dvb_t2mi/payload/
fef_subpart.rs

1//! T2-MI payload type 0x33: FEF sub-part — §5.2.12.
2//!
3//! Carries individual sub-parts of a composite FEF part.
4//! Sub-part variety determines the body format:
5//! - 0x0000: Null (reserved_for_future_use 32 bits)
6//! - 0x0001: IQ (reserved 32 bits + iq_data variable)
7//! - 0x0002: PRBS (prbs_type 8 bits + reserved 96 bits)
8//! - 0x0003: TX-SIG FEF (reserved 32 bits)
9//! - 0x0004..0xFFFF: Reserved for future use
10
11use std::fmt;
12
13use num_enum::TryFromPrimitive;
14
15use dvb_common::{Parse, Serialize};
16
17/// Sub-part variety per §5.2.12 Table 13.
18#[derive(Debug, Clone, Copy, PartialEq, Eq, TryFromPrimitive)]
19#[cfg_attr(feature = "serde", derive(serde::Serialize))]
20#[repr(u16)]
21pub enum SubpartVariety {
22    /// Null — `reserved_for_future_use(32)` = 0.
23    Null = 0x0000,
24    /// IQ — `reserved_for_future_use(32)` + `iq_data`.
25    Iq = 0x0001,
26    /// PRBS — `prbs_type(8)` + `reserved_for_future_use(96)`.
27    Prbs = 0x0002,
28    /// TX-SIG FEF — `reserved_for_future_use(32)`.
29    TxSigFef = 0x0003,
30}
31
32impl From<SubpartVariety> for u16 {
33    fn from(sv: SubpartVariety) -> Self {
34        sv as u16
35    }
36}
37
38impl From<num_enum::TryFromPrimitiveError<SubpartVariety>> for crate::error::Error {
39    fn from(_: num_enum::TryFromPrimitiveError<SubpartVariety>) -> Self {
40        // subpart_variety is a 16-bit field — casting the offending value to u8
41        // would truncate it, and InvalidPacketType is the wrong category anyway.
42        crate::error::Error::ReservedBitsViolation {
43            field: "subpart_variety",
44            reason: "Must be 0x0000..=0x0003 per ETSI TS 102 773 §5.2.12 Table 13",
45        }
46    }
47}
48
49/// PRBS type for SubpartVariety::Prbs.
50#[derive(Debug, Clone, Copy, PartialEq, Eq, TryFromPrimitive)]
51#[cfg_attr(feature = "serde", derive(serde::Serialize))]
52#[repr(u8)]
53pub enum PrbsType {
54    /// User-defined test/measurement.
55    UserDefined = 0x00,
56}
57
58impl From<PrbsType> for u8 {
59    fn from(pt: PrbsType) -> Self {
60        pt as u8
61    }
62}
63
64/// FEF sub-part payload (type 0x33) per ETSI TS 102 773 §5.2.12.
65///
66/// Layout (Figure 16):
67/// - byte 0: fef_idx (8 bits)
68/// - bytes 1-2: tx_identifier (16 bits)
69/// - bytes 3-6: rfu1 (32 bits) — must be 0
70/// - bytes 7-8: subpart_idx (16 bits)
71/// - bytes 9-10: subpart_variety (16 bits)
72/// - bytes 11-14: rfu2 (10 bits) + subpart_length (22 bits)
73/// - bytes 15..: subpart data (variable, format per variety)
74#[derive(Debug, Clone, PartialEq, Eq)]
75#[cfg_attr(feature = "serde", derive(serde::Serialize))]
76pub struct FefSubPartPayload<'a> {
77    /// FEF index within super-frame.
78    pub fef_idx: u8,
79    /// Transmitter identifier (0x0000 = broadcast).
80    pub tx_identifier: u16,
81    /// Sub-part index p.
82    pub subpart_idx: u16,
83    /// Sub-part variety (Null/IQ/PRBS/TX-SIG).
84    pub subpart_variety: SubpartVariety,
85    /// Length in elementary time periods.
86    pub subpart_length: u32,
87    /// Raw sub-part data (format depends on variety).
88    pub subpart_data: &'a [u8],
89}
90
91/// Total header bytes before subpart_data: fef_idx(1) + tx_id(2) + rfu1(4) +
92/// subpart_idx(2) + variety(2) + rfu2+subpart_len(4) = 15.
93const FEF_SUBPART_HEADER_LEN: usize = 15;
94
95/// Mask for 22-bit subpart_length field.
96const SUBPART_LENGTH_MASK: u32 = 0x003F_FFFF;
97
98impl<'a> Parse<'a> for FefSubPartPayload<'a> {
99    type Error = crate::error::Error;
100
101    fn parse(bytes: &'a [u8]) -> Result<Self, crate::error::Error> {
102        if bytes.len() < FEF_SUBPART_HEADER_LEN {
103            return Err(crate::Error::BufferTooShort {
104                need: FEF_SUBPART_HEADER_LEN,
105                have: bytes.len(),
106                what: "FefSubPartPayload header",
107            });
108        }
109
110        // rfu1: bytes 3-6 (32 bits) — must be 0
111        if bytes[3] != 0 || bytes[4] != 0 || bytes[5] != 0 || bytes[6] != 0 {
112            return Err(crate::Error::ReservedBitsViolation {
113                field: "32-bit RFU (rfu1)",
114                reason: "Must be zero (ETSI TS 102 773 §5.2.12)",
115            });
116        }
117
118        let variety = SubpartVariety::try_from(u16::from_be_bytes([bytes[9], bytes[10]]))?;
119
120        // rfu2: byte 11 (8 bits) + byte 12 [7:6] (2 bits) = 10 bits — must be 0
121        if bytes[11] != 0 || (bytes[12] & 0xC0 != 0) {
122            return Err(crate::Error::ReservedBitsViolation {
123                field: "10-bit RFU (rfu2)",
124                reason: "Must be zero (ETSI TS 102 773 §5.2.12)",
125            });
126        }
127
128        // subpart_length: byte 12 [5:0] (6 bits) + byte 13 (8 bits) + byte 14 (8 bits) = 22 bits
129        let subpart_length =
130            ((bytes[12] & 0x3F) as u32) << 16 | (bytes[13] as u32) << 8 | (bytes[14] as u32);
131
132        Ok(FefSubPartPayload {
133            fef_idx: bytes[0],
134            tx_identifier: u16::from_be_bytes([bytes[1], bytes[2]]),
135            subpart_idx: u16::from_be_bytes([bytes[7], bytes[8]]),
136            subpart_variety: variety,
137            subpart_length,
138            subpart_data: &bytes[FEF_SUBPART_HEADER_LEN..],
139        })
140    }
141}
142
143impl<'a> crate::traits::PayloadDef<'a> for FefSubPartPayload<'a> {
144    const PACKET_TYPE: u8 = 0x33;
145    const NAME: &'static str = "FEF_SUBPART";
146}
147
148impl Serialize for FefSubPartPayload<'_> {
149    type Error = crate::error::Error;
150
151    fn serialized_len(&self) -> usize {
152        FEF_SUBPART_HEADER_LEN + self.subpart_data.len()
153    }
154
155    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize, crate::error::Error> {
156        if buf.len() < self.serialized_len() {
157            return Err(crate::Error::OutputBufferTooSmall {
158                need: self.serialized_len(),
159                have: buf.len(),
160            });
161        }
162
163        if self.subpart_length > SUBPART_LENGTH_MASK {
164            return Err(crate::Error::ReservedBitsViolation {
165                field: "subpart_length",
166                reason: "Must fit in 22 bits",
167            });
168        }
169
170        buf[0] = self.fef_idx;
171        let tx_id = self.tx_identifier.to_be_bytes();
172        buf[1] = tx_id[0];
173        buf[2] = tx_id[1];
174        // rfu1 = 0
175        buf[3] = 0;
176        buf[4] = 0;
177        buf[5] = 0;
178        buf[6] = 0;
179        let sub_idx = self.subpart_idx.to_be_bytes();
180        buf[7] = sub_idx[0];
181        buf[8] = sub_idx[1];
182        let variety = u16::from(self.subpart_variety);
183        buf[9] = (variety >> 8) as u8;
184        buf[10] = (variety & 0xFF) as u8;
185        // rfu2 = 0 (top 2 bits byte 12) + rfu2 = 0 (byte 11)
186        buf[11] = 0;
187        // subpart_length: 22 bits → byte 12 [5:0] = top 6, byte 13 = mid 8, byte 14 = bot 8
188        buf[12] = ((self.subpart_length >> 16) & 0x3F) as u8;
189        buf[13] = (self.subpart_length >> 8) as u8;
190        buf[14] = (self.subpart_length & 0xFF) as u8;
191
192        if !self.subpart_data.is_empty() {
193            buf[FEF_SUBPART_HEADER_LEN..FEF_SUBPART_HEADER_LEN + self.subpart_data.len()]
194                .copy_from_slice(self.subpart_data);
195        }
196
197        Ok(self.serialized_len())
198    }
199}
200
201impl fmt::Display for FefSubPartPayload<'_> {
202    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
203        write!(
204            f,
205            "FEF SubPart {{ fef_idx: {}, tx_id: 0x{:04X}, subpart_idx: {}, variety: {:?}, length: {} }}",
206            self.fef_idx, self.tx_identifier, self.subpart_idx, self.subpart_variety, self.subpart_length
207        )
208    }
209}
210
211#[cfg(test)]
212mod tests {
213    use super::*;
214
215    #[test]
216    fn parse_extracts_fields() {
217        // subpart_length = 4096 = 0x1000.
218        // 22-bit: byte 12 [5:0] = (0x1000 >> 16) & 0x3F = 0,
219        //         byte 13 = (0x1000 >> 8) & 0xFF = 0x10,
220        //         byte 14 = 0x1000 & 0xFF = 0x00.
221        let mut buf = [0u8; 15];
222        buf[0] = 0x02; // fef_idx
223        buf[1] = 0x00;
224        buf[2] = 0x01; // tx_id = 1
225                       // bytes 3-6 = rfu1 = 0
226        buf[7] = 0x00;
227        buf[8] = 0x05; // subpart_idx = 5
228        buf[9] = 0x00;
229        buf[10] = 0x01; // variety = IQ
230                        // byte 11 = rfu2 = 0
231                        // byte 12 top 2 = rfu2 = 0, bottom 6 = subpart top = 0
232                        // byte 13 = subpart mid = 0x10
233        buf[13] = 0x10;
234        // byte 14 = subpart bot = 0
235        // subpart_data starts at offset 15
236
237        let result = FefSubPartPayload::parse(&buf).unwrap();
238        assert_eq!(result.fef_idx, 2);
239        assert_eq!(result.tx_identifier, 0x0001);
240        assert_eq!(result.subpart_idx, 5);
241        assert_eq!(result.subpart_variety, SubpartVariety::Iq);
242        assert_eq!(result.subpart_length, 0x1000);
243    }
244
245    #[test]
246    fn parse_rejects_invalid_variety() {
247        let mut buf = [0u8; 15];
248        buf[9] = 0x00;
249        buf[10] = 0x04; // variety = 0x0004 (reserved)
250        assert!(FefSubPartPayload::parse(&buf).is_err());
251    }
252
253    #[test]
254    fn parse_rejects_nonzero_rfu1() {
255        let mut buf = [0u8; 15];
256        buf[3] = 0x01;
257        assert!(FefSubPartPayload::parse(&buf).is_err());
258    }
259
260    #[test]
261    fn parse_rejects_nonzero_rfu2_byte11() {
262        let mut buf = [0u8; 15];
263        buf[11] = 0x01;
264        assert!(FefSubPartPayload::parse(&buf).is_err());
265    }
266
267    #[test]
268    fn parse_rejects_nonzero_rfu2_byte12_top() {
269        let mut buf = [0u8; 15];
270        buf[12] = 0xC0;
271        assert!(FefSubPartPayload::parse(&buf).is_err());
272    }
273
274    #[test]
275    fn parse_rejects_short_buffer() {
276        let buf = [0u8; 14];
277        assert!(FefSubPartPayload::parse(&buf).is_err());
278    }
279
280    #[test]
281    fn serialize_round_trip() {
282        let orig = FefSubPartPayload {
283            fef_idx: 1,
284            tx_identifier: 0x0000,
285            subpart_idx: 3,
286            subpart_variety: SubpartVariety::Null,
287            subpart_length: 2048,
288            subpart_data: &[],
289        };
290        let mut buf = vec![0u8; orig.serialized_len()];
291        orig.serialize_into(&mut buf).unwrap();
292        let parsed = FefSubPartPayload::parse(&buf).unwrap();
293        assert_eq!(orig, parsed);
294    }
295
296    #[test]
297    fn broadcast_tx_identifier() {
298        let buf = [0u8; 15];
299        let result = FefSubPartPayload::parse(&buf).unwrap();
300        assert_eq!(result.tx_identifier, 0x0000);
301    }
302
303    #[test]
304    fn subpart_variety_try_from_all() {
305        assert_eq!(SubpartVariety::try_from(0x0000), Ok(SubpartVariety::Null));
306        assert_eq!(SubpartVariety::try_from(0x0001), Ok(SubpartVariety::Iq));
307        assert_eq!(SubpartVariety::try_from(0x0002), Ok(SubpartVariety::Prbs));
308        assert_eq!(
309            SubpartVariety::try_from(0x0003),
310            Ok(SubpartVariety::TxSigFef)
311        );
312    }
313
314    #[test]
315    fn subpart_variety_try_from_reserved() {
316        assert!(SubpartVariety::try_from(0x0004).is_err());
317        assert!(SubpartVariety::try_from(0xFFFF).is_err());
318    }
319
320    #[test]
321    fn exhaustive_subpart_variety_sweep() {
322        let mut matched = 0u32;
323        for value in 0u16..=0xFFFF {
324            if let Ok(v) = SubpartVariety::try_from(value) {
325                assert_eq!(v as u16, value, "round-trip failed for {value:#06x}");
326                matched += 1;
327            }
328        }
329        assert_eq!(matched, 4, "expected 4 matched variants");
330    }
331
332    #[test]
333    fn exhaustive_prbs_type_sweep() {
334        let mut matched = 0u16;
335        for byte in 0u8..=0xFF {
336            if let Ok(v) = PrbsType::try_from(byte) {
337                assert_eq!(v as u8, byte, "round-trip failed for {byte:#04x}");
338                matched += 1;
339            }
340        }
341        assert_eq!(matched, 1, "expected 1 matched variant");
342    }
343}
dvb_t2mi/payload/fef_subpart.rs

dvb_t2mi/payload/
fef_subpart.rs
