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<?php
namespace Box\Spout\Reader\XLSX\Helper;
use Box\Spout\Common\Exception\InvalidArgumentException;
/**
* Class CellHelper
* This class provides helper functions when working with cells
*/
class CellHelper
{
// Using ord() is super slow... Using a pre-computed hash table instead.
private static $columnLetterToIndexMapping = [
'A' => 0, 'B' => 1, 'C' => 2, 'D' => 3, 'E' => 4, 'F' => 5, 'G' => 6,
'H' => 7, 'I' => 8, 'J' => 9, 'K' => 10, 'L' => 11, 'M' => 12, 'N' => 13,
'O' => 14, 'P' => 15, 'Q' => 16, 'R' => 17, 'S' => 18, 'T' => 19, 'U' => 20,
'V' => 21, 'W' => 22, 'X' => 23, 'Y' => 24, 'Z' => 25,
];
/**
* Returns the base 10 column index associated to the cell index (base 26).
* Excel uses A to Z letters for column indexing, where A is the 1st column,
* Z is the 26th and AA is the 27th.
* The mapping is zero based, so that A1 maps to 0, B2 maps to 1, Z13 to 25 and AA4 to 26.
*
* @param string $cellIndex The Excel cell index ('A1', 'BC13', ...)
* @throws \Box\Spout\Common\Exception\InvalidArgumentException When the given cell index is invalid
* @return int
*/
public static function getColumnIndexFromCellIndex($cellIndex)
{
if (!self::isValidCellIndex($cellIndex)) {
throw new InvalidArgumentException('Cannot get column index from an invalid cell index.');
}
$columnIndex = 0;
// Remove row information
$columnLetters = \preg_replace('/\d/', '', $cellIndex);
// strlen() is super slow too... Using isset() is way faster and not too unreadable,
// since we checked before that there are between 1 and 3 letters.
$columnLength = isset($columnLetters[1]) ? (isset($columnLetters[2]) ? 3 : 2) : 1;
// Looping over the different letters of the column is slower than this method.
// Also, not using the pow() function because it's slooooow...
switch ($columnLength) {
case 1:
$columnIndex = (self::$columnLetterToIndexMapping[$columnLetters]);
break;
case 2:
$firstLetterIndex = (self::$columnLetterToIndexMapping[$columnLetters[0]] + 1) * 26;
$secondLetterIndex = self::$columnLetterToIndexMapping[$columnLetters[1]];
$columnIndex = $firstLetterIndex + $secondLetterIndex;
break;
case 3:
$firstLetterIndex = (self::$columnLetterToIndexMapping[$columnLetters[0]] + 1) * 676;
$secondLetterIndex = (self::$columnLetterToIndexMapping[$columnLetters[1]] + 1) * 26;
$thirdLetterIndex = self::$columnLetterToIndexMapping[$columnLetters[2]];
$columnIndex = $firstLetterIndex + $secondLetterIndex + $thirdLetterIndex;
break;
}
return $columnIndex;
}
/**
* Returns whether a cell index is valid, in an Excel world.
* To be valid, the cell index should start with capital letters and be followed by numbers.
* There can only be 3 letters, as there can only be 16,384 rows, which is equivalent to 'XFE'.
*
* @param string $cellIndex The Excel cell index ('A1', 'BC13', ...)
* @return bool
*/
protected static function isValidCellIndex($cellIndex)
{
return (\preg_match('/^[A-Z]{1,3}\d+$/', $cellIndex) === 1);
}
}
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