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use crate::{encode_section, Encode, Section, SectionId};
/// An encoder for the memory section.
///
/// Memory sections are only supported for modules.
///
/// # Example
///
/// ```
/// use wasm_encoder::{Module, MemorySection, MemoryType};
///
/// let mut memories = MemorySection::new();
/// memories.memory(MemoryType {
/// minimum: 1,
/// maximum: None,
/// memory64: false,
/// shared: false,
/// page_size_log2: None,
/// });
///
/// let mut module = Module::new();
/// module.section(&memories);
///
/// let wasm_bytes = module.finish();
/// ```
#[derive(Clone, Default, Debug)]
pub struct MemorySection {
bytes: Vec<u8>,
num_added: u32,
}
impl MemorySection {
/// Create a new memory section encoder.
pub fn new() -> Self {
Self::default()
}
/// The number of memories 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 memory.
pub fn memory(&mut self, memory_type: MemoryType) -> &mut Self {
memory_type.encode(&mut self.bytes);
self.num_added += 1;
self
}
}
impl Encode for MemorySection {
fn encode(&self, sink: &mut Vec<u8>) {
encode_section(sink, self.num_added, &self.bytes);
}
}
impl Section for MemorySection {
fn id(&self) -> u8 {
SectionId::Memory.into()
}
}
/// A memory's type.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub struct MemoryType {
/// Minimum size, in pages, of this memory
pub minimum: u64,
/// Maximum size, in pages, of this memory
pub maximum: Option<u64>,
/// Whether or not this is a 64-bit memory.
pub memory64: bool,
/// Whether or not this memory is shared.
pub shared: bool,
/// The log base 2 of a custom page size for this memory.
///
/// The default page size for Wasm memories is 64KiB, i.e. 2<sup>16</sup> or
/// `65536`.
///
/// After the introduction of [the custom-page-sizes
/// customize the page size. It must be a power of two that is less than or
/// equal to 64KiB. Attempting to encode an invalid page size may panic.
pub page_size_log2: Option<u32>,
}
impl Encode for MemoryType {
fn encode(&self, sink: &mut Vec<u8>) {
let mut flags = 0;
if self.maximum.is_some() {
flags |= 0b0001;
}
if self.shared {
flags |= 0b0010;
}
if self.memory64 {
flags |= 0b0100;
}
if self.page_size_log2.is_some() {
flags |= 0b1000;
}
sink.push(flags);
self.minimum.encode(sink);
if let Some(max) = self.maximum {
max.encode(sink);
}
if let Some(p) = self.page_size_log2 {
p.encode(sink);
}
}
}