressed: ', Length(compressed));
WriteLn('Version:    ', ZSTDVersion);

Compression Levels

var fastest := CompressLevel(data, ZSTD_LEVEL_FAST);    // 1
var balanced := CompressLevel(data, ZSTD_LEVEL_DEFAULT); // 3
var good     := CompressLevel(data, ZSTD_LEVEL_GOOD);    // 9
var best     := CompressLevel(data, ZSTD_LEVEL_BEST);    // 19
var ultra    := CompressLevel(data, ZSTD_LEVEL_ULTRA);   // 22

Reusable Contexts (high throughput)

// Create once, reuse for many compressions — avoids per-call allocation
var cctx := NewCompressor(ZSTD_LEVEL_DEFAULT);
var dctx := NewDecompressor;

for I := 0 to Length(records) - 1 do begin
  var packed := CompressCtx(cctx, records[I]);
  // store packed...
end;

FreeCompressor(cctx);
FreeDecompressor(dctx);

Dictionary Mode

When compressing many small, similar buffers (e.g. JSON records, log lines), train a dictionary from samples to dramatically improve ratio:

// Train once
var dict := TrainDictionary(samples, 112 * 1024);  // 112 KB dict
var dictBytes := DictToBytes(dict);
SaveFile('/data/zstd.dict', dictBytes);

// Compress with dictionary
var cctx := NewCompressor(3);
var packed := CompressWithDict(cctx, record, dict);

// Decompress with same dictionary
var dctx := NewDecompressor;
var back := DecompressWithDict(dctx, packed, dict);

FreeDict(dict);

File Compression

CompressFile('/data/dump.sql', '/data/dump.sql.zst');
CompressFileLevel('/data/large.bin', '/data/large.bin.zst', 9);
DecompressFile('/data/dump.sql.zst', '/data/dump.sql');