Add support for stream resources in FinfoMimeTypeDetector::detectMimeType()

src/FinfoMimeTypeDetector.php

@@ -39,6 +39,11 @@ class FinfoMimeTypeDetector implements MimeTypeDetector, ExtensionLookup
      */
     private $inconclusiveMimetypes;
 
+    /**
+     * Buffer size to read from streams if no other bufferSampleSize is defined.
+     */
+    const STREAM_BUFFER_SAMPLE_SIZE_DEFAULT = 4100;
+
     public function __construct(
         string $magicFile = '',
         ExtensionToMimeTypeMap $extensionMap = null,
@@ -53,9 +58,17 @@ public function __construct(
 
     public function detectMimeType(string $path, $contents): ?string
     {
-        $mimeType = is_string($contents)
-            ? (@$this->finfo->buffer($this->takeSample($contents)) ?: null)
-            : null;
+        $mimeType = null;
+        if (is_string($contents)) {
+            $mimeType = @$this->finfo->buffer($this->takeSample($contents));
+        } elseif (
+            is_resource($contents)
+            && get_resource_type($contents) === 'stream'
+            && ($streamMetaData = stream_get_meta_data($contents))
+            && !empty($streamMetaData['seekable'])
+        ) {
+            $mimeType = @$this->finfo->buffer($this->takeResourceSample($contents));
+        }
 
         if ($mimeType !== null && ! in_array($mimeType, $this->inconclusiveMimetypes)) {
             return $mimeType;
@@ -90,6 +103,37 @@ private function takeSample(string $contents): string
         return (string) substr($contents, 0, $this->bufferSampleSize);
     }
 
+    /**
+     * Fetches a sample of a resource while maintaining its pointer.
+     */
+    private function takeResourceSample($contents): string
+    {
+        if (is_resource($contents) && get_resource_type($contents) === 'stream') {
+            // Memory optimization: given a length stream_get_contents()
+            // immediately allocates an internal buffer.
+            // However, stream_copy_to_stream() reads up to the defined length
+            // without pre-allocating any extra buffer.
+            // Given the relatively large STREAM_BUFFER_SAMPLE_SIZE_DEFAULT this
+            // avoids unnecessary memory hogging.
+            $streamContentBuffer = fopen('php://temp/maxmemory:' . self::STREAM_BUFFER_SAMPLE_SIZE_DEFAULT, 'w+b');
+
+            $streamPosition = ftell($contents);
+            rewind($contents);
+            stream_copy_to_stream(
+                $contents,
+                $streamContentBuffer,
+                $this->bufferSampleSize ?? self::STREAM_BUFFER_SAMPLE_SIZE_DEFAULT,
+                0
+            );
+            rewind($streamContentBuffer);
+            $streamSample = stream_get_contents($streamContentBuffer);
+            fclose($streamContentBuffer);
+            fseek($contents, $streamPosition);
+            return $streamSample;
+        }
+        return '';
+    }
+
     public function lookupExtension(string $mimetype): ?string
     {
         return $this->extensionMap instanceof ExtensionLookup

src/FinfoMimeTypeDetectorTest.php

@@ -101,7 +101,7 @@ public function detecting_from_a_file_location(): void
     /**
      * @test
      */
-    public function detecting_uses_extensions_when_a_resource_is_presented(): void
+    public function detecting_uses_extensions_when_a_invalid_resource_is_presented(): void
     {
         /** @var resource $handle */
         $handle = fopen(__DIR__ . '/../test_files/flysystem.svg', 'r+');
@@ -111,4 +111,45 @@ public function detecting_uses_extensions_when_a_resource_is_presented(): void
 
         $this->assertEquals('image/svg+xml', $mimeType);
     }
+
+    /**
+     * @test
+     */
+    public function detecting_uses_stream_contents_when_a_valid_resource_is_presented(): void
+    {
+        /** @var resource $handle */
+        $handle = fopen(__DIR__ . '/../test_files/flysystem.svg', 'r+');
+
+        $mimeType = $this->detector->detectMimeType('flysystem.unknown', $handle);
+        fclose($handle);
+
+        $this->assertEquals('image/svg+xml', $mimeType);
+    }
+
+    /**
+     * @test
+     */
+    public function detecting_keeps_stream_contents_positions_unchanged(): void
+    {
+        /** @var resource $handle */
+        $handle = fopen(__DIR__ . '/../test_files/flysystem.svg', 'r+');
+        fseek($handle, 10);
+        $mimeType = $this->detector->detectMimeType('flysystem.unknown', $handle);
+        $this->assertEquals('image/svg+xml', $mimeType);
+        $this->assertEquals(10, ftell($handle));
+        fclose($handle);
+    }
+
+    /**
+     * @test
+     */
+    public function detecting_non_seekable_streams_are_not_sampling(): void
+    {
+        /** @var resource $handle */
+        $handle = fopen('https://github.com/thephpleague/mime-type-detection', 'r');
+        $mimeType = $this->detector->detectMimeType('flysystem.unknown', $handle);
+        $this->assertEquals(null, $mimeType);
+        $this->assertEquals(0, ftell($handle));
+        fclose($handle);
+    }
 }