Macros for converting between binary and hex

src/error.rs

@@ -3,10 +3,22 @@ use thiserror::Error;
 /// Errors that can occur in the chorus crate
 #[derive(Error, Debug)]
 pub enum Error {
+    // Bad hex input
+    #[error("Bad hex input")]
+    BadHexInput,
+
+    // Output buffer too small
+    #[error("Output buffer too small")]
+    BufferTooSmall,
+
     // Config
     #[error("Config: {0}")]
     Config(#[from] ron::error::SpannedError),
 
+    // End of Input
+    #[error("End of input")]
+    EndOfInput,
+
     // I/O Error
     #[error("I/O: {0}")]
     Io(#[from] std::io::Error),

src/macros.rs

@@ -0,0 +1,57 @@
+static HEX_CHARS: &[u8; 16] = b"0123456789abcdef";
+#[allow(clippy::zero_prefixed_literal)]
+static HEX_INVERSE: [u8; 128] = {
+    const __: u8 = 255;
+    [
+        //  1  2  3   4  5  6  7   8  9  A  B   C  D  E  F
+        __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 0
+        __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 1
+        __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 2
+        00, 01, 02, 03, 04, 05, 06, 07, 08, 09, __, __, __, __, __, __, // 3
+        __, 10, 11, 12, 13, 14, 15, __, __, __, __, __, __, __, __, __, // 4
+        __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 5
+        __, 10, 11, 12, 13, 14, 15, __, __, __, __, __, __, __, __, __, // 6
+        __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, // 7
+    ]
+};
+
+macro_rules! write_hex {
+    ($input:expr, $output:expr, $bytelen:expr) => {{
+        assert_eq!($input.len(), $bytelen);
+        if $output.len() != $bytelen * 2 {
+            Err(Error::BufferTooSmall)
+        } else {
+            for (i, byte) in $input.iter().enumerate() {
+                $output[i * 2] = crate::HEX_CHARS[((byte & 0xF0) >> 4) as usize];
+                $output[i * 2 + 1] = crate::HEX_CHARS[(byte & 0x0F) as usize];
+            }
+            Ok(())
+        }
+    }};
+}
+
+macro_rules! read_hex {
+    ($input:expr, $output:expr, $bytelen:expr) => {{
+        assert_eq!($output.len(), $bytelen);
+        if $input.len() != $bytelen * 2 {
+            Err(Error::EndOfInput)
+        } else {
+            let mut i = 0;
+            loop {
+                let high = crate::HEX_INVERSE[$input[i * 2] as usize];
+                if high == 255 {
+                    break Err(Error::BadHexInput);
+                }
+                let low = crate::HEX_INVERSE[$input[i * 2 + 1] as usize];
+                if low == 255 {
+                    break Err(Error::BadHexInput);
+                }
+                $output[i] = high * 16 + low;
+                i += 1;
+                if i == $bytelen {
+                    break Ok(());
+                }
+            }
+        }
+    }};
+}

src/main.rs

@@ -1,3 +1,4 @@
+include!("macros.rs");
 
 pub mod config;
 pub mod error;