dvb-common

Shared primitives for the DVB crate family. Every sibling crate (dvb-si, dvb-t2mi, dvb-bbframe, …) depends on this crate and nothing else.

no_std + alloc support

dvb-common is #![no_std] when the std feature is disabled. Only alloc is required — suitable for embedded/RTOS targets with a heap. The std feature (on by default) re-enables std::error::Error integration and chrono's wall-clock support. core::error::Error is used for the error trait bound in no_std builds (stabilised in Rust 1.81). The MJD↔calendar float arithmetic uses libm::floor uniformly in both std and no_std builds, so the output is bit-identical on all targets.

What's in here

Parse<'a> and Serialize traits (traits)

The symmetric contract every wire type across the family implements:

pub trait Parse<'a>: Sized {
    type Error;
    fn parse(bytes: &'a [u8]) -> Result<Self, Self::Error>;
}

pub trait Serialize {
    type Error;
    fn serialized_len(&self) -> usize;
    fn serialize_into(&self, buf: &mut [u8]) -> Result<usize, Self::Error>;
    fn to_bytes(&self) -> Vec<u8> where Self::Error: core::fmt::Debug;
}

Parse is lifetime-parametric so parsed structs can borrow directly from the input buffer (zero-copy). Serialize is split from Parse so owned types can implement it without carrying a lifetime. to_bytes() is a convenience allocator; serialize_into is the low-level building block.

CRC-32 MPEG-2 (crc32_mpeg2)

Polynomial 0x04C1_1DB7, initial value 0xFFFF_FFFF, MSB-first, no reflection, no final XOR — the CRC used by every PSI/SI section and every T2-MI packet. A precomputed 256-entry table is built at compile time (zero runtime initialisation cost).

let crc = dvb_common::crc32_mpeg2::compute(&section_bytes[..section_bytes.len() - 4]);

BCD codec (bcd)

Binary-coded decimal helpers for the packed nibble fields throughout DVB (frequencies, symbol rates, HHMMSS time fields, HHMM offsets). Every encode has a symmetric decode; both return None rather than producing garbage on out-of-range input.

use dvb_common::bcd;
assert_eq!(bcd::from_bcd_byte(0x42), Some(42));
assert_eq!(bcd::to_bcd_byte(42),     Some(0x42));

MJD+BCD time codec (time)

Decodes the 5-byte DVB UTC wire format (16-bit Modified Julian Date + 24-bit BCD HHMMSS) to a plain MjdBcdDateTime struct (no dependency required) or, if the chrono feature is enabled, to a chrono::DateTime<Utc>. The Duration / HHMMSS helpers for event durations are always available without chrono.

Bit-field codec (bits)

BitReader and BitWriter for big-endian MSB-first sub-byte fields — the bit order used throughout DVB/MPEG physical-layer signalling (L1-pre, L1-post, MATYPE, …). Fields can span byte boundaries; up to 64 bits per field. Both sides are symmetric.

use dvb_common::bits::{BitReader, BitWriter};

let mut buf = [0u8; 2];
let mut w = BitWriter::new(&mut buf);
w.write_bits(0b101, 3).unwrap();
w.write_bits(0x1FF, 9).unwrap();

let mut r = BitReader::new(&buf);
assert_eq!(r.read_bits(3).unwrap(), 0b101);
assert_eq!(r.read_bits(9).unwrap(), 0x1FF);

impl_spec_display! macro

Project-wide helper that generates a Display impl for spec/field enums that delegate to an inherent fn name(&self) -> &'static str. Keeps spec token labels next to variant docs and greppable; removes identical boilerplate.

Feature flags

MSRV

1.81 — required for core::error::Error (used as the error trait bound in no_std builds).

Non-goals

• A shared error enum. Each DVB crate owns a domain-specific Error; the shared traits keep it that way via type Error.
• CRC-8 (used only by dvb-bbframe). Lives in the consumer.
• Anything with a non-trivial dependency. If a helper needs bytes / serde, it belongs in a consumer with the matching feature flag.

License

MIT OR Apache-2.0, at your option.