Add option to generate typed constants from DBC BA_ attributes

README.md

@@ -112,6 +112,47 @@ Config::builder()
     .check_ranges(FeatureConfig::Never);
 ```
 
+### Attribute-driven constants
+
+Many DBCs contain additional metadata in `BA_` attributes, e.g. parameters describing an AUTOSAR E2E protection scheme. `attribute_structs` lets you expose these as typed constants in the generated message types.
+
+You declare a struct that your own crate owns and map each field to a DBC attribute, derived signal, or a literal:
+
+```rust,no_run
+use dbc_codegen::{AttributeField, AttributeScope, AttributeStruct, Config, FieldSource};
+
+// `data_protection::E2EDataIdInfo { data_id, start_byte, width_bit }` is a type defined in your crate.
+let e2e = AttributeStruct {
+    type_path: "data_protection::E2EDataIdInfo",
+    const_name: "E2E",
+    scope: AttributeScope::Signal,   // One const per matching signal
+    require: "E2EDataId",            // Only signals carrying this attribute
+    fields: &[
+        AttributeField { name: "data_id",    source: FieldSource::Attr("E2EDataId") },
+        AttributeField { name: "start_byte",  source: FieldSource::StartByte },
+        AttributeField { name: "width_bit",   source: FieldSource::Attr("E2EDataLength") },
+    ],
+};
+
+let dbc_file = "";
+Config::builder()
+    .dbc_name("example.dbc")
+    .dbc_content(dbc_file)
+    .attribute_structs(&[e2e])
+    .build()
+    .generate()
+    .unwrap();
+```
+
+For every signal that carries an `E2EDataId` attribute, this generates:
+
+```rust,ignore
+impl SomeMessage {
+    pub const SOME_SIGNAL_E2E: data_protection::E2EDataIdInfo =
+        data_protection::E2EDataIdInfo { data_id: 373, start_byte: 0, width_bit: 48 };
+}
+```
+
 ### `no_std`
 
 The generated code is `no_std` compatible, unless you enable `impl_error`.

examples/attribute_structs.rs

@@ -0,0 +1,82 @@
+//! Demonstrates [`Config::attribute_structs`].
+//! Emits constants for AUTOSAR E2E / SecOC-style metdata from DBC 'BA_' attributes.
+
+use dbc_codegen::{AttributeField, AttributeScope, AttributeStruct, Config, FieldSource};
+
+const DBC: &str = r#"VERSION ""
+
+NS_ :
+
+BS_:
+
+BU_: ECU1
+
+BO_ 256 Protected: 8 ECU1
+ SG_ Speed_CRC : 16|8@1+ (1,0) [0|255] "" ECU1
+
+BA_DEF_ BO_  "SCP_FreshnessValueId" INT 0 65535;
+BA_DEF_ SG_  "E2EDataId" INT 0 65535;
+BA_DEF_ SG_  "E2EDataLength" INT 0 65535;
+BA_DEF_ SG_  "E2EProfile" STRING ;
+BA_DEF_DEF_  "SCP_FreshnessValueId" 0;
+BA_DEF_DEF_  "E2EDataId" 0;
+BA_DEF_DEF_  "E2EDataLength" 0;
+BA_DEF_DEF_  "E2EProfile" "none";
+BA_ "SCP_FreshnessValueId" BO_ 256 1002;
+BA_ "E2EDataId" SG_ 256 Speed_CRC 373;
+BA_ "E2EDataLength" SG_ 256 Speed_CRC 48;
+BA_ "E2EProfile" SG_ 256 Speed_CRC "P01";
+"#;
+
+fn field(name: &'static str, source: FieldSource<'static>) -> AttributeField<'static> {
+    AttributeField { name, source }
+}
+
+fn main() {
+    let e2e = AttributeStruct {
+        type_path: "data_protection::E2EDataIdInfo",
+        const_name: "E2E",
+        scope: AttributeScope::Signal,
+        require: "E2EDataId",
+        fields: &[
+            field("data_id", FieldSource::Attr("E2EDataId")),
+            field("start_byte", FieldSource::StartByte),
+            field("width_bit", FieldSource::Attr("E2EDataLength")),
+            field("profile", FieldSource::Attr("E2EProfile")),
+        ],
+    };
+    let secoc = AttributeStruct {
+        type_path: "data_protection::SecOcInfo",
+        const_name: "SEC_OC",
+        scope: AttributeScope::Message,
+        require: "SCP_FreshnessValueId",
+        fields: &[field(
+            "freshness_id",
+            FieldSource::Attr("SCP_FreshnessValueId"),
+        )],
+    };
+
+    let code = Config::builder()
+        .dbc_name("example")
+        .dbc_content(DBC)
+        .attribute_structs(&[e2e, secoc])
+        .build()
+        .generate()
+        .expect("generate");
+
+    // Print just the associated consts to keep the output readable.
+    for line in code.lines() {
+        let t = line.trim_start();
+        if t.starts_with("pub const")
+            || t.starts_with("data_id")
+            || t.starts_with("start_byte")
+            || t.starts_with("width_bit")
+            || t.starts_with("profile")
+            || t.starts_with("freshness_id")
+            || t.contains("E2EDataIdInfo {")
+            || t.contains("SecOcInfo {")
+        {
+            println!("{line}");
+        }
+    }
+}