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201 lines
6.9 KiB
201 lines
6.9 KiB
<?php
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/** @license MIT
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* Copyright 2018 J. King et al.
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* See LICENSE and AUTHORS files for details */
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declare(strict_types=1);
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namespace MensBeam\Intl\Encoding;
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trait GenericEncoding {
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protected $string;
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protected $posByte = 0;
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protected $posChar = 0;
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protected $lenByte = null;
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protected $lenChar = null;
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protected $errMode = self::MODE_REPLACE;
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/** Constructs a new decoder
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*
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* If $fatal is true, an exception will be thrown whenever an invalid code sequence is encountered; otherwise replacement characters will be substituted
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*/
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public function __construct(string $string, bool $fatal = false) {
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$this->string = $string;
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$this->lenByte = strlen($string);
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$this->errMode = $fatal ? self::MODE_FATAL_DEC : self::MODE_REPLACE;
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}
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/** Returns the current byte position of the decoder */
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public function posByte(): int {
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return $this->posByte;
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}
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/** Returns the current character position of the decoder */
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public function posChar(): int {
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return $this->posChar;
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}
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/** Seeks to the start of the string
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*
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* This is usually faster than using the seek method for the same purpose
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*/
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public function rewind() {
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$this->posByte = 0;
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$this->posChar = 0;
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}
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/** Retrieve the next character in the string, in UTF-8 encoding
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*
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* The returned character may be a replacement character, or the empty string if the end of the string has been reached
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*/
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public function nextChar(): string {
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// get the byte at the current position
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$b = @$this->string[$this->posByte];
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if ($b === "") {
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// if the byte is end of input, simply return it
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return "";
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} elseif (ord($b) < 0x80) {
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// if the byte is an ASCII character, simply return it
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$this->posChar++;
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$this->posByte++;
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return $b;
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} else {
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// otherwise return the serialization of the code point at the current position
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return UTF8::encode($this->nextCode());
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}
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}
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/** Advance $distance characters through the string
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*
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* If $distance is negative, the operation will be performed in reverse
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*
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* If the end (or beginning) of the string was reached before the end of the operation, the remaining number of requested characters is returned
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*/
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public function seek(int $distance): int {
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if ($distance > 0) {
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if ($this->posByte == strlen($this->string)) {
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return $distance;
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}
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do {
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$p = $this->nextCode();
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} while (--$distance && $p !== false);
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return $distance;
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} elseif ($distance < 0) {
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$distance = abs($distance);
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if (!$this->posChar) {
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return $distance;
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}
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$mode = $this->errMode;
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$this->errMode = self::MODE_NULL;
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$out = $this->seekBack($distance);
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$this->errMode = $mode;
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return $out;
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} else {
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return 0;
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}
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}
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/** Retrieves the next $num characters (in UTF-8 encoding) from the string without advancing the character pointer */
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public function peekChar(int $num = 1): string {
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$out = "";
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$state = $this->stateSave();
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try {
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while ($num-- > 0 && ($b = $this->nextChar()) !== "") {
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$out .= $b;
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}
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} finally {
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$this->stateApply($state);
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}
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return $out;
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}
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/** Retrieves the next $num code points from the string, without advancing the character pointer */
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public function peekCode(int $num = 1): array {
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$out = [];
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$state = $this->stateSave();
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try {
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while ($num-- > 0 && ($b = $this->nextCode()) !== false) {
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$out[] = $b;
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}
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} finally {
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$this->stateApply($state);
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}
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return $out;
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}
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/** Calculates the length of the string in bytes */
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public function lenByte(): int {
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return $this->lenByte;
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}
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/** Calculates the length of the string in code points
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*
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* Note that this may involve processing to the end of the string
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*/
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public function lenChar(): int {
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return $this->lenChar ?? (function() {
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$state = $this->stateSave();
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while ($this->nextCode() !== false);
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$this->lenChar = $this->posChar;
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$this->stateApply($state);
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return $this->lenChar;
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})();
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}
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/** Returns whether the character pointer is at the end of the string */
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public function eof(): bool {
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return $this->posByte >= $this->lenByte;
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}
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/** Generates an iterator which steps through each character in the string */
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public function chars(): \Generator {
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while (($c = $this->nextChar()) !== "") {
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yield ($this->posChar - 1) => $c;
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}
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}
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/** Generates an iterator which steps through each code point in the string */
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public function codes(): \Generator {
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while (($c = $this->nextCode()) !== false) {
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yield ($this->posChar - 1) => $c;
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}
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}
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/** Returns a copy of the decoder's state to keep in memory */
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protected function stateSave(): array {
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return [
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'posChar' => $this->posChar,
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'posByte' => $this->posByte,
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];
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}
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/** Sets the decoder's state to the values specified */
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protected function stateApply(array $state) {
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foreach ($state as $key => $value) {
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$this->$key = $value;
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}
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}
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/** Handles decoding and encoding errors */
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protected static function err(int $mode, $data = null) {
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switch ($mode) {
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case self::MODE_NULL:
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// used internally during backward seeking for some encodings
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return null; // @codeCoverageIgnore
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case self::MODE_REPLACE:
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// standard "replace" mode
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return 0xFFFD;
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case self::MODE_HTML:
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// the "html" replacement mode; not applicable to Unicode transformation formats
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return "&#".(string) $data.";";
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case self::MODE_FATAL_DEC:
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// fatal replacement mode for decoders
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throw new DecoderException("Invalid code sequence at character offset {$data[0]} (byte offset {$data[1]})", self::E_INVALID_BYTE);
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case self::MODE_FATAL_ENC:
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// fatal replacement mode for decoders; not applicable to Unicode transformation formats
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throw new EncoderException("Code point $data not available in target encoding", self::E_UNAVAILABLE_CODE_POINT);
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default:
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// indicative of internal bug; should never be triggered
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throw new DecoderException("Invalid replacement mode {$mode}", self::E_INVALID_MODE); // @codeCoverageIgnore
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}
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}
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}
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