no_flash: init

README.md

@@ -13,7 +13,6 @@ For details see `trait StoreBackend`.
 
 ## TODO
 
-* NoFlash backend
 * read_int()
 * write_str()
 * automatic value coercion

src/lib.rs

@@ -9,6 +9,7 @@ mod iter;
 use iter::Iter;
 mod fmt;
 use fmt::FmtWrapper;
+pub mod no_flash;
 mod test;
 
 pub trait StoreBackend {

src/no_flash.rs

@@ -0,0 +1,33 @@
+use crate::StoreBackend;
+use core::fmt;
+
+/// expect this for any write operation to `NoFlash`
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct NoFlashError;
+
+impl fmt::Display for NoFlashError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "no flash")
+    }
+}
+
+/// a valid `StoreBackend` that can be used for configurations lacking a flash
+#[derive(Debug, Clone, Copy)]
+pub struct NoFlash;
+
+impl StoreBackend for NoFlash {
+    type Data = [u8; 0];
+
+    fn data(&self) -> &Self::Data {
+        &[]
+    }
+
+    type Error = NoFlashError;
+    fn erase(&mut self) -> Result<(), Self::Error> {
+        Err(NoFlashError)
+    }
+
+    fn program(&mut self, _: usize, _: &[u8]) -> Result<(), Self::Error> {
+        Err(NoFlashError)
+    }
+}

src/test.rs

@@ -1,6 +1,6 @@
 #![cfg(test)]
 
-use crate::{Store, StoreBackend};
+use crate::{Error, no_flash, Store, StoreBackend, WriteError};
 
 const SIZE: usize = 1024;
 
@@ -77,3 +77,13 @@ fn write_many() {
     assert_eq!(store.read("foo").unwrap().unwrap(), b"do not compact away");
     assert_eq!(store.read("bar").unwrap().unwrap(), b"SPAM");
 }
+
+#[test]
+fn no_flash() {
+    let mut store = Store::new(no_flash::NoFlash);
+    assert_eq!(store.read("foo").unwrap(), None);
+    assert_eq!(
+        store.write("foo", b"bar"),
+        Err(Error::Write(WriteError::Backend(no_flash::NoFlashError)))
+    );
+}