Merge pull request ZipArchive#443 from palmin/legacy-filename-encoding

don't assume entries made from dos have utf-8 filename unless flag says so

SSZipArchive/SSZipArchive.m

@@ -359,7 +359,10 @@ + (BOOL)unzipFileAtPath:(NSString *)path
 
             BOOL fileIsSymbolicLink = _fileIsSymbolicLink(&fileInfo);
 
-            NSString * strPath = [SSZipArchive _filenameStringWithCString:filename size:fileInfo.size_filename];
+            NSString * strPath = [SSZipArchive _filenameStringWithCString:filename
+                                                          version_made_by:fileInfo.version
+                                                     general_purpose_flag:fileInfo.flag
+                                                                     size:fileInfo.size_filename];
             if ([strPath hasPrefix:@"__MACOSX/"]) {
                 // ignoring resource forks: https://superuser.com/questions/104500/what-is-macosx-folder
                 unzCloseCurrentFile(zip);
@@ -856,8 +859,37 @@ - (BOOL)close
 
 #pragma mark - Private
 
-+ (NSString *)_filenameStringWithCString:(const char *)filename size:(uint16_t)size_filename
-{
++ (NSString *)_filenameStringWithCString:(const char *)filename
+                         version_made_by:(uint16_t)version_made_by
+                    general_purpose_flag:(uint16_t)flag
+                                    size:(uint16_t)size_filename {
+
+    // Respect Language encoding flag only reading filename as UTF-8 when this is set
+    // when file entry created on dos system.
+    //
+    // https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT
+    //   Bit 11: Language encoding flag (EFS).  If this bit is set,
+    //           the filename and comment fields for this file
+    //           MUST be encoded using UTF-8. (see APPENDIX D)
+    uint16_t made_by = version_made_by >> 8;
+    BOOL made_on_dos = made_by == 0;
+    BOOL languageEncoding = (flag & (1 << 11)) != 0;
+    if(!languageEncoding && made_on_dos) {
+        // APPNOTE.TXT D.1:
+        //   D.2 If general purpose bit 11 is unset, the file name and comment should conform
+        //   to the original ZIP character encoding.  If general purpose bit 11 is set, the
+        //   filename and comment must support The Unicode Standard, Version 4.1.0 or
+        //   greater using the character encoding form defined by the UTF-8 storage
+        //   specification.  The Unicode Standard is published by the The Unicode
+        //   Consortium (www.unicode.org).  UTF-8 encoded data stored within ZIP files
+        //   is expected to not include a byte order mark (BOM).
+
+        //  Code Page 437 corresponds to kCFStringEncodingDOSLatinUS
+        NSStringEncoding encoding = CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingDOSLatinUS);
+        NSString* strPath = [NSString stringWithCString:filename encoding:encoding];
+        if(strPath) return strPath;
+    }
+
     // attempting unicode encoding
     NSString * strPath = @(filename);
     if (strPath) {