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<?php |
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declare(strict_types=1); |
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namespace Remorhaz\Lexer\Runtime\IO; |
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use function array_slice; |
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final class PreviewBuffer implements PreviewBufferInterface |
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{ |
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/** |
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* @var SymbolReaderInterface |
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*/ |
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private $input; |
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/** |
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* @var SymbolInterface[] |
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* @psalm-var array<int,SymbolInterface> |
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*/ |
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private $buffer = []; |
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/** |
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* @var int |
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*/ |
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private $previewOffset; |
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/** |
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* @var int |
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*/ |
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private $tokenOffset; |
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public function __construct(SymbolReaderInterface $input) |
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{ |
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$this->input = $input; |
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$this->tokenOffset = $input->getOffset(); |
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$this->previewOffset = $this->tokenOffset; |
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} |
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public function getPreviewSymbol(): SymbolInterface |
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{ |
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if (!isset($this->buffer[$this->previewOffset])) { |
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$this->buffer[$this->previewOffset] = $this->input->read(); |
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} |
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return $this->buffer[$this->previewOffset]; |
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} |
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public function resetPreview(): void |
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{ |
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$this->previewOffset = $this->tokenOffset; |
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} |
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public function previewNext(): void |
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{ |
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if (!isset($this->buffer[$this->previewOffset])) { |
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$this->buffer[$this->previewOffset] = $this->input->read(); |
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} |
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$this->previewOffset++; |
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} |
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public function previewPrevious(): void |
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{ |
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if ($this->previewOffset == $this->tokenOffset) { |
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throw new Exception\InvalidPreviewOffsetException($this->tokenOffset); |
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} |
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$this->previewOffset--; |
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} |
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/** |
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* @return bool |
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* @psalm-pure |
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*/ |
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public function isFinished(): bool |
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{ |
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return !isset($this->buffer[$this->previewOffset]) && $this->input->isFinished(); |
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} |
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public function acceptLexeme(): LexemeInterface |
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{ |
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$length = $this->previewOffset - $this->tokenOffset; |
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$lexeme = new Lexeme(...array_slice($this->buffer, $this->tokenOffset, $length)); |
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$this->tokenOffset = $this->previewOffset; |
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return $lexeme; |
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} |
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/** |
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* @return LexemeInterface |
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* @psalm-pure |
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*/ |
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public function getEmptyLexeme(): LexemeInterface |
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{ |
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if (isset($this->buffer[$this->previewOffset])) { |
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$symbol = $this->buffer[$this->previewOffset]; |
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return EmptyLexeme::fromOffsets(...$symbol->getLexeme()->getStartOffsets()); |
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} |
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return $this->input->getEmptyLexeme(); |
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} |
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} |
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remorhaz /
php-lexer-runtime
