Restore multipart RAR open strategy for JVM extractor

Bring back callback-first RAR multipart opening with explicit RAR5/RAR fallback while keeping 7z.001 on VolumedArchiveInStream to improve 7z-JBinding compatibility on split RAR sets.

resources/extractor-jvm/src/com/sucukdeluxe/extractor/JBindExtractorMain.java

@@ -11,6 +11,7 @@ import net.sf.sevenzipjbinding.IInStream;
 import net.sf.sevenzipjbinding.ISequentialOutStream;
 import net.sf.sevenzipjbinding.ICryptoGetTextPassword;
 import net.sf.sevenzipjbinding.PropID;
+import net.sf.sevenzipjbinding.ArchiveFormat;
 import net.sf.sevenzipjbinding.SevenZip;
 import net.sf.sevenzipjbinding.SevenZipException;
 import net.sf.sevenzipjbinding.impl.RandomAccessFileInStream;
@@ -42,6 +43,8 @@ public final class JBindExtractorMain {
     private static final Pattern NUMBERED_ZIP_SPLIT_RE = Pattern.compile("(?i).*\\.zip\\.\\d{3}$");
     private static final Pattern OLD_ZIP_SPLIT_RE = Pattern.compile("(?i).*\\.z\\d{2,3}$");
     private static final Pattern SEVEN_ZIP_SPLIT_RE = Pattern.compile("(?i).*\\.7z\\.001$");
+    private static final Pattern RAR_MULTIPART_RE = Pattern.compile("(?i).*\\.part\\d+\\.rar$");
+    private static final Pattern RAR_OLDSPLIT_RE = Pattern.compile("(?i).*\\.r\\d{2,3}$");
     private static volatile boolean sevenZipInitialized = false;
 
     private JBindExtractorMain() {
@@ -327,21 +330,78 @@ public final class JBindExtractorMain {
         SevenZipVolumeCallback callback = new SevenZipVolumeCallback(archiveFile, effectivePassword);
 
         // VolumedArchiveInStream is ONLY for .7z.001 split archives.
+        // It internally checks for the ".7z.001" suffix and rejects everything else.
         if (SEVEN_ZIP_SPLIT_RE.matcher(nameLower).matches()) {
             VolumedArchiveInStream volumed = new VolumedArchiveInStream(archiveFile.getName(), callback);
             IInArchive archive = SevenZip.openInArchive(null, volumed, callback);
             return new SevenZipArchiveContext(archive, null, volumed, callback);
         }
 
-        // All other archives (including multi-part RAR): use RandomAccessFileInStream
+        // Multi-part RAR (.part1.rar, .part2.rar or old-style .rar/.r01/.r02):
-        // with auto-detection. The IArchiveOpenVolumeCallback handles additional
+        // The first stream MUST be obtained via the callback so the volume name
-        // volumes when 7z-JBinding requests them.
+        // tracker is properly initialized. 7z-JBinding uses getProperty(NAME)
+        // to compute subsequent volume filenames.
+        boolean isMultiPartRar = RAR_MULTIPART_RE.matcher(nameLower).matches()
+            || hasOldStyleRarSplits(archiveFile);
+
+        if (isMultiPartRar) {
+            IInStream inStream = callback.getStream(archiveFile.getAbsolutePath());
+            if (inStream == null) {
+                throw new IOException("Archiv konnte nicht geoeffnet werden: " + archiveFile.getAbsolutePath());
+            }
+            // Try RAR5 first (modern), then RAR4, then auto-detect
+            Exception lastError = null;
+            ArchiveFormat[] rarFormats = { ArchiveFormat.RAR5, ArchiveFormat.RAR, null };
+            for (ArchiveFormat fmt : rarFormats) {
+                try {
+                    inStream.seek(0L, 0);
+                    IInArchive archive = SevenZip.openInArchive(fmt, inStream, callback);
+                    return new SevenZipArchiveContext(archive, null, null, callback);
+                } catch (Exception e) {
+                    lastError = e;
+                }
+            }
+            callback.close();
+            throw lastError != null ? lastError : new IOException("Archiv konnte nicht geoeffnet werden");
+        }
+
+        // Single-file archives: open directly with auto-detection
         RandomAccessFile raf = new RandomAccessFile(archiveFile, "r");
         RandomAccessFileInStream stream = new RandomAccessFileInStream(raf);
         IInArchive archive = SevenZip.openInArchive(null, stream, callback);
         return new SevenZipArchiveContext(archive, stream, null, callback);
     }
 
+    private static boolean hasOldStyleRarSplits(File archiveFile) {
+        // Old-style RAR splits: main.rar + main.r01, main.r02, ...
+        String name = archiveFile.getName();
+        if (!name.toLowerCase(Locale.ROOT).endsWith(".rar")) {
+            return false;
+        }
+        File parent = archiveFile.getParentFile();
+        if (parent == null || !parent.exists()) {
+            return false;
+        }
+        File[] siblings = parent.listFiles();
+        if (siblings == null) {
+            return false;
+        }
+        String stem = name.substring(0, name.length() - 4);
+        for (File sibling : siblings) {
+            if (!sibling.isFile()) {
+                continue;
+            }
+            String sibName = sibling.getName();
+            if (sibName.length() > stem.length() + 1 && sibName.substring(0, stem.length()).equalsIgnoreCase(stem)) {
+                String suffix = sibName.substring(stem.length());
+                if (RAR_OLDSPLIT_RE.matcher(suffix).matches() || suffix.toLowerCase(Locale.ROOT).matches("\\.r\\d{2,3}")) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
     private static boolean isWrongPassword(ZipException error, boolean encrypted) {
         if (error == null) {
             return false;