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125 lines
4.6 KiB
125 lines
4.6 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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class UTF8 extends AbstractEncoding implements Coder, Decoder {
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const NAME = "UTF-8";
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const LABELS = [
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"unicode-1-1-utf-8",
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"unicode11utf8",
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"unicode20utf8",
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"utf-8",
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"utf8",
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"x-unicode20utf8",
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];
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protected $selfSynchronizing = true;
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public function nextCode() {
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// this function effectively implements https://encoding.spec.whatwg.org/#utf-8-decoder
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// optimization for ASCII characters
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$b = @$this->string[$this->posByte];
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if ($b === "") {
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return false;
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} elseif (($b = ord($b)) < 0x80) {
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$this->posChar++;
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$this->posByte++;
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return $b;
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}
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$this->posChar++;
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$point = 0;
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$seen = 0;
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$needed = 1;
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$lower = 0x80;
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$upper = 0xBF;
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while ($seen < $needed) {
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$b = ord(@$this->string[$this->posByte++]);
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if (!$seen) {
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if ($b >= 0xC2 && $b <= 0xDF) { // two-byte character
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$needed = 2;
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$point = $b & 0x1F;
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} elseif ($b >= 0xE0 && $b <= 0xEF) { // three-byte character
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$needed = 3;
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if ($b==0xE0) {
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$lower = 0xA0;
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} elseif ($b==0xED) {
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$upper = ($this->allowSurrogates) ? 0xBF : 0x9F;
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}
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$point = $b & 0xF;
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} elseif ($b >= 0xF0 && $b <= 0xF4) { // four-byte character
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$needed = 4;
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if ($b==0xF0) {
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$lower = 0x90;
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} elseif ($b==0xF4) {
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$upper = 0x8F;
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}
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$point = $b & 0x7;
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} else { // invalid byte
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return $this->errDec($this->errMode, $this->posChar, $this->posByte);
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}
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} elseif ($b < $lower || $b > $upper) {
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return $this->errDec($this->errMode, $this->posChar, $this->posByte--);
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} else {
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$lower = 0x80;
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$upper = 0xBF;
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$point = ($point << 6) | ($b & 0x3F);
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}
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$seen++;
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}
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return $point;
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}
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public static function encode(int $codePoint, bool $fatal = true): string {
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// this function implements https://encoding.spec.whatwg.org/#utf-8-encoder
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if ($codePoint < 0 || $codePoint > 0x10FFFF) {
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throw new EncoderException("Encountered code point outside Unicode range ($codePoint)", self::E_INVALID_CODE_POINT);
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} elseif ($codePoint < 128) {
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return chr($codePoint);
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} elseif ($codePoint < 0x800) {
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$count = 1;
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$offset = 0xC0;
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} elseif ($codePoint < 0x10000) {
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$count = 2;
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$offset = 0xE0;
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} else {
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$count = 3;
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$offset = 0xF0;
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}
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$bytes = chr(($codePoint >> (6 * $count)) + $offset);
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while ($count > 0) {
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$bytes .= chr(0x80 | (($codePoint >> (6 * ($count - 1))) & 0x3F));
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$count--;
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}
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return $bytes;
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}
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/** Implements backward seeking $distance characters */
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protected function seekBack(int $distance): int {
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while ($distance > 0 && $this->posByte > 0) {
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$distance--;
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$this->posChar--;
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$b = ord(@$this->string[$this->posByte - 1]);
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if ($b < 0x80) {
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// if the byte is an ASCII byte or the end of input, then this is already a synchronized position
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$this->posByte--;
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} else {
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$s = $this->posByte;
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$pos = $s - 1;
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while ($b >= 0x80 && $b <= 0xBF && $pos > 0 && ($s - $pos) < 4) { // go back at most four bytes, no further than the start of the string, and only as long as the byte remains a continuation byte
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$b = ord(@$this->string[--$pos]);
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}
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$this->posByte = $pos;
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// decrement the character position because nextCode() increments it
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$this->posChar--;
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// check for overlong sequences: if the sequence is overlong consuming the character will yield an earlier position than where we started
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$this->nextCode();
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$this->posByte = ($this->posByte < $s) ? $s - 1 : $pos;
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}
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}
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return $distance;
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}
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}
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