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use super::*;
/// An encoder for the global section.
///
/// # Example
///
/// ```
/// use wasm_encoder::{Module, GlobalSection, GlobalType, Instruction, ValType};
///
/// let mut globals = GlobalSection::new();
/// globals.global(
/// GlobalType {
/// val_type: ValType::I32,
/// mutable: false,
/// },
/// &Instruction::I32Const(42),
/// );
///
/// let mut module = Module::new();
/// module.section(&globals);
///
/// let wasm_bytes = module.finish();
/// ```
#[derive(Clone, Default, Debug)]
pub struct GlobalSection {
bytes: Vec<u8>,
num_added: u32,
}
impl GlobalSection {
/// Create a new global section encoder.
pub fn new() -> Self {
Self::default()
}
/// How many globals have been defined inside this section so far?
pub fn len(&self) -> u32 {
self.num_added
}
/// Determines if the section is empty.
pub fn is_empty(&self) -> bool {
self.num_added == 0
}
/// Define a global.
pub fn global(&mut self, global_type: GlobalType, init_expr: &Instruction<'_>) -> &mut Self {
global_type.encode(&mut self.bytes);
init_expr.encode(&mut self.bytes);
Instruction::End.encode(&mut self.bytes);
self.num_added += 1;
self
}
/// Add a raw byte slice into this code section as a global.
pub fn raw(&mut self, data: &[u8]) -> &mut Self {
self.bytes.extend(data);
self.num_added += 1;
self
}
}
impl Section for GlobalSection {
fn id(&self) -> u8 {
SectionId::Global.into()
}
fn encode<S>(&self, sink: &mut S)
where
S: Extend<u8>,
{
let num_added = encoders::u32(self.num_added);
let n = num_added.len();
sink.extend(
encoders::u32(u32::try_from(n + self.bytes.len()).unwrap())
.chain(num_added)
.chain(self.bytes.iter().copied()),
);
}
}
/// A global's type.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct GlobalType {
/// This global's value type.
pub val_type: ValType,
/// Whether this global is mutable or not.
pub mutable: bool,
}
impl GlobalType {
pub(crate) fn encode(&self, bytes: &mut Vec<u8>) {
bytes.push(self.val_type.into());
bytes.push(self.mutable as u8);
}
}