Revision control
Copy as Markdown
Other Tools
use crate::{encode_section, encoding_size, ConstExpr, Encode, Section, SectionId};
/// An encoder for the data section.
///
/// Data sections are only supported for modules.
///
/// # Example
///
/// ```
/// use wasm_encoder::{
/// ConstExpr, DataSection, Instruction, MemorySection, MemoryType,
/// Module,
/// };
///
/// let mut memory = MemorySection::new();
/// memory.memory(MemoryType {
/// minimum: 1,
/// maximum: None,
/// memory64: false,
/// shared: false,
/// page_size_log2: None,
/// });
///
/// let mut data = DataSection::new();
/// let memory_index = 0;
/// let offset = ConstExpr::i32_const(42);
/// let segment_data = b"hello";
/// data.active(memory_index, &offset, segment_data.iter().copied());
///
/// let mut module = Module::new();
/// module
/// .section(&memory)
/// .section(&data);
///
/// let wasm_bytes = module.finish();
/// ```
#[derive(Clone, Default, Debug)]
pub struct DataSection {
bytes: Vec<u8>,
num_added: u32,
}
/// A segment in the data section.
#[derive(Clone, Debug)]
pub struct DataSegment<'a, D> {
/// This data segment's mode.
pub mode: DataSegmentMode<'a>,
/// This data segment's data.
pub data: D,
}
/// A data segment's mode.
#[derive(Clone, Debug)]
pub enum DataSegmentMode<'a> {
/// An active data segment.
Active {
/// The memory this segment applies to.
memory_index: u32,
/// The offset where this segment's data is initialized at.
offset: &'a ConstExpr,
},
/// A passive data segment.
///
/// Passive data segments are part of the bulk memory proposal.
Passive,
}
impl DataSection {
/// Create a new data section encoder.
pub fn new() -> Self {
Self::default()
}
/// The number of data segments in the section.
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 data segment.
pub fn segment<D>(&mut self, segment: DataSegment<D>) -> &mut Self
where
D: IntoIterator<Item = u8>,
D::IntoIter: ExactSizeIterator,
{
match segment.mode {
DataSegmentMode::Passive => {
self.bytes.push(0x01);
}
DataSegmentMode::Active {
memory_index: 0,
offset,
} => {
self.bytes.push(0x00);
offset.encode(&mut self.bytes);
}
DataSegmentMode::Active {
memory_index,
offset,
} => {
self.bytes.push(0x02);
memory_index.encode(&mut self.bytes);
offset.encode(&mut self.bytes);
}
}
let data = segment.data.into_iter();
data.len().encode(&mut self.bytes);
self.bytes.extend(data);
self.num_added += 1;
self
}
/// Define an active data segment.
pub fn active<D>(&mut self, memory_index: u32, offset: &ConstExpr, data: D) -> &mut Self
where
D: IntoIterator<Item = u8>,
D::IntoIter: ExactSizeIterator,
{
self.segment(DataSegment {
mode: DataSegmentMode::Active {
memory_index,
offset,
},
data,
})
}
/// Define a passive data segment.
///
/// Passive data segments are part of the bulk memory proposal.
pub fn passive<D>(&mut self, data: D) -> &mut Self
where
D: IntoIterator<Item = u8>,
D::IntoIter: ExactSizeIterator,
{
self.segment(DataSegment {
mode: DataSegmentMode::Passive,
data,
})
}
/// Copy an already-encoded data segment into this data section.
pub fn raw(&mut self, already_encoded_data_segment: &[u8]) -> &mut Self {
self.bytes.extend_from_slice(already_encoded_data_segment);
self.num_added += 1;
self
}
}
impl Encode for DataSection {
fn encode(&self, sink: &mut Vec<u8>) {
encode_section(sink, self.num_added, &self.bytes);
}
}
impl Section for DataSection {
fn id(&self) -> u8 {
SectionId::Data.into()
}
}
/// An encoder for the data count section.
#[derive(Clone, Copy, Debug)]
pub struct DataCountSection {
/// The number of segments in the data section.
pub count: u32,
}
impl Encode for DataCountSection {
fn encode(&self, sink: &mut Vec<u8>) {
encoding_size(self.count).encode(sink);
self.count.encode(sink);
}
}
impl Section for DataCountSection {
fn id(&self) -> u8 {
SectionId::DataCount.into()
}
}