Code scaffolding for displaystring 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 +278,39 @@ private static function parseString(string &$string): string
         throw new ParseException("Invalid end of string");
     }
 
+    private static function parseDisplayString(string &$string): DisplayString
+    {
+        $string = substr($string, 1);
+
+        $output_string = '';
+        while (strlen($string)) {
+            $char = $string[0];
+            $string = substr($string, 1);
+
+            // @todo properly parse value
+
+            if ($char == '\\') {
+                if ($string == '') {
+                    throw new ParseException("Invalid end of string");
+                }
+
+                $char = $string[0];
+                $string = substr($string, 1);
+                if ($char != '"' && $char != '\\') {
+                    throw new ParseException('Invalid escaped character in string');
+                }
+            } elseif ($char == '"') {
+                return new DisplayString($output_string);
+            } elseif (ord($char) <= 0x1f || ord($char) >= 0x7f) {
+                throw new ParseException('Invalid character in string');
+            }
+
+            $output_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 +211,12 @@ private static function serializeString(string $value): string
         return '"' . preg_replace('/(["\\\])/', '\\\$1', $value) . '"';
     }
 
+    private static function serializeDisplayString(string $value): string
+    {
+        // @todo properly encode value.
+        return '%"' . $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);
             }
         }