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<?php |
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declare(strict_types=1); |
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namespace SPSS; |
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/** |
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* Class ByteCodeWriter |
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* Abstracts bytecode (de)compression |
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* @package SPSS |
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*/ |
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class ByteCodeWriter |
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{ |
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private const BYTE_SYS_MISSING = 255; |
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private const BYTE_SPACES = 254; |
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private const BYTE_LITERAL = 253; |
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private const BYTE_NUL = 0; |
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/** @var Buffer */ |
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private $buffer; |
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private $commandBuffer = []; |
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private $dataBuffer = ''; |
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private $data = ''; |
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public function __construct(Buffer $buffer) |
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{ |
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$this->buffer = $buffer; |
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} |
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/** |
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* Appends data, data might not actually be written until flush is called |
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*/ |
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public function append(string $data): void |
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{ |
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$data = $this->dataBuffer . $data; |
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$this->dataBuffer = ''; |
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while(strlen($data) >= 8) { |
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$block = substr($data, 0, 8); |
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$data = substr($data, 8); |
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switch ($block) { |
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case pack('d', -PHP_FLOAT_MAX): |
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$this->commandBuffer[] = self::BYTE_SYS_MISSING; |
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break; |
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case ' ': |
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$this->commandBuffer[] = self::BYTE_SPACES; |
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break; |
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default: |
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$this->commandBuffer[] = self::BYTE_LITERAL; |
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$this->data .= $block; |
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} |
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$this->writeBlock(); |
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} |
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$this->dataBuffer .= $data; |
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} |
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private function writeBlock(): void |
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{ |
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if (count($this->commandBuffer) === 8) { |
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$commandBlock = ''; |
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foreach ($this->commandBuffer as $cmd) { |
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$commandBlock .= chr($cmd); |
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} |
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$this->buffer->write($commandBlock . $this->data); |
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$this->data = ''; |
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$this->commandBuffer = []; |
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} |
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} |
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/** |
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* Fills the command buffer with nuls and writes the remaining data. |
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*/ |
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public function flush(): void |
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{ |
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// Write remaining data by padding with spaces. |
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if (!empty($this->dataBuffer)) { |
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$this->append(str_repeat(' ', 8 - strlen($this->dataBuffer))); |
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} |
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if (!empty($this->commandBuffer)) { |
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$this->commandBuffer = array_pad($this->commandBuffer, 8, self::BYTE_NUL); |
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$this->writeBlock(); |
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} |
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if (!empty($this->dataBuffer) || !empty($this->commandBuffer)) { |
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throw new \Exception('Failed to flush one of the buffers'); |
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} |
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} |
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} |
collecthor /
spss
