116 lines
3.2 KiB
PHP
116 lines
3.2 KiB
PHP
<?php
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class MarkovDictionary {
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private const MAGIC = 'FMkD';
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private const VERSION = 1;
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private $handle;
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private int $segmentSize;
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private int $totalSegments;
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private int $startSegments;
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public function __construct(string $path) {
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if(!is_file($path))
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throw new InvalidArgumentException('$path does not exist.');
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$this->handle = $handle = fopen($path, 'rb');
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$magic = fread($handle, 4);
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if($magic !== self::MAGIC)
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throw new InvalidArgumentException('$path is not a valid markov dictionary.');
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$header = fread($handle, 12);
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if(strlen($header) !== 12)
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throw new InvalidArgumentException('$path is missing header data.');
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extract(unpack('Cversion/Cunused1/Cunused2/CsegmentSize/VtotalSegments/VstartSegments', $header));
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if($version !== self::VERSION)
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throw new InvalidArgumentException('$path version is incompatible.');
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$this->segmentSize = $segmentSize;
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$this->totalSegments = $totalSegments;
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$this->startSegments = $startSegments;
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}
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public function close(): void {
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if($this->handle !== null) {
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fclose($this->handle);
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$this->handle = null;
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}
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}
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public function __destruct() {
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$this->close();
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}
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private function reset(): void {
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fseek($this->handle, 16, SEEK_SET);
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}
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public function getStartPosition(): int {
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$randomStart = mt_rand(0, $this->startSegments) - 2;
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if($randomStart > 0) {
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for(;;) {
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fseek($this->handle, 4 * $this->segmentSize, SEEK_CUR);
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$isStart = fgetc($this->handle) !== "\0";
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if($isStart) {
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if($randomStart < 1)
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break;
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--$randomStart;
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}
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extract(unpack('vnextSegments', fread($this->handle, 2)));
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fseek($this->handle, 6 * $nextSegments, SEEK_CUR);
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}
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fseek($this->handle, -(4 * $this->segmentSize) - 1, SEEK_CUR);
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}
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$startPos = ftell($this->handle);
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$this->reset();
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return $startPos;
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}
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public function generate(int $safety = 2000, int $start = -1): string {
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if($start < 0)
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$start = $this->getStartPosition();
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fseek($this->handle, $start, SEEK_SET);
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$string = '';
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for($s = 0; $s < $safety; ++$s) {
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$string .= fread($this->handle, 4 * $this->segmentSize);
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fseek($this->handle, 1, SEEK_CUR);
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extract(unpack('vnextSegments', fread($this->handle, 2)));
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if($nextSegments < 1)
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break;
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$nexts = [];
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// really shitty weighting system
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for($i = 0; $i < $nextSegments; ++$i) {
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extract(unpack('Voffset/vweight', fread($this->handle, 6)));
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for($j = 0; $j < $weight; ++$j)
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$nexts[] = $offset;
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}
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$offset = $nexts[array_rand($nexts)];
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fseek($this->handle, $offset, SEEK_SET);
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}
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$this->reset();
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$string = mb_convert_encoding($string, 'utf-8', 'utf-32le');
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return trim($string);
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}
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}
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