Infer CSV delimiter if it hasn't been set explicitly

Closes #141

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Initial implementation of SUMIFS() function
 - Additional codepages
 - MemoryDrawing not working in HTML writer [#808](https://github.com/PHPOffice/PHPExcel/issues/808)
+- CSV Reader can auto-detect the separator used in file [#141](https://github.com/PHPOffice/PhpSpreadsheet/pull/141)
 
 ### Changed
 

docs/topics/reading-and-writing-to-file.md

@@ -435,11 +435,15 @@ $spreadsheet = $reader->load("sample.csv");
 
 #### Setting CSV options
 
-Often, CSV files are not really "comma separated", or use semicolon (;)
+Often, CSV files are not really "comma separated", or use semicolon (`;`)
 as a separator. You can instruct
 \PhpOffice\PhpSpreadsheet\Reader\Csv some options before reading a CSV
 file.
 
+The separator will be auto-detected, so in most cases it should not be necessary
+to specify it. But in cases where auto-detection does not fit the use-case, then
+it can be set manually.
+
 Note that \PhpOffice\PhpSpreadsheet\Reader\Csv by default assumes that
 the loaded CSV file is UTF-8 encoded. If you are reading CSV files that
 were created in Microsoft Office Excel the correct input encoding may

docs/topics/reading-files.md

@@ -523,15 +523,17 @@ CSV       | YES | HTML   | NO
 
 ### Pipe or Tab Separated Value Files
 
-The CSV loader defaults to loading a file where comma is used as the
-separator, but you can modify this to load tab- or pipe-separated value
-files using the `setDelimiter()` method.
+The CSV loader will attempt to auto-detect the separator used in the file. If it
+cannot auto-detect, it will default to the comma. If this does not fit your
+use-case, you can manually specify a separator by using the `setDelimiter()`
+method.
 
 ``` php
 $inputFileType = 'Csv';
 $inputFileName = './sampleData/example1.tsv';
 
-/**  Create a new Reader of the type defined in $inputFileType  **/ $reader = \PhpOffice\PhpSpreadsheet\IOFactory::createReader($inputFileType);
+/**  Create a new Reader of the type defined in $inputFileType  **/
+$reader = \PhpOffice\PhpSpreadsheet\IOFactory::createReader($inputFileType);
 /**  Set the delimiter to a TAB character  **/
 $reader->setDelimiter("\t");
 //    $reader->setDelimiter('|');

src/PhpSpreadsheet/Reader/Csv.php

@@ -40,7 +40,7 @@ class Csv extends BaseReader implements IReader
      *
      * @var string
      */
-    private $delimiter = ',';
+    private $delimiter = null;
 
     /**
      * Enclosure.
@@ -152,6 +152,86 @@ protected function checkSeparator()
         return $this->skipBOM();
     }
 
+    /**
+     * Infer the separator if it isn't explicitly set in the file or specified by the user.
+     */
+    protected function inferSeparator()
+    {
+        if ($this->delimiter !== null) {
+            return;
+        }
+
+        $potentialDelimiters = [',', ';', "\t", '|', ':', ' '];
+        $counts = [];
+        foreach ($potentialDelimiters as $delimiter) {
+            $counts[$delimiter] = [];
+        }
+
+        // Count how many times each of the potential delimiters appears in each line
+        $numberLines = 0;
+        while (($line = fgets($this->fileHandle)) !== false && (++$numberLines < 1000)) {
+            $countLine = [];
+            for ($i = strlen($line) - 1; $i >= 0; --$i) {
+                $char = $line[$i];
+                if (isset($counts[$char])) {
+                    if (!isset($countLine[$char])) {
+                        $countLine[$char] = 0;
+                    }
+                    ++$countLine[$char];
+                }
+            }
+            foreach ($potentialDelimiters as $delimiter) {
+                $counts[$delimiter][] = isset($countLine[$delimiter])
+                    ? $countLine[$delimiter]
+                    : 0;
+            }
+        }
+
+        // Calculate the mean square deviations for each delimiter (ignoring delimiters that haven't been found consistently)
+        $meanSquareDeviations = [];
+        $middleIdx = floor(($numberLines - 1) / 2);
+
+        foreach ($potentialDelimiters as $delimiter) {
+            $series = $counts[$delimiter];
+            sort($series);
+
+            $median = ($numberLines % 2)
+                ? $series[$middleIdx]
+                : ($series[$middleIdx] + $series[$middleIdx + 1]) / 2;
+
+            if ($median === 0) {
+                continue;
+            }
+
+            $meanSquareDeviations[$delimiter] = array_reduce(
+                $series,
+                function ($sum, $value) use ($median) {
+                    return $sum + pow($value - $median, 2);
+                }
+            ) / count($series);
+        }
+
+        // ... and pick the delimiter with the smallest mean square deviation (in case of ties, the order in potentialDelimiters is respected)
+        $min = INF;
+        foreach ($potentialDelimiters as $delimiter) {
+            if (!isset($meanSquareDeviations[$delimiter])) {
+                continue;
+            }
+
+            if ($meanSquareDeviations[$delimiter] < $min) {
+                $min = $meanSquareDeviations[$delimiter];
+                $this->delimiter = $delimiter;
+            }
+        }
+
+        // If no delimiter could be detected, fall back to the default
+        if ($this->delimiter === null) {
+            $this->delimiter = reset($potentialDelimiters);
+        }
+
+        return $this->skipBOM();
+    }
+
     /**
      * Return worksheet info (Name, Last Column Letter, Last Column Index, Total Rows, Total Columns).
      *
@@ -171,6 +251,7 @@ public function listWorksheetInfo($pFilename)
         // Skip BOM, if any
         $this->skipBOM();
         $this->checkSeparator();
+        $this->inferSeparator();
 
         $worksheetInfo = [];
         $worksheetInfo[0]['worksheetName'] = 'Worksheet';
@@ -237,6 +318,7 @@ public function loadIntoExisting($pFilename, Spreadsheet $spreadsheet)
         // Skip BOM, if any
         $this->skipBOM();
         $this->checkSeparator();
+        $this->inferSeparator();
 
         // Create new PhpSpreadsheet object
         while ($spreadsheet->getSheetCount() <= $this->sheetIndex) {

tests/PhpSpreadsheetTests/Reader/CsvTest.php

@@ -24,4 +24,18 @@ public function testEnclosure()
         $actual = $reloadedSpreadsheet->getActiveSheet()->getCell('A1')->getCalculatedValue();
         $this->assertSame($value, $actual, 'should be able to write and read strings with multiples quotes');
     }
+
+    public function testDelimiterDetection()
+    {
+        $reader = new \PhpOffice\PhpSpreadsheet\Reader\Csv();
+        $this->assertNull($reader->getDelimiter());
+
+        $filename = __DIR__ . '/../../data/Reader/CSV/semicolon_separated.csv';
+        $spreadsheet = $reader->load($filename);
+
+        $this->assertSame(';', $reader->getDelimiter(), 'should be able to infer the delimiter');
+
+        $actual = $spreadsheet->getActiveSheet()->getCell('C2')->getValue();
+        $this->assertSame('25,5', $actual, 'should be able to retrieve values with commas');
+    }
 }

tests/data/Reader/CSV/semicolon_separated.csv

@@ -0,0 +1,3 @@
+This;Are;Headers
+Cell A2;Number with comma;25,5
+Two colons and a comma;B|3;:,: