fn read_vpcc()

in mp4parse/src/lib.rs [4813:4881]
63 lines of code
3 McCabe index (conditional complexity)

fn read_vpcc<T: Read>(src: &mut BMFFBox<T>) -> Result<VPxConfigBox> {
    let (version, _) = read_fullbox_extra(src)?;
    let supported_versions = [0, 1];
    if !supported_versions.contains(&version) {
        return Err(Error::Unsupported("unknown vpcC version"));
    }

    let profile = src.read_u8()?;
    let level = src.read_u8()?;
    let (
        bit_depth,
        colour_primaries,
        chroma_subsampling,
        transfer_characteristics,
        matrix_coefficients,
        video_full_range_flag,
    ) = if version == 0 {
        let (bit_depth, colour_primaries) = {
            let byte = src.read_u8()?;
            ((byte >> 4) & 0x0f, byte & 0x0f)
        };
        // Note, transfer_characteristics was known as transfer_function in v0
        let (chroma_subsampling, transfer_characteristics, video_full_range_flag) = {
            let byte = src.read_u8()?;
            ((byte >> 4) & 0x0f, (byte >> 1) & 0x07, (byte & 1) == 1)
        };
        (
            bit_depth,
            colour_primaries,
            chroma_subsampling,
            transfer_characteristics,
            None,
            video_full_range_flag,
        )
    } else {
        let (bit_depth, chroma_subsampling, video_full_range_flag) = {
            let byte = src.read_u8()?;
            ((byte >> 4) & 0x0f, (byte >> 1) & 0x07, (byte & 1) == 1)
        };
        let colour_primaries = src.read_u8()?;
        let transfer_characteristics = src.read_u8()?;
        let matrix_coefficients = src.read_u8()?;

        (
            bit_depth,
            colour_primaries,
            chroma_subsampling,
            transfer_characteristics,
            Some(matrix_coefficients),
            video_full_range_flag,
        )
    };

    let codec_init_size = be_u16(src)?;
    let codec_init = read_buf(src, codec_init_size.into())?;

    // TODO(rillian): validate field value ranges.
    Ok(VPxConfigBox {
        profile,
        level,
        bit_depth,
        colour_primaries,
        chroma_subsampling,
        transfer_characteristics,
        matrix_coefficients,
        video_full_range_flag,
        codec_init,
    })
}