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<?php |
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namespace FluentCart\OpenSpout\Writer\Common\Helper; |
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|
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/** |
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* This class provides helper functions when working with cells. |
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*/ |
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class CellHelper |
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{ |
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/** @var array Cache containing the mapping column index => column letters */ |
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private static $columnIndexToColumnLettersCache = []; |
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/** |
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* Returns the column letters (base 26) associated to the base 10 column index. |
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* Excel uses A to Z letters for column indexing, where A is the 1st column, |
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* Z is the 26th and AA is the 27th. |
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* The mapping is zero based, so that 0 maps to A, B maps to 1, Z to 25 and AA to 26. |
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* |
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* @param int $columnIndexZeroBased The Excel column index (0, 42, ...) |
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* |
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* @return string The associated cell index ('A', 'BC', ...) |
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*/ |
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public static function getColumnLettersFromColumnIndex($columnIndexZeroBased) |
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{ |
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$originalColumnIndex = $columnIndexZeroBased; |
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// Using isset here because it is way faster than array_key_exists... |
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if (!isset(self::$columnIndexToColumnLettersCache[$originalColumnIndex])) { |
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$columnLetters = ''; |
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$capitalAAsciiValue = \ord('A'); |
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do { |
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$modulus = $columnIndexZeroBased % 26; |
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$columnLetters = \chr($capitalAAsciiValue + $modulus) . $columnLetters; |
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// substracting 1 because it's zero-based |
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$columnIndexZeroBased = (int) ($columnIndexZeroBased / 26) - 1; |
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} while ($columnIndexZeroBased >= 0); |
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self::$columnIndexToColumnLettersCache[$originalColumnIndex] = $columnLetters; |
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} |
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return self::$columnIndexToColumnLettersCache[$originalColumnIndex]; |
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} |
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} |
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