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86 lines
2.8 KiB
86 lines
2.8 KiB
<?php
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declare(strict_types=1);
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namespace dW\HTML5;
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use MensBeam\Intl\Encoding;
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abstract class Charset {
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/** Matches an encoding label (e.g. "utf-8") to a compatible decoder class.
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*
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* @param string $value The encoding label to match
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*/
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public static function fromCharset(string $value): ?string {
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$encoding = Encoding::matchLabel($value);
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if ($encoding) {
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return $encoding['class'];
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}
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return null;
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}
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/** Extracts an encoding from an HTTP Content-Type header-field
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* and returns the class name of a compatible decoder.
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*
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* @param string $contentType The value of a Content-Type header-field
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*/
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public static function fromTransport(string $contentType): ?string {
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// Try to sniff out a charset from a Content-Type header-field.
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// This does cut some corners, but should be sufficient for practical use
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$s = preg_replace("/\s+/", " ", strtolower($contentType));
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$pos = 0;
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$end = strlen($s);
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// skip the type
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while ($pos < $end && @$s[$pos++] !== "/");
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// skip the subtype
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while ($pos < $end && @$s[$pos++] !== ";");
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// check parameters in sequence
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while ($pos < $end) {
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// skip any leading whitespace
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if (@$s[$pos] === " ") {
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$pos++;
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}
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// collect characters for the parameter name
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$param = "";
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while ($pos < $end && @$s[$pos] !== "=") {
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$param .= @$s[$pos++];
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}
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// skip the equals sign
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$pos++;
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if ($s[$pos] === '"') {
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// Value is a quoted-string
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$pos++;
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$value = "";
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while (!in_array($c = @$s[$pos++], ['"', ""])) {
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if ($c === "\\") {
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$value .= @$s[$pos++];
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} else {
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$value .= $c;
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}
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}
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// only interpret the value if a closing quotation mark was seen
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if ($c !== '"') {
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$value = "";
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}
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} else {
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// Value is a bare token
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$value = "";
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while (!in_array($c = @$s[$pos++], [';', " ", ""])) {
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$value .= $c;
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}
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}
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// if the parameter was the character set, interpret its value and return
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if ($param === "charset") {
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$encoding = Encoding::matchLabel($value);
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if ($encoding) {
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return $encoding['class'];
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} else {
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return null;
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}
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}
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}
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return null;
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}
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public static function fromPrescan(string $data): ?string {
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return null;
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}
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}
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