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<?php |
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namespace ale\StringArray; |
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/** |
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* Class StringArray |
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* A simple implementation of a C-style array as a string. |
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*/ |
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class StringArray |
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{ |
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/** |
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* The width of the simulated array. |
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* |
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* This is not currently used actively, but might be handy (eg. in case we |
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* want to initialize the whole string in advance.) |
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* |
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* @var int |
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*/ |
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private $width; |
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/** |
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* The height of the simulated array. |
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* |
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* @var int |
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*/ |
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private $height; |
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/** |
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* The size in bytes of each value in the array. |
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* |
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* @var int |
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*/ |
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private $cellSize; |
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/** |
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* Storage for the actual data. |
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* |
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* @var string |
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*/ |
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private $data = ''; |
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1 |
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* A cache of the unprintable ASCII characters. |
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* |
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* @var array |
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*/ |
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private $unprintableChars = array(); |
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1 |
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/** |
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* The type of data this StringArray can handle. |
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* |
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* @var string |
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*/ |
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private $type = 'UINT32'; |
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/** |
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* List of types supported by this class. |
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* |
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* @var array |
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*/ |
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private $types = array( |
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'UINT32' => array('size' => 4, 'format' => 'L'), |
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'DOUBLE' => array('size' => 8, 'format' => 'd'), |
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); |
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public function __construct($width, $height, $type = 'UINT32') { |
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// @todo - handle type and cell size internally. |
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// Initialize the string so that PHP won't think it's an array when we |
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// start using offsets. |
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$this->data = str_pad('', 1, chr(0)); |
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$this->width = $width; |
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$this->height = $height; |
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$this->type = $type; |
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// @TODO - validate types. |
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$this->cellSize = $this->types[$type]['size']; |
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} |
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/** |
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* Inserts a value at the requested position. |
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* |
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* @param int $i |
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* The first dimension position to store the value. |
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* @param int $j |
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* The second dimension position to store the value. |
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* @param mixed $value |
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* The value to store. |
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*/ |
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public function insert($i, $j, $value) { |
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// @todo - validate that the passed value fits in the dimensions. |
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$index = $this->getIndex($i, $j); |
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// @todo - generalise hardcoded type. |
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$encoded = pack($this->types[$this->type]['format'], $value); |
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// I think this is the fastest way to splice this value into storage, |
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// but maybe worth checking. |
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for ($i = 0; $i < $this->types[$this->type]['size']; ++$i) { |
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$this->data[$index + $i] = $encoded[$i]; |
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} |
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} |
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/** |
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* Retrieves a value from the given position. |
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* |
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* @param int $i |
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* The first dimension position to retrieve. |
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* @param int $j |
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* the second dimension position to retrieve. |
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* @return mixed |
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* The retrieved value. |
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*/ |
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public function retrieve($i, $j) { |
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$index = $this->getIndex($i, $j); |
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$encoded = substr($this->data, $index, $this->types[$this->type]['size']); |
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// Appending "value" to the unpack format forces the result to be in the |
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// returned array under that key. |
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return unpack($this->types[$this->type]['format'] . 'value', $encoded)['value']; |
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} |
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/** |
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* Gets an index into the storage string |
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* |
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* @param int $i |
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* The first dimension position. |
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1 |
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* @param int $j |
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* The second dimension position. |
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* @return int |
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* The caluculated increment into the storage string. |
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*/ |
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private function getIndex($i, $j) { |
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return ($i * $this->height + $j) * $this->cellSize; |
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} |
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/** |
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* Dump the internal storage, replacing some unprintable characters. |
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*/ |
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public function dump() { |
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// Set up the excluded characters list just once if it hasn't been set. |
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if (empty($this->unprintableChars)) { |
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for ($i = 0; $i <= 31; ++$i) { |
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$this->unprintableChars[] = chr($i); |
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} |
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} |
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return str_replace($this->unprintableChars, '*', $this->data); |
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} |
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/** |
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* Gets the size of the internal storage of the array. |
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* |
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* @return int |
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* The size, in bytes, taken by the internal array storage. |
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*/ |
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public function size() { |
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return strlen($this->data); |
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} |
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} |
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alanevans /
string-array
