Split struct Crc into trait Crc and struct Stm32Crc

There are different ways to implement the CRC check:  For testing, we
might want to calulate the CRC in the software.  On STM32 MCUs, we want
to use the CRC peripheral.

This patch splits the struct Crc into the Crc trait and the Stm32Crc
struct implementing Crc using the CRC peripheral.  The Nitrokey struct
can now accept any Crc implementation.

1 files changed, 21 insertions, 11 deletions

diff --git a/src/crc.rs b/src/crc.rs
index cfcf982..6219e8c 100644
--- a/src/crc.rs
+++ b/src/crc.rs
@@ -1,23 +1,25 @@
 // Copyright 2019 Robin Krahl <robin.krahl@ireas.org>
 // SPDX-License-Identifier: GPL-3.0-or-later
 
+use core::iter::Iterator;
+
 use hal::stm32::CRC;
 
-pub struct Crc {
+pub trait Crc {
+    fn get(&self, data: &[u8]) -> u32 {
+        self.get_u32(data.chunks(4).map(slice_to_u32))
+    }
+
+    fn get_u32<I: Iterator<Item = u32>>(&self, iter: I) -> u32;
+}
+
+pub struct Stm32Crc {
     crc: CRC,
 }
 
-impl Crc {
+impl Stm32Crc {
     pub fn new(crc: CRC) -> Self {
-        Crc { crc }
-    }
-
-    pub fn get(&self, data: &[u8]) -> u32 {
-        self.reset();
-        data.chunks(4)
-            .map(slice_to_u32)
-            .for_each(|val| self.write(val));
-        self.read()
+        Self { crc }
     }
 
     fn write(&self, val: u32) {
@@ -33,6 +35,14 @@ impl Crc {
     }
 }
 
+impl Crc for Stm32Crc {
+    fn get_u32<I: Iterator<Item = u32>>(&self, iter: I) -> u32 {
+        self.reset();
+        iter.for_each(|val| self.write(val));
+        self.read()
+    }
+}
+
 fn slice_to_u32(data: &[u8]) -> u32 {
     data.iter()
         .enumerate()