Make a proc macro for more easily defining VIF tables

Lexicality · Lexicality · commit b31975970fa6 · 2024-04-19T18:58:01.000+01:00
I'm not sure this is a remotely sensible way to do this but it sure does
seem to be working so let's go right ahead!
diff --git a/Cargo.lock b/Cargo.lock
diff --git a/Cargo.toml b/Cargo.toml
@@ -1,3 +1,7 @@
+[workspace]
+
+members = ["libmbus_macros"]
+
 [package]
 name = "libmbus"
 license = "EUPL-1.2"
@@ -10,3 +14,4 @@ edition = "2021"
 chrono = "0.4.23"
 encoding_rs = "0.8.32"
 winnow = "0.6.5"
+libmbus_macros = { path = "./libmbus_macros" }
diff --git a/libmbus_macros/Cargo.toml b/libmbus_macros/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "libmbus_macros"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[lib]
+proc-macro = true
+
+[dependencies]
+winnow = "0.6.6"
diff --git a/libmbus_macros/src/lib.rs b/libmbus_macros/src/lib.rs
@@ -0,0 +1,37 @@
+use proc_macro::TokenStream;
+use winnow::ascii;
+use winnow::combinator::repeat;
+use winnow::error::InputError;
+use winnow::prelude::*;
+use winnow::Str;
+
+#[proc_macro]
+pub fn vif(input: TokenStream) -> TokenStream {
+	let raw_input = input.to_string();
+
+	let (_, upper_bits, _, lower_bits, ns) = (
+		'E'.void(),
+		ascii::digit1::<_, InputError<Str>>.map(|s| u8::from_str_radix(s, 2).unwrap()),
+		' '.void(),
+		ascii::digit0.map(|s| u8::from_str_radix(s, 2).unwrap()),
+		repeat::<_, _, String, _, _>(0..=4, 'n'),
+	)
+		.parse(raw_input.as_str())
+		.unwrap();
+
+	let base = (upper_bits << 4) | (lower_bits << ns.len());
+
+	let mask_inv = 0xFF << ns.len();
+	let mask = !mask_inv;
+
+	let range_start = base & mask_inv;
+	let range_end = base | mask;
+
+	if range_start == range_end {
+		format!(r"{range_start}")
+	} else {
+		format!(r"{range_start}..={range_end}")
+	}
+	.parse()
+	.unwrap()
+}
diff --git a/src/parse/application_layer/vib.rs b/src/parse/application_layer/vib.rs
@@ -5,6 +5,7 @@
 use crate::parse::error::MBResult;
 use crate::parse::types::string::parse_length_prefix_ascii;
 use crate::parse::types::BitsInput;
+use libmbus_macros::vif;
 use winnow::binary::bits;
 use winnow::error::{AddContext, ErrMode, ErrorKind, ParserError, StrContext};
 use winnow::prelude::*;
@@ -135,7 +136,7 @@ impl ValueInfoBlock {
 
 fn parse_table_10(value: u8) -> Option<ValueType> {
 	Some(match value {
-		0b0111_0100..=0b0111_0111 => {
+		vif!(E111 01nn) => {
 			ValueType::ActualityDuration(DurationType::decode_nn(value & DURATION_MASK))
 		}
 		_ => todo!("table 10 {value} {value:x} {value:b}"),
