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fix: Extensions, Special Functions #91

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Merged
maebli merged 3 commits into from
May 7, 2026
Merged

fix: Extensions, Special Functions #91

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304e80a
Combinable VIFE Following VIFE = FC
alvskar Apr 20, 2026
242291c
Process text LVAR data as text according to ISO/IEC 8859-1 rather than
alvskar Apr 23, 2026
acb075e
Process Special Functions
alvskar Apr 23, 2026
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66 changes: 46 additions & 20 deletions crates/m-bus-application-layer/src/data_information.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -119,10 +119,12 @@ impl DataInformationField {
const fn has_extension(&self) -> bool {
self.data & 0x80 != 0
}
}

impl DataInformationFieldExtension {
const fn special_function(&self) -> SpecialFunctions {
pub const fn is_special_function(&self) -> bool {
self.data & 0x0F == 0x0F
}

pub const fn special_function(&self) -> SpecialFunctions {
match self.data {
0x0F => SpecialFunctions::ManufacturerSpecific,
0x1F => SpecialFunctions::MoreRecordsFollow,
Expand Down Expand Up @@ -208,10 +210,7 @@ impl TryFrom<&DataInformationBlock<'_>> for DataInformation {
let mut extension_index = 1;
let mut tariff = 0;
let mut device = 0;
let mut first_dife = None;

if let Some(difes) = possible_difes {
first_dife = difes.clone().next();
let mut tariff_index = 0;
for (device_index, dife) in difes.clone().enumerate() {
if extension_index > MAXIMUM_DATA_INFORMATION_SIZE {
Expand Down Expand Up @@ -250,8 +249,8 @@ impl TryFrom<&DataInformationBlock<'_>> for DataInformation {
0b1101 => DataFieldCoding::VariableLength,
0b1110 => DataFieldCoding::BCDDigit12,
0b1111 => DataFieldCoding::SpecialFunctions(
first_dife
.ok_or(DataInformationError::DataTooShort)?
data_information_block
.data_information_field
.special_function(),
),
_ => unreachable!(), // This case should never occur due to the 4-bit width
Expand Down Expand Up @@ -293,17 +292,15 @@ impl PartialEq<str> for TextUnit<'_> {
#[cfg(feature = "std")]
impl std::fmt::Display for TextUnit<'_> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
let value: Vec<u8> = self.0.iter().copied().rev().collect();
let value = String::from_utf8(value).unwrap_or_default();
let value: String = self.0.iter().rev().map(|&b| b as char).collect();
write!(f, "{}", value)
}
}

#[cfg(feature = "std")]
impl From<TextUnit<'_>> for String {
fn from(value: TextUnit<'_>) -> Self {
let value: Vec<u8> = value.0.iter().copied().rev().collect();
String::from_utf8(value).unwrap_or_default()
value.0.iter().rev().map(|&b| b as char).collect()
}
}

Expand Down Expand Up @@ -733,14 +730,25 @@ impl DataFieldCoding {
}
}

Self::SpecialFunctions(_code) => {
// Special functions parsing based on the code
Err(DataRecordError::DataInformationError(
DataInformationError::Unimplemented {
feature: "Special functions data parsing",
},
))
}
Self::SpecialFunctions(code) => match code {
SpecialFunctions::ManufacturerSpecific | SpecialFunctions::MoreRecordsFollow => {
Ok(Data {
value: Some(DataType::ManufacturerSpecific(input)),
size: input.len(),
})
}
SpecialFunctions::IdleFiller => Ok(Data {
value: None,
size: 0,
}),
SpecialFunctions::GlobalReadoutRequest => Ok(Data {
value: None,
size: 0,
}),
SpecialFunctions::Reserved => Err(DataRecordError::DataInformationError(
DataInformationError::InvalidValueInformation,
)),
},

Self::DateTypeG => {
let day = parse_single_or_every!(
Expand Down Expand Up @@ -1004,6 +1012,24 @@ mod tests {
assert_eq!(&parsed, "igal");
}

#[cfg(feature = "std")]
#[test]
fn text_unit_latin1_swedish_characters() {
// "Malmö" in Latin-1 (reversed byte order per M-Bus)
let bytes = [0xF6, 0x6D, 0x6C, 0x61, 0x4D]; // ö m l a M
let text = TextUnit::new(&bytes);
assert_eq!(String::from(text), "Malmö");
}

#[cfg(feature = "std")]
#[test]
fn text_unit_latin1_superscript_three() {
// "m³/h" in Latin-1 (reversed byte order per M-Bus)
let bytes = [0x68, 0x2F, 0xB3, 0x6D]; // h / ³ m
let text = TextUnit::new(&bytes);
assert_eq!(String::from(text), "m³/h");
}

#[test]
fn test_invalid_data_information() {
let data = [
Expand Down
52 changes: 23 additions & 29 deletions crates/m-bus-application-layer/src/data_record.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -69,43 +69,29 @@ impl<'a> DataRecord<'a> {
fixed_data_header: Option<&'a LongTplHeader>,
) -> Result<Self, DataRecordError> {
let data_record_header = DataRecordHeader::try_from(data)?;
let mut header_size = data_record_header.get_size();
if data_record_header
.raw_data_record_header
.data_information_block
.data_information_field
.data
== 0x0F
{
header_size = 0;
}
let header_size = data_record_header.get_size();
if data.len() < header_size {
return Err(DataRecordError::InsufficientData);
}
let offset = header_size;
let mut data_out = Data {
value: Some(DataType::ManufacturerSpecific(
let data_out = if let Some(data_info) = &data_record_header
.processed_data_record_header
.data_information
{
data_info.data_field_coding.parse(
data.get(offset..)
.ok_or(DataRecordError::InsufficientData)?,
)),
size: data.len() - offset,
};
if data_record_header
.raw_data_record_header
.value_information_block
.is_some()
{
if let Some(data_info) = &data_record_header
.processed_data_record_header
.data_information
{
data_out = data_info.data_field_coding.parse(
fixed_data_header,
)?
} else {
Data {
value: Some(DataType::ManufacturerSpecific(
data.get(offset..)
.ok_or(DataRecordError::InsufficientData)?,
fixed_data_header,
)?;
)),
size: data.len() - offset,
}
}
};

let mut record_size = data_record_header.get_size() + data_out.get_size();
if record_size > data.len() {
Expand Down Expand Up @@ -154,7 +140,7 @@ impl<'a> TryFrom<&'a [u8]> for RawDataRecordHeader<'a> {

let mut vifb = None;

if difb.data_information_field.data != 0x0F {
if !difb.data_information_field.is_special_function() {
vifb = Some(ValueInformationBlock::try_from(
data.get(offset..)
.ok_or(DataRecordError::InsufficientData)?,
Expand Down Expand Up @@ -194,6 +180,14 @@ impl TryFrom<&RawDataRecordHeader<'_>> for ProcessedDataRecordHeader {

value_information = Some(v);
data_information = Some(d);
} else if raw_data_record_header
.data_information_block
.data_information_field
.is_special_function()
{
data_information = Some(DataInformation::try_from(
&raw_data_record_header.data_information_block,
)?);
}

Ok(Self {
Expand Down
70 changes: 49 additions & 21 deletions crates/m-bus-application-layer/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -46,31 +46,51 @@ impl<'a> Iterator for DataRecords<'a> {
type Item = Result<DataRecord<'a>, DataRecordError>;

fn next(&mut self) -> Option<Self::Item> {
let mut _more_records_follow = false;

while self.offset < self.data.len() {
match self.data.get(self.offset)? {
0x1F => {
/* TODO: parse manufacturer specific */
_more_records_follow = true;
self.offset = self.data.len();
}
0x2F => {
self.offset += 1;
}
_ => {
let record = if let Some(long_tpl_header) = self.long_tpl_header {
DataRecord::try_from((self.data.get(self.offset..)?, long_tpl_header))
} else {
DataRecord::try_from(self.data.get(self.offset..)?)
};
if let Ok(record) = record {
self.offset += record.get_size();
return Some(Ok(record));
} else {
let dif = data_information::DataInformationField::from(*self.data.get(self.offset)?);

if dif.is_special_function() {
match dif.special_function() {
data_information::SpecialFunctions::IdleFiller => {
self.offset += 1;
}
data_information::SpecialFunctions::ManufacturerSpecific
| data_information::SpecialFunctions::MoreRecordsFollow => {
let remaining = self.data.get(self.offset..)?;
self.offset = self.data.len();
let record = if let Some(long_tpl_header) = self.long_tpl_header {
DataRecord::try_from((remaining, long_tpl_header))
} else {
DataRecord::try_from(remaining)
};
return Some(record);
}
data_information::SpecialFunctions::GlobalReadoutRequest => {
let remaining = self.data.get(self.offset..)?;
self.offset += 1;
let record = if let Some(long_tpl_header) = self.long_tpl_header {
DataRecord::try_from((remaining, long_tpl_header))
} else {
DataRecord::try_from(remaining)
};
return Some(record);
}
data_information::SpecialFunctions::Reserved => {
self.offset += 1;
}
}
} else {
let record = if let Some(long_tpl_header) = self.long_tpl_header {
DataRecord::try_from((self.data.get(self.offset..)?, long_tpl_header))
} else {
DataRecord::try_from(self.data.get(self.offset..)?)
};
if let Ok(record) = record {
self.offset += record.get_size();
return Some(Ok(record));
} else {
self.offset = self.data.len();
}
}
}
None
Expand Down Expand Up @@ -1485,4 +1505,12 @@ mod tests {
}
}
}

#[test]
fn global_readout_request_does_not_consume_following_records() {
// 0x7F followed by a valid 8-bit integer record: DIF=0x01, VIF=0x13, data=0x05
let data: &[u8] = &[0x7F, 0x01, 0x13, 0x05];
let records: Vec<_> = DataRecords::new(data, None).flatten().collect();
assert_eq!(records.len(), 2);
}
}
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