Merge pull request #36 from joshtrichards/patch-1

fix: generate exception if codec/layer versions or channel headers are unrecognized

Author: wapmorgan

src/Mp3Info.php

@@ -373,7 +373,6 @@ private function readMpegFrame($fp) {
 
         switch ($header_bytes[1] >> 3 & 0b11) {
             case 0b00: $this->codecVersion = self::MPEG_25; break;
-            case 0b01: $this->codecVersion = self::CODEC_UNDEFINED; break;
             case 0b10: $this->codecVersion = self::MPEG_2; break;
             case 0b11: $this->codecVersion = self::MPEG_1; break;
         }
@@ -384,6 +383,9 @@ private function readMpegFrame($fp) {
             case 0b11: $this->layerVersion = self::LAYER_1; break;
         }
 
+        if (!isset($this->codecVersion) || !isset($this->layerVersion) || !isset($header_bytes[2])) {
+            throw new \Exception('Unrecognized codecVersion or layerVersion headers!');
+        }
         $this->bitRate = self::$_bitRateTable[$this->codecVersion][$this->layerVersion][$header_bytes[2] >> 4];
         $this->sampleRate = self::$_sampleRateTable[$this->codecVersion][($header_bytes[2] >> 2) & 0b11];
 
@@ -394,6 +396,9 @@ private function readMpegFrame($fp) {
             case 0b11: $this->channel = self::MONO; break;
         }
 
+        if (!isset($this->channel)) {
+            throw new \Exception('Unrecognized channel header!');
+        }
         $vbr_offset = self::$_vbrOffsets[$this->codecVersion][$this->channel == self::MONO ? 0 : 1];
 
         // check for VBR