scuffle_mp4/boxes/types/
padb.rs

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use std::io;

use byteorder::{BigEndian, ReadBytesExt, WriteBytesExt};
use bytes::Bytes;

use crate::boxes::header::{BoxHeader, FullBoxHeader};
use crate::boxes::traits::BoxType;

#[derive(Debug, Clone, PartialEq)]
/// Padding bits box.
/// ISO/IEC 14496-12:2022(E) - 8.7.6
pub struct Padb {
    pub header: FullBoxHeader,
    pub samples: Vec<u8>,
}

impl BoxType for Padb {
    const NAME: [u8; 4] = *b"padb";

    fn demux(header: BoxHeader, data: Bytes) -> io::Result<Self> {
        let mut reader = io::Cursor::new(data);

        let header = FullBoxHeader::demux(header, &mut reader)?;

        let sample_count = (reader.read_u32::<BigEndian>()?).div_ceil(2);
        let mut samples = Vec::with_capacity(sample_count as usize);

        for _ in 0..sample_count {
            let byte = reader.read_u8()?;
            samples.push(byte);
        }

        Ok(Self { header, samples })
    }

    fn primitive_size(&self) -> u64 {
        let mut size = self.header.size();
        size += 4; // sample_count
        size + (self.samples.len() as u64) // samples
    }

    fn primitive_mux<T: io::Write>(&self, writer: &mut T) -> io::Result<()> {
        self.header.mux(writer)?;

        writer.write_u32::<BigEndian>((self.samples.len() as u32) * 2 - 1)?;

        for byte in &self.samples {
            writer.write_u8(*byte)?;
        }

        Ok(())
    }

    fn validate(&self) -> io::Result<()> {
        if self.header.version != 0 {
            return Err(io::Error::new(io::ErrorKind::InvalidData, "padb box version must be 0"));
        }

        if self.header.flags != 0 {
            return Err(io::Error::new(io::ErrorKind::InvalidData, "padb box flags must be 0"));
        }

        Ok(())
    }
}