Implement compression

[thekid]

Implements feature suggested in #61

Supported compressors

• snappy (1)
• zlib (2) - via https://www.php.net/zlib
• zstd (3) - via https://github.com/kjdev/php-ext-zstd

Negotiation

To enable compression, add the preferred compressors to the connection URI as follows

mongodb://username:password@host/test?compressors=zstd,zlib[&zlibCompressionLevel=6][&zstdCompressionLevel=3]

The server will answer with the compressors it supports, which in turn will be matched against the list of PHP extensions loaded. The client will align its preference with the order in which the server returns the compressors.

The compression levels, if not specified, default to -1, which will in turn use the defaults for the given compressor.

Debugging

use com\mongodb\MongoConnection;
use util\cmd\Console;

$c= new MongoConnection($dsn);
$c->connect();

// Compression: com.mongodb.io.Compression@[
//   com.mongodb.io.Zlib(id: 2, level: -1)
//   com.mongodb.io.Zstd(id: 3, level: -1)
// ]
Console::writeLine('Compression: ', current($c->protocol()->connections())->compression);

[thekid]

Snappy might be doable by porting https://github.com/zhipeng-jia/snappyjs

[thekid]

Released in https://github.com/xp-forge/mongodb/releases/tag/v3.4.0