dvb_si/descriptors/

data_broadcast_id.rs

//! Data Broadcast Id Descriptor — ETSI EN 300 468 §6.2.13 (tag 0x66).
//!
//! Table 32 (PDF p. 72). Identifies the data broadcast specification used by a
//! data component, plus a raw `id_selector_byte` tail whose interpretation
//! depends on the `data_broadcast_id` (see ETSI TS 101 162).

use super::descriptor_body;
use crate::error::{Error, Result};
use dvb_common::{Parse, Serialize};

/// Descriptor tag for data_broadcast_id_descriptor.
pub const TAG: u8 = 0x66;
const HEADER_LEN: usize = 2;
/// Fixed prefix length: the 16-bit data_broadcast_id (EN 300 468 Table 32).
const ID_LEN: usize = 2;

/// Returns the well-known name for a `data_broadcast_id`, or `None` if the
/// ID is not recognised.
///
/// Verified entries from the DVB Services registry.
#[must_use]
pub fn data_broadcast_id_name(id: u16) -> Option<&'static str> {
    match id {
        0x0005 => Some("Multiprotocol Encapsulation (MPE)"),
        0x0006 => Some("Data Carousel"),
        0x0007 => Some("Object Carousel"),
        0x000A => Some("System Software Update (SSU)"),
        0x000B => Some("IP/MAC Notification (INT)"),
        0x00F0 => Some("MHP Object Carousel"),
        0x0123 => Some("HbbTV"),
        _ => None,
    }
}

/// Data Broadcast Id Descriptor (tag 0x66).
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize))]
#[cfg_attr(feature = "yoke", derive(yoke::Yokeable))]
pub struct DataBroadcastIdDescriptor<'a> {
    /// 16-bit data_broadcast_id (ETSI TS 101 162 registration).
    pub data_broadcast_id: u16,
    /// Raw id_selector_byte tail — interpretation depends on data_broadcast_id.
    /// Kept raw deliberately; decode via id-specific parsers per TS 101 162.
    pub id_selector: &'a [u8],
}

impl<'a> Parse<'a> for DataBroadcastIdDescriptor<'a> {
    type Error = crate::error::Error;
    fn parse(bytes: &'a [u8]) -> Result<Self> {
        let body = descriptor_body(
            bytes,
            TAG,
            "DataBroadcastIdDescriptor",
            "unexpected tag for data_broadcast_id_descriptor",
        )?;
        if body.len() < ID_LEN {
            return Err(Error::InvalidDescriptor {
                tag: TAG,
                reason: "data_broadcast_id_descriptor body shorter than 2 bytes",
            });
        }
        let data_broadcast_id = u16::from_be_bytes([body[0], body[1]]);
        let id_selector = &body[ID_LEN..];
        Ok(Self {
            data_broadcast_id,
            id_selector,
        })
    }
}

impl Serialize for DataBroadcastIdDescriptor<'_> {
    type Error = crate::error::Error;
    fn serialized_len(&self) -> usize {
        HEADER_LEN + ID_LEN + self.id_selector.len()
    }

    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize> {
        let len = self.serialized_len();
        let body = ID_LEN + self.id_selector.len();
        if body > u8::MAX as usize {
            return Err(Error::InvalidDescriptor {
                tag: TAG,
                reason: "data_broadcast_id_descriptor body exceeds 255 bytes",
            });
        }
        if buf.len() < len {
            return Err(Error::OutputBufferTooSmall {
                need: len,
                have: buf.len(),
            });
        }
        buf[0] = TAG;
        buf[1] = body as u8;
        buf[HEADER_LEN..HEADER_LEN + ID_LEN].copy_from_slice(&self.data_broadcast_id.to_be_bytes());
        let sel_start = HEADER_LEN + ID_LEN;
        buf[sel_start..sel_start + self.id_selector.len()].copy_from_slice(self.id_selector);
        Ok(len)
    }
}
impl<'a> crate::traits::DescriptorDef<'a> for DataBroadcastIdDescriptor<'a> {
    const TAG: u8 = TAG;
    const NAME: &'static str = "DATA_BROADCAST_ID";
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn parse_extracts_id_and_selector() {
        let bytes = [TAG, 0x05, 0x00, 0x0B, 0xAA, 0xBB, 0xCC];
        let d = DataBroadcastIdDescriptor::parse(&bytes).unwrap();
        assert_eq!(d.data_broadcast_id, 0x000B);
        assert_eq!(d.id_selector, &[0xAA, 0xBB, 0xCC]);
    }

    #[test]
    fn parse_accepts_empty_selector() {
        let bytes = [TAG, 0x02, 0x00, 0x0A];
        let d = DataBroadcastIdDescriptor::parse(&bytes).unwrap();
        assert_eq!(d.data_broadcast_id, 0x000A);
        assert!(d.id_selector.is_empty());
    }

    #[test]
    fn data_broadcast_id_name_verified() {
        assert_eq!(
            data_broadcast_id_name(0x0005),
            Some("Multiprotocol Encapsulation (MPE)")
        );
        assert_eq!(data_broadcast_id_name(0x0006), Some("Data Carousel"));
        assert_eq!(data_broadcast_id_name(0x0007), Some("Object Carousel"));
        assert_eq!(
            data_broadcast_id_name(0x000A),
            Some("System Software Update (SSU)")
        );
        assert_eq!(
            data_broadcast_id_name(0x000B),
            Some("IP/MAC Notification (INT)")
        );
        assert_eq!(data_broadcast_id_name(0x00F0), Some("MHP Object Carousel"));
        assert_eq!(data_broadcast_id_name(0x0123), Some("HbbTV"));
    }

    #[test]
    fn data_broadcast_id_name_removed_entries_return_none() {
        assert_eq!(data_broadcast_id_name(0x00F1), None);
        assert_eq!(data_broadcast_id_name(0x00F2), None);
        assert_eq!(data_broadcast_id_name(0x00F3), None);
        assert_eq!(data_broadcast_id_name(0x00F4), None);
    }

    #[test]
    fn data_broadcast_id_name_unknown() {
        assert_eq!(data_broadcast_id_name(0x0000), None);
        assert_eq!(data_broadcast_id_name(0xFFFF), None);
    }

    #[test]
    fn parse_rejects_wrong_tag() {
        let err = DataBroadcastIdDescriptor::parse(&[0x65, 0x02, 0x00, 0x0A]).unwrap_err();
        assert!(matches!(err, Error::InvalidDescriptor { tag: 0x65, .. }));
    }

    #[test]
    fn parse_rejects_short_buffer() {
        let err = DataBroadcastIdDescriptor::parse(&[TAG]).unwrap_err();
        assert!(matches!(err, Error::BufferTooShort { .. }));
    }

    #[test]
    fn parse_rejects_body_too_short() {
        // length=1: not even the 16-bit id fits.
        let err = DataBroadcastIdDescriptor::parse(&[TAG, 0x01, 0x00]).unwrap_err();
        assert!(matches!(err, Error::InvalidDescriptor { .. }));
    }

    #[test]
    fn parse_rejects_length_overrun() {
        // length=5 but only 3 payload bytes available.
        let err = DataBroadcastIdDescriptor::parse(&[TAG, 0x05, 0x00, 0x0B, 0xAA]).unwrap_err();
        assert!(matches!(err, Error::BufferTooShort { .. }));
    }

    #[test]
    fn serialize_round_trip() {
        let d = DataBroadcastIdDescriptor {
            data_broadcast_id: 0x0123,
            id_selector: &[0xDE, 0xAD, 0xBE, 0xEF],
        };
        let mut buf = vec![0u8; d.serialized_len()];
        d.serialize_into(&mut buf).unwrap();
        let re = DataBroadcastIdDescriptor::parse(&buf).unwrap();
        assert_eq!(d, re);
    }

    #[test]
    fn serialize_rejects_too_small_buffer() {
        let d = DataBroadcastIdDescriptor {
            data_broadcast_id: 0x0001,
            id_selector: &[0x01],
        };
        let mut tiny = [0u8; 2];
        let err = d.serialize_into(&mut tiny).unwrap_err();
        assert!(matches!(err, Error::OutputBufferTooSmall { .. }));
    }

    #[test]
    fn serialize_rejects_over_range_body() {
        // 254 selector bytes + 2 id bytes = 256 > 255.
        let sel = vec![0u8; 254];
        let d = DataBroadcastIdDescriptor {
            data_broadcast_id: 0x0001,
            id_selector: &sel,
        };
        let mut buf = vec![0u8; d.serialized_len()];
        let err = d.serialize_into(&mut buf).unwrap_err();
        assert!(matches!(err, Error::InvalidDescriptor { tag: TAG, .. }));
    }

    #[cfg(feature = "serde")]
    #[test]
    fn serde_serialize_is_stable() {
        let d = DataBroadcastIdDescriptor {
            data_broadcast_id: 0x000B,
            id_selector: &[0x01, 0x02],
        };
        let json = serde_json::to_string(&d).unwrap();
        assert!(json.contains("\"data_broadcast_id\""));
        assert!(json.contains("\"id_selector\""));
        assert!(json.contains("11"));
    }
}