fix converting to utf for some invalid byte sequences

composer.json

@@ -18,9 +18,7 @@
   "require-dev": {
     "tedivm/dovecottesting": "1.2.3",
     "phpunit/phpunit": "4.2.*",
-    "fabpot/php-cs-fixer": "0.5.*",
+    "fabpot/php-cs-fixer": "0.5.*"
-    "satooshi/php-coveralls": "dev-master"
-
     },
   "autoload": {
     "psr-0": {"Fetch": "src/"}

src/Fetch/UTF8.php

@@ -6,47 +6,57 @@ final class UTF8
 {
     public static function fix($text)
     {
-        if(!is_string($text)) {
+        if (!is_string($text) || !$text) {
             return $text;
         }
 
+        if (\function_exists('mb_convert_encoding')) {
+            if ($val = @mb_convert_encoding($text, 'utf-8', 'utf-8')) {
+                return $val;
+            }
+        }
+
         $buf = '';
         for ($i = 0, $max = strlen($text); $i < $max; $i++) {
             $c1 = $text{$i};
-            if ($c1 >= "\xc0") { //Should be converted to UTF8, if it's not UTF8 already
+
+            if ($c1 <= "\x7F") { // single byte
+                $buf .= $c1;
+            } elseif ($c1 <= "\xC1") { // single byte (invalid)
+                $buf .= '?';
+            } elseif ($c1 <= "\xDF") { // 2 byte
+                $c2 = $i + 1 >= $max ? "\x00" : $text[$i + 1];
+
+                if ($c2 >= "\x80" && $c2 <= "\xBF") {
+                    $buf .= $c1 . $c2;
+                    $i   += 1;
+                } else {
+                    $buf .= '?';
+                }
+            } elseif ($c1 <= "\xEF") { // 3 bytes
+                $c2 = $i + 1 >= $max ? "\x00" : $text[$i + 1];
+                $c3 = $i + 2 >= $max ? "\x00" : $text[$i + 2];
+
+                if ($c2 >= "\x80" && $c2 <= "\xbf" && $c3 >= "\x80" && $c3 <= "\xbf") {
+                    $buf .= $c1 . $c2 . $c3;
+                    $i   += 2;
+                } else {
+                    $buf .= '?';
+                }
+            } else if ($c1 <= "\xF4") { //Should be converted to UTF8, if it's not UTF8 already
                 $c2 = $i + 1 >= $max ? "\x00" : $text[$i + 1];
                 $c3 = $i + 2 >= $max ? "\x00" : $text[$i + 2];
                 $c4 = $i + 3 >= $max ? "\x00" : $text[$i + 3];
 
-                if ($c1 >= "\xc0" & $c1 <= "\xdf") { //looks like 2 bytes UTF8
+                if ($c2 >= "\x80" && $c2 <= "\xbf" && $c3 >= "\x80" && $c3 <= "\xbf" && $c4 >= "\x80" && $c4 <= "\xbf") {
-                    if ($c2 >= "\x80" && $c2 <= "\xbf") { //yeah, almost sure it's UTF8 already
-                        $buf .= $c1 . $c2;
-                        $i++;
-                    } else { //not valid UTF8.  Convert it.
-                        $buf .= '?';
-                    }
-                } elseif ($c1 >= "\xe0" & $c1 <= "\xef") { //looks like 3 bytes UTF8
-                    if ($c2 >= "\x80" && $c2 <= "\xbf" && $c3 >= "\x80" && $c3 <= "\xbf") { //yeah, almost sure it's UTF8 already
-                        $buf .= $c1 . $c2 . $c3;
-                        $i   += 2;
-                    } else { //not valid UTF8.  Convert it.
-                        $buf .= '?';
-                    }
-                } elseif ($c1 >= "\xf0" & $c1 <= "\xf7") { //looks like 4 bytes UTF8
-                    if ($c2 >= "\x80" && $c2 <= "\xbf" && $c3 >= "\x80" && $c3 <= "\xbf" && $c4 >= "\x80" && $c4 <= "\xbf") { //yeah, almost sure it's UTF8 already
                     $buf .= $c1 . $c2 . $c3 . $c4;
                     $i   += 3;
-                    } else { //not valid UTF8.  Convert it.
+                } else {
                     $buf .= '?';
                 }
-                } else { //doesn't look like UTF8, but should be converted
+            } else { // invalid
                 $buf .= '?';
             }
-            } elseif (($c1 & "\xc0") === "\x80") { // needs conversion
-                $buf .= '?';
-            } else { // it doesn't need conversion
-                $buf .= $c1;
-            }
         }
 
         return $buf;

tests/Fetch/Test/UTF8Test.php

@@ -0,0 +1,39 @@
+<?php
+
+namespace Fetch\Test;
+
+use Fetch\UTF8;
+
+/**
+ * @package Fetch
+ * @author  Robert Hafner <tedivm@tedivm.com>
+ * @author  Sergey Linnik <linniksa@gmail.com>
+ */
+class UTF8Test extends \PHPUnit_Framework_TestCase
+{
+    public function dataFix()
+    {
+        return array(
+            array(
+                'ab11 ? ?????.jpg',
+                "\x61\x62\x31\x31\x20\x97\x20\x3f\x3f\x3f\x3f\x3f\x2e\x6a\x70\x67",
+            ),
+            array(
+                ' ??????????????',
+                base64_decode('IKytrKastKyhrMCsu6yq'),
+            )
+        );
+    }
+
+    /**
+     * @dataProvider dataFix
+     *
+     * @param string $expected
+     * @param string $text
+     * @param string $charset
+     */
+    public function testFix($expected, $text)
+    {
+        self::assertSame($expected, UTF8::fix($text));
+    }
+}