distinguish between general i/o error and write exception when copying files

src/main/java/eu/siacs/conversations/http/HttpDownloadConnection.java

@@ -25,6 +25,7 @@ import eu.siacs.conversations.persistance.FileBackend;
 import eu.siacs.conversations.services.AbstractConnectionManager;
 import eu.siacs.conversations.services.XmppConnectionService;
 import eu.siacs.conversations.utils.CryptoHelper;
+import eu.siacs.conversations.utils.FileWriterException;
 
 public class HttpDownloadConnection implements Transferable {
 
@@ -141,16 +142,12 @@ public class HttpDownloadConnection implements Transferable {
 		mXmppConnectionService.updateConversationUi();
 	}
 
-	private class WriteException extends IOException {
-
-	}
-
 	private void showToastForException(Exception e) {
 		if (e instanceof java.net.UnknownHostException) {
 			mXmppConnectionService.showErrorToastInUi(R.string.download_failed_server_not_found);
 		} else if (e instanceof java.net.ConnectException) {
 			mXmppConnectionService.showErrorToastInUi(R.string.download_failed_could_not_connect);
-		} else if (e instanceof WriteException) {
+		} else if (e instanceof FileWriterException) {
 			mXmppConnectionService.showErrorToastInUi(R.string.download_failed_could_not_write_file);
 		} else if (!(e instanceof  CancellationException)) {
 			mXmppConnectionService.showErrorToastInUi(R.string.download_failed_file_not_found);
@@ -305,7 +302,7 @@ public class HttpDownloadConnection implements Transferable {
 					try {
 						os.write(buffer, 0, count);
 					} catch (IOException e) {
-						throw new WriteException();
+						throw new FileWriterException();
 					}
 					updateProgress((int) ((((double) transmitted) / expected) * 100));
 					if (canceled) {
@@ -315,7 +312,7 @@ public class HttpDownloadConnection implements Transferable {
 				try {
 					os.flush();
 				} catch (IOException e) {
-					throw new WriteException();
+					throw new FileWriterException();
 				}
 			} catch (CancellationException | IOException e) {
 				throw e;

src/main/java/eu/siacs/conversations/persistance/FileBackend.java

@@ -54,6 +54,7 @@ import eu.siacs.conversations.services.XmppConnectionService;
 import eu.siacs.conversations.utils.CryptoHelper;
 import eu.siacs.conversations.utils.ExifHelper;
 import eu.siacs.conversations.utils.FileUtils;
+import eu.siacs.conversations.utils.FileWriterException;
 import eu.siacs.conversations.xmpp.pep.Avatar;
 
 public class FileBackend {
@@ -238,11 +239,21 @@ public class FileBackend {
 			byte[] buffer = new byte[1024];
 			int length;
 			while ((length = is.read(buffer)) > 0) {
+				try {
 					os.write(buffer, 0, length);
+				} catch (IOException e) {
+					throw new FileWriterException();
 				}
+			}
+			try {
 				os.flush();
+			} catch (IOException e) {
+				throw new FileWriterException();
+			}
 		} catch(FileNotFoundException e) {
 			throw new FileCopyException(R.string.error_file_not_found);
+		} catch(FileWriterException e) {
+			throw new FileCopyException(R.string.error_unable_to_create_temporary_file);
 		} catch (IOException e) {
 			e.printStackTrace();
 			throw new FileCopyException(R.string.error_io_exception);
@@ -287,8 +298,13 @@ public class FileBackend {
 		InputStream is = null;
 		OutputStream os = null;
 		try {
-			file.createNewFile();
+			if (!file.exists() && !file.createNewFile()) {
+				throw new FileCopyException(R.string.error_unable_to_create_temporary_file);
+			}
 			is = mXmppConnectionService.getContentResolver().openInputStream(image);
+			if (is == null) {
+				throw new FileCopyException(R.string.error_not_an_image_file);
+			}
 			Bitmap originalBitmap;
 			BitmapFactory.Options options = new BitmapFactory.Options();
 			int inSampleSize = (int) Math.pow(2, sampleSize);
@@ -315,7 +331,6 @@ public class FileBackend {
 				quality -= 5;
 			}
 			scaledBitmap.recycle();
-			return;
 		} catch (FileNotFoundException e) {
 			throw new FileCopyException(R.string.error_file_not_found);
 		} catch (IOException e) {
@@ -330,8 +345,6 @@ public class FileBackend {
 			} else {
 				throw new FileCopyException(R.string.error_out_of_memory);
 			}
-		} catch (NullPointerException e) {
-			throw new FileCopyException(R.string.error_io_exception);
 		} finally {
 			close(os);
 			close(is);

src/main/java/eu/siacs/conversations/utils/FileWriterException.java

@@ -0,0 +1,4 @@
+package eu.siacs.conversations.utils;
+
+public class FileWriterException extends Exception {
+}