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)]
21#[non_exhaustive]
22pub enum SubpartVariety {
23    /// Null — `reserved_for_future_use(32)` = 0.
24    Null = 0x0000,
25    /// IQ — `reserved_for_future_use(32)` + `iq_data`.
26    Iq = 0x0001,
27    /// PRBS — `prbs_type(8)` + `reserved_for_future_use(96)`.
28    Prbs = 0x0002,
29    /// TX-SIG FEF — `reserved_for_future_use(32)`.
30    TxSigFef = 0x0003,
31}
32
33impl From<SubpartVariety> for u16 {
34    fn from(sv: SubpartVariety) -> Self {
35        sv as u16
36    }
37}
38
39impl From<num_enum::TryFromPrimitiveError<SubpartVariety>> for crate::error::Error {
40    fn from(_: num_enum::TryFromPrimitiveError<SubpartVariety>) -> Self {
41        // subpart_variety is a 16-bit field — casting the offending value to u8
42        // would truncate it, and InvalidPacketType is the wrong category anyway.
43        crate::error::Error::ReservedBitsViolation {
44            field: "subpart_variety",
45            reason: "Must be 0x0000..=0x0003 per ETSI TS 102 773 §5.2.12 Table 13",
46        }
47    }
48}
49
50/// PRBS type for SubpartVariety::Prbs.
51#[derive(Debug, Clone, Copy, PartialEq, Eq, TryFromPrimitive)]
52#[cfg_attr(feature = "serde", derive(serde::Serialize))]
53#[repr(u8)]
54#[non_exhaustive]
55pub enum PrbsType {
56    /// User-defined test/measurement.
57    UserDefined = 0x00,
58}
59
60impl From<PrbsType> for u8 {
61    fn from(pt: PrbsType) -> Self {
62        pt as u8
63    }
64}
65
66/// FEF sub-part payload (type 0x33) per ETSI TS 102 773 §5.2.12.
67///
68/// Layout (Figure 16):
69/// - byte 0: fef_idx (8 bits)
70/// - bytes 1-2: tx_identifier (16 bits)
71/// - bytes 3-6: rfu1 (32 bits) — must be 0
72/// - bytes 7-8: subpart_idx (16 bits)
73/// - bytes 9-10: subpart_variety (16 bits)
74/// - bytes 11-14: rfu2 (10 bits) + subpart_length (22 bits)
75/// - bytes 15..: subpart data (variable, format per variety)
76#[derive(Debug, Clone, PartialEq, Eq)]
77#[cfg_attr(feature = "serde", derive(serde::Serialize))]
78#[cfg_attr(feature = "yoke", derive(yoke::Yokeable))]
79pub struct FefSubPartPayload<'a> {
80    /// FEF index within super-frame.
81    pub fef_idx: u8,
82    /// Transmitter identifier (0x0000 = broadcast).
83    pub tx_identifier: u16,
84    /// Sub-part index p.
85    pub subpart_idx: u16,
86    /// Sub-part variety (Null/IQ/PRBS/TX-SIG).
87    pub subpart_variety: SubpartVariety,
88    /// Length in elementary time periods.
89    pub subpart_length: u32,
90    /// Raw sub-part data (format depends on variety).
91    pub subpart_data: &'a [u8],
92}
93
94/// Total header bytes before subpart_data: fef_idx(1) + tx_id(2) + rfu1(4) +
95/// subpart_idx(2) + variety(2) + rfu2+subpart_len(4) = 15.
96const FEF_SUBPART_HEADER_LEN: usize = 15;
97
98/// Mask for 22-bit subpart_length field.
99const SUBPART_LENGTH_MASK: u32 = 0x003F_FFFF;
100
101impl<'a> Parse<'a> for FefSubPartPayload<'a> {
102    type Error = crate::error::Error;
103
104    fn parse(bytes: &'a [u8]) -> Result<Self, crate::error::Error> {
105        if bytes.len() < FEF_SUBPART_HEADER_LEN {
106            return Err(crate::Error::BufferTooShort {
107                need: FEF_SUBPART_HEADER_LEN,
108                have: bytes.len(),
109                what: "FefSubPartPayload header",
110            });
111        }
112
113        // rfu1: bytes 3-6 (32 bits) — must be 0
114        if bytes[3] != 0 || bytes[4] != 0 || bytes[5] != 0 || bytes[6] != 0 {
115            return Err(crate::Error::ReservedBitsViolation {
116                field: "32-bit RFU (rfu1)",
117                reason: "Must be zero (ETSI TS 102 773 §5.2.12)",
118            });
119        }
120
121        let variety = SubpartVariety::try_from(u16::from_be_bytes([bytes[9], bytes[10]]))?;
122
123        // rfu2: byte 11 (8 bits) + byte 12 [7:6] (2 bits) = 10 bits — must be 0
124        if bytes[11] != 0 || (bytes[12] & 0xC0 != 0) {
125            return Err(crate::Error::ReservedBitsViolation {
126                field: "10-bit RFU (rfu2)",
127                reason: "Must be zero (ETSI TS 102 773 §5.2.12)",
128            });
129        }
130
131        // subpart_length: byte 12 [5:0] (6 bits) + byte 13 (8 bits) + byte 14 (8 bits) = 22 bits
132        let subpart_length =
133            ((bytes[12] & 0x3F) as u32) << 16 | (bytes[13] as u32) << 8 | (bytes[14] as u32);
134
135        Ok(FefSubPartPayload {
136            fef_idx: bytes[0],
137            tx_identifier: u16::from_be_bytes([bytes[1], bytes[2]]),
138            subpart_idx: u16::from_be_bytes([bytes[7], bytes[8]]),
139            subpart_variety: variety,
140            subpart_length,
141            subpart_data: &bytes[FEF_SUBPART_HEADER_LEN..],
142        })
143    }
144}
145
146impl<'a> crate::traits::PayloadDef<'a> for FefSubPartPayload<'a> {
147    const PACKET_TYPE: u8 = 0x33;
148    const NAME: &'static str = "FEF_SUBPART";
149}
150
151impl Serialize for FefSubPartPayload<'_> {
152    type Error = crate::error::Error;
153
154    fn serialized_len(&self) -> usize {
155        FEF_SUBPART_HEADER_LEN + self.subpart_data.len()
156    }
157
158    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize, crate::error::Error> {
159        if buf.len() < self.serialized_len() {
160            return Err(crate::Error::OutputBufferTooSmall {
161                need: self.serialized_len(),
162                have: buf.len(),
163            });
164        }
165
166        if self.subpart_length > SUBPART_LENGTH_MASK {
167            return Err(crate::Error::ReservedBitsViolation {
168                field: "subpart_length",
169                reason: "Must fit in 22 bits",
170            });
171        }
172
173        buf[0] = self.fef_idx;
174        let tx_id = self.tx_identifier.to_be_bytes();
175        buf[1] = tx_id[0];
176        buf[2] = tx_id[1];
177        // rfu1 = 0
178        buf[3] = 0;
179        buf[4] = 0;
180        buf[5] = 0;
181        buf[6] = 0;
182        let sub_idx = self.subpart_idx.to_be_bytes();
183        buf[7] = sub_idx[0];
184        buf[8] = sub_idx[1];
185        let variety = u16::from(self.subpart_variety);
186        buf[9] = (variety >> 8) as u8;
187        buf[10] = (variety & 0xFF) as u8;
188        // rfu2 = 0 (top 2 bits byte 12) + rfu2 = 0 (byte 11)
189        buf[11] = 0;
190        // subpart_length: 22 bits → byte 12 [5:0] = top 6, byte 13 = mid 8, byte 14 = bot 8
191        buf[12] = ((self.subpart_length >> 16) & 0x3F) as u8;
192        buf[13] = (self.subpart_length >> 8) as u8;
193        buf[14] = (self.subpart_length & 0xFF) as u8;
194
195        if !self.subpart_data.is_empty() {
196            buf[FEF_SUBPART_HEADER_LEN..FEF_SUBPART_HEADER_LEN + self.subpart_data.len()]
197                .copy_from_slice(self.subpart_data);
198        }
199
200        Ok(self.serialized_len())
201    }
202}
203
204impl fmt::Display for FefSubPartPayload<'_> {
205    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
206        write!(
207            f,
208            "FEF SubPart {{ fef_idx: {}, tx_id: 0x{:04X}, subpart_idx: {}, variety: {:?}, length: {} }}",
209            self.fef_idx, self.tx_identifier, self.subpart_idx, self.subpart_variety, self.subpart_length
210        )
211    }
212}
213
214#[cfg(test)]
215mod tests {
216    use super::*;
217
218    #[test]
219    fn parse_extracts_fields() {
220        // subpart_length = 4096 = 0x1000.
221        // 22-bit: byte 12 [5:0] = (0x1000 >> 16) & 0x3F = 0,
222        //         byte 13 = (0x1000 >> 8) & 0xFF = 0x10,
223        //         byte 14 = 0x1000 & 0xFF = 0x00.
224        let mut buf = [0u8; 15];
225        buf[0] = 0x02; // fef_idx
226        buf[1] = 0x00;
227        buf[2] = 0x01; // tx_id = 1
228                       // bytes 3-6 = rfu1 = 0
229        buf[7] = 0x00;
230        buf[8] = 0x05; // subpart_idx = 5
231        buf[9] = 0x00;
232        buf[10] = 0x01; // variety = IQ
233                        // byte 11 = rfu2 = 0
234                        // byte 12 top 2 = rfu2 = 0, bottom 6 = subpart top = 0
235                        // byte 13 = subpart mid = 0x10
236        buf[13] = 0x10;
237        // byte 14 = subpart bot = 0
238        // subpart_data starts at offset 15
239
240        let result = FefSubPartPayload::parse(&buf).unwrap();
241        assert_eq!(result.fef_idx, 2);
242        assert_eq!(result.tx_identifier, 0x0001);
243        assert_eq!(result.subpart_idx, 5);
244        assert_eq!(result.subpart_variety, SubpartVariety::Iq);
245        assert_eq!(result.subpart_length, 0x1000);
246    }
247
248    #[test]
249    fn parse_rejects_invalid_variety() {
250        let mut buf = [0u8; 15];
251        buf[9] = 0x00;
252        buf[10] = 0x04; // variety = 0x0004 (reserved)
253        assert!(FefSubPartPayload::parse(&buf).is_err());
254    }
255
256    #[test]
257    fn parse_rejects_nonzero_rfu1() {
258        let mut buf = [0u8; 15];
259        buf[3] = 0x01;
260        assert!(FefSubPartPayload::parse(&buf).is_err());
261    }
262
263    #[test]
264    fn parse_rejects_nonzero_rfu2_byte11() {
265        let mut buf = [0u8; 15];
266        buf[11] = 0x01;
267        assert!(FefSubPartPayload::parse(&buf).is_err());
268    }
269
270    #[test]
271    fn parse_rejects_nonzero_rfu2_byte12_top() {
272        let mut buf = [0u8; 15];
273        buf[12] = 0xC0;
274        assert!(FefSubPartPayload::parse(&buf).is_err());
275    }
276
277    #[test]
278    fn parse_rejects_short_buffer() {
279        let buf = [0u8; 14];
280        assert!(FefSubPartPayload::parse(&buf).is_err());
281    }
282
283    #[test]
284    fn serialize_round_trip() {
285        let orig = FefSubPartPayload {
286            fef_idx: 1,
287            tx_identifier: 0x0000,
288            subpart_idx: 3,
289            subpart_variety: SubpartVariety::Null,
290            subpart_length: 2048,
291            subpart_data: &[],
292        };
293        let mut buf = vec![0u8; orig.serialized_len()];
294        orig.serialize_into(&mut buf).unwrap();
295        let parsed = FefSubPartPayload::parse(&buf).unwrap();
296        assert_eq!(orig, parsed);
297    }
298
299    #[test]
300    fn broadcast_tx_identifier() {
301        let buf = [0u8; 15];
302        let result = FefSubPartPayload::parse(&buf).unwrap();
303        assert_eq!(result.tx_identifier, 0x0000);
304    }
305
306    #[test]
307    fn subpart_variety_try_from_all() {
308        assert_eq!(SubpartVariety::try_from(0x0000), Ok(SubpartVariety::Null));
309        assert_eq!(SubpartVariety::try_from(0x0001), Ok(SubpartVariety::Iq));
310        assert_eq!(SubpartVariety::try_from(0x0002), Ok(SubpartVariety::Prbs));
311        assert_eq!(
312            SubpartVariety::try_from(0x0003),
313            Ok(SubpartVariety::TxSigFef)
314        );
315    }
316
317    #[test]
318    fn subpart_variety_try_from_reserved() {
319        assert!(SubpartVariety::try_from(0x0004).is_err());
320        assert!(SubpartVariety::try_from(0xFFFF).is_err());
321    }
322
323    #[test]
324    fn exhaustive_subpart_variety_sweep() {
325        let mut matched = 0u32;
326        for value in 0u16..=0xFFFF {
327            if let Ok(v) = SubpartVariety::try_from(value) {
328                assert_eq!(v as u16, value, "round-trip failed for {value:#06x}");
329                matched += 1;
330            }
331        }
332        assert_eq!(matched, 4, "expected 4 matched variants");
333    }
334
335    #[test]
336    fn exhaustive_prbs_type_sweep() {
337        let mut matched = 0u16;
338        for byte in 0u8..=0xFF {
339            if let Ok(v) = PrbsType::try_from(byte) {
340                assert_eq!(v as u8, byte, "round-trip failed for {byte:#04x}");
341                matched += 1;
342            }
343        }
344        assert_eq!(matched, 1, "expected 1 matched variant");
345    }
346}
dvb_t2mi/payload/fef_subpart.rs

dvb_t2mi/payload/
fef_subpart.rs
