Stream Filter Support

[tonurics]

Please create a Stream Filter context on zstd.* that can be used with the stream_filter_append and stream_filter_prepend Stream Functions.

This would bring the Zstd extension in parity with the current Zlib extension.

Reference: zlib_filter.c

Related Tickets:

• Support incremental compression and decompression #64
• Is an "ob_zstdhandler" function possible? #71

[tonurics]

Adding additional reference material on Compression Stream Filters: https://www.php.net/manual/en/filters.compression.php

[tonurics]

While we wait for Stream Filter contexts to be natively supported by the extension, here is an implementation for Zstd compression using php_user_filter:

<?php
namespace lib\Type\Filter\Zstd{
	class Compress extends \php_user_filter{
		public \Zstd\Compress\Context|FALSE $handle;
		function filter(
			$in,
			$out,
			&$consumed,
			bool $closing,
		):int{
			if(empty($this->handle)){
				$this->handle=zstd_compress_init(
					level:$this->params[0]??\ZSTD_COMPRESS_LEVEL_DEFAULT,
					dict:$this->params[1]??NULL,
				);
			}
			if($this->handle){
				unset($_);
				while($_=stream_bucket_make_writeable(
					brigade:$in,
				)){
					$_->data=zstd_compress_add(
						context:$this->handle,
						data:$_->data,
					);
					$consumed+=$_->datalen;
					stream_bucket_append(
						brigade:$out,
						bucket:$_,
					);
				}
			}
			return PSFS_PASS_ON;
		}
	}
}

Usage:

stream_filter_register('_zstd.compress','lib\\Type\\Filter\\Zstd\\Compress');
unset($fp);
if($fp=fopen('php://output','wb')){
	stream_filter_append(
		$fp,					//resource	$stream
		'_zstd.compress',		//string	$filtername
		STREAM_FILTER_WRITE,	//int		$read_write
		[
			\ZSTD_COMPRESS_LEVEL_DEFAULT,
		],						//mixed		$params
	);
	fputs($fp,<<<STRING
		Hello world.
		STRING
	);
}