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use crate::core::*;
use crate::kw;
use crate::parser::{Parse, Parser, Peek, Result};
use crate::token::{Id, Index, LParen, NameAnnotation, Span};
/// A WebAssembly `table` directive in a module.
#[derive(Debug)]
pub struct Table<'a> {
/// Where this table was defined.
pub span: Span,
/// An optional name to refer to this table by.
pub id: Option<Id<'a>>,
/// An optional name for this function stored in the custom `name` section.
pub name: Option<NameAnnotation<'a>>,
/// If present, inline export annotations which indicate names this
/// definition should be exported under.
pub exports: InlineExport<'a>,
/// How this table is textually defined in the module.
pub kind: TableKind<'a>,
}
/// Different ways to textually define a table.
#[derive(Debug)]
pub enum TableKind<'a> {
/// This table is actually an inlined import definition.
#[allow(missing_docs)]
Import {
import: InlineImport<'a>,
ty: TableType<'a>,
},
/// A typical memory definition which simply says the limits of the table.
Normal {
/// Table type.
ty: TableType<'a>,
/// Optional items initializer expression.
init_expr: Option<Expression<'a>>,
},
/// The elem segments of this table, starting from 0, explicitly listed.
Inline {
/// The element type of this table.
elem: RefType<'a>,
/// Whether or not this will be creating a 64-bit table.
is64: bool,
/// Whether this table is shared or not.
shared: bool,
/// The element table entries to have, and the length of this list is
/// the limits of the table as well.
payload: ElemPayload<'a>,
},
}
impl<'a> Parse<'a> for Table<'a> {
fn parse(parser: Parser<'a>) -> Result<Self> {
let span = parser.parse::<kw::table>()?.0;
let id = parser.parse()?;
let name = parser.parse()?;
let exports = parser.parse()?;
// Afterwards figure out which style this is, either:
//
// * inline: `elemtype (elem ...)`
// * normal: `tabletype`
// * import: `(import "a" "b") tabletype`
//
// Where `tabletype := shared? index_type limits reftype`
let mut l = parser.lookahead1();
let is_shared = l.peek::<kw::shared>()?;
let has_index_type = l.peek::<kw::i32>()? | l.peek::<kw::i64>()?;
let kind = if l.peek::<RefType>()?
|| ((is_shared || has_index_type) && parser.peek2::<RefType>()?)
{
let shared = parser.parse::<Option<kw::shared>>()?.is_some();
let is64 = if parser.parse::<Option<kw::i32>>()?.is_some() {
false
} else {
parser.parse::<Option<kw::i64>>()?.is_some()
};
let elem = parser.parse()?;
let payload = parser.parens(|p| {
p.parse::<kw::elem>()?;
if p.peek::<LParen>()? {
ElemPayload::parse_exprs(p, elem)
} else {
ElemPayload::parse_indices(p, Some(elem))
}
})?;
TableKind::Inline {
elem,
is64,
shared,
payload,
}
} else if is_shared || has_index_type || l.peek::<u64>()? {
TableKind::Normal {
ty: parser.parse()?,
init_expr: if !parser.is_empty() {
Some(parser.parse::<Expression>()?)
} else {
None
},
}
} else if let Some(import) = parser.parse()? {
TableKind::Import {
import,
ty: parser.parse()?,
}
} else {
return Err(l.error());
};
Ok(Table {
span,
id,
name,
exports,
kind,
})
}
}
/// An `elem` segment in a WebAssembly module.
#[derive(Debug)]
pub struct Elem<'a> {
/// Where this `elem` was defined.
pub span: Span,
/// An optional name by which to refer to this segment.
pub id: Option<Id<'a>>,
/// An optional name for this element stored in the custom `name` section.
pub name: Option<NameAnnotation<'a>>,
/// The way this segment was defined in the module.
pub kind: ElemKind<'a>,
/// The payload of this element segment, typically a list of functions.
pub payload: ElemPayload<'a>,
}
/// Different ways to define an element segment in an mdoule.
#[derive(Debug)]
pub enum ElemKind<'a> {
/// A passive segment that isn't associated with a table and can be used in
/// various bulk-memory instructions.
Passive,
/// A declared element segment that is purely used to declare function
/// references.
Declared,
/// An active segment associated with a table.
Active {
/// The table this `elem` is initializing.
table: Index<'a>,
/// The offset within `table` that we'll initialize at.
offset: Expression<'a>,
},
}
/// Different ways to define the element segment payload in a module.
#[derive(Debug)]
pub enum ElemPayload<'a> {
/// This element segment has a contiguous list of function indices
Indices(Vec<Index<'a>>),
/// This element segment has a list of optional function indices,
/// represented as expressions using `ref.func` and `ref.null`.
Exprs {
/// The desired type of each expression below.
ty: RefType<'a>,
/// The expressions in this segment.
exprs: Vec<Expression<'a>>,
},
}
impl<'a> Parse<'a> for Elem<'a> {
fn parse(parser: Parser<'a>) -> Result<Self> {
let span = parser.parse::<kw::elem>()?.0;
let id = parser.parse()?;
let name = parser.parse()?;
// Element segments can start in a number of different ways:
//
// * `(elem ...`
// * `(elem declare ...`
// * `(elem (table ...`
// * `(elem (offset ...`
// * `(elem (<instr> ...` (omitted `offset`)
let mut table_omitted = false;
let kind = if parser.peek::<kw::declare>()? {
parser.parse::<kw::declare>()?;
ElemKind::Declared
} else if parser.peek::<u32>()?
|| (parser.peek::<LParen>()? && !parser.peek::<RefType>()?)
{
let table = if parser.peek::<u32>()? {
// FIXME: this is only here to accomodate
// proposals/threads/imports.wast at this current moment in
// time, this probably should get removed when the threads
// proposal is rebased on the current spec.
table_omitted = true;
Index::Num(parser.parse()?, span)
} else if parser.peek2::<kw::table>()? {
parser.parens(|p| {
p.parse::<kw::table>()?;
p.parse()
})?
} else {
table_omitted = true;
Index::Num(0, span)
};
let offset = parse_expr_or_single_instr::<kw::offset>(parser)?;
ElemKind::Active { table, offset }
} else {
ElemKind::Passive
};
// Element segments can have a number of ways to specify their element
// lists:
//
// * `func 0 1 ...` - list of indices
// * `<reftype> (ref.null func) ...` - list of expressions
// * `0 1 ...` - list of indices, only if the table was omitted for the
// legacy way tables were printed.
let indices = if parser.peek::<kw::func>()? {
parser.parse::<kw::func>()?;
true
} else if parser.peek::<RefType>()? {
false
} else if table_omitted {
true
} else {
false // this will fall through to failing to parse a `RefType`
};
let payload = if indices {
ElemPayload::parse_indices(parser, None)?
} else {
let ty = parser.parse()?;
ElemPayload::parse_exprs(parser, ty)?
};
Ok(Elem {
span,
id,
name,
kind,
payload,
})
}
}
impl<'a> ElemPayload<'a> {
fn parse_indices(parser: Parser<'a>, ty: Option<RefType<'a>>) -> Result<Self> {
let mut ret = match ty {
// If there is no requested type, then it's ok to parse a list of
// indices.
None => ElemPayload::Indices(Vec::new()),
// If the requested type is a `funcref` type then a list of indices
// can be parsed. This is because the list-of-indices encoding in
// the binary format can only accomodate the `funcref` type.
Some(ty) if ty == RefType::func() => ElemPayload::Indices(Vec::new()),
// Otherwise silently translate this list-of-indices into a
// list-of-expressions because that's the only way to accomodate a
// non-funcref type.
Some(ty) => ElemPayload::Exprs {
ty,
exprs: Vec::new(),
},
};
while !parser.is_empty() {
let func = parser.parse()?;
match &mut ret {
ElemPayload::Indices(list) => list.push(func),
ElemPayload::Exprs { exprs, .. } => {
let expr = Expression::one(Instruction::RefFunc(func));
exprs.push(expr);
}
}
}
Ok(ret)
}
fn parse_exprs(parser: Parser<'a>, ty: RefType<'a>) -> Result<Self> {
let mut exprs = Vec::new();
while !parser.is_empty() {
let expr = parse_expr_or_single_instr::<kw::item>(parser)?;
exprs.push(expr);
}
Ok(ElemPayload::Exprs { exprs, ty })
}
}
// Parses either `(T expr)` or `(instr)`, returning the resulting expression.
fn parse_expr_or_single_instr<'a, T>(parser: Parser<'a>) -> Result<Expression<'a>>
where
T: Parse<'a> + Peek,
{
if parser.peek2::<T>()? {
parser.parens(|parser| {
parser.parse::<T>()?;
parser.parse()
})
} else {
// Without `T` this is "sugar" for a single instruction (still possibly folded).
Ok(Expression::parse_folded_instruction(parser)?)
}
}