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//! Memories used in a wasm module.
use crate::emit::{Emit, EmitContext};
use crate::map::IdHashSet;
use crate::parse::IndicesToIds;
use crate::tombstone_arena::{Id, Tombstone, TombstoneArena};
use crate::{Data, ImportId, Module, Result};
/// The id of a memory.
pub type MemoryId = Id<Memory>;
/// A memory in the wasm.
#[derive(Debug)]
pub struct Memory {
id: MemoryId,
/// Whether or not this is a “shared” memory
///
/// This is part of the threads proposal.
pub shared: bool,
/// Whether or not this is a 64-bit memory.
///
/// This is part of the memory64 proposal.
pub memory64: bool,
/// Initial size of this memory, in wasm pages.
pub initial: u64,
/// Optional maximum size of this memory, in wasm pages.
pub maximum: Option<u64>,
///The log base 2 of the memory’s custom page size.
///
/// Memory pages are, by default, 64KiB large (i.e. 216 or 65536).
///
/// The custom-page-sizes proposal allows changing it to other values.
pub page_size_log2: Option<u32>,
/// Whether or not this memory is imported, and if so from where.
pub import: Option<ImportId>,
/// Active data segments that will be used to initialize this memory.
pub data_segments: IdHashSet<Data>,
/// The name of this memory, used for debugging purposes in the `name`
/// custom section.
pub name: Option<String>,
}
impl Tombstone for Memory {
fn on_delete(&mut self) {
self.data_segments = Default::default();
}
}
impl Memory {
/// Return the id of this memory
pub fn id(&self) -> MemoryId {
self.id
}
}
/// The set of memories in this module.
#[derive(Debug, Default)]
pub struct ModuleMemories {
arena: TombstoneArena<Memory>,
}
impl ModuleMemories {
/// Add an imported memory
pub fn add_import(
&mut self,
shared: bool,
memory64: bool,
initial: u64,
maximum: Option<u64>,
page_size_log2: Option<u32>,
import: ImportId,
) -> MemoryId {
let id = self.arena.next_id();
let id2 = self.arena.alloc(Memory {
id,
shared,
memory64,
initial,
maximum,
page_size_log2,
import: Some(import),
data_segments: Default::default(),
name: None,
});
debug_assert_eq!(id, id2);
id
}
/// Construct a new memory, that does not originate from any of the input
/// wasm memories.
pub fn add_local(
&mut self,
shared: bool,
memory64: bool,
initial: u64,
maximum: Option<u64>,
page_size_log2: Option<u32>,
) -> MemoryId {
let id = self.arena.next_id();
let id2 = self.arena.alloc(Memory {
id,
shared,
memory64,
initial,
maximum,
page_size_log2,
import: None,
data_segments: Default::default(),
name: None,
});
debug_assert_eq!(id, id2);
id
}
/// Gets a reference to a memory given its id
pub fn get(&self, id: MemoryId) -> &Memory {
&self.arena[id]
}
/// Gets a reference to a memory given its id
pub fn get_mut(&mut self, id: MemoryId) -> &mut Memory {
&mut self.arena[id]
}
/// Removes a memory from this module.
///
/// It is up to you to ensure that any potential references to the deleted
/// memory are also removed, eg `mem.load` expressions and exports.
pub fn delete(&mut self, id: MemoryId) {
self.arena.delete(id);
}
/// Get a shared reference to this module's memories.
pub fn iter(&self) -> impl Iterator<Item = &Memory> {
self.arena.iter().map(|(_, f)| f)
}
/// Get a mutable reference to this module's memories.
pub fn iter_mut(&mut self) -> impl Iterator<Item = &mut Memory> {
self.arena.iter_mut().map(|(_, f)| f)
}
/// Get the number of memories in this module
pub fn len(&self) -> usize {
self.arena.len()
}
/// Checks if there are no memories in this module
pub fn is_empty(&self) -> bool {
self.arena.len() == 0
}
}
impl Module {
/// Construct a new, empty set of memories for a module.
pub(crate) fn parse_memories(
&mut self,
section: wasmparser::MemorySectionReader,
ids: &mut IndicesToIds,
) -> Result<()> {
log::debug!("parse memory section");
for m in section {
let m = m?;
let id = self.memories.add_local(
m.shared,
m.memory64,
m.initial,
m.maximum,
m.page_size_log2,
);
ids.push_memory(id);
}
Ok(())
}
}
impl Emit for ModuleMemories {
fn emit(&self, cx: &mut EmitContext) {
log::debug!("emit memory section");
let mut wasm_memory_section = wasm_encoder::MemorySection::new();
// imported memories are emitted earlier
let memories = self.iter().filter(|m| m.import.is_none()).count();
if memories == 0 {
return;
}
for memory in self.iter().filter(|m| m.import.is_none()) {
cx.indices.push_memory(memory.id());
wasm_memory_section.memory(wasm_encoder::MemoryType {
minimum: memory.initial,
maximum: memory.maximum,
memory64: memory.memory64,
shared: memory.shared,
page_size_log2: memory.page_size_log2,
});
}
cx.wasm_module.section(&wasm_memory_section);
}
}
#[cfg(test)]
mod tests {
use crate::Module;
#[test]
fn memories_len() {
let mut module = Module::default();
assert_eq!(module.memories.len(), 0);
module.memories.add_local(false, false, 0, Some(1024), None);
assert_eq!(module.memories.len(), 1);
module
.memories
.add_local(true, true, 1024, Some(2048), Some(16));
assert_eq!(module.memories.len(), 2);
}
}