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::descriptors::DescriptorLoop;
8use crate::error::{Error, Result};
9use crate::traits::Table;
10use dvb_common::{Parse, Serialize};
11
12/// PMT table_id (ISO/IEC 13818-1 Table 2-30).
13pub const TABLE_ID: u8 = 0x02;
14/// PMT PIDs are programme-specific and signalled via PAT; 0x0000 is a
15/// placeholder meaning "no well-known PID".
16pub const PID: u16 = 0x0000;
17
18const MIN_HEADER_LEN: usize = 3;
19const EXTENSION_HEADER_LEN: usize = 5;
20const PCR_PID_LEN: usize = 2;
21const PROG_INFO_LEN_BYTES: usize = 2;
22const CRC_LEN: usize = 4;
23const STREAM_HEADER_LEN: usize = 5;
24
25/// One elementary stream entry in the PMT's ES loop.
26#[derive(Debug, Clone, PartialEq, Eq)]
27#[cfg_attr(feature = "serde", derive(serde::Serialize))]
28#[cfg_attr(feature = "yoke", derive(yoke::Yokeable))]
29pub struct PmtStream<'a> {
30    /// MPEG-2 stream_type byte (ISO/IEC 13818-1 Table 2-34).
31    pub stream_type: u8,
32    /// 13-bit elementary stream PID.
33    pub elementary_pid: u16,
34    /// Raw ES_info descriptor bytes; parsing lives in crate::descriptors.
35    /// Elementary-stream descriptor loop. Serializes as the typed descriptor
36    /// sequence; `.raw()` yields the wire bytes.
37    pub es_info: DescriptorLoop<'a>,
38}
39
40/// Program Map Table.
41#[derive(Debug, Clone, PartialEq, Eq)]
42#[cfg_attr(feature = "serde", derive(serde::Serialize))]
43#[cfg_attr(feature = "yoke", derive(yoke::Yokeable))]
44pub struct Pmt<'a> {
45    /// Programme number from the table_id_extension field.
46    pub program_number: u16,
47    /// 5-bit version_number.
48    pub version_number: u8,
49    /// current_next_indicator bit.
50    pub current_next_indicator: bool,
51    /// 13-bit PCR PID.
52    pub pcr_pid: u16,
53    /// Raw program_info descriptor bytes.
54    /// Program-info descriptor loop. Serializes as the typed descriptor
55    /// sequence; `.raw()` yields the wire bytes.
56    pub program_info: DescriptorLoop<'a>,
57    /// Elementary streams in wire order.
58    pub streams: Vec<PmtStream<'a>>,
59}
60
61impl<'a> Parse<'a> for Pmt<'a> {
62    type Error = crate::error::Error;
63    fn parse(bytes: &'a [u8]) -> Result<Self> {
64        let min_len =
65            MIN_HEADER_LEN + EXTENSION_HEADER_LEN + PCR_PID_LEN + PROG_INFO_LEN_BYTES + CRC_LEN;
66        if bytes.len() < min_len {
67            return Err(Error::BufferTooShort {
68                need: min_len,
69                have: bytes.len(),
70                what: "Pmt",
71            });
72        }
73        if bytes[0] != TABLE_ID {
74            return Err(Error::UnexpectedTableId {
75                table_id: bytes[0],
76                what: "Pmt",
77                expected: &[TABLE_ID],
78            });
79        }
80
81        let section_length = ((bytes[1] & 0x0F) as u16) << 8 | bytes[2] as u16;
82        let total = MIN_HEADER_LEN + section_length as usize;
83        if bytes.len() < total {
84            return Err(Error::SectionLengthOverflow {
85                declared: section_length as usize,
86                available: bytes.len() - MIN_HEADER_LEN,
87            });
88        }
89
90        let program_number = u16::from_be_bytes([bytes[3], bytes[4]]);
91        let version_number = (bytes[5] >> 1) & 0x1F;
92        let current_next_indicator = (bytes[5] & 0x01) != 0;
93
94        let pcr_pid = (((bytes[8] & 0x1F) as u16) << 8) | bytes[9] as u16;
95        let program_info_length = (((bytes[10] & 0x0F) as usize) << 8) | bytes[11] as usize;
96
97        let prog_info_start =
98            MIN_HEADER_LEN + EXTENSION_HEADER_LEN + PCR_PID_LEN + PROG_INFO_LEN_BYTES;
99        let prog_info_end = prog_info_start + program_info_length;
100        let stream_loop_end = total - CRC_LEN;
101        if prog_info_end > stream_loop_end {
102            return Err(Error::SectionLengthOverflow {
103                declared: program_info_length,
104                available: stream_loop_end - prog_info_start,
105            });
106        }
107        let program_info = DescriptorLoop::new(&bytes[prog_info_start..prog_info_end]);
108
109        let mut streams = Vec::new();
110        let mut pos = prog_info_end;
111        while pos + STREAM_HEADER_LEN <= stream_loop_end {
112            let stream_type = bytes[pos];
113            let elementary_pid = (((bytes[pos + 1] & 0x1F) as u16) << 8) | bytes[pos + 2] as u16;
114            let es_info_length =
115                (((bytes[pos + 3] & 0x0F) as usize) << 8) | bytes[pos + 4] as usize;
116            let es_start = pos + STREAM_HEADER_LEN;
117            let es_end = es_start + es_info_length;
118            if es_end > stream_loop_end {
119                return Err(Error::SectionLengthOverflow {
120                    declared: es_info_length,
121                    available: stream_loop_end - es_start,
122                });
123            }
124            streams.push(PmtStream {
125                stream_type,
126                elementary_pid,
127                es_info: DescriptorLoop::new(&bytes[es_start..es_end]),
128            });
129            pos = es_end;
130        }
131
132        Ok(Pmt {
133            program_number,
134            version_number,
135            current_next_indicator,
136            pcr_pid,
137            program_info,
138            streams,
139        })
140    }
141}
142
143impl Serialize for Pmt<'_> {
144    type Error = crate::error::Error;
145    fn serialized_len(&self) -> usize {
146        let streams_bytes: usize = self
147            .streams
148            .iter()
149            .map(|s| STREAM_HEADER_LEN + s.es_info.len())
150            .sum();
151        MIN_HEADER_LEN
152            + EXTENSION_HEADER_LEN
153            + PCR_PID_LEN
154            + PROG_INFO_LEN_BYTES
155            + self.program_info.len()
156            + streams_bytes
157            + CRC_LEN
158    }
159
160    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
161        let len = self.serialized_len();
162        if buf.len() < len {
163            return Err(Error::OutputBufferTooSmall {
164                need: len,
165                have: buf.len(),
166            });
167        }
168
169        let section_length: u16 = (len - MIN_HEADER_LEN) as u16;
170        buf[0] = TABLE_ID;
171        buf[1] = 0xB0 | ((section_length >> 8) as u8 & 0x0F);
172        buf[2] = (section_length & 0xFF) as u8;
173        buf[3..5].copy_from_slice(&self.program_number.to_be_bytes());
174        buf[5] = 0xC0 | ((self.version_number & 0x1F) << 1) | u8::from(self.current_next_indicator);
175        buf[6] = 0;
176        buf[7] = 0;
177        buf[8] = 0xE0 | ((self.pcr_pid >> 8) as u8 & 0x1F);
178        buf[9] = (self.pcr_pid & 0xFF) as u8;
179        let pil = self.program_info.len() as u16;
180        buf[10] = 0xF0 | ((pil >> 8) as u8 & 0x0F);
181        buf[11] = (pil & 0xFF) as u8;
182
183        let prog_info_start =
184            MIN_HEADER_LEN + EXTENSION_HEADER_LEN + PCR_PID_LEN + PROG_INFO_LEN_BYTES;
185        buf[prog_info_start..prog_info_start + self.program_info.len()]
186            .copy_from_slice(self.program_info.raw());
187
188        let mut pos = prog_info_start + self.program_info.len();
189        for stream in &self.streams {
190            buf[pos] = stream.stream_type;
191            buf[pos + 1] = 0xE0 | ((stream.elementary_pid >> 8) as u8 & 0x1F);
192            buf[pos + 2] = (stream.elementary_pid & 0xFF) as u8;
193            let esl = stream.es_info.len() as u16;
194            buf[pos + 3] = 0xF0 | ((esl >> 8) as u8 & 0x0F);
195            buf[pos + 4] = (esl & 0xFF) as u8;
196            let es_start = pos + STREAM_HEADER_LEN;
197            buf[es_start..es_start + stream.es_info.len()].copy_from_slice(stream.es_info.raw());
198            pos = es_start + stream.es_info.len();
199        }
200
201        let crc_pos = len - CRC_LEN;
202        let crc = dvb_common::crc32_mpeg2::compute(&buf[..crc_pos]);
203        buf[crc_pos..len].copy_from_slice(&crc.to_be_bytes());
204        Ok(len)
205    }
206}
207
208impl<'a> Table<'a> for Pmt<'a> {
209    const TABLE_ID: u8 = TABLE_ID;
210    const PID: u16 = PID;
211}
212
213impl<'a> crate::traits::TableDef<'a> for Pmt<'a> {
214    const TABLE_ID_RANGES: &'static [(u8, u8)] = &[(TABLE_ID, TABLE_ID)];
215    const NAME: &'static str = "PROGRAM_MAP";
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.raw(), &[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            &[(0x02, 0x102, vec![0x11, 0x22]), (0x1B, 0x103, vec![0x33])],
285        );
286        let pmt = Pmt::parse(&bytes).unwrap();
287        assert_eq!(pmt.streams.len(), 2);
288        assert_eq!(pmt.streams[0].stream_type, 0x02);
289        assert_eq!(pmt.streams[0].elementary_pid, 0x102);
290        assert_eq!(pmt.streams[0].es_info.raw(), &[0x11, 0x22]);
291        assert_eq!(pmt.streams[1].stream_type, 0x1B);
292        assert_eq!(pmt.streams[1].elementary_pid, 0x103);
293        assert_eq!(pmt.streams[1].es_info.raw(), &[0x33]);
294    }
295
296    #[test]
297    fn parse_rejects_wrong_table_id() {
298        let mut bytes = build_pmt(1, 0, 0x100, &[], &[]);
299        bytes[0] = 0x00;
300        let err = Pmt::parse(&bytes).unwrap_err();
301        assert!(matches!(
302            err,
303            Error::UnexpectedTableId { table_id: 0x00, .. }
304        ));
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: DescriptorLoop::new(&[]),
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: DescriptorLoop::new(&prog_info),
340            streams: vec![
341                PmtStream {
342                    stream_type: 0x02,
343                    elementary_pid: 0x100,
344                    es_info: DescriptorLoop::new(&es1),
345                },
346                PmtStream {
347                    stream_type: 0x03,
348                    elementary_pid: 0x101,
349                    es_info: DescriptorLoop::new(&es2),
350                },
351                PmtStream {
352                    stream_type: 0x1B,
353                    elementary_pid: 0x102,
354                    es_info: DescriptorLoop::new(&[]),
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.raw(), &pi[..]);
377    }
378}
dvb_si/tables/pmt.rs

dvb_si/tables/
pmt.rs
