Respect display names of Android content URIs

* java/org/gnu/emacs/EmacsNative.java (displayNameHash): New
function.

* java/org/gnu/emacs/EmacsService.java (buildContentName): New
argument RESOLVER.  Generate names holding URI's display name if
available.  All callers changed.

* lisp/international/mule-cmds.el (set-default-coding-systems):
Fix file name coding system as utf-8-unix on Android as on Mac
OS.

* src/androidvfs.c (enum android_vnode_type): New enum
ANDROID_VNODE_CONTENT_AUTHORITY_NAMED.
(android_content_name): Register root directories for this new
type.
(displayNameHash): New function.
(android_get_content_name): New argument WITH_CHECKSUM.  If
present, treat the final two components as a pair of checksum
and display name, and verify and exclude the two.
(android_authority_name): Provide new argument as appropriate.
(android_authority_initial_name): New function.

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

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

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;
 
-    builder = new StringBuilder ("/content/by-authority/");
+    displayName = null;
+    cursor      = null;
+
+    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 ();
   }