small updates.

[vamsas.git] / src / org / vamsas / client / simpleclient / FileWatcher.java

diff --git a/src/org/vamsas/client/simpleclient/FileWatcher.java b/src/org/vamsas/client/simpleclient/FileWatcher.java
index bc9f705..a3225db 100644 (file)
--- a/src/org/vamsas/client/simpleclient/FileWatcher.java
+++ b/src/org/vamsas/client/simpleclient/FileWatcher.java
@@ -18,23 +18,29 @@ public class FileWatcher {
   private long lastStat[];
   boolean waslocked=false;
   boolean exists = false;
-
   /**
-   * Make a watcher for a particular file. If the file doesn't exist, the
-   * watcher will watch for its creation (and indicate a change of state) 
-   * For locked files, the removal of a lock constitutes a change of 
-   * state if the file was modified.
-   * 
-   * @param subject
+   * transient lock on subject - can be passed back to calling class
+   * to preserve new state of file for immediate reading.
    */
+  private Lock subjectLock = null;
+  
+  private void clearLock() {
+    if (subjectLock!=null)
+      subjectLock.release();
+    subjectLock=null;
+  }
+  
   private boolean checkLock() {
     if (subject!=null && subject.exists()) {
-      Lock tl = new Lock(subject);
-      if (tl.isLocked()) {
-        tl.release();
+      if (subjectLock!=null) {
+        subjectLock.release();
+      }
+      subjectLock = new Lock(subject);
+      if (subjectLock.isLocked()) {
+        // subjectLock.release();
         return false;
       }
-      tl.release();
+      clearLock();
       return true;
     }
     return false;
@@ -51,7 +57,7 @@ public class FileWatcher {
   /**
    * Detect changes in file state and release of any
    * lock in place during change.
-   * @return true if file state has changed
+   * @return true if file state has changed. Leaves lock in subjectLock (ready to be passed to caller)
    */
   private boolean check() {
     if (subject != null) {
@@ -87,21 +93,54 @@ public class FileWatcher {
     }
     return false;
   }
+  /**
+   * updates internal record of file state when caller has intentionally
+   * modified subject. (ignores locked-state of subject)
+   */
   public void setState() {
     if (subject!=null) {
-      lastStat = getStat(subject);
-      exists = subject.exists();
-      waslocked = checkLock();
+      if (exists = subject.exists()) {
+        lastStat = getStat(subject);
+        waslocked = false;
+      }
     }
   }
   
+  /**
+   * Make a watcher for a particular file. If the file doesn't exist, the
+   * watcher will watch for its creation (and indicate a change of state) 
+   * For locked files, the removal of a lock constitutes a change of 
+   * state if the file was modified.
+   * 
+   * @param subject
+   */
+  
   public FileWatcher(File subject) {
     // TODO Auto-generated constructor stub
     this.subject = subject;
     setState();
   }
-
+  /**
+   * Test for change in file state. Only indicates a change 
+   * after any lock on a file has been released.
+   * @return true if file has been modified.
+   */
   public boolean hasChanged() {
-    return check();
+    boolean res = check();
+    clearLock();
+    return res;
+  }
+  /**
+   * passes lock back to caller if hasChanged returned true.
+   * @return
+   */
+  public Lock getChangedState() {
+    boolean res = check();
+    if (res)
+      return subjectLock;
+    else {
+      clearLock();
+      return null;
+    }
   }
 }