dvb_si/tables/
pmt.rs

1//! Program Map Table — MPEG-2 ISO/IEC 13818-1 §2.4.4.8.
2//!
3//! PMT describes the elementary streams that make up one programme.
4//! Carried on a per-programme PID signalled by the PAT, with table_id 0x02.
5//! Descriptor parsing is out of scope for this commit — raw bytes only.
6
7use crate::error::{Error, Result};
8use crate::traits::Table;
9use dvb_common::{Parse, Serialize};
10
11/// PMT table_id (ISO/IEC 13818-1 Table 2-30).
12pub const TABLE_ID: u8 = 0x02;
13/// PMT PIDs are programme-specific and signalled via PAT; 0x0000 is a
14/// placeholder meaning "no well-known PID".
15pub const PID: u16 = 0x0000;
16
17const MIN_HEADER_LEN: usize = 3;
18const EXTENSION_HEADER_LEN: usize = 5;
19const PCR_PID_LEN: usize = 2;
20const PROG_INFO_LEN_BYTES: usize = 2;
21const CRC_LEN: usize = 4;
22const STREAM_HEADER_LEN: usize = 5;
23
24/// One elementary stream entry in the PMT's ES loop.
25#[derive(Debug, Clone, PartialEq, Eq)]
26#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
27pub struct PmtStream<'a> {
28    /// MPEG-2 stream_type byte (ISO/IEC 13818-1 Table 2-34).
29    pub stream_type: u8,
30    /// 13-bit elementary stream PID.
31    pub elementary_pid: u16,
32    /// Raw ES_info descriptor bytes; parsing lives in crate::descriptors.
33    #[cfg_attr(feature = "serde", serde(borrow))]
34    pub es_info: &'a [u8],
35}
36
37/// Program Map Table.
38#[derive(Debug, Clone, PartialEq, Eq)]
39#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
40pub struct Pmt<'a> {
41    /// Programme number from the table_id_extension field.
42    pub program_number: u16,
43    /// 5-bit version_number.
44    pub version_number: u8,
45    /// current_next_indicator bit.
46    pub current_next_indicator: bool,
47    /// 13-bit PCR PID.
48    pub pcr_pid: u16,
49    /// Raw program_info descriptor bytes.
50    #[cfg_attr(feature = "serde", serde(borrow))]
51    pub program_info: &'a [u8],
52    /// Elementary streams in wire order.
53    #[cfg_attr(feature = "serde", serde(borrow))]
54    pub streams: Vec<PmtStream<'a>>,
55}
56
57impl<'a> Parse<'a> for Pmt<'a> {
58    type Error = crate::error::Error;
59    fn parse(bytes: &'a [u8]) -> Result<Self> {
60        let min_len = MIN_HEADER_LEN
61            + EXTENSION_HEADER_LEN
62            + PCR_PID_LEN
63            + PROG_INFO_LEN_BYTES
64            + CRC_LEN;
65        if bytes.len() < min_len {
66            return Err(Error::BufferTooShort {
67                need: min_len,
68                have: bytes.len(),
69                what: "Pmt",
70            });
71        }
72        if bytes[0] != TABLE_ID {
73            return Err(Error::UnexpectedTableId {
74                table_id: bytes[0],
75                what: "Pmt",
76                expected: &[TABLE_ID],
77            });
78        }
79
80        let section_length = ((bytes[1] & 0x0F) as u16) << 8 | bytes[2] as u16;
81        let total = MIN_HEADER_LEN + section_length as usize;
82        if bytes.len() < total {
83            return Err(Error::SectionLengthOverflow {
84                declared: section_length as usize,
85                available: bytes.len() - MIN_HEADER_LEN,
86            });
87        }
88
89        let program_number = u16::from_be_bytes([bytes[3], bytes[4]]);
90        let version_number = (bytes[5] >> 1) & 0x1F;
91        let current_next_indicator = (bytes[5] & 0x01) != 0;
92
93        let pcr_pid = (((bytes[8] & 0x1F) as u16) << 8) | bytes[9] as u16;
94        let program_info_length =
95            (((bytes[10] & 0x0F) as usize) << 8) | bytes[11] as usize;
96
97        let prog_info_start = MIN_HEADER_LEN
98            + EXTENSION_HEADER_LEN
99            + PCR_PID_LEN
100            + PROG_INFO_LEN_BYTES;
101        let prog_info_end = prog_info_start + program_info_length;
102        let stream_loop_end = total - CRC_LEN;
103        if prog_info_end > stream_loop_end {
104            return Err(Error::SectionLengthOverflow {
105                declared: program_info_length,
106                available: stream_loop_end - prog_info_start,
107            });
108        }
109        let program_info = &bytes[prog_info_start..prog_info_end];
110
111        let mut streams = Vec::new();
112        let mut pos = prog_info_end;
113        while pos + STREAM_HEADER_LEN <= stream_loop_end {
114            let stream_type = bytes[pos];
115            let elementary_pid =
116                (((bytes[pos + 1] & 0x1F) as u16) << 8) | bytes[pos + 2] as u16;
117            let es_info_length =
118                (((bytes[pos + 3] & 0x0F) as usize) << 8) | bytes[pos + 4] as usize;
119            let es_start = pos + STREAM_HEADER_LEN;
120            let es_end = es_start + es_info_length;
121            if es_end > stream_loop_end {
122                return Err(Error::SectionLengthOverflow {
123                    declared: es_info_length,
124                    available: stream_loop_end - es_start,
125                });
126            }
127            streams.push(PmtStream {
128                stream_type,
129                elementary_pid,
130                es_info: &bytes[es_start..es_end],
131            });
132            pos = es_end;
133        }
134
135        Ok(Pmt {
136            program_number,
137            version_number,
138            current_next_indicator,
139            pcr_pid,
140            program_info,
141            streams,
142        })
143    }
144}
145
146impl Serialize for Pmt<'_> {
147    type Error = crate::error::Error;
148    fn serialized_len(&self) -> usize {
149        let streams_bytes: usize = self
150            .streams
151            .iter()
152            .map(|s| STREAM_HEADER_LEN + s.es_info.len())
153            .sum();
154        MIN_HEADER_LEN
155            + EXTENSION_HEADER_LEN
156            + PCR_PID_LEN
157            + PROG_INFO_LEN_BYTES
158            + self.program_info.len()
159            + streams_bytes
160            + CRC_LEN
161    }
162
163    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
164        let len = self.serialized_len();
165        if buf.len() < len {
166            return Err(Error::OutputBufferTooSmall {
167                need: len,
168                have: buf.len(),
169            });
170        }
171
172        let section_length: u16 = (len - MIN_HEADER_LEN) as u16;
173        buf[0] = TABLE_ID;
174        buf[1] = 0xB0 | ((section_length >> 8) as u8 & 0x0F);
175        buf[2] = (section_length & 0xFF) as u8;
176        buf[3..5].copy_from_slice(&self.program_number.to_be_bytes());
177        buf[5] = 0xC0 | ((self.version_number & 0x1F) << 1) | u8::from(self.current_next_indicator);
178        buf[6] = 0;
179        buf[7] = 0;
180        buf[8] = 0xE0 | ((self.pcr_pid >> 8) as u8 & 0x1F);
181        buf[9] = (self.pcr_pid & 0xFF) as u8;
182        let pil = self.program_info.len() as u16;
183        buf[10] = 0xF0 | ((pil >> 8) as u8 & 0x0F);
184        buf[11] = (pil & 0xFF) as u8;
185
186        let prog_info_start = MIN_HEADER_LEN
187            + EXTENSION_HEADER_LEN
188            + PCR_PID_LEN
189            + PROG_INFO_LEN_BYTES;
190        buf[prog_info_start..prog_info_start + self.program_info.len()]
191            .copy_from_slice(self.program_info);
192
193        let mut pos = prog_info_start + self.program_info.len();
194        for stream in &self.streams {
195            buf[pos] = stream.stream_type;
196            buf[pos + 1] = 0xE0 | ((stream.elementary_pid >> 8) as u8 & 0x1F);
197            buf[pos + 2] = (stream.elementary_pid & 0xFF) as u8;
198            let esl = stream.es_info.len() as u16;
199            buf[pos + 3] = 0xF0 | ((esl >> 8) as u8 & 0x0F);
200            buf[pos + 4] = (esl & 0xFF) as u8;
201            let es_start = pos + STREAM_HEADER_LEN;
202            buf[es_start..es_start + stream.es_info.len()].copy_from_slice(stream.es_info);
203            pos = es_start + stream.es_info.len();
204        }
205
206        let crc_pos = len - CRC_LEN;
207        let crc = dvb_common::crc32_mpeg2::compute(&buf[..crc_pos]);
208        buf[crc_pos..len].copy_from_slice(&crc.to_be_bytes());
209        Ok(len)
210    }
211}
212
213impl<'a> Table<'a> for Pmt<'a> {
214    const TABLE_ID: u8 = TABLE_ID;
215    const PID: u16 = PID;
216}
217
218#[cfg(test)]
219mod tests {
220    use super::*;
221
222    /// Build a PMT section with given fields. Placeholder CRC.
223    fn build_pmt(
224        program_number: u16,
225        version: u8,
226        pcr_pid: u16,
227        program_info: &[u8],
228        streams: &[(u8, u16, Vec<u8>)],
229    ) -> Vec<u8> {
230        let streams_bytes: usize = streams
231            .iter()
232            .map(|(_, _, es)| STREAM_HEADER_LEN + es.len())
233            .sum();
234        let section_length: u16 = (EXTENSION_HEADER_LEN
235            + PCR_PID_LEN
236            + PROG_INFO_LEN_BYTES
237            + program_info.len()
238            + streams_bytes
239            + CRC_LEN) as u16;
240        let mut v = Vec::new();
241        v.push(TABLE_ID);
242        v.push(0xB0 | ((section_length >> 8) as u8 & 0x0F));
243        v.push((section_length & 0xFF) as u8);
244        v.extend_from_slice(&program_number.to_be_bytes());
245        v.push(0xC0 | ((version & 0x1F) << 1) | 0x01);
246        v.push(0);
247        v.push(0);
248        v.push(0xE0 | ((pcr_pid >> 8) as u8 & 0x1F));
249        v.push((pcr_pid & 0xFF) as u8);
250        v.push(0xF0 | ((program_info.len() >> 8) as u8 & 0x0F));
251        v.push((program_info.len() & 0xFF) as u8);
252        v.extend_from_slice(program_info);
253        for (stype, pid, es) in streams {
254            v.push(*stype);
255            v.push(0xE0 | ((pid >> 8) as u8 & 0x1F));
256            v.push((pid & 0xFF) as u8);
257            v.push(0xF0 | ((es.len() >> 8) as u8 & 0x0F));
258            v.push((es.len() & 0xFF) as u8);
259            v.extend_from_slice(es);
260        }
261        v.extend_from_slice(&[0, 0, 0, 0]);
262        v
263    }
264
265    #[test]
266    fn parse_extracts_pcr_pid_and_program_info() {
267        let bytes = build_pmt(42, 5, 0x0100, &[0xAA, 0xBB], &[]);
268        let pmt = Pmt::parse(&bytes).unwrap();
269        assert_eq!(pmt.program_number, 42);
270        assert_eq!(pmt.version_number, 5);
271        assert!(pmt.current_next_indicator);
272        assert_eq!(pmt.pcr_pid, 0x0100);
273        assert_eq!(pmt.program_info, &[0xAA, 0xBB]);
274        assert_eq!(pmt.streams.len(), 0);
275    }
276
277    #[test]
278    fn parse_elementary_streams_and_es_info_slices() {
279        let bytes = build_pmt(
280            1,
281            0,
282            0x101,
283            &[],
284            &[
285                (0x02, 0x102, vec![0x11, 0x22]),
286                (0x1B, 0x103, vec![0x33]),
287            ],
288        );
289        let pmt = Pmt::parse(&bytes).unwrap();
290        assert_eq!(pmt.streams.len(), 2);
291        assert_eq!(pmt.streams[0].stream_type, 0x02);
292        assert_eq!(pmt.streams[0].elementary_pid, 0x102);
293        assert_eq!(pmt.streams[0].es_info, &[0x11, 0x22]);
294        assert_eq!(pmt.streams[1].stream_type, 0x1B);
295        assert_eq!(pmt.streams[1].elementary_pid, 0x103);
296        assert_eq!(pmt.streams[1].es_info, &[0x33]);
297    }
298
299    #[test]
300    fn parse_rejects_wrong_table_id() {
301        let mut bytes = build_pmt(1, 0, 0x100, &[], &[]);
302        bytes[0] = 0x00;
303        let err = Pmt::parse(&bytes).unwrap_err();
304        assert!(matches!(err, Error::UnexpectedTableId { table_id: 0x00, .. }));
305    }
306
307    #[test]
308    fn parse_rejects_short_buffer() {
309        let err = Pmt::parse(&[0x02, 0x00]).unwrap_err();
310        assert!(matches!(err, Error::BufferTooShort { .. }));
311    }
312
313    #[test]
314    fn serialize_round_trip_empty_program() {
315        let pmt = Pmt {
316            program_number: 1,
317            version_number: 0,
318            current_next_indicator: true,
319            pcr_pid: 0x100,
320            program_info: &[],
321            streams: vec![],
322        };
323        let mut buf = vec![0u8; pmt.serialized_len()];
324        pmt.serialize_into(&mut buf).unwrap();
325        let re = Pmt::parse(&buf).unwrap();
326        assert_eq!(pmt, re);
327    }
328
329    #[test]
330    fn serialize_round_trip_with_streams_and_descriptors() {
331        let prog_info: [u8; 3] = [0x09, 0x01, 0xFF];
332        let es1: [u8; 4] = [0x52, 0x02, 0xAA, 0xBB];
333        let es2: [u8; 2] = [0x0A, 0x00];
334        let pmt = Pmt {
335            program_number: 0xABCD,
336            version_number: 7,
337            current_next_indicator: true,
338            pcr_pid: 0x1F0,
339            program_info: &prog_info,
340            streams: vec![
341                PmtStream {
342                    stream_type: 0x02,
343                    elementary_pid: 0x100,
344                    es_info: &es1,
345                },
346                PmtStream {
347                    stream_type: 0x03,
348                    elementary_pid: 0x101,
349                    es_info: &es2,
350                },
351                PmtStream {
352                    stream_type: 0x1B,
353                    elementary_pid: 0x102,
354                    es_info: &[],
355                },
356            ],
357        };
358        let mut buf = vec![0u8; pmt.serialized_len()];
359        pmt.serialize_into(&mut buf).unwrap();
360        let re = Pmt::parse(&buf).unwrap();
361        assert_eq!(pmt, re);
362    }
363
364    #[test]
365    fn zero_elementary_streams_is_valid() {
366        let bytes = build_pmt(99, 0, 0x0100, &[], &[]);
367        let pmt = Pmt::parse(&bytes).unwrap();
368        assert_eq!(pmt.streams.len(), 0);
369    }
370
371    #[test]
372    fn parse_preserves_raw_program_info_bytes() {
373        let pi = vec![0x09, 0x04, 0x01, 0x02, 0x03, 0x04];
374        let bytes = build_pmt(1, 0, 0x100, &pi, &[]);
375        let pmt = Pmt::parse(&bytes).unwrap();
376        assert_eq!(pmt.program_info, &pi[..]);
377    }
378}
dvb_si/tables/pmt.rs

dvb_si/tables/
pmt.rs
