Add VDir.isEmpty() method

- Add also in VFSBase
- Add implementations everywhere
- Use in CaseInsensitiveFS to differentiate between a clean new VFS
  or a VFS without the index file

Change-Id: I699afbb6c0ca5985a2e6424ebcc0899033a6f6a7

7 files changed, 40 insertions, 8 deletions

diff --git a/sched/src/com/android/sched/vfs/BaseVDir.java b/sched/src/com/android/sched/vfs/BaseVDir.java
index 73dd3796..8ee6a96f 100644
--- a/sched/src/com/android/sched/vfs/BaseVDir.java
+++ b/sched/src/com/android/sched/vfs/BaseVDir.java
@@ -129,6 +129,11 @@ abstract class BaseVDir extends BaseVElement implements VDir {
   }
 
   @Override
+  public boolean isEmpty() {
+    return vfs.isEmpty(this);
+  }
+
+  @Override
   public boolean isVDir() {
     return true;
   }
diff --git a/sched/src/com/android/sched/vfs/BaseVFS.java b/sched/src/com/android/sched/vfs/BaseVFS.java
index a5c5ba9a..e5ba32bb 100644
--- a/sched/src/com/android/sched/vfs/BaseVFS.java
+++ b/sched/src/com/android/sched/vfs/BaseVFS.java
@@ -74,7 +74,9 @@ abstract class BaseVFS<DIR extends BaseVDir, FILE extends BaseVFile> implements
   abstract void delete(@Nonnull FILE file) throws CannotDeleteFileException;
 
   @Nonnull
-  abstract Collection<? extends BaseVElement> list(DIR dir);
+  abstract Collection<? extends BaseVElement> list(@Nonnull DIR dir);
+
+  abstract boolean isEmpty(@Nonnull DIR dir);
 
   //
   // Location related
diff --git a/sched/src/com/android/sched/vfs/CaseInsensitiveFS.java b/sched/src/com/android/sched/vfs/CaseInsensitiveFS.java
index 4a021e75..acd3bf86 100644
--- a/sched/src/com/android/sched/vfs/CaseInsensitiveFS.java
+++ b/sched/src/com/android/sched/vfs/CaseInsensitiveFS.java
@@ -150,7 +150,11 @@ public class CaseInsensitiveFS extends BaseVFS<CaseInsensitiveVDir, CaseInsensit
       try {
         file = vfs.getRootDir().getVFile(INDEX_NAME);
       } catch (NoSuchFileException e) {
-        // No file index, consider FS empty
+        if (!vfs.getRootDir().isEmpty()) {
+          // If VFS is not empty, index file is missing
+          throw new WrongVFSFormatException(this, vfs.getLocation(), e);
+        }
+
         return;
       } catch (NotFileException e) {
         throw new WrongVFSFormatException(this, vfs.getLocation(), e);
@@ -366,6 +370,11 @@ public class CaseInsensitiveFS extends BaseVFS<CaseInsensitiveVDir, CaseInsensit
     throw new UnsupportedOperationException();
   }
 
+  @Override
+  boolean isEmpty(@Nonnull CaseInsensitiveVDir dir) {
+    throw new UnsupportedOperationException();
+  }
+
   //
   // Location
   //
@@ -417,10 +426,6 @@ public class CaseInsensitiveFS extends BaseVFS<CaseInsensitiveVDir, CaseInsensit
     return vfs.needsSequentialWriting();
   }
 
-  synchronized boolean isClosed() {
-    return closed;
-  }
-
   //
   // Encode / Decode
   //
diff --git a/sched/src/com/android/sched/vfs/DeflateFS.java b/sched/src/com/android/sched/vfs/DeflateFS.java
index 3a362d9c..84815813 100644
--- a/sched/src/com/android/sched/vfs/DeflateFS.java
+++ b/sched/src/com/android/sched/vfs/DeflateFS.java
@@ -106,6 +106,11 @@ public class DeflateFS extends BaseVFS<BaseVDir, BaseVFile> implements VFS{
   }
 
   @Override
+  boolean isEmpty(@Nonnull BaseVDir dir) {
+    return vfs.isEmpty(dir);
+  }
+
+  @Override
   @Nonnull
   BaseVFile createVFile(@Nonnull BaseVDir parent, @Nonnull String name)
       throws CannotCreateFileException {
diff --git a/sched/src/com/android/sched/vfs/DirectFS.java b/sched/src/com/android/sched/vfs/DirectFS.java
index 030c30e1..fbf1f9c9 100644
--- a/sched/src/com/android/sched/vfs/DirectFS.java
+++ b/sched/src/com/android/sched/vfs/DirectFS.java
@@ -147,6 +147,14 @@ public class DirectFS extends BaseVFS<ParentVDir, ParentVFile> implements VFS {
   }
 
   @Override
+  boolean isEmpty(@Nonnull ParentVDir dir) {
+    assert !isClosed();
+    assert (permissions & Permission.READ) != 0;
+
+    return getNativeFile(dir.getPath()).listFiles().length == 0;
+  }
+
+  @Override
   @Nonnull
   ParentVFile createVFile(@Nonnull ParentVDir parent, @Nonnull String name)
       throws CannotCreateFileException {
diff --git a/sched/src/com/android/sched/vfs/InMemoryVDir.java b/sched/src/com/android/sched/vfs/InMemoryVDir.java
index 43809ad0..8d476b52 100644
--- a/sched/src/com/android/sched/vfs/InMemoryVDir.java
+++ b/sched/src/com/android/sched/vfs/InMemoryVDir.java
@@ -33,8 +33,8 @@ import javax.annotation.Nonnull;
  * A 'in-memory' implementation of a {@link VDir}. All sub-elements are cached in-memory for ever.
  *
  * When using this {@link VDir} implementation, a {@link BaseVFS} implementation has no need to
- * implement {@link BaseVFS#getVFile(BaseVDir, String)}, {@link BaseVFS#getVDir(BaseVDir, String)}
- * and {@link BaseVFS#list(BaseVDir)}.
+ * implement {@link BaseVFS#getVFile(BaseVDir, String)}, {@link BaseVFS#getVDir(BaseVDir, String)},
+ * {@link BaseVFS#isEmpty(BaseVDir)} and {@link BaseVFS#list(BaseVDir)}.
  */
 abstract class InMemoryVDir extends BaseVDir {
   @Nonnull
@@ -132,5 +132,10 @@ abstract class InMemoryVDir extends BaseVDir {
 
     return Collections.unmodifiableCollection(map.values());
   }
+
+  @Override
+  public boolean isEmpty() {
+    return map.isEmpty();
+  }
 }
 
diff --git a/sched/src/com/android/sched/vfs/VDir.java b/sched/src/com/android/sched/vfs/VDir.java
index 63792e75..2720ecdf 100644
--- a/sched/src/com/android/sched/vfs/VDir.java
+++ b/sched/src/com/android/sched/vfs/VDir.java
@@ -34,6 +34,8 @@ public interface VDir extends VElement, HasLocation {
   @Nonnull
   VPath getPath();
 
+  boolean isEmpty();
+
   @Nonnull
   Collection<? extends VElement> list();