Display String support

src/DisplayString.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace gapple\StructuredFields;
+
+class DisplayString
+{
+ /**
+ * @var string
+ */
+ private $value;
+
+ public function __construct(string $value)
+ {
+ $this->value = $value;
+ }
+
+ public function __toString(): string
+ {
+ return $this->value;
+ }
+}

src/Parser.php

@@ -169,6 +169,8 @@ private static function parseBareItem(string &$string)
  $value = self::parseBoolean($string);
  } elseif ($string[0] == '@') {
  $value = self::parseDate($string);
+ } elseif ($string[0] == '%') {
+ $value = self::parseDisplayString($string);
  } elseif (preg_match('/^([a-z*])/i', $string)) {
  $value = self::parseToken($string);
  } else {
@@ -276,6 +278,50 @@ private static function parseString(string &$string): string
  throw new ParseException("Invalid end of string");
  }
 
+ private static function parseDisplayString(string &$string): DisplayString
+ {
+ if (strpos($string, '%"') !== 0) {
+ throw new ParseException("Invalid start of display string");
+ }
+
+ $string = substr($string, 2);
+
+ $encoded_string = '';
+ while (strlen($string)) {
+ $char = $string[0];
+ $string = substr($string, 1);
+
+ if (ord($char) <= 0x1f || ord($char) >= 0x7f) {
+ throw new ParseException('Invalid character in display string');
+ } elseif ($char == '%') {
+ if (strlen($string) < 2) {
+ throw new ParseException("Invalid end of display string");
+ }
+
+ $hex = substr($string, 0, 2);
+ $string = substr($string, 2);
+
+ if (!preg_match('/^[0-9a-z]{2}$/', $hex)) {
+ throw new ParseException('Invalid hex values in display string');
+ }
+
+ $encoded_string .= $char . $hex;
+ } elseif ($char == '"') {
+ $display_string = new DisplayString(rawurldecode($encoded_string));
+ // An invalid UTF-8 subject will cause the preg_* function to match nothing.
+ // @see https://www.php.net/manual/en/reference.pcre.pattern.modifiers.php
+ if (!preg_match('/^\X*$/u', $display_string)) {
+ throw new ParseException("Invalid byte sequence in display string");
+ }
+ return $display_string;
+ } else {
+ $encoded_string .= $char;
+ }
+ }
+
+ throw new ParseException("Invalid end of display string");
+ }
+
  private static function parseToken(string &$string): Token
  {
  // Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing

src/Serializer.php

@@ -162,6 +162,8 @@ private static function serializeBareItem($value): string
  return self::serializeByteSequence($value);
  } elseif ($value instanceof Date) {
  return self::serializeDate($value);
+ } elseif ($value instanceof DisplayString) {
+ return self::serializeDisplayString($value);
  } elseif (is_string($value) || (is_object($value) && method_exists($value, '__toString'))) {
  return self::serializeString((string) $value);
  }
@@ -209,6 +211,16 @@ private static function serializeString(string $value): string
  return '"' . preg_replace('/(["\\\])/', '\\\$1', $value) . '"';
  }
 
+ private static function serializeDisplayString(DisplayString $value): string
+ {
+ $encode_pattern = '/[%"\x00-\x1F\x7F-\xFF]/';
+ $encode_callback = function ($matches) {
+ return strtolower(rawurlencode($matches[0]));
+ };
+
+ return '%"' . preg_replace_callback($encode_pattern, $encode_callback, $value) . '"';
+ }
+
  private static function serializeToken(Token $value): string
  {
  // Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing

tests/Httpwg/DisplayStringTest.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace gapple\Tests\StructuredFields\Httpwg;
+
+class DisplayStringTest extends HttpwgTest
+{
+ protected $ruleset = 'display-string';
+}

tests/Httpwg/HttpwgTest.php

@@ -5,6 +5,7 @@
 use gapple\StructuredFields\Bytes;
 use gapple\StructuredFields\Date;
 use gapple\StructuredFields\Dictionary;
+use gapple\StructuredFields\DisplayString;
 use gapple\StructuredFields\InnerList;
 use gapple\StructuredFields\Item;
 use gapple\StructuredFields\OuterList;
@@ -186,6 +187,8 @@ private static function convertValue($data)
  return new Bytes(Base32::decodeUpper($data->value));
  case 'date':
  return new Date($data->value);
+ case 'displaystring':
+ return new DisplayString($data->value);
  }
  }