From 6d89245f2c190ee8a116508f25b9a0d862b60e18 Mon Sep 17 00:00:00 2001
From: Robert <robert.altner11@gmail.com>
Date: Sun, 18 Dec 2022 18:04:18 +0100
Subject: [PATCH] create macro for more convenient usart reading

---
 src/b15f.rs  | 29 ++++++++++-------------------
 src/lib.rs   |  2 +-
 src/usart.rs | 27 +++++++++++++++++++++++++++
 3 files changed, 38 insertions(+), 20 deletions(-)
 create mode 100644 src/usart.rs

diff --git a/src/b15f.rs b/src/b15f.rs
index e23f560..221e823 100644
--- a/src/b15f.rs
+++ b/src/b15f.rs
@@ -6,7 +6,7 @@ use std::{process::Command, time::Duration, fmt::Debug, thread::sleep};
 use rand::Rng;
 use serialport::SerialPort;
 
-use crate::{assert::assert_in_range, error::Error, request::Request, build_request};
+use crate::{assert::assert_in_range, error::Error, request::Request, usart::read_sized, build_request, read_typed};
 
 macro_rules! log {
 	($text: literal, $($arg:tt)*) => (println!(concat!("[B15F] ", $text), $($arg)*));
@@ -150,10 +150,8 @@ impl B15F {
 		
 		self.usart.write(build_request![request, reversed])?;
 
-		let mut aw: [u8; 1] = [0; 1];
-		self.usart.read(&mut aw)?;
-
-		if aw[0] != B15F::MSG_OK {
+		let aw: u8 = read_typed!(self.usart, u8);
+		if aw != B15F::MSG_OK {
 			return Err(format!("Setting Port {} failed", PORT).into());
 		}
 
@@ -195,10 +193,8 @@ impl B15F {
 		self.usart.clear(serialport::ClearBuffer::Input)?;
 		self.usart.write(build_request![request])?;
 
-		let mut aw: [u8; 1] = [0; 1];
-		self.usart.read(&mut aw)?;
-
-		Ok(u8::reverse_bits(aw[0]))
+		let aw: u8 = read_typed!(self.usart, u8);
+		Ok(u8::reverse_bits(aw))
 	}
 
 	/// Yields information about the installed firmware on the B15
@@ -251,11 +247,9 @@ impl B15F {
 			data_count[0] -= 1;
 		}
 
-		let mut aw: [u8; 1] = [0; 1];		
-		self.usart.read(&mut aw)?;		
-
-		if aw[0] != B15F::MSG_OK {
-			return Err(format!("Board info is faulty: code {}", aw[0]).into());
+		let aw: u8 = read_typed!(self.usart, u8);
+		if aw != B15F::MSG_OK {
+			return Err(format!("Board info is faulty: code {}", aw).into());
 		}		
 
 		Ok(info)
@@ -285,11 +279,8 @@ impl B15F {
 		
 		self.usart.write(build_request!(Request::IntTest, dummy & 0xFF, dummy >> 8))?;
 
-		let mut aw: [u8; 2] = [0; 2];
-		self.usart.read(&mut aw)?;
-
-		let result = u16::from_le_bytes(aw);
-		if result != dummy * 3 {
+		let aw: u16 = read_typed!(self.usart, u16);
+		if aw != dummy * 3 {
 			return Err("Int conversion failed".into());
 		}
 
diff --git a/src/lib.rs b/src/lib.rs
index 84b63dd..7c4ef49 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,7 +1,6 @@
 #![deny(missing_docs,
     missing_debug_implementations,
     trivial_casts,
-    unsafe_code,
     unstable_features,
     unused_import_braces, unused_qualifications)]
 
@@ -14,6 +13,7 @@
 //! [`original`]: https://github.com/devfix/b15f
 
 pub mod b15f;
+mod usart;
 mod request;
 mod error;
 mod assert;
diff --git a/src/usart.rs b/src/usart.rs
new file mode 100644
index 0000000..41e5b77
--- /dev/null
+++ b/src/usart.rs
@@ -0,0 +1,27 @@
+use serialport::SerialPort;
+use crate::error::Error;
+
+/// Reads from a USART connecction and casts the result into the specified type
+/// 
+/// # Errors
+/// This macro may throw an `error::Error` when reading from the connection fails.
+/// Due to the implementation of this macro, an erroneous result is returned early
+/// with the `?` operator, and not unwrapped.
+/// 
+/// # Unsafe
+/// This macro makes use of `std::mem::transmute`.
+#[macro_export]
+macro_rules! read_typed {
+	($usart: expr, $T: ty) => {
+		unsafe {
+			std::mem::transmute(read_sized::<{ std::mem::size_of::<$T>() }>(&mut $usart)?)
+		}
+	};
+}
+
+pub fn read_sized<const N: usize> (usart: &mut Box<dyn SerialPort>) -> Result<[u8; N], Error> {
+	let mut buf: [u8; N] = [0; N];
+	
+	usart.read(&mut buf)?;
+	Ok(buf)
+}
\ No newline at end of file