Add erase_storage application example (#352)

deploy.py

@@ -951,7 +951,16 @@ def main(args):
       dest="application",
       action="store_const",
       const="store_latency",
-      help=("Compiles and installs the store_latency example."))
+      help=("Compiles and installs the store_latency example which print "
+            "latency statistics of the persistent store library."))
+  apps_group.add_argument(
+      "--erase_storage",
+      dest="application",
+      action="store_const",
+      const="erase_storage",
+      help=("Compiles and installs the erase_storage example which erases "
+            "the storage. During operation the dongle red light is on. Once "
+            "the operation is completed the dongle green light is on."))
   apps_group.add_argument(
       "--panic_test",
       dest="application",

examples/erase_storage.rs

@@ -0,0 +1,53 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#![no_std]
+
+extern crate lang_items;
+
+use core::fmt::Write;
+use ctap2::embedded_flash::new_storage;
+use libtock_drivers::console::Console;
+use libtock_drivers::led;
+use libtock_drivers::result::FlexUnwrap;
+use persistent_store::{Storage, StorageIndex};
+
+fn is_page_erased(storage: &dyn Storage, page: usize) -> bool {
+    let index = StorageIndex { page, byte: 0 };
+    let length = storage.page_size();
+    storage
+        .read_slice(index, length)
+        .unwrap()
+        .iter()
+        .all(|&x| x == 0xff)
+}
+
+fn main() {
+    led::get(1).flex_unwrap().on().flex_unwrap(); // red on dongle
+    const NUM_PAGES: usize = 20; // should be at least ctap::storage::NUM_PAGES
+    let mut storage = new_storage(NUM_PAGES);
+    writeln!(Console::new(), "Erase {} pages of storage:", NUM_PAGES).unwrap();
+    for page in 0..NUM_PAGES {
+        write!(Console::new(), "- Page {} ", page).unwrap();
+        if is_page_erased(&storage, page) {
+            writeln!(Console::new(), "skipped (was already erased).").unwrap();
+        } else {
+            storage.erase_page(page).unwrap();
+            writeln!(Console::new(), "erased.").unwrap();
+        }
+    }
+    writeln!(Console::new(), "Done.").unwrap();
+    led::get(1).flex_unwrap().off().flex_unwrap();
+    led::get(0).flex_unwrap().on().flex_unwrap(); // green on dongle
+}