3 files changed, 91 insertions, 8 deletions

diff --git a/java/org/gnu/emacs/EmacsNative.java b/java/org/gnu/emacs/EmacsNative.java
index 898eaef41a7..654e94b1a7d 100644
--- a/java/org/gnu/emacs/EmacsNative.java
+++ b/java/org/gnu/emacs/EmacsNative.java
@@ -281,7 +281,7 @@ public final class EmacsNative
   public static native int[] getSelection (short window);
 
 
-  /* Graphics functions used as a replacement for potentially buggy
+  /* Graphics functions used as replacements for potentially buggy
      Android APIs.  */
 
   public static native void blitRect (Bitmap src, Bitmap dest, int x1,
@@ -289,7 +289,6 @@ public final class EmacsNative
 
   /* Increment the generation ID of the specified BITMAP, forcing its
      texture to be re-uploaded to the GPU.  */
-
   public static native void notifyPixelsChanged (Bitmap bitmap);
 
 
@@ -313,6 +312,13 @@ public final class EmacsNative
      in the process.  */
   public static native boolean ftruncate (int fd);
 
+
+  /* Functions that assist in generating content file names.  */
+
+  /* Calculate an 8 digit checksum for the byte array DISPLAYNAME
+     suitable for inclusion in a content file name.  */
+  public static native String displayNameHash (byte[] displayName);
+
   static
   {
     /* Older versions of Android cannot link correctly with shared
diff --git a/java/org/gnu/emacs/EmacsOpenActivity.java b/java/org/gnu/emacs/EmacsOpenActivity.java
index 9ae1bf353dd..2cdfa2ec776 100644
--- a/java/org/gnu/emacs/EmacsOpenActivity.java
+++ b/java/org/gnu/emacs/EmacsOpenActivity.java
@@ -252,7 +252,7 @@ public final class EmacsOpenActivity extends Activity
 
     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT)
       {
-        content = EmacsService.buildContentName (uri);
+        content = EmacsService.buildContentName (uri, getContentResolver ());
         return content;
       }
 
@@ -423,6 +423,7 @@ public final class EmacsOpenActivity extends Activity
     /* Obtain the intent that started Emacs.  */
     intent = getIntent ();
     action = intent.getAction ();
+    resolver = getContentResolver ();
 
     if (action == null)
       {
@@ -536,7 +537,7 @@ public final class EmacsOpenActivity extends Activity
                 if ((scheme = uri.getScheme ()) != null
                     && scheme.equals ("content"))
                   {
-                    tem1 = EmacsService.buildContentName (uri);
+                    tem1 = EmacsService.buildContentName (uri, resolver);
                     attachmentString = ("'(\"" + (tem1.replace ("\\", "\\\\")
                                                   .replace ("\"", "\\\"")
                                                   .replace ("$", "\\$"))
@@ -568,7 +569,8 @@ public final class EmacsOpenActivity extends Activity
                             && (scheme = uri.getScheme ()) != null
                             && scheme.equals ("content"))
                           {
-                            tem1 = EmacsService.buildContentName (uri);
+                            tem1
+                              = EmacsService.buildContentName (uri, resolver);
                             builder.append ("\"");
                             builder.append (tem1.replace ("\\", "\\\\")
                                             .replace ("\"", "\\\"")
@@ -609,7 +611,6 @@ public final class EmacsOpenActivity extends Activity
                    underlying file, but it cannot be found without
                    opening the file and doing readlink on its file
                    descriptor in /proc/self/fd.  */
-                resolver = getContentResolver ();
                 fd = null;
 
                 try
diff --git a/java/org/gnu/emacs/EmacsService.java b/java/org/gnu/emacs/EmacsService.java
index 9bc40d63311..19aa3dee456 100644
--- a/java/org/gnu/emacs/EmacsService.java
+++ b/java/org/gnu/emacs/EmacsService.java
@@ -79,6 +79,7 @@ import android.os.VibrationEffect;
 
 import android.provider.DocumentsContract;
 import android.provider.DocumentsContract.Document;
+import android.provider.OpenableColumns;
 import android.provider.Settings;
 
 import android.util.Log;
@@ -1033,22 +1034,87 @@ public final class EmacsService extends Service
     return false;
   }
 
+  /* Return a 8 character checksum for the string STRING, after encoding
+     as UTF-8 data.  */
+
+  public static String
+  getDisplayNameHash (String string)
+  {
+    byte[] encoded;
+
+    try
+      {
+        encoded = string.getBytes ("UTF-8");
+        return EmacsNative.displayNameHash (encoded);
+      }
+    catch (UnsupportedEncodingException exception)
+      {
+        /* This should be impossible.  */
+        return "error";
+      }
+  }
+
   /* Build a content file name for URI.
 
      Return a file name within the /contents/by-authority
      pseudo-directory that `android_get_content_name' can then
      transform back into an encoded URI.
 
+     If a display name can be requested from URI (using the resolver
+     RESOLVER), append it to this file name.
+
      A content name consists of any number of unencoded path segments
      separated by `/' characters, possibly followed by a question mark
      and an encoded query string.  */
 
   public static String
-  buildContentName (Uri uri)
+  buildContentName (Uri uri, ContentResolver resolver)
   {
     StringBuilder builder;
+    String displayName;
+    String[] projection;
+    Cursor cursor;
+    int column;
+
+    displayName = null;
+    cursor      = null;
 
-    builder = new StringBuilder ("/content/by-authority/");
+    try
+      {
+        projection = new String[] { OpenableColumns.DISPLAY_NAME, };
+        cursor = resolver.query (uri, projection, null, null, null);
+
+        if (cursor != null)
+          {
+            cursor.moveToFirst ();
+            column
+              = cursor.getColumnIndexOrThrow (OpenableColumns.DISPLAY_NAME);
+            displayName
+              = cursor.getString (column);
+
+            /* Verify that the display name is valid, i.e. it
+               contains no characters unsuitable for a file name and
+               is nonempty.  */
+            if (displayName.isEmpty () || displayName.contains ("/"))
+              displayName = null;
+          }
+      }
+    catch (Exception e)
+      {
+        /* Ignored.  */
+      }
+    finally
+      {
+        if (cursor != null)
+          cursor.close ();
+      }
+
+    /* If a display name is available, at this point it should be the
+       value of displayName.  */
+
+    builder = new StringBuilder (displayName != null
+                                 ? "/content/by-authority-named/"
+                                 : "/content/by-authority/");
     builder.append (uri.getAuthority ());
 
     /* First, append each path segment.  */
@@ -1065,6 +1131,16 @@ public final class EmacsService extends Service
     if (uri.getEncodedQuery () != null)
       builder.append ('?').append (uri.getEncodedQuery ());
 
+    /* Append the display name.  */
+
+    if (displayName != null)
+      {
+        builder.append ('/');
+        builder.append (getDisplayNameHash (displayName));
+        builder.append ('/');
+        builder.append (displayName);
+      }
+
     return builder.toString ();
   }