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

dvb_si/tables/
pmt.rs
