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//! High-performance decoding for Message.
use super::Message;
impl Message {
/// Decode all signals into the output buffer (physical values).
///
/// This is a zero-allocation decode path for high-speed CAN processing.
/// Signals are decoded in order and written to the output buffer.
///
/// # Arguments
/// * `data` - Raw CAN payload bytes
/// * `out` - Output buffer for physical values (must be at least `signals().len()` long)
///
/// # Returns
/// Number of signals decoded, or 0 if payload is too short.
///
/// # Example
/// ```rust,ignore
/// let msg = dbc.messages().find_by_id(256).unwrap();
/// let mut values = [0.0f64; 64];
/// let count = msg.decode_into(&payload, &mut values);
/// for i in 0..count {
/// let signal = msg.signals().at(i).unwrap();
/// println!("{}: {}", signal.name(), values[i]);
/// }
/// ```
#[inline]
pub fn decode_into(&self, data: &[u8], out: &mut [f64]) -> usize {
// Check minimum payload length
let min_bytes = self.min_bytes_required() as usize;
if data.len() < min_bytes {
return 0;
}
// Use zip to avoid redundant bounds checks - iterates min(signals, out) times
let mut count = 0;
for (out_val, signal) in out.iter_mut().zip(self.signals().iter()) {
// decode_raw returns (raw_value, physical_value)
*out_val = signal.decode_raw(data).map(|(_, p)| p).unwrap_or(0.0);
count += 1;
}
count
}
/// Decode all signals into the output buffer (raw integer values).
///
/// Returns raw values before factor/offset conversion.
/// Useful for encoding or debugging.
///
/// # Arguments
/// * `data` - Raw CAN payload bytes
/// * `out` - Output buffer for raw values (must be at least `signals().len()` long)
///
/// # Returns
/// Number of signals decoded, or 0 if payload is too short.
#[inline]
pub fn decode_raw_into(&self, data: &[u8], out: &mut [i64]) -> usize {
let min_bytes = self.min_bytes_required() as usize;
if data.len() < min_bytes {
return 0;
}
// Use zip to avoid redundant bounds checks
let mut count = 0;
for (out_val, signal) in out.iter_mut().zip(self.signals().iter()) {
*out_val = signal.decode_raw(data).map(|(r, _)| r).unwrap_or(0);
count += 1;
}
count
}
/// Decode a single signal by index.
///
/// Returns the physical value or `None` if index is out of bounds or decode fails.
#[inline]
pub fn decode_signal(&self, index: usize, data: &[u8]) -> Option<f64> {
let signal = self.signals().at(index)?;
signal.decode_raw(data).ok().map(|(_, physical)| physical)
}
/// Decode a single signal by index (raw value).
///
/// Returns the raw integer value or `None` if index is out of bounds or decode fails.
#[inline]
pub fn decode_signal_raw(&self, index: usize, data: &[u8]) -> Option<i64> {
let signal = self.signals().at(index)?;
signal.decode_raw(data).ok().map(|(raw, _)| raw)
}
}
#[cfg(test)]
mod tests {
use crate::Dbc;
#[test]
fn test_decode_into_basic() {
let dbc = Dbc::parse(
r#"VERSION "1.0"
BU_: ECM
BO_ 256 Engine : 8 ECM
SG_ RPM : 0|16@1+ (0.25,0) [0|8000] "rpm" *
SG_ Temp : 16|8@1- (1,-40) [-40|215] "C" *
"#,
)
.unwrap();
let msg = dbc.messages().find_by_id(256).unwrap();
// RPM = 2000 (raw 8000 = 0x1F40), Temp = 50°C (raw 90 = 0x5A)
let payload = [0x40, 0x1F, 0x5A, 0x00, 0x00, 0x00, 0x00, 0x00];
let mut values = [0.0f64; 8];
let count = msg.decode_into(&payload, &mut values);
assert_eq!(count, 2);
assert_eq!(values[0], 2000.0); // RPM
assert_eq!(values[1], 50.0); // Temp
}
#[test]
fn test_decode_raw_into() {
let dbc = Dbc::parse(
r#"VERSION "1.0"
BU_: ECM
BO_ 256 Engine : 8 ECM
SG_ RPM : 0|16@1+ (0.25,0) [0|8000] "rpm" *
"#,
)
.unwrap();
let msg = dbc.messages().find_by_id(256).unwrap();
let payload = [0x40, 0x1F, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00];
let mut raw_values = [0i64; 8];
let count = msg.decode_raw_into(&payload, &mut raw_values);
assert_eq!(count, 1);
assert_eq!(raw_values[0], 8000); // Raw before factor
}
#[test]
fn test_decode_into_payload_too_short() {
let dbc = Dbc::parse(
r#"VERSION "1.0"
BU_: ECM
BO_ 256 Engine : 8 ECM
SG_ RPM : 0|16@1+ (1,0) [0|65535] "rpm" *
"#,
)
.unwrap();
let msg = dbc.messages().find_by_id(256).unwrap();
// Payload too short (need 2 bytes for 16-bit signal)
let payload = [0x40];
let mut values = [0.0f64; 8];
let count = msg.decode_into(&payload, &mut values);
assert_eq!(count, 0);
}
#[test]
fn test_decode_signal_by_index() {
let dbc = Dbc::parse(
r#"VERSION "1.0"
BU_: ECM
BO_ 256 Engine : 8 ECM
SG_ RPM : 0|16@1+ (0.25,0) [0|8000] "rpm" *
SG_ Temp : 16|8@1- (1,-40) [-40|215] "C" *
"#,
)
.unwrap();
let msg = dbc.messages().find_by_id(256).unwrap();
let payload = [0x40, 0x1F, 0x5A, 0x00, 0x00, 0x00, 0x00, 0x00];
assert_eq!(msg.decode_signal(0, &payload), Some(2000.0));
assert_eq!(msg.decode_signal(1, &payload), Some(50.0));
assert_eq!(msg.decode_signal(2, &payload), None); // Out of bounds
}
#[test]
fn test_decode_into_buffer_smaller_than_signals() {
let dbc = Dbc::parse(
r#"VERSION "1.0"
BU_: ECM
BO_ 256 Engine : 8 ECM
SG_ Sig1 : 0|8@1+ (1,0) [0|255] "" *
SG_ Sig2 : 8|8@1+ (1,0) [0|255] "" *
SG_ Sig3 : 16|8@1+ (1,0) [0|255] "" *
"#,
)
.unwrap();
let msg = dbc.messages().find_by_id(256).unwrap();
let payload = [0x01, 0x02, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00];
// Buffer only has space for 2 values, but message has 3 signals
let mut values = [0.0f64; 2];
let count = msg.decode_into(&payload, &mut values);
assert_eq!(count, 2);
assert_eq!(values[0], 1.0);
assert_eq!(values[1], 2.0);
}
}