Range requests: Extracted stream output handling to new class

app/Http/RangeSupportedStream.php

@@ -0,0 +1,57 @@
+<?php
+
+namespace BookStack\Http;
+
+use BookStack\Util\WebSafeMimeSniffer;
+use Symfony\Component\HttpFoundation\HeaderBag;
+
+class RangeSupportedStream
+{
+    protected string $sniffContent;
+
+    public function __construct(
+        protected $stream,
+        protected int $fileSize,
+        protected HeaderBag $requestHeaders,
+    ) {
+    }
+
+    /**
+     * Sniff a mime type from the stream.
+     */
+    public function sniffMime(): string
+    {
+        $offset = min(2000, $this->fileSize);
+        $this->sniffContent = fread($this->stream, $offset);
+
+        return (new WebSafeMimeSniffer())->sniff($this->sniffContent);
+    }
+
+    /**
+     * Output the current stream to stdout before closing out the stream.
+     */
+    public function outputAndClose(): void
+    {
+        // End & flush the output buffer, if we're in one, otherwise we still use memory.
+        // Output buffer may or may not exist depending on PHP `output_buffering` setting.
+        // Ignore in testing since output buffers are used to gather a response.
+        if (!empty(ob_get_status()) && !app()->runningUnitTests()) {
+            ob_end_clean();
+        }
+
+        $outStream = fopen('php://output', 'w');
+        $offset = 0;
+
+        if (!empty($this->sniffContent)) {
+            fwrite($outStream, $this->sniffContent);
+            $offset = strlen($this->sniffContent);
+        }
+
+        $toWrite = $this->fileSize - $offset;
+        stream_copy_to_stream($this->stream, $outStream, $toWrite);
+        fpassthru($this->stream);
+
+        fclose($this->stream);
+        fclose($outStream);
+    }
+}