feat: use mbstring if iconv is not working

Signed-off-by: Jack Cherng <jfcherng@gmail.com>

Author: jfcherng

composer.json

@@ -36,6 +36,10 @@
         "phan/phan": "^5",
         "phpunit/phpunit": "^9 || ^10"
     },
+    "suggest": {
+        "ext-iconv": "Either \"ext-iconv\" or \"ext-mbstring\" is requried.",
+        "ext-mbstring": "Either \"ext-iconv\" or \"ext-mbstring\" is requried."
+    },
     "scripts": {
         "analyze": [
             "phan --color"

composer.lock

@@ -17,6 +17,16 @@
  */
 class MbString extends \ArrayObject implements \Stringable
 {
+    public const MBSTRING_CONVMETHOD_ICONV = 1;
+    public const MBSTRING_CONVMETHOD_MBSTRING = 2;
+
+    /**
+     * The way to convert text encoding.
+     *
+     * @var int
+     */
+    public static $convMethod;
+
     /**
      * UTF-32 string without endian bytes.
      *
@@ -46,7 +56,8 @@ class MbString extends \ArrayObject implements \Stringable
      */
     public function __construct(string $str = '', string $encoding = 'UTF-8')
     {
-        static::$utf32Header = static::$utf32Header ?? static::getUtf32Header();
+        static::$convMethod ??= static::detectConvEncoding();
+        static::$utf32Header ??= static::getUtf32Header();
 
         $this->encoding = $encoding;
         $this->set($str);
@@ -328,11 +339,37 @@ public function count(): int
     protected static function getUtf32Header(): string
     {
         // just use any string to get the endian header, here we use "A"
-        $tmp = iconv('UTF-8', 'UTF-32', 'A');
+        $tmp = self::convEncoding('A', 'UTF-8', 'UTF-32');
         // some distributions like "php alpine" docker image won't generate the header
         return $tmp && \strlen($tmp) > 4 ? substr($tmp, 0, 4) : '';
     }
 
+    protected static function detectConvEncoding(): int
+    {
+        if (\function_exists('iconv') && iconv('UTF-8', 'UTF-32', 'A') !== false) {
+            return static::MBSTRING_CONVMETHOD_ICONV;
+        }
+
+        if (\function_exists('mb_convert_encoding') && mb_convert_encoding('A', 'UTF-32', 'UTF-8') !== false) {
+            return static::MBSTRING_CONVMETHOD_MBSTRING;
+        }
+
+        throw new \RuntimeException('Either "iconv" or "mbstring" extension is required.');
+    }
+
+    protected static function convEncoding(string $str, string $from, string $to): string
+    {
+        if (static::$convMethod === static::MBSTRING_CONVMETHOD_ICONV) {
+            return iconv($from, $to, $str);
+        }
+
+        if (static::$convMethod === static::MBSTRING_CONVMETHOD_MBSTRING) {
+            return mb_convert_encoding($str, $to, $from);
+        }
+
+        throw new \RuntimeException('Unknown conversion method.');
+    }
+
     /**
      * Convert the output string to its original encoding.
      *
@@ -344,7 +381,7 @@ protected function outputConv(string $str): string
             return '';
         }
 
-        return iconv('UTF-32', $this->encoding, static::$utf32Header . $str);
+        return static::convEncoding(static::$utf32Header . $str, 'UTF-32', $this->encoding);
     }
 
     /**
@@ -358,6 +395,6 @@ protected function inputConv(string $str): string
             return '';
         }
 
-        return substr(iconv($this->encoding, 'UTF-32', $str), \strlen(static::$utf32Header));
+        return substr(static::convEncoding($str, $this->encoding, 'UTF-32'), \strlen(static::$utf32Header));
     }
 }