use super::*;

/// An encoder for the start section.

///

/// # Example

///

/// Note: this doesn't actually define the function at index 0, its type, or its

/// code body, so the resulting Wasm module will be invalid. See `TypeSection`,

/// `FunctionSection`, and `CodeSection` for details on how to generate those

/// things.

///

/// ```

/// use wasm_encoder::{Module, StartSection};

///

/// let start = StartSection { function_index: 0 };

///

/// let mut module = Module::new();

/// module.section(&start);

///

/// let wasm_bytes = module.finish();

/// ```

#[derive(Clone, Copy, Debug)]

pub struct StartSection {

    /// The index of the start function.

    pub function_index: u32,

}

impl Section for StartSection {

    fn id(&self) -> u8 {

        SectionId::Start.into()

    }

    fn encode<S>(&self, sink: &mut S)

    where

        S: Extend<u8>,

    {

        let f = encoders::u32(self.function_index);

        let n = f.len();

        sink.extend(encoders::u32(n as u32).chain(f));

    }

}