/* Copyright 2018 Mozilla Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*
http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
use crate::{BinaryReader, ConstExpr, FromReader, Result, SectionLimited, TableType};
/// A reader for the table section of a WebAssembly module.
pub type TableSectionReader<'a> = SectionLimited<'a, Table<'a>>;
/// Type information about a table defined in the table section of a WebAssembly
/// module.
#[derive(Clone, Debug)]
pub struct Table<'a> {
/// The type of this table, including its element type and its limits.
pub ty: TableType,
/// The initialization expression for the table.
pub init: TableInit<'a>,
}
/// Different modes of initializing a table.
#[derive(Clone, Debug)]
pub enum TableInit<'a> {
/// The table is initialized to all null elements.
RefNull,
/// Each element in the table is initialized with the specified constant
/// expression.
Expr(ConstExpr<'a>),
}
impl<'a> FromReader<'a> for Table<'a> {
fn from_reader(reader: &mut BinaryReader<'a>) -> Result<Self> {
let has_init_expr = if reader.peek()? == 0x40 {
reader.read_u8()?;
true
} else {
false
};
if has_init_expr {
if reader.read_u8()? != 0x00 {
bail!(reader.original_position() - 1, "invalid table encoding");
}
}
let ty = reader.read::<TableType>()?;
let init = if has_init_expr {
TableInit::Expr(reader.read()?)
} else {
TableInit::RefNull
};
Ok(Table { ty, init })
}
}
impl<'a> FromReader<'a> for TableType {
fn from_reader(reader: &mut BinaryReader<'a>) -> Result<Self> {
let element_type = reader.read()?;
let pos = reader.original_position();
let flags = reader.read_u8()?;
if (flags & !0b111) != 0 {
bail!(pos, "invalid table resizable limits flags");
}
let has_max = (flags & 0b001) != 0;
let shared = (flags & 0b010) != 0;
let table64 = (flags & 0b100) != 0;
Ok(TableType {
element_type,
table64,
initial: if table64 {
reader.read_var_u64()?
} else {
reader.read_var_u32()?.into()
},
maximum: if !has_max {
None
} else if table64 {
Some(reader.read_var_u64()?)
} else {
Some(reader.read_var_u32()?.into())
},
shared,
})
}
}
