Adapters

Provide your own Brotli implementation when neither the PHP extension nor the brotli executable fits the runtime that writes your fonts: another Brotli binding, a service that compresses remotely, or a test double. Woff2Writer accepts any BrotliCompressorInterface.

Implement a compressor

compress() receives the transformed table data and returns one raw Brotli stream, without a WOFF2 header, length prefix, or padding:

<?php

use Alto\Font\Compression\BrotliCompressorInterface;
use Alto\Font\Writer\Woff2Writer;

final class RemoteBrotliCompressor implements BrotliCompressorInterface
{
    public function compress(string $data): string
    {
        // Send $data to the compression service and return the raw Brotli stream.
    }
}

$writer = new Woff2Writer(new RemoteBrotliCompressor());

Throw CompressionException when the stream cannot be produced, so that callers can catch one exception type for every adapter.

Stream instead of holding bytes

An adapter that also implements BrotliStreamCompressorInterface lets write() stream at the compression boundary. compressStream($input, $output) reads from the current position of $input to its end, writes the raw Brotli stream at the current position of $output, and leaves both resources open without rewinding them. The parsed font and the table transforms still occupy memory; neither method promises constant memory for the whole operation.

BrotliProcessCompressor streams; BrotliExtensionCompressor materializes the compressed data for both write() and dump().

Files or bytes

write() creates a new file and never replaces an existing path. dump() returns the complete WOFF2 as one string, for a storage API that accepts bytes.

Check the runtime

The runtime that writes the fonts is the one to check, not your terminal: a PHP-FPM worker, a queue consumer, or a container can have a different set of extensions and a different PATH.

• Extension adapter: function_exists('brotli_compress') and defined('BROTLI_FONT') must both be true.
• Process adapter: the executable must be found through PATH or the binary argument, proc_open() must not be disabled, and sys_get_temp_dir() must be writable.

Reading WOFF2 detects the extension or the executable on its own; writing needs the explicit adapter even when both are installed.