Initial working implementation.

Several nice to haves are still missing. But I will add those later.

Author: marchermans

src/main/java/cpw/mods/niofs/layzip/LayeredZipFileSystemProvider.java

@@ -0,0 +1,137 @@
+package cpw.mods.niofs.layzip;
+
+import cpw.mods.niofs.pathfs.PathFileSystemProvider;
+import cpw.mods.niofs.pathfs.PathPath;
+
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.nio.file.FileSystem;
+import java.nio.file.FileSystems;
+import java.nio.file.Path;
+import java.util.Locale;
+import java.util.Map;
+
+public class LayeredZipFileSystemProvider extends PathFileSystemProvider
+{
+    public static final String SCHEME    = "jij";
+    public static final String INDICATOR = "!";
+    public static final String SEPARATOR =  INDICATOR + "/";
+
+
+    @Override
+    public String getScheme() {
+        return SCHEME;
+    }
+
+    @Override
+    public FileSystem newFileSystem(final URI uri, final Map<String, ?> env) throws IOException
+    {
+        final String[] sections = uri.getRawSchemeSpecificPart().split(SEPARATOR);
+        FileSystem workingSystem = FileSystems.getDefault(); //Grab the normal disk FS.
+
+        String keyPrefix = "";
+
+        if (sections.length > 1) {
+            for (int i = 0; i < sections.length - 1; i++)
+            {
+                String section = sections[i];
+                if (section.startsWith("//"))
+                    section = section.substring(2);
+
+                section = handleAbsolutePrefixOnWindows(workingSystem, section);
+                final Path path = workingSystem.getPath(section).toAbsolutePath();
+                workingSystem = getOrCreateNewSystem(keyPrefix, path);
+                keyPrefix += path.toString().replace("\\", "/") + INDICATOR;
+            }
+        }
+
+        String lastSection = sections[sections.length - 1];
+        if (lastSection.startsWith("//"))
+            lastSection = lastSection.substring(2);
+
+
+        final Path lastPath = workingSystem.getPath(lastSection).toAbsolutePath();
+        return getOrCreateNewSystem(keyPrefix, lastPath);
+    }
+
+    private String handleAbsolutePrefixOnWindows(final FileSystem workingSystem, String section)
+    {
+        if (workingSystem.getClass().getName().toLowerCase(Locale.ROOT).contains("windows")) {
+            //This special casing is needed, since else the rooted paths crash on Windows system because:
+            // /D:/something is not a valid path on Windows.
+            //However, the JDK does not expose the Windows FS types and there are no marker classes, so we use the classname.
+            //Because we are fancy like that.
+            if (section.startsWith("/"))
+                section = section.substring(1); //Turns /D:/something into D:/Something which is a valid windows path.
+        }
+        return section;
+    }
+
+    private FileSystem getOrCreateNewSystem(final Path path)
+    {
+        return getOrCreateNewSystem("", path);
+    }
+
+    private FileSystem getOrCreateNewSystem(String keyPrefix, final Path path)
+    {
+        final Map<String, ?> args = Map.of("packagePath", path.toAbsolutePath());
+        try
+        {
+            return super.newFileSystem(new URI(super.getScheme() + ":" + keyPrefix + path.toString().replace("\\", "/")), args);
+        }
+        catch (Exception e)
+        {
+            throw new UncheckedIOException("Failed to create intermediary FS.", new IOException("Failed to process data.", e));
+        }
+    }
+
+    @Override
+    public Path getPath(final URI uri)
+    {
+        final String[] sections = uri.getRawSchemeSpecificPart().split("~");
+        FileSystem workingSystem = FileSystems.getDefault(); //Grab the normal disk FS.
+        if (sections.length > 1) {
+            for (int i = 0; i < sections.length - 1; i++)
+            {
+                final String section = sections[i];
+                final Path path = workingSystem.getPath(section);
+                workingSystem = getOrCreateNewSystem(path);
+            }
+        }
+
+        final String lastSection = sections[sections.length - 1];
+        return workingSystem.getPath(lastSection);
+    }
+
+    @Override
+    public FileSystem getFileSystem(final URI uri)
+    {
+        final String[] sections = uri.getRawSchemeSpecificPart().split("~");
+        FileSystem workingSystem = FileSystems.getDefault(); //Grab the normal disk FS.
+        if (sections.length > 1) {
+            for (int i = 0; i < sections.length - 1; i++)
+            {
+                final String section = sections[i];
+                final Path path = workingSystem.getPath(section);
+                workingSystem = getOrCreateNewSystem(path);
+            }
+        }
+
+        final String lastSection = sections[sections.length - 1];
+        final Path lastPath = workingSystem.getPath(lastSection);
+        return getOrCreateNewSystem(lastPath);
+    }
+
+    @Override
+    protected URI buildUriFor(final PathPath path) throws URISyntaxException, IllegalArgumentException
+    {
+        String prefix = "";
+
+        final URI outerUri = path.getFileSystem().getTarget().toUri();
+        prefix = outerUri.getRawSchemeSpecificPart() + SEPARATOR;
+
+        return URI.create("%s:%s%s".formatted(SCHEME, prefix, path).replace("%s/".formatted(SEPARATOR), SEPARATOR));
+    }
+}

src/main/java/cpw/mods/niofs/pathfs/PathFSUtils.java

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+package cpw.mods.niofs.pathfs;
+
+import java.io.IOException;
+import java.nio.file.DirectoryStream;
+import java.nio.file.Path;
+import java.util.Iterator;
+import java.util.function.Function;
+
+class PathFSUtils
+{
+
+    private PathFSUtils()
+    {
+        throw new IllegalStateException("Can not instantiate an instance of: PathFSUtils. This is a utility class");
+    }
+
+    public static final DirectoryStream<Path> NULL_STREAM = new DirectoryStream<>()
+    {
+        @Override
+        public Iterator<Path> iterator()
+        {
+            return new Iterator<>()
+            {
+                @Override
+                public boolean hasNext()
+                {
+                    return false;
+                }
+
+                @Override
+                public Path next()
+                {
+                    return null;
+                }
+            };
+        }
+
+        @Override
+        public void close() throws IOException
+        {
+
+        }
+    };
+
+    public static DirectoryStream<Path> adapt(final DirectoryStream<Path> inner, final Function<Path, Path> adapter) {
+        return new DirectoryStream<Path>() {
+            @Override
+            public Iterator<Path> iterator()
+            {
+                final Iterator<Path> targetIterator = inner.iterator();
+
+                return new Iterator<Path>() {
+                    @Override
+                    public boolean hasNext()
+                    {
+                        return targetIterator.hasNext();
+                    }
+
+                    @Override
+                    public Path next()
+                    {
+                        final Path targetPath = targetIterator.next();
+                        return adapter.apply(targetPath);
+                    }
+                };
+            }
+
+            @Override
+            public void close() throws IOException
+            {
+                inner.close();
+            }
+        };
+    }
+}