Bug #81390: mb_detect_encoding should not prematurely stop processing…

… input

As a performance optimization, mb_detect_encoding tries to stop
processing the input string early when there is only one 'candidate'
encoding which the input string is valid in. However, the code which
keeps count of how many candidate encodings have already been rejected
was buggy. This caused mb_detect_encoding to prematurely stop
processing the input when it should have continued.

As a result, it did not notice that in the test case provided by Alec,
the input string was not valid in UTF-16.

ext/mbstring/libmbfl/mbfl/mbfilter.c

@@ -352,9 +352,10 @@ int mbfl_encoding_detector_feed(mbfl_encoding_detector *identd, mbfl_string *str
 	while (n--) {
 		for (int i = 0; i < num; i++) {
 			mbfl_convert_filter *filter = identd->filter_list[i];
-			if (!filter->num_illegalchar) {
+			mbfl_encoding_detector_data *data = &identd->filter_data[i];
+			if (!data->num_illegalchars) {
 				(*filter->filter_function)(*p, filter);
-				if (identd->filter_data[i].num_illegalchars) {
+				if (data->num_illegalchars) {
 					bad++;
 				}
 			}

ext/mbstring/tests/mb_detect_encoding.phpt

@@ -34,8 +34,6 @@ $s = $euc_jp;
 $s = mb_detect_encoding($s, 'JIS,EUC-JP');
 print("EUC-JP: $s\n");
 
-
-
 // Using Encoding List Array
 echo "== ARRAY ENCODING LIST ==\n";
 
@@ -53,6 +51,15 @@ $s = $sjis;
 $s = mb_detect_encoding($s, $a);
 print("SJIS: $s\n");
 
+$test = "CHARSET=windows-1252:Do\xeb;John";
+$encodings = ['UTF-8', 'SJIS', 'GB2312',
+         'ISO-8859-1', 'ISO-8859-2', 'ISO-8859-3', 'ISO-8859-4',
+         'ISO-8859-5', 'ISO-8859-6', 'ISO-8859-7', 'ISO-8859-8', 'ISO-8859-9',
+         'ISO-8859-10', 'ISO-8859-13', 'ISO-8859-14', 'ISO-8859-15', 'ISO-8859-16',
+         'WINDOWS-1252', 'WINDOWS-1251', 'EUC-JP', 'EUC-TW', 'KOI8-R', 'BIG-5',
+         'ISO-2022-KR', 'ISO-2022-JP', 'UTF-16'
+];
+echo mb_detect_encoding($test, $encodings), "\n";
 
 // Using Detect Order
 echo "== DETECT ORDER ==\n";
@@ -100,6 +107,7 @@ EUC-JP: EUC-JP
 JIS: JIS
 EUC-JP: EUC-JP
 SJIS: SJIS
+ISO-8859-1
 == DETECT ORDER ==
 JIS: JIS
 EUC-JP: EUC-JP