Avoid caching file status when they are about to change

* java/org/gnu/emacs/EmacsSafThread.java (EmacsSafThread)
(cacheFileStatus): New argument NO_CACHE.
(cacheDirectoryFromCursor, statDocument1):
* java/org/gnu/emacs/EmacsService.java (EmacsService)
(statDocument): Plumb that argument through each of these wrapper
functions.
* src/android.c (android_init_emacs_service): Adjust JNI
function signatures to agree with statDocument1.
* src/androidvfs.c (android_saf_stat): Plumb that argument
through here.
(android_saf_tree_stat, android_saf_file_open): And don't cache
file status if a write is imminent.

2 files changed, 19 insertions, 9 deletions

diff --git a/src/android.c b/src/android.c
index 7f263bc83d1..705ef227df3 100644
--- a/src/android.c
+++ b/src/android.c
@@ -1564,7 +1564,7 @@ android_init_emacs_service (void)
                "(Ljava/lang/String;Ljava/lang/String;)"
                "Ljava/lang/String;");
   FIND_METHOD (stat_document, "statDocument",
-               "(Ljava/lang/String;Ljava/lang/String;)[J");
+               "(Ljava/lang/String;Ljava/lang/String;Z)[J");
   FIND_METHOD (access_document, "accessDocument",
                "(Ljava/lang/String;Ljava/lang/String;Z)I");
   FIND_METHOD (open_document_directory, "openDocumentDirectory",
diff --git a/src/androidvfs.c b/src/androidvfs.c
index 8e742f8b26f..0385e7348c6 100644
--- a/src/androidvfs.c
+++ b/src/androidvfs.c
@@ -3932,12 +3932,15 @@ android_saf_exception_check (int n, ...)
 /* Return file status for the document designated by ID_NAME within
    the document tree identified by URI_NAME.
 
+   If NO_CACHE, don't cache the resulting file status.  Enable this
+   option if the file status is subject to imminent change.
+
    If the file status is available, place it within *STATB and return
    0.  If not, return -1 and set errno to EPERM.  */
 
 static int
 android_saf_stat (const char *uri_name, const char *id_name,
-                  struct stat *statb)
+                  struct stat *statb, bool no_cache)
 {
   jmethodID method;
   jstring uri, id;
@@ -3969,10 +3972,12 @@ android_saf_stat (const char *uri_name, const char *id_name,
   /* Try to retrieve the file status.  */
   method = service_class.stat_document;
   inside_saf_critical_section = true;
-  status = (*android_java_env)->CallNonvirtualObjectMethod (android_java_env,
-                                                            emacs_service,
-                                                            service_class.class,
-                                                            method, uri, id);
+  status
+    = (*android_java_env)->CallNonvirtualObjectMethod (android_java_env,
+                                                       emacs_service,
+                                                       service_class.class,
+                                                       method, uri, id,
+                                                       (jboolean) no_cache);
   inside_saf_critical_section = false;
 
   /* Check for exceptions and release unneeded local references.  */
@@ -5076,7 +5081,7 @@ android_saf_tree_stat (struct android_vnode *vnode,
   vp = (struct android_saf_tree_vnode *) vnode;
 
   return android_saf_stat (vp->tree_uri, vp->document_id,
-                           statb);
+                           statb, false);
 }
 
 static int
@@ -5716,10 +5721,15 @@ android_saf_file_open (struct android_vnode *vnode, int flags,
   ANDROID_DELETE_LOCAL_REF (descriptor);
 
   /* Try to retrieve the modification time of this file from the
-     content provider.  */
+     content provider.
+
+     Refrain from introducing the file status into the file status
+     cache if FLAGS & O_RDWR or FLAGS & O_WRONLY: the cached file
+     status will contain a size and modification time inconsistent
+     with the result of any modifications that later transpire.  */
 
   if (!android_saf_stat (vp->tree_uri, vp->document_id,
-                         &statb))
+                         &statb, write))
     info->mtime = get_stat_mtime (&statb);
   else
     info->mtime = invalid_timespec ();