Remove non-obvious BaseReader's dependency

BaseReader called `isValidFormat` despite it doesn't require it to be
implemented. Instead we replaced `isValidFormat` by a proper implementation
of `canRead` in each classes. This also remove the semantic amibguity between
those two methods.

FIX #32

src/PhpSpreadsheet/Reader/BaseReader.php

@@ -244,28 +244,6 @@ abstract class BaseReader implements IReader
         }
     }
 
-    /**
-     * Can the current IReader read the file?
-     *
-     * @param     string         $pFilename
-     * @throws Exception
-     * @return bool
-     */
-    public function canRead($pFilename)
-    {
-        // Check if file exists
-        try {
-            $this->openFile($pFilename);
-        } catch (Exception $e) {
-            return false;
-        }
-
-        $readable = $this->isValidFormat();
-        fclose($this->fileHandle);
-
-        return $readable;
-    }
-
     /**
      * Scan theXML for use of <!ENTITY to prevent XXE/XEE attacks
      *

src/PhpSpreadsheet/Reader/CSV.php

@@ -78,16 +78,6 @@ class CSV extends BaseReader implements IReader
         $this->readFilter = new DefaultReadFilter();
     }
 
-    /**
-     * Validate that the current file is a CSV file
-     *
-     * @return bool
-     */
-    protected function isValidFormat()
-    {
-        return true;
-    }
-
     /**
      * Set input encoding
      *
@@ -171,11 +161,10 @@ class CSV extends BaseReader implements IReader
     public function listWorksheetInfo($pFilename)
     {
         // Open file
-        $this->openFile($pFilename);
+        if (!$this->canRead($pFilename)) {
-        if (!$this->isValidFormat()) {
-            fclose($this->fileHandle);
             throw new Exception($pFilename . ' is an Invalid Spreadsheet file.');
         }
+        $this->openFile($pFilename);
         $fileHandle = $this->fileHandle;
 
         // Skip BOM, if any
@@ -236,11 +225,10 @@ class CSV extends BaseReader implements IReader
         ini_set('auto_detect_line_endings', true);
 
         // Open file
-        $this->openFile($pFilename);
+        if (!$this->canRead($pFilename)) {
-        if (!$this->isValidFormat()) {
-            fclose($this->fileHandle);
             throw new Exception($pFilename . ' is an Invalid Spreadsheet file.');
         }
+        $this->openFile($pFilename);
         $fileHandle = $this->fileHandle;
 
         // Skip BOM, if any
@@ -394,4 +382,25 @@ class CSV extends BaseReader implements IReader
     {
         return $this->contiguous;
     }
+
+    /**
+     * Can the current IReader read the file?
+     *
+     * @param     string         $pFilename
+     * @throws Exception
+     * @return bool
+     */
+    public function canRead($pFilename)
+    {
+        // Check if file exists
+        try {
+            $this->openFile($pFilename);
+        } catch (Exception $e) {
+            return false;
+        }
+
+        fclose($this->fileHandle);
+
+        return true;
+    }
 }

src/PhpSpreadsheet/Reader/HTML.php

@@ -127,25 +127,27 @@ class HTML extends BaseReader implements IReader
     /**
      * Validate that the current file is an HTML file
      *
+     * @param     string         $pFilename
+     * @throws Exception
      * @return bool
      */
-    protected function isValidFormat()
+    public function canRead($pFilename)
     {
+        // Check if file exists
+        try {
+            $this->openFile($pFilename);
+        } catch (Exception $e) {
+            return false;
+        }
+
         $beginning = $this->readBeginning();
+        $startWithTag = self::startsWithTag($beginning);
+        $containsTags = self::containsTags($beginning);
+        $endsWithTag = self::endsWithTag($this->readEnding());
 
-        if (!self::startsWithTag($beginning)) {
+        fclose($this->fileHandle);
-            return false;
-        }
 
-        if (!self::containsTags($beginning)) {
+        return $startWithTag && $containsTags && $endsWithTag;
-            return false;
-        }
-
-        if (!self::endsWithTag($this->readEnding())) {
-            return false;
-        }
-
-        return true;
     }
 
     private function readBeginning()
@@ -492,14 +494,10 @@ class HTML extends BaseReader implements IReader
      */
     public function loadIntoExisting($pFilename, Spreadsheet $spreadsheet)
     {
-        // Open file to validate
+        // Validate
-        $this->openFile($pFilename);
+        if (!$this->canRead($pFilename)) {
-        if (!$this->isValidFormat()) {
-            fclose($this->fileHandle);
             throw new Exception($pFilename . ' is an Invalid HTML file.');
         }
-        //    Close after validating
-        fclose($this->fileHandle);
 
         // Create new sheet
         while ($spreadsheet->getSheetCount() <= $this->sheetIndex) {

src/PhpSpreadsheet/Reader/SYLK.php

@@ -65,26 +65,33 @@ class SYLK extends BaseReader implements IReader
     /**
      * Validate that the current file is a SYLK file
      *
+     * @param     string         $pFilename
+     * @throws Exception
      * @return bool
      */
-    protected function isValidFormat()
+    public function canRead($pFilename)
     {
+        // Check if file exists
+        try {
+            $this->openFile($pFilename);
+        } catch (Exception $e) {
+            return false;
+        }
+
         // Read sample data (first 2 KB will do)
         $data = fread($this->fileHandle, 2048);
 
         // Count delimiters in file
         $delimiterCount = substr_count($data, ';');
-        if ($delimiterCount < 1) {
+        $hasDelimiter = $delimiterCount > 0;
-            return false;
-        }
 
         // Analyze first line looking for ID; signature
         $lines = explode("\n", $data);
-        if (substr($lines[0], 0, 4) != 'ID;P') {
+        $hasId = substr($lines[0], 0, 4) === 'ID;P';
-            return false;
-        }
 
-        return true;
+        fclose($this->fileHandle);
+
+        return $hasDelimiter && $hasId;
     }
 
     /**
@@ -118,11 +125,10 @@ class SYLK extends BaseReader implements IReader
     public function listWorksheetInfo($pFilename)
     {
         // Open file
-        $this->openFile($pFilename);
+        if (!$this->canRead($pFilename)) {
-        if (!$this->isValidFormat()) {
-            fclose($this->fileHandle);
             throw new Exception($pFilename . ' is an Invalid Spreadsheet file.');
         }
+        $this->openFile($pFilename);
         $fileHandle = $this->fileHandle;
         rewind($fileHandle);
 
@@ -205,11 +211,10 @@ class SYLK extends BaseReader implements IReader
     public function loadIntoExisting($pFilename, \PhpOffice\PhpSpreadsheet\Spreadsheet $spreadsheet)
     {
         // Open file
-        $this->openFile($pFilename);
+        if (!$this->canRead($pFilename)) {
-        if (!$this->isValidFormat()) {
-            fclose($this->fileHandle);
             throw new Exception($pFilename . ' is an Invalid Spreadsheet file.');
         }
+        $this->openFile($pFilename);
         $fileHandle = $this->fileHandle;
         rewind($fileHandle);