Android: Add content provider support to File::ScanDirectoryTree

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/utils/ContentHandler.java

@@ -14,15 +14,16 @@ import androidx.annotation.Keep;
 import org.dolphinemu.dolphinemu.DolphinApplication;
 
 import java.io.FileNotFoundException;
+import java.util.List;
 
 public class ContentHandler
 {
   @Keep
-  public static int openFd(String uri, String mode)
+  public static int openFd(@NonNull String uri, @NonNull String mode)
   {
     try
     {
-      return getContentResolver().openFileDescriptor(Uri.parse(uri), mode).detachFd();
+      return getContentResolver().openFileDescriptor(unmangle(uri), mode).detachFd();
     }
     catch (SecurityException e)
     {
@@ -38,11 +39,11 @@ public class ContentHandler
   }
 
   @Keep
-  public static boolean delete(String uri)
+  public static boolean delete(@NonNull String uri)
   {
     try
     {
-      return DocumentsContract.deleteDocument(getContentResolver(), Uri.parse(uri));
+      return DocumentsContract.deleteDocument(getContentResolver(), unmangle(uri));
     }
     catch (SecurityException e)
     {
@@ -60,8 +61,9 @@ public class ContentHandler
   {
     try
     {
+      Uri documentUri = treeToDocument(unmangle(uri));
       final String[] projection = new String[]{Document.COLUMN_MIME_TYPE, Document.COLUMN_SIZE};
-      try (Cursor cursor = getContentResolver().query(Uri.parse(uri), projection, null, null, null))
+      try (Cursor cursor = getContentResolver().query(documentUri, projection, null, null, null))
       {
         return cursor != null && cursor.getCount() > 0;
       }
@@ -70,6 +72,9 @@ public class ContentHandler
     {
       Log.error("Tried to check if " + uri + " exists without permission");
     }
+    catch (FileNotFoundException ignored)
+    {
+    }
 
     return false;
   }
@@ -78,38 +83,53 @@ public class ContentHandler
    * @return -1 if not found, -2 if directory, file size otherwise
    */
   @Keep
-  public static long getSizeAndIsDirectory(String uri)
+  public static long getSizeAndIsDirectory(@NonNull String uri)
   {
-    final String[] projection = new String[]{Document.COLUMN_MIME_TYPE, Document.COLUMN_SIZE};
-    try (Cursor cursor = getContentResolver().query(Uri.parse(uri), projection, null, null, null))
+    try
     {
-      if (cursor != null && cursor.moveToFirst())
+      Uri documentUri = treeToDocument(unmangle(uri));
+      final String[] projection = new String[]{Document.COLUMN_MIME_TYPE, Document.COLUMN_SIZE};
+      try (Cursor cursor = getContentResolver().query(documentUri, projection, null, null, null))
       {
-        if (Document.MIME_TYPE_DIR.equals(cursor.getString(0)))
-          return -2;
-        else
-          return cursor.isNull(1) ? 0 : cursor.getLong(1);
+        if (cursor != null && cursor.moveToFirst())
+        {
+          if (Document.MIME_TYPE_DIR.equals(cursor.getString(0)))
+            return -2;
+          else
+            return cursor.isNull(1) ? 0 : cursor.getLong(1);
+        }
       }
     }
     catch (SecurityException e)
     {
       Log.error("Tried to get metadata for " + uri + " without permission");
     }
+    catch (FileNotFoundException ignored)
+    {
+    }
 
     return -1;
   }
 
   @Nullable @Keep
-  public static String getDisplayName(String uri)
+  public static String getDisplayName(@NonNull String uri)
   {
-    return getDisplayName(Uri.parse(uri));
+    try
+    {
+      return getDisplayName(unmangle(uri));
+    }
+    catch (FileNotFoundException e)
+    {
+      return null;
+    }
   }
 
   @Nullable
   public static String getDisplayName(@NonNull Uri uri)
   {
     final String[] projection = new String[]{Document.COLUMN_DISPLAY_NAME};
-    try (Cursor cursor = getContentResolver().query(uri, projection, null, null, null))
+    Uri documentUri = treeToDocument(uri);
+    try (Cursor cursor = getContentResolver().query(documentUri, projection, null, null, null))
     {
       if (cursor != null && cursor.moveToFirst())
       {
@@ -124,6 +144,163 @@ public class ContentHandler
     return null;
   }
 
+  @NonNull @Keep
+  public static String[] getChildNames(@NonNull String uri)
+  {
+    try
+    {
+      Uri unmangledUri = unmangle(uri);
+      String documentId = DocumentsContract.getDocumentId(treeToDocument(unmangledUri));
+      Uri childrenUri = DocumentsContract.buildChildDocumentsUriUsingTree(unmangledUri, documentId);
+
+      final String[] projection = new String[]{Document.COLUMN_DISPLAY_NAME};
+      try (Cursor cursor = getContentResolver().query(childrenUri, projection, null, null, null))
+      {
+        if (cursor != null)
+        {
+          String[] result = new String[cursor.getCount()];
+          for (int i = 0; i < result.length; i++)
+          {
+            cursor.moveToNext();
+            result[i] = cursor.getString(0);
+          }
+          return result;
+        }
+      }
+    }
+    catch (SecurityException e)
+    {
+      Log.error("Tried to get children of " + uri + " without permission");
+    }
+    catch (FileNotFoundException ignored)
+    {
+    }
+
+    return new String[0];
+  }
+
+  @NonNull
+  private static Uri getChild(@NonNull Uri parentUri, @NonNull String childName)
+          throws FileNotFoundException, SecurityException
+  {
+    String parentId = DocumentsContract.getDocumentId(treeToDocument(parentUri));
+    Uri childrenUri = DocumentsContract.buildChildDocumentsUriUsingTree(parentUri, parentId);
+
+    final String[] projection = new String[]{Document.COLUMN_DISPLAY_NAME,
+            Document.COLUMN_DOCUMENT_ID};
+    final String selection = Document.COLUMN_DISPLAY_NAME + "=?";
+    final String[] selectionArgs = new String[]{childName};
+    try (Cursor cursor = getContentResolver().query(childrenUri, projection, selection,
+            selectionArgs, null))
+    {
+      if (cursor != null)
+      {
+        while (cursor.moveToNext())
+        {
+          // FileProvider seemingly doesn't support selections, so we have to manually filter here
+          if (childName.equals(cursor.getString(0)))
+          {
+            return DocumentsContract.buildDocumentUriUsingTree(parentUri, cursor.getString(1));
+          }
+        }
+      }
+    }
+    catch (SecurityException e)
+    {
+      Log.error("Tried to get child " + childName + " of " + parentUri + " without permission");
+    }
+
+    throw new FileNotFoundException(parentUri + "/" + childName);
+  }
+
+  /**
+   * Since our C++ code was written under the assumption that it would be running under a filesystem
+   * which supports normal paths, it appends a slash followed by a file name when it wants to access
+   * a file in a directory. This function translates that into the type of URI that SAF requires.
+   *
+   * In order to detect whether a URI is mangled or not, we make the assumption that an
+   * unmangled URI contains at least one % and does not contain any slashes after the last %.
+   * This seems to hold for all common storage providers, but it is theoretically for a storage
+   * provider to use URIs without any % characters.
+   */
+  @NonNull
+  private static Uri unmangle(@NonNull String uri) throws FileNotFoundException, SecurityException
+  {
+    int lastComponentEnd = getLastComponentEnd(uri);
+    int lastComponentStart = getLastComponentStart(uri, lastComponentEnd);
+
+    if (lastComponentStart == 0)
+    {
+      return Uri.parse(uri.substring(0, lastComponentEnd));
+    }
+    else
+    {
+      Uri parentUri = unmangle(uri.substring(0, lastComponentStart));
+      String childName = uri.substring(lastComponentStart, lastComponentEnd);
+      return getChild(parentUri, childName);
+    }
+  }
+
+  /**
+   * Returns the last character which is not a slash.
+   */
+  private static int getLastComponentEnd(@NonNull String uri)
+  {
+    int i = uri.length();
+    while (i > 0 && uri.charAt(i - 1) == '/')
+      i--;
+    return i;
+  }
+
+  /**
+   * Scans backwards starting from lastComponentEnd and returns the index after the first slash
+   * it finds, but only if there is a % before that slash and there is no % after it.
+   */
+  private static int getLastComponentStart(@NonNull String uri, int lastComponentEnd)
+  {
+    int i = lastComponentEnd;
+    while (i > 0 && uri.charAt(i - 1) != '/')
+    {
+      i--;
+      if (uri.charAt(i) == '%')
+        return 0;
+    }
+
+    int j = i;
+    while (j > 0)
+    {
+      j--;
+      if (uri.charAt(j) == '%')
+        return i;
+    }
+
+    return 0;
+  }
+
+  @NonNull
+  private static Uri treeToDocument(@NonNull Uri uri)
+  {
+    if (isTreeUri(uri))
+    {
+      String documentId = DocumentsContract.getTreeDocumentId(uri);
+      return DocumentsContract.buildDocumentUriUsingTree(uri, documentId);
+    }
+    else
+    {
+      return uri;
+    }
+  }
+
+  /**
+   * This is like DocumentsContract.isTreeUri, except it doesn't return true for URIs like
+   * content://com.example/tree/12/document/24/. We want to treat those as documents, not trees.
+   */
+  private static boolean isTreeUri(@NonNull Uri uri)
+  {
+    final List<String> pathSegments = uri.getPathSegments();
+    return pathSegments.size() == 2 && "tree".equals(pathSegments.get(0));
+  }
+
   private static ContentResolver getContentResolver()
   {
     return DolphinApplication.getAppContext().getContentResolver();

Source/Android/jni/AndroidCommon/AndroidCommon.cpp

@@ -121,6 +121,15 @@ std::string GetAndroidContentDisplayName(const std::string& uri)
   return display_name ? GetJString(env, reinterpret_cast<jstring>(display_name)) : "";
 }
 
+std::vector<std::string> GetAndroidContentChildNames(const std::string& uri)
+{
+  JNIEnv* env = IDCache::GetEnvForThread();
+  jobject children =
+      env->CallStaticObjectMethod(IDCache::GetContentHandlerClass(),
+                                  IDCache::GetContentHandlerGetChildNames(), ToJString(env, uri));
+  return JStringArrayToVector(env, reinterpret_cast<jobjectArray>(children));
+}
+
 int GetNetworkIpAddress()
 {
   JNIEnv* env = IDCache::GetEnvForThread();

Source/Android/jni/AndroidCommon/AndroidCommon.h

@@ -6,6 +6,7 @@
 
 #include <ios>
 #include <string>
+#include <vector>
 
 #include <jni.h>
 
@@ -34,6 +35,9 @@ jlong GetAndroidContentSizeAndIsDirectory(const std::string& uri);
 // An empty string will be returned for files which do not exist.
 std::string GetAndroidContentDisplayName(const std::string& uri);
 
+// Returns the display names of all children of a directory.
+std::vector<std::string> GetAndroidContentChildNames(const std::string& uri);
+
 int GetNetworkIpAddress();
 int GetNetworkPrefixLength();
 int GetNetworkGateway();

Source/Android/jni/AndroidCommon/IDCache.cpp

@@ -46,6 +46,7 @@ static jmethodID s_content_handler_open_fd;
 static jmethodID s_content_handler_delete;
 static jmethodID s_content_handler_get_size_and_is_directory;
 static jmethodID s_content_handler_get_display_name;
+static jmethodID s_content_handler_get_child_names;
 
 static jclass s_network_helper_class;
 static jmethodID s_network_helper_get_network_ip_address;
@@ -222,6 +223,11 @@ jmethodID GetContentHandlerGetDisplayName()
   return s_content_handler_get_display_name;
 }
 
+jmethodID GetContentHandlerGetChildNames()
+{
+  return s_content_handler_get_child_names;
+}
+
 jclass GetNetworkHelperClass()
 {
   return s_network_helper_class;
@@ -323,6 +329,8 @@ jint JNI_OnLoad(JavaVM* vm, void* reserved)
       s_content_handler_class, "getSizeAndIsDirectory", "(Ljava/lang/String;)J");
   s_content_handler_get_display_name = env->GetStaticMethodID(
       s_content_handler_class, "getDisplayName", "(Ljava/lang/String;)Ljava/lang/String;");
+  s_content_handler_get_child_names = env->GetStaticMethodID(
+      s_content_handler_class, "getChildNames", "(Ljava/lang/String;)[Ljava/lang/String;");
 
   const jclass network_helper_class =
       env->FindClass("org/dolphinemu/dolphinemu/utils/NetworkHelper");

Source/Android/jni/AndroidCommon/IDCache.h

@@ -46,6 +46,7 @@ jmethodID GetContentHandlerOpenFd();
 jmethodID GetContentHandlerDelete();
 jmethodID GetContentHandlerGetSizeAndIsDirectory();
 jmethodID GetContentHandlerGetDisplayName();
+jmethodID GetContentHandlerGetChildNames();
 
 jclass GetNetworkHelperClass();
 jmethodID GetNetworkHelperGetNetworkIpAddress();