Merge pull request #104 from maebli/feature/application-layer-parsing

Improve application layer parsing API

Author: maebli

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+- Added direct application-layer parsing APIs, record accessors, and a crate-local data-record example.
+- Moved full-frame application-layer coverage to the top-level crate.
+- Fixed data-record iteration to report malformed records instead of silently stopping.
 - Fixed mojibake in decrypted variable-length UTF-8 text while preserving ISO-8859-1 fallback decoding.
 
 ## [0.1.3] - 2026-06-11

README.md

@@ -164,7 +164,7 @@ m-bus-parser = "0.1"
 ```rust
 use m_bus_parser::{Address, WiredFrame, Function};
 use m_bus_parser::mbus_data::MbusData;
-use m_bus_parser::user_data::{DataRecords, UserDataBlock};
+use m_bus_parser::user_data::parse_application_layer;
 
 let frame_bytes: Vec<u8> = vec![
     0x68, 0x4D, 0x4D, 0x68, 0x08, 0x01, 0x72, 0x01,
@@ -174,21 +174,31 @@ let frame_bytes: Vec<u8> = vec![
 let frame = WiredFrame::try_from(frame_bytes.as_slice())?;
 
 if let WiredFrame::LongFrame { function, address, data } = frame {
-    if let Ok(user_data) = UserDataBlock::try_from(data) {
-        if let UserDataBlock::VariableDataStructureWithLongTplHeader {
-            long_tpl_header,
-            variable_data_block,
-            ..
-        } = user_data {
-            let records = DataRecords::from((variable_data_block, &long_tpl_header));
-            for record in records.flatten() {
-                println!("{}", record.data);
-            }
+    let application_layer = parse_application_layer(data)?;
+    if let Some(records) = application_layer.data_records() {
+        for record in records {
+            println!("{:?}", record?.value());
         }
     }
 }
 ```
 
+### Parse application-layer data records
+
+When the link and transport headers have already been removed, parse the DIF/VIF
+records directly:
+
+```rust
+use m_bus_parser::user_data::parse_data_records;
+
+let data = [0x03, 0x13, 0x15, 0x31, 0x00];
+for record in parse_data_records(&data) {
+    let record = record?;
+    println!("value: {:?}", record.value());
+    println!("value information: {:?}", record.value_information());
+}
+```
+
 ### Serialize to any format
 
 ```rust

crates/m-bus-application-layer/Cargo.toml

@@ -5,6 +5,7 @@ edition = "2021"
 description = "M-Bus application layer parser (DIF/VIF, data records)"
 license = "MIT"
 repository = "https://github.com/maebli/m-bus-parser"
+readme = "README.md"
 
 [features]
 default = []
@@ -20,6 +21,3 @@ defmt = { version = "1.0.1", optional = true }
 bitflags = "2.8.0"
 arrayvec = { version = "0.7.4", default-features = false }
 m-bus-core = { version = "0.1.3", path = "../m-bus-core" }
-
-[dev-dependencies]
-wired-mbus-link-layer = { path = "../wired-mbus-link-layer" }

crates/m-bus-application-layer/README.md

@@ -0,0 +1,28 @@
+# M-Bus application layer
+
+This crate parses EN 13757-3 application-layer data without requiring a wired
+or wireless link-layer frame.
+
+Use `parse_application_layer` when the input begins with a CI field, or
+`parse_data_records` when the CI and transport headers have already been
+removed:
+
+```rust
+use m_bus_application_layer::parse_data_records;
+
+let data = [0x03, 0x13, 0x15, 0x31, 0x00];
+for record in parse_data_records(&data) {
+    let record = record?;
+    println!("value: {:?}", record.value());
+    println!("value information: {:?}", record.value_information());
+}
+```
+
+Run the complete data-record example from the workspace root:
+
+```console
+cargo run -p m-bus-application-layer --example parse_data_records
+```
+
+The parser is allocation-free and supports `no_std`; formatting and standard
+error traits are enabled by the optional `std` feature.

crates/m-bus-application-layer/examples/parse_data_records.rs

@@ -0,0 +1,24 @@
+use m_bus_application_layer::{parse_data_records, DataRecordError};
+
+fn main() -> Result<(), DataRecordError> {
+    // Application-layer records only: no wired/wireless frame or CI/TPL header.
+    let data = [
+        0x03, 0x13, 0x15, 0x31, 0x00, // Volume: 12_565 x 10^-3 m³
+        0x02, 0x5A, 0xD7, 0x04, // Flow temperature: 1_239 x 10^-1 °C
+    ];
+
+    for (index, record) in parse_data_records(&data).enumerate() {
+        let record = record?;
+
+        println!("Record {}", index + 1);
+        println!("  value: {:?}", record.value());
+        if let Some(value_information) = record.value_information() {
+            println!("  labels: {:?}", value_information.labels);
+            println!("  scale: 10^{}", value_information.decimal_scale_exponent);
+            println!("  units: {:?}", value_information.units);
+        }
+        println!("  raw bytes: {:02X?}", record.raw_bytes());
+    }
+
+    Ok(())
+}

crates/m-bus-application-layer/src/data_record.rs

@@ -29,6 +29,36 @@ pub struct DataRecord<'a> {
 }
 
 impl DataRecord<'_> {
+    /// Returns the parsed value carried by this record.
+    #[must_use]
+    pub fn value(&self) -> Option<&DataType<'_>> {
+        self.data.value.as_ref()
+    }
+
+    /// Returns the processed data information (DIF and DIFE fields).
+    #[must_use]
+    pub fn data_information(&self) -> Option<&DataInformation> {
+        self.data_record_header
+            .processed_data_record_header
+            .data_information
+            .as_ref()
+    }
+
+    /// Returns the processed value information (VIF and VIFE fields).
+    #[must_use]
+    pub fn value_information(&self) -> Option<&ValueInformation> {
+        self.data_record_header
+            .processed_data_record_header
+            .value_information
+            .as_ref()
+    }
+
+    /// Returns all raw bytes consumed by this record.
+    #[must_use]
+    pub fn raw_bytes(&self) -> &[u8] {
+        self.raw_bytes
+    }
+
     #[must_use]
     pub fn get_size(&self) -> usize {
         self.raw_bytes.len()

crates/m-bus-application-layer/src/extended_link_layer.rs

@@ -30,9 +30,9 @@ pub struct EncryptionFields {
 pub enum EllFormat {
     /// Extended Link Layer I (2 bytes: CC, ACC)
     FormatI,
-    /// Extended Link Layer II (8 bytes: CC, ACC, SN[4], CRC[2])
+    /// Extended Link Layer II (8 bytes: CC, ACC, `SN[4]`, `CRC[2]`)
     FormatII,
-    /// Extended Link Layer III (16 bytes: CC, ACC, MFR[2], ADDR[6], SN[4], CRC[2])
+    /// Extended Link Layer III (16 bytes: CC, ACC, `MFR[2]`, `ADDR[6]`, `SN[4]`, `CRC[2]`)
     FormatIII,
 }