src/block/extension/mod.rs


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mod application;
mod graphiccontrol;

pub use graphiccontrol::{DisposalMethod, GraphicControl};

pub use self::application::Application;

pub enum Extension {
    GraphicControl(GraphicControl),
    Looping(u16),
    Comment(Vec<u8>), // Plain Text
    Application(Application),
}

impl From<&Extension> for Box<[u8]> {
    fn from(ext: &Extension) -> Self {
        let mut vec = vec![];
        vec.push(0x21); // Push the extension introducer

        match ext {
            Extension::GraphicControl(gc) => {
                vec.push(0xF9); // Graphic control label
                vec.push(0x04); // Block size for this extension is always 4
                vec.push(gc.packed);
                vec.extend_from_slice(&gc.delay_time.to_le_bytes());
                vec.push(gc.transparency_index);
            }
            Extension::Looping(count) => {
                vec.push(0xFF); // Application extension label
                vec.push(0x0B); // 11 bytes in this block
                vec.extend_from_slice(b"NETSCAPE2.0"); // App. ident. and "auth code"
                vec.push(0x03); // Sub-block length
                vec.push(0x01); // Identifies netscape looping extension
                vec.extend_from_slice(&count.to_le_bytes());
            }
            Extension::Comment(_) => todo!(),
            Extension::Application(_) => todo!(),
        }

        vec.push(0x00); // Zero-length data block indicates end of extension
        vec.into_boxed_slice()
    }
}

impl From<GraphicControl> for Extension {
    fn from(gce: GraphicControl) -> Self {
        Extension::GraphicControl(gce)
    }
}