scuffle_mp4/boxes/types/
elst.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)]
/// Edit List Box
/// ISO/IEC 14496-12:2022(E) - 8.6.6
pub struct Elst {
    pub header: FullBoxHeader,
    pub entries: Vec<ElstEntry>,
}

impl Elst {
    pub fn new(entries: Vec<ElstEntry>) -> Self {
        Self {
            header: FullBoxHeader::new(Self::NAME, 0, 0),
            entries,
        }
    }
}

#[derive(Debug, Clone, PartialEq)]
/// Entry in the Edit List Box
pub struct ElstEntry {
    pub segment_duration: u64,
    pub media_time: i64,
    pub media_rate_integer: i16,
    pub media_rate_fraction: i16,
}

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

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

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

        let entry_count = reader.read_u32::<BigEndian>()?;

        let mut entries = Vec::with_capacity(entry_count as usize);

        for _ in 0..entry_count {
            let (segment_duration, media_time, media_rate_integer, media_rate_fraction) = if header.version == 1 {
                (
                    reader.read_u64::<BigEndian>()?, // segment_duration
                    reader.read_i64::<BigEndian>()?, // media_time
                    reader.read_i16::<BigEndian>()?, // media_rate_integer
                    reader.read_i16::<BigEndian>()?, // media_rate_fraction
                )
            } else {
                (
                    reader.read_u32::<BigEndian>()? as u64, // segment_duration
                    reader.read_i32::<BigEndian>()? as i64, // media_time
                    reader.read_i16::<BigEndian>()?,        // media_rate_integer
                    reader.read_i16::<BigEndian>()?,        // media_rate_fraction
                )
            };

            entries.push(ElstEntry {
                segment_duration,
                media_time,
                media_rate_integer,
                media_rate_fraction,
            });
        }

        Ok(Self { header, entries })
    }

    fn primitive_size(&self) -> u64 {
        self.header.size()
        + 4 // entry_count
        + (self.entries.len() as u64) * if self.header.version == 1 {
            8 + 8 + 2 + 2 // segment_duration + media_time + media_rate_integer + media_rate_fraction
        } else {
            4 + 4 + 2 + 2 // segment_duration + media_time + media_rate_integer + media_rate_fraction
        }
    }

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

        writer.write_u32::<BigEndian>(self.entries.len() as u32)?;

        for entry in &self.entries {
            if self.header.version == 1 {
                writer.write_u64::<BigEndian>(entry.segment_duration)?;
                writer.write_i64::<BigEndian>(entry.media_time)?;
            } else {
                writer.write_u32::<BigEndian>(entry.segment_duration as u32)?;
                writer.write_i32::<BigEndian>(entry.media_time as i32)?;
            }

            writer.write_i16::<BigEndian>(entry.media_rate_integer)?;
            writer.write_i16::<BigEndian>(entry.media_rate_fraction)?;
        }

        Ok(())
    }

    fn validate(&self) -> io::Result<()> {
        if self.header.flags != 0 {
            return Err(io::Error::new(io::ErrorKind::InvalidData, "elst: version 1 is not supported"));
        }

        if self.header.version > 1 {
            return Err(io::Error::new(io::ErrorKind::InvalidData, "elst: version must be 0 or 1"));
        }

        if self.header.version == 1 {
            for entry in &self.entries {
                if entry.segment_duration > u32::MAX as u64 {
                    return Err(io::Error::new(
                        io::ErrorKind::InvalidData,
                        "elst: segment_duration must be u32",
                    ));
                }

                if entry.media_time > i32::MAX as i64 {
                    return Err(io::Error::new(io::ErrorKind::InvalidData, "elst: media_time must be i32"));
                }
            }
        }

        Ok(())
    }
}