wasmparser 0.17.2

/* Copyright 2017 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 std::cmp::min;
use std::result;
use std::collections::HashSet;
use std::vec::Vec;

use parser::{WasmDecoder, Parser, ParserState, ParserInput, BinaryReaderError, FuncType, Type,
             Operator, ResizableLimits, TableType, ImportSectionEntryType, GlobalType, MemoryType,
             ExternalKind, SectionCode, MemoryImmediate, BinaryReader, Result};
use limits::{MAX_WASM_MEMORY_PAGES, MAX_WASM_TABLES, MAX_WASM_MEMORIES, MAX_WASM_TYPES,
             MAX_WASM_GLOBALS, MAX_WASM_FUNCTIONS};

type ValidatorResult<'a, T> = result::Result<T, ParserState<'a>>;

struct BlockState {
    return_types: Vec<Type>,
    stack_starts_at: usize,
    jump_to_top: bool,
    is_else_allowed: bool,
    is_dead_code: bool,
    polymorphic_values: Option<usize>,
}

impl BlockState {
    fn is_stack_polymorphic(&self) -> bool {
        self.polymorphic_values.is_some()
    }
}

struct FuncState {
    local_types: Vec<Type>,
    blocks: Vec<BlockState>,
    stack_types: Vec<Type>,
    end_function: bool,
}

impl FuncState {
    fn block_at(&self, depth: usize) -> &BlockState {
        assert!(depth < self.blocks.len());
        &self.blocks[self.blocks.len() - 1 - depth]
    }
    fn last_block(&self) -> &BlockState {
        self.blocks.last().unwrap()
    }
    fn assert_stack_type_at(&self, index: usize, expected: Type) -> bool {
        let stack_starts_at = self.last_block().stack_starts_at;
        if self.last_block().is_stack_polymorphic() &&
           stack_starts_at + index >= self.stack_types.len() {
            return true;
        }
        assert!(stack_starts_at + index < self.stack_types.len());
        self.stack_types[self.stack_types.len() - 1 - index] == expected
    }
    fn assert_block_stack_len(&self, depth: usize, minimal_len: usize) -> bool {
        assert!(depth < self.blocks.len());
        let blocks_end = self.blocks.len();
        let block_offset = blocks_end - 1 - depth;
        for i in block_offset..blocks_end {
            if self.blocks[i].is_stack_polymorphic() {
                return true;
            }
        }
        let block_starts_at = self.blocks[block_offset].stack_starts_at;
        self.stack_types.len() >= block_starts_at + minimal_len
    }
    fn assert_last_block_stack_len_exact(&self, len: usize) -> bool {
        let block_starts_at = self.last_block().stack_starts_at;
        if self.last_block().is_stack_polymorphic() {
            let polymorphic_values = self.last_block().polymorphic_values.unwrap();
            self.stack_types.len() + polymorphic_values <= block_starts_at + len
        } else {
            self.stack_types.len() == block_starts_at + len
        }
    }
}

struct InitExpressionState {
    ty: Type,
    global_count: usize,
    validated: bool,
}

#[derive(Copy,Clone,PartialOrd,Ord,PartialEq,Eq)]
enum SectionOrderState {
    Initial,
    Type,
    Import,
    Function,
    Table,
    Memory,
    Global,
    Export,
    Start,
    Element,
    Code,
    Data,
}

impl SectionOrderState {
    pub fn from_section_code(code: &SectionCode) -> Option<SectionOrderState> {
        match *code {
            SectionCode::Type => Some(SectionOrderState::Type),
            SectionCode::Import => Some(SectionOrderState::Import),
            SectionCode::Function => Some(SectionOrderState::Function),
            SectionCode::Table => Some(SectionOrderState::Table),
            SectionCode::Memory => Some(SectionOrderState::Memory),
            SectionCode::Global => Some(SectionOrderState::Global),
            SectionCode::Export => Some(SectionOrderState::Export),
            SectionCode::Start => Some(SectionOrderState::Start),
            SectionCode::Element => Some(SectionOrderState::Element),
            SectionCode::Code => Some(SectionOrderState::Code),
            SectionCode::Data => Some(SectionOrderState::Data),
            _ => None,
        }
    }
}

#[derive(Copy,Clone,PartialEq,Eq)]
enum BlockType {
    Block,
    Loop,
    If,
}

enum OperatorAction {
    None,
    ChangeFrame(usize),
    ChangeFrameWithType(usize, Type),
    ChangeFrameWithTypes(usize, Vec<Type>),
    ChangeFrameToExactTypes(Vec<Type>),
    ChangeFrameAfterSelect(Option<Type>),
    PushBlock(Type, BlockType),
    PopBlock,
    ResetBlock,
    DeadCode,
    EndFunction,
}

impl OperatorAction {
    fn remove_frame_stack_types(func_state: &mut FuncState, remove_count: usize) {
        if remove_count == 0 {
            return;
        }
        let last_block = func_state.blocks.last_mut().unwrap();
        if last_block.is_stack_polymorphic() {
            let len = func_state.stack_types.len();
            let non_polymorphic_len = len - last_block.stack_starts_at;
            let remove_non_polymorphic = min(non_polymorphic_len, remove_count);
            func_state
                .stack_types
                .truncate(len - remove_non_polymorphic);
            let polymorphic_values = last_block.polymorphic_values.unwrap();
            let remove_polymorphic = min(remove_count - remove_non_polymorphic, polymorphic_values);
            last_block.polymorphic_values = Some(polymorphic_values - remove_polymorphic);
        } else {
            assert!(func_state.stack_types.len() >=
                    last_block.stack_starts_at + remove_count);
            let keep = func_state.stack_types.len() - remove_count;
            func_state.stack_types.truncate(keep);
        }
    }
    fn update(&self, func_state: &mut FuncState) {
        match *self {
            OperatorAction::None => (),
            OperatorAction::PushBlock(ty, block_type) => {
                let return_types = match ty {
                    Type::EmptyBlockType => Vec::with_capacity(0),
                    _ => vec![ty],
                };
                if block_type == BlockType::If {
                    func_state.stack_types.pop();
                }
                let stack_starts_at = func_state.stack_types.len();
                func_state
                    .blocks
                    .push(BlockState {
                              return_types,
                              stack_starts_at,
                              jump_to_top: block_type == BlockType::Loop,
                              is_else_allowed: block_type == BlockType::If,
                              is_dead_code: false,
                              polymorphic_values: None,
                          });
            }
            OperatorAction::PopBlock => {
                assert!(func_state.blocks.len() > 1);
                let last_block = func_state.blocks.pop().unwrap();
                if last_block.is_stack_polymorphic() {
                    assert!(func_state.stack_types.len() <=
                            last_block.return_types.len() + last_block.stack_starts_at);
                } else {
                    assert!(func_state.stack_types.len() ==
                            last_block.return_types.len() + last_block.stack_starts_at);
                }
                let keep = last_block.stack_starts_at;
                func_state.stack_types.truncate(keep);
                func_state
                    .stack_types
                    .extend_from_slice(&last_block.return_types);
            }
            OperatorAction::ResetBlock => {
                assert!(func_state.last_block().is_else_allowed);
                let last_block = func_state.blocks.last_mut().unwrap();
                let keep = last_block.stack_starts_at;
                func_state.stack_types.truncate(keep);
                last_block.is_else_allowed = false;
                last_block.polymorphic_values = None;
            }
            OperatorAction::ChangeFrame(remove_count) => {
                OperatorAction::remove_frame_stack_types(func_state, remove_count);
            }
            OperatorAction::ChangeFrameWithType(remove_count, ty) => {
                OperatorAction::remove_frame_stack_types(func_state, remove_count);
                func_state.stack_types.push(ty);
            }
            OperatorAction::ChangeFrameWithTypes(remove_count, ref new_items) => {
                OperatorAction::remove_frame_stack_types(func_state, remove_count);
                if new_items.len() == 0 {
                    return;
                }
                func_state.stack_types.extend_from_slice(new_items);
            }
            OperatorAction::ChangeFrameToExactTypes(ref items) => {
                let last_block = func_state.blocks.last_mut().unwrap();
                let keep = last_block.stack_starts_at;
                func_state.stack_types.truncate(keep);
                func_state.stack_types.extend_from_slice(items);
                last_block.polymorphic_values = None;
            }
            OperatorAction::ChangeFrameAfterSelect(ty) => {
                OperatorAction::remove_frame_stack_types(func_state, 3);
                if ty.is_none() {
                    let last_block = func_state.blocks.last_mut().unwrap();
                    assert!(last_block.is_stack_polymorphic());
                    last_block.polymorphic_values = Some(last_block.polymorphic_values.unwrap() +
                                                         1);
                    return;
                }
                func_state.stack_types.push(ty.unwrap())
            }
            OperatorAction::DeadCode => {
                let last_block = func_state.blocks.last_mut().unwrap();
                let keep = last_block.stack_starts_at;
                func_state.stack_types.truncate(keep);
                last_block.is_dead_code = true;
                last_block.polymorphic_values = Some(0);
            }
            OperatorAction::EndFunction => {
                func_state.end_function = true;
            }
        }
    }
}

pub trait WasmModuleResources {
    fn types(&self) -> &[FuncType];
    fn tables(&self) -> &[TableType];
    fn memories(&self) -> &[MemoryType];
    fn globals(&self) -> &[GlobalType];
    fn func_type_indices(&self) -> &[u32];
}

type OperatorValidatorResult<T> = result::Result<T, &'static str>;

#[derive(Copy,Clone)]
pub struct OperatorValidatorConfig {
    pub enable_threads: bool,
}

const DEFAULT_OPERATOR_VALIDATOR_CONFIG: OperatorValidatorConfig =
    OperatorValidatorConfig { enable_threads: false };

struct OperatorValidator {
    func_state: FuncState,
    config: OperatorValidatorConfig,
}

impl OperatorValidator {
    pub fn new(func_type: &FuncType,
               locals: &Vec<(u32, Type)>,
               config: OperatorValidatorConfig)
               -> OperatorValidator {
        let mut local_types = Vec::new();
        local_types.extend_from_slice(func_type.params.as_slice());
        for local in locals {
            for _ in 0..local.0 {
                local_types.push(local.1);
            }
        }

        let mut blocks = Vec::new();
        let mut last_returns = Vec::new();
        last_returns.extend_from_slice(func_type.returns.as_slice());
        blocks.push(BlockState {
                        return_types: last_returns,
                        stack_starts_at: 0,
                        jump_to_top: false,
                        is_else_allowed: false,
                        is_dead_code: false,
                        polymorphic_values: None,
                    });

        OperatorValidator {
            func_state: FuncState {
                local_types,
                blocks,
                stack_types: Vec::new(),
                end_function: false,
            },
            config,
        }
    }

    pub fn is_dead_code(&self) -> bool {
        self.func_state.last_block().is_dead_code
    }

    fn check_frame_size(&self,
                        func_state: &FuncState,
                        require_count: usize)
                        -> OperatorValidatorResult<()> {
        if !func_state.assert_block_stack_len(0, require_count) {
            Err("not enough operands")
        } else {
            Ok(())
        }
    }

    fn check_operands_1(&self,
                        func_state: &FuncState,
                        operand: Type)
                        -> OperatorValidatorResult<()> {
        self.check_frame_size(func_state, 1)?;
        if !func_state.assert_stack_type_at(0, operand) {
            return Err("stack operand type mismatch");
        }
        Ok(())
    }

    fn check_operands_2(&self,
                        func_state: &FuncState,
                        operand1: Type,
                        operand2: Type)
                        -> OperatorValidatorResult<()> {
        self.check_frame_size(func_state, 2)?;
        if !func_state.assert_stack_type_at(1, operand1) {
            return Err("stack operand type mismatch");
        }
        if !func_state.assert_stack_type_at(0, operand2) {
            return Err("stack operand type mismatch");
        }
        Ok(())
    }

    fn check_operands(&self,
                      func_state: &FuncState,
                      expected_types: &[Type])
                      -> OperatorValidatorResult<()> {
        let len = expected_types.len();
        self.check_frame_size(func_state, len)?;
        for i in 0..len {
            if !func_state.assert_stack_type_at(len - 1 - i, expected_types[i]) {
                return Err("stack operand type mismatch");
            }
        }
        Ok(())
    }

    fn check_block_return_types(&self,
                                func_state: &FuncState,
                                block: &BlockState,
                                reserve_items: usize)
                                -> OperatorValidatorResult<()> {
        let len = block.return_types.len();
        for i in 0..len {
            if !func_state
                    .assert_stack_type_at(len - 1 - i + reserve_items, block.return_types[i]) {
                return Err("stack item type does not match block item type");
            }
        }
        Ok(())
    }

    fn check_block_return(&self, func_state: &FuncState) -> OperatorValidatorResult<()> {
        let len = func_state.last_block().return_types.len();
        if !func_state.assert_last_block_stack_len_exact(len) {
            return Err("stack size does not match block type");
        }
        self.check_block_return_types(func_state, func_state.last_block(), 0)
    }

    fn check_jump_from_block(&self,
                             func_state: &FuncState,
                             relative_depth: u32,
                             reserve_items: usize)
                             -> OperatorValidatorResult<()> {
        if relative_depth as usize >= func_state.blocks.len() {
            return Err("invalid block depth");
        }
        let block = func_state.block_at(relative_depth as usize);
        if block.jump_to_top {
            if !func_state.assert_last_block_stack_len_exact(reserve_items) {
                return Err("stack size does not match target loop type");
            }
            return Ok(());
        }

        let len = block.return_types.len();
        if !func_state.assert_block_stack_len(0, len + reserve_items) {
            return Err("stack size does not match target block type");
        }
        self.check_block_return_types(func_state, block, reserve_items)
    }

    fn match_block_return(&self,
                          func_state: &FuncState,
                          depth1: u32,
                          depth2: u32)
                          -> OperatorValidatorResult<()> {
        if depth1 as usize >= func_state.blocks.len() {
            return Err("invalid block depth");
        }
        if depth2 as usize >= func_state.blocks.len() {
            return Err("invalid block depth");
        }
        let block1 = func_state.block_at(depth1 as usize);
        let block2 = func_state.block_at(depth2 as usize);
        let ref return_types1 = block1.return_types;
        let ref return_types2 = block2.return_types;
        if block1.jump_to_top || block2.jump_to_top {
            if block1.jump_to_top {
                if !block2.jump_to_top && return_types2.len() != 0 {
                    return Err("block types do not match");
                }
            } else if return_types1.len() != 0 {
                return Err("block types do not match");
            }
        } else if *return_types1 != *return_types2 {
            return Err("block types do not match");
        }
        Ok(())
    }

    fn check_memory_index(&self,
                          memory_index: u32,
                          resources: &WasmModuleResources)
                          -> OperatorValidatorResult<()> {
        if memory_index as usize >= resources.memories().len() {
            return Err("no liner memories are present");
        }
        Ok(())
    }

    fn check_shared_memory_index(&self,
                                 memory_index: u32,
                                 resources: &WasmModuleResources)
                                 -> OperatorValidatorResult<()> {
        if memory_index as usize >= resources.memories().len() {
            return Err("no liner memories are present");
        }
        if !resources.memories()[memory_index as usize].shared {
            return Err("atomic accesses require shared memory");
        }
        Ok(())
    }

    fn check_memarg(&self,
                    memarg: &MemoryImmediate,
                    max_align: u32,
                    resources: &WasmModuleResources)
                    -> OperatorValidatorResult<()> {
        self.check_memory_index(0, resources)?;
        let align = memarg.flags;
        if align > max_align {
            return Err("align is required to be at most the number of accessed bytes");
        }
        Ok(())
    }

    fn check_threads_enabled(&self) -> OperatorValidatorResult<()> {
        if !self.config.enable_threads {
            return Err("threads support is not enabled");
        }
        Ok(())
    }

    fn check_shared_memarg_wo_align(&self,
                                    _: &MemoryImmediate,
                                    resources: &WasmModuleResources)
                                    -> OperatorValidatorResult<()> {
        self.check_shared_memory_index(0, resources)?;
        Ok(())
    }

    fn check_block_type(&self, ty: Type) -> OperatorValidatorResult<()> {
        match ty {
            Type::EmptyBlockType | Type::I32 | Type::I64 | Type::F32 | Type::F64 => Ok(()),
            _ => Err("invalid block return type"),
        }
    }

    fn check_select(&self, func_state: &FuncState) -> OperatorValidatorResult<Option<Type>> {
        self.check_frame_size(func_state, 3)?;
        let last_block = func_state.last_block();
        Ok(if last_block.is_stack_polymorphic() {
               match func_state.stack_types.len() - last_block.stack_starts_at {
                   0 => None,
                   1 => {
                       self.check_operands_1(func_state, Type::I32)?;
                       None
                   }
                   2 => {
                       self.check_operands_1(func_state, Type::I32)?;
                       Some(func_state.stack_types[func_state.stack_types.len() - 2])
                   }
                   _ => {
                       let ty = func_state.stack_types[func_state.stack_types.len() - 3];
                       self.check_operands_2(func_state, ty, Type::I32)?;
                       Some(ty)
                   }
               }
           } else {
               let ty = func_state.stack_types[func_state.stack_types.len() - 3];
               self.check_operands_2(func_state, ty, Type::I32)?;
               Some(ty)
           })
    }

    fn process_operator(&self,
                        operator: &Operator,
                        resources: &WasmModuleResources)
                        -> OperatorValidatorResult<OperatorAction> {
        let ref func_state = self.func_state;
        if func_state.end_function {
            return Err("unexpected operator");
        }
        Ok(match *operator {
               Operator::Unreachable => OperatorAction::DeadCode,
               Operator::Nop => OperatorAction::None,
               Operator::Block { ty } => {
                   self.check_block_type(ty)?;
                   OperatorAction::PushBlock(ty, BlockType::Block)
               }
               Operator::Loop { ty } => {
                   self.check_block_type(ty)?;
                   OperatorAction::PushBlock(ty, BlockType::Loop)
               }
               Operator::If { ty } => {
                   self.check_block_type(ty)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::PushBlock(ty, BlockType::If)
               }
               Operator::Else => {
                   if !func_state.last_block().is_else_allowed {
                       return Err("unexpected else: if block is not started");
                   }
                   self.check_block_return(func_state)?;
                   OperatorAction::ResetBlock
               }
               Operator::End => {
                   self.check_block_return(func_state)?;
                   let ref last_block = func_state.last_block();
                   if func_state.blocks.len() == 1 {
                       OperatorAction::EndFunction
                   } else {
                       if last_block.is_else_allowed && last_block.return_types.len() > 0 {
                           return Err("else is expected: if block has type");
                       }
                       OperatorAction::PopBlock
                   }
               }
               Operator::Br { relative_depth } => {
                   self.check_jump_from_block(func_state, relative_depth, 0)?;
                   OperatorAction::DeadCode
               }
               Operator::BrIf { relative_depth } => {
                   self.check_operands_1(func_state, Type::I32)?;
                   self.check_jump_from_block(func_state, relative_depth, 1)?;
                   if func_state.last_block().is_stack_polymorphic() {
                       let block = func_state.block_at(relative_depth as usize);
                       OperatorAction::ChangeFrameToExactTypes(block.return_types.clone())
                   } else {
                       OperatorAction::ChangeFrame(1)
                   }
               }
               Operator::BrTable { ref table } => {
                   self.check_operands_1(func_state, Type::I32)?;
                   let mut depth0: Option<u32> = None;
                   for relative_depth in table {
                       if depth0.is_none() {
                           self.check_jump_from_block(func_state, relative_depth, 1)?;
                           depth0 = Some(relative_depth);
                           continue;
                       }
                       self.match_block_return(func_state, relative_depth, depth0.unwrap())?;
                   }
                   OperatorAction::DeadCode
               }
               Operator::Return => {
                   let depth = (func_state.blocks.len() - 1) as u32;
                   self.check_jump_from_block(func_state, depth, 0)?;
                   OperatorAction::DeadCode
               }
               Operator::Call { function_index } => {
                   if function_index as usize >= resources.func_type_indices().len() {
                       return Err("function index out of bounds");
                   }
                   let type_index = resources.func_type_indices()[function_index as usize];
                   let ref ty = resources.types()[type_index as usize];
                   self.check_operands(func_state, &ty.params)?;
                   OperatorAction::ChangeFrameWithTypes(ty.params.len(), ty.returns.clone())
               }
               Operator::CallIndirect { index, table_index } => {
                   if table_index as usize >= resources.tables().len() {
                       return Err("table index out of bounds");
                   }
                   if index as usize >= resources.types().len() {
                       return Err("type index out of bounds");
                   }
                   let ref ty = resources.types()[index as usize];
                   let mut types = Vec::with_capacity(ty.params.len() + 1);
                   types.extend_from_slice(&ty.params);
                   types.push(Type::I32);
                   self.check_operands(func_state, &types)?;
                   OperatorAction::ChangeFrameWithTypes(ty.params.len() + 1, ty.returns.clone())
               }
               Operator::Drop => {
                   self.check_frame_size(func_state, 1)?;
                   OperatorAction::ChangeFrame(1)
               }
               Operator::Select => {
                   let ty = self.check_select(func_state)?;
                   OperatorAction::ChangeFrameAfterSelect(ty)
               }
               Operator::GetLocal { local_index } => {
                   if local_index as usize >= func_state.local_types.len() {
                       return Err("local index out of bounds");
                   }
                   let local_type = func_state.local_types[local_index as usize];
                   OperatorAction::ChangeFrameWithType(0, local_type)
               }
               Operator::SetLocal { local_index } => {
                   if local_index as usize >= func_state.local_types.len() {
                       return Err("local index out of bounds");
                   }
                   let local_type = func_state.local_types[local_index as usize];
                   self.check_operands_1(func_state, local_type)?;
                   OperatorAction::ChangeFrame(1)
               }
               Operator::TeeLocal { local_index } => {
                   if local_index as usize >= func_state.local_types.len() {
                       return Err("local index out of bounds");
                   }
                   let local_type = func_state.local_types[local_index as usize];
                   self.check_operands_1(func_state, local_type)?;
                   OperatorAction::ChangeFrameWithType(1, local_type)
               }
               Operator::GetGlobal { global_index } => {
                   if global_index as usize >= resources.globals().len() {
                       return Err("global index out of bounds");
                   }
                   let ref ty = resources.globals()[global_index as usize];
                   OperatorAction::ChangeFrameWithType(0, ty.content_type)
               }
               Operator::SetGlobal { global_index } => {
                   if global_index as usize >= resources.globals().len() {
                       return Err("global index out of bounds");
                   }
                   let ref ty = resources.globals()[global_index as usize];
                   // FIXME
                   //    if !ty.mutable {
                   //        return self.create_error("global expected to be mutable");
                   //    }
                   self.check_operands_1(func_state, ty.content_type)?;
                   OperatorAction::ChangeFrame(1)
               }
               Operator::I32Load { ref memarg } => {
                   self.check_memarg(memarg, 2, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }
               Operator::I64Load { ref memarg } => {
                   self.check_memarg(memarg, 3, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I64)
               }
               Operator::F32Load { ref memarg } => {
                   self.check_memarg(memarg, 2, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::F32)
               }
               Operator::F64Load { ref memarg } => {
                   self.check_memarg(memarg, 3, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::F64)
               }
               Operator::I32Load8S { ref memarg } => {
                   self.check_memarg(memarg, 0, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }
               Operator::I32Load8U { ref memarg } => {
                   self.check_memarg(memarg, 0, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }
               Operator::I32Load16S { ref memarg } => {
                   self.check_memarg(memarg, 1, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }
               Operator::I32Load16U { ref memarg } => {
                   self.check_memarg(memarg, 1, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }
               Operator::I64Load8S { ref memarg } => {
                   self.check_memarg(memarg, 0, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I64)
               }
               Operator::I64Load8U { ref memarg } => {
                   self.check_memarg(memarg, 0, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I64)
               }
               Operator::I64Load16S { ref memarg } => {
                   self.check_memarg(memarg, 1, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I64)
               }
               Operator::I64Load16U { ref memarg } => {
                   self.check_memarg(memarg, 1, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I64)
               }
               Operator::I64Load32S { ref memarg } => {
                   self.check_memarg(memarg, 2, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I64)
               }
               Operator::I64Load32U { ref memarg } => {
                   self.check_memarg(memarg, 2, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I64)
               }
               Operator::I32Store { ref memarg } => {
                   self.check_memarg(memarg, 2, resources)?;
                   self.check_operands_2(func_state, Type::I32, Type::I32)?;
                   OperatorAction::ChangeFrame(2)
               }
               Operator::I64Store { ref memarg } => {
                   self.check_memarg(memarg, 3, resources)?;
                   self.check_operands_2(func_state, Type::I32, Type::I64)?;
                   OperatorAction::ChangeFrame(2)
               }
               Operator::F32Store { ref memarg } => {
                   self.check_memarg(memarg, 2, resources)?;
                   self.check_operands_2(func_state, Type::I32, Type::F32)?;
                   OperatorAction::ChangeFrame(2)
               }
               Operator::F64Store { ref memarg } => {
                   self.check_memarg(memarg, 3, resources)?;
                   self.check_operands_2(func_state, Type::I32, Type::F64)?;
                   OperatorAction::ChangeFrame(2)
               }
               Operator::I32Store8 { ref memarg } => {
                   self.check_memarg(memarg, 0, resources)?;
                   self.check_operands_2(func_state, Type::I32, Type::I32)?;
                   OperatorAction::ChangeFrame(2)
               }
               Operator::I32Store16 { ref memarg } => {
                   self.check_memarg(memarg, 1, resources)?;
                   self.check_operands_2(func_state, Type::I32, Type::I32)?;
                   OperatorAction::ChangeFrame(2)
               }
               Operator::I64Store8 { ref memarg } => {
                   self.check_memarg(memarg, 0, resources)?;
                   self.check_operands_2(func_state, Type::I32, Type::I64)?;
                   OperatorAction::ChangeFrame(2)
               }
               Operator::I64Store16 { ref memarg } => {
                   self.check_memarg(memarg, 1, resources)?;
                   self.check_operands_2(func_state, Type::I32, Type::I64)?;
                   OperatorAction::ChangeFrame(2)
               }
               Operator::I64Store32 { ref memarg } => {
                   self.check_memarg(memarg, 2, resources)?;
                   self.check_operands_2(func_state, Type::I32, Type::I64)?;
                   OperatorAction::ChangeFrame(2)
               }
               Operator::MemorySize { reserved: memory_index } => {
                   self.check_memory_index(memory_index, resources)?;
                   OperatorAction::ChangeFrameWithType(0, Type::I32)
               }
               Operator::MemoryGrow { reserved: memory_index } => {
                   self.check_memory_index(memory_index, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }
               Operator::I32Const { .. } => OperatorAction::ChangeFrameWithType(0, Type::I32),
               Operator::I64Const { .. } => OperatorAction::ChangeFrameWithType(0, Type::I64),
               Operator::F32Const { .. } => OperatorAction::ChangeFrameWithType(0, Type::F32),
               Operator::F64Const { .. } => OperatorAction::ChangeFrameWithType(0, Type::F64),
               Operator::I32Eqz => {
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }
               Operator::I32Eq | Operator::I32Ne | Operator::I32LtS | Operator::I32LtU |
               Operator::I32GtS | Operator::I32GtU | Operator::I32LeS | Operator::I32LeU |
               Operator::I32GeS | Operator::I32GeU => {
                   self.check_operands_2(func_state, Type::I32, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(2, Type::I32)
               }
               Operator::I64Eqz => {
                   self.check_operands_1(func_state, Type::I64)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }
               Operator::I64Eq | Operator::I64Ne | Operator::I64LtS | Operator::I64LtU |
               Operator::I64GtS | Operator::I64GtU | Operator::I64LeS | Operator::I64LeU |
               Operator::I64GeS | Operator::I64GeU => {
                   self.check_operands_2(func_state, Type::I64, Type::I64)?;
                   OperatorAction::ChangeFrameWithType(2, Type::I32)
               }
               Operator::F32Eq | Operator::F32Ne | Operator::F32Lt | Operator::F32Gt |
               Operator::F32Le | Operator::F32Ge => {
                   self.check_operands_2(func_state, Type::F32, Type::F32)?;
                   OperatorAction::ChangeFrameWithType(2, Type::I32)
               }
               Operator::F64Eq | Operator::F64Ne | Operator::F64Lt | Operator::F64Gt |
               Operator::F64Le | Operator::F64Ge => {
                   self.check_operands_2(func_state, Type::F64, Type::F64)?;
                   OperatorAction::ChangeFrameWithType(2, Type::I32)
               }
               Operator::I32Clz |
               Operator::I32Ctz |
               Operator::I32Popcnt => {
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }
               Operator::I32Add |
               Operator::I32Sub |
               Operator::I32Mul |
               Operator::I32DivS |
               Operator::I32DivU |
               Operator::I32RemS |
               Operator::I32RemU |
               Operator::I32And |
               Operator::I32Or |
               Operator::I32Xor |
               Operator::I32Shl |
               Operator::I32ShrS |
               Operator::I32ShrU |
               Operator::I32Rotl |
               Operator::I32Rotr => {
                   self.check_operands_2(func_state, Type::I32, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(2, Type::I32)
               }
               Operator::I64Clz |
               Operator::I64Ctz |
               Operator::I64Popcnt => {
                   self.check_operands_1(func_state, Type::I64)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I64)
               }
               Operator::I64Add |
               Operator::I64Sub |
               Operator::I64Mul |
               Operator::I64DivS |
               Operator::I64DivU |
               Operator::I64RemS |
               Operator::I64RemU |
               Operator::I64And |
               Operator::I64Or |
               Operator::I64Xor |
               Operator::I64Shl |
               Operator::I64ShrS |
               Operator::I64ShrU |
               Operator::I64Rotl |
               Operator::I64Rotr => {
                   self.check_operands_2(func_state, Type::I64, Type::I64)?;
                   OperatorAction::ChangeFrameWithType(2, Type::I64)
               }
               Operator::F32Abs |
               Operator::F32Neg |
               Operator::F32Ceil |
               Operator::F32Floor |
               Operator::F32Trunc |
               Operator::F32Nearest |
               Operator::F32Sqrt => {
                   self.check_operands_1(func_state, Type::F32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::F32)
               }
               Operator::F32Add |
               Operator::F32Sub |
               Operator::F32Mul |
               Operator::F32Div |
               Operator::F32Min |
               Operator::F32Max |
               Operator::F32Copysign => {
                   self.check_operands_2(func_state, Type::F32, Type::F32)?;
                   OperatorAction::ChangeFrameWithType(2, Type::F32)
               }
               Operator::F64Abs |
               Operator::F64Neg |
               Operator::F64Ceil |
               Operator::F64Floor |
               Operator::F64Trunc |
               Operator::F64Nearest |
               Operator::F64Sqrt => {
                   self.check_operands_1(func_state, Type::F64)?;
                   OperatorAction::ChangeFrameWithType(1, Type::F64)
               }
               Operator::F64Add |
               Operator::F64Sub |
               Operator::F64Mul |
               Operator::F64Div |
               Operator::F64Min |
               Operator::F64Max |
               Operator::F64Copysign => {
                   self.check_operands_2(func_state, Type::F64, Type::F64)?;
                   OperatorAction::ChangeFrameWithType(2, Type::F64)
               }
               Operator::I32WrapI64 => {
                   self.check_operands_1(func_state, Type::I64)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }
               Operator::I32TruncSF32 |
               Operator::I32TruncUF32 => {
                   self.check_operands_1(func_state, Type::F32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }
               Operator::I32TruncSF64 |
               Operator::I32TruncUF64 => {
                   self.check_operands_1(func_state, Type::F64)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }
               Operator::I64ExtendSI32 |
               Operator::I64ExtendUI32 => {
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I64)
               }
               Operator::I64TruncSF32 |
               Operator::I64TruncUF32 => {
                   self.check_operands_1(func_state, Type::F32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I64)
               }
               Operator::I64TruncSF64 |
               Operator::I64TruncUF64 => {
                   self.check_operands_1(func_state, Type::F64)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I64)
               }
               Operator::F32ConvertSI32 |
               Operator::F32ConvertUI32 => {
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::F32)
               }
               Operator::F32ConvertSI64 |
               Operator::F32ConvertUI64 => {
                   self.check_operands_1(func_state, Type::I64)?;
                   OperatorAction::ChangeFrameWithType(1, Type::F32)
               }
               Operator::F32DemoteF64 => {
                   self.check_operands_1(func_state, Type::F64)?;
                   OperatorAction::ChangeFrameWithType(1, Type::F32)
               }
               Operator::F64ConvertSI32 |
               Operator::F64ConvertUI32 => {
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::F64)
               }
               Operator::F64ConvertSI64 |
               Operator::F64ConvertUI64 => {
                   self.check_operands_1(func_state, Type::I64)?;
                   OperatorAction::ChangeFrameWithType(1, Type::F64)
               }
               Operator::F64PromoteF32 => {
                   self.check_operands_1(func_state, Type::F32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::F64)
               }
               Operator::I32ReinterpretF32 => {
                   self.check_operands_1(func_state, Type::F32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }
               Operator::I64ReinterpretF64 => {
                   self.check_operands_1(func_state, Type::F64)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I64)
               }
               Operator::F32ReinterpretI32 => {
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::F32)
               }
               Operator::F64ReinterpretI64 => {
                   self.check_operands_1(func_state, Type::I64)?;
                   OperatorAction::ChangeFrameWithType(1, Type::F64)
               }
               Operator::I32TruncSSatF32 |
               Operator::I32TruncUSatF32 => {
                   self.check_operands_1(func_state, Type::F32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }
               Operator::I32TruncSSatF64 |
               Operator::I32TruncUSatF64 => {
                   self.check_operands_1(func_state, Type::F64)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }
               Operator::I64TruncSSatF32 |
               Operator::I64TruncUSatF32 => {
                   self.check_operands_1(func_state, Type::F32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I64)
               }
               Operator::I64TruncSSatF64 |
               Operator::I64TruncUSatF64 => {
                   self.check_operands_1(func_state, Type::F64)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I64)
               }
               Operator::I32Extend16S |
               Operator::I32Extend8S => {
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }

               Operator::I64Extend32S |
               Operator::I64Extend16S |
               Operator::I64Extend8S => {
                   self.check_operands_1(func_state, Type::I64)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I64)
               }

               Operator::I32AtomicLoad { ref memarg } |
               Operator::I32AtomicLoad16U { ref memarg } |
               Operator::I32AtomicLoad8U { ref memarg } => {
                   self.check_threads_enabled()?;
                   self.check_shared_memarg_wo_align(memarg, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I32)
               }
               Operator::I64AtomicLoad { ref memarg } |
               Operator::I64AtomicLoad32U { ref memarg } |
               Operator::I64AtomicLoad16U { ref memarg } |
               Operator::I64AtomicLoad8U { ref memarg } => {
                   self.check_threads_enabled()?;
                   self.check_shared_memarg_wo_align(memarg, resources)?;
                   self.check_operands_1(func_state, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(1, Type::I64)
               }
               Operator::I32AtomicStore { ref memarg } |
               Operator::I32AtomicStore16 { ref memarg } |
               Operator::I32AtomicStore8 { ref memarg } => {
                   self.check_threads_enabled()?;
                   self.check_shared_memarg_wo_align(memarg, resources)?;
                   self.check_operands_2(func_state, Type::I32, Type::I32)?;
                   OperatorAction::ChangeFrame(2)
               }
               Operator::I64AtomicStore { ref memarg } |
               Operator::I64AtomicStore32 { ref memarg } |
               Operator::I64AtomicStore16 { ref memarg } |
               Operator::I64AtomicStore8 { ref memarg } => {
                   self.check_threads_enabled()?;
                   self.check_shared_memarg_wo_align(memarg, resources)?;
                   self.check_operands_2(func_state, Type::I32, Type::I64)?;
                   OperatorAction::ChangeFrame(2)
               }
               Operator::I32AtomicRmwAdd { ref memarg } |
               Operator::I32AtomicRmwSub { ref memarg } |
               Operator::I32AtomicRmwAnd { ref memarg } |
               Operator::I32AtomicRmwOr { ref memarg } |
               Operator::I32AtomicRmwXor { ref memarg } |
               Operator::I32AtomicRmw16UAdd { ref memarg } |
               Operator::I32AtomicRmw16USub { ref memarg } |
               Operator::I32AtomicRmw16UAnd { ref memarg } |
               Operator::I32AtomicRmw16UOr { ref memarg } |
               Operator::I32AtomicRmw16UXor { ref memarg } |
               Operator::I32AtomicRmw8UAdd { ref memarg } |
               Operator::I32AtomicRmw8USub { ref memarg } |
               Operator::I32AtomicRmw8UAnd { ref memarg } |
               Operator::I32AtomicRmw8UOr { ref memarg } |
               Operator::I32AtomicRmw8UXor { ref memarg } => {
                   self.check_threads_enabled()?;
                   self.check_shared_memarg_wo_align(memarg, resources)?;
                   self.check_operands_2(func_state, Type::I32, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(2, Type::I32)
               }
               Operator::I64AtomicRmwAdd { ref memarg } |
               Operator::I64AtomicRmwSub { ref memarg } |
               Operator::I64AtomicRmwAnd { ref memarg } |
               Operator::I64AtomicRmwOr { ref memarg } |
               Operator::I64AtomicRmwXor { ref memarg } |
               Operator::I64AtomicRmw32UAdd { ref memarg } |
               Operator::I64AtomicRmw32USub { ref memarg } |
               Operator::I64AtomicRmw32UAnd { ref memarg } |
               Operator::I64AtomicRmw32UOr { ref memarg } |
               Operator::I64AtomicRmw32UXor { ref memarg } |
               Operator::I64AtomicRmw16UAdd { ref memarg } |
               Operator::I64AtomicRmw16USub { ref memarg } |
               Operator::I64AtomicRmw16UAnd { ref memarg } |
               Operator::I64AtomicRmw16UOr { ref memarg } |
               Operator::I64AtomicRmw16UXor { ref memarg } |
               Operator::I64AtomicRmw8UAdd { ref memarg } |
               Operator::I64AtomicRmw8USub { ref memarg } |
               Operator::I64AtomicRmw8UAnd { ref memarg } |
               Operator::I64AtomicRmw8UOr { ref memarg } |
               Operator::I64AtomicRmw8UXor { ref memarg } => {
                   self.check_threads_enabled()?;
                   self.check_shared_memarg_wo_align(memarg, resources)?;
                   self.check_operands_2(func_state, Type::I32, Type::I64)?;
                   OperatorAction::ChangeFrameWithType(2, Type::I64)
               }
               Operator::I32AtomicRmwXchg { ref memarg } |
               Operator::I32AtomicRmw16UXchg { ref memarg } |
               Operator::I32AtomicRmw8UXchg { ref memarg } => {
                   self.check_threads_enabled()?;
                   self.check_shared_memarg_wo_align(memarg, resources)?;
                   self.check_operands_2(func_state, Type::I32, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(2, Type::I32)
               }
               Operator::I32AtomicRmwCmpxchg { ref memarg } |
               Operator::I32AtomicRmw16UCmpxchg { ref memarg } |
               Operator::I32AtomicRmw8UCmpxchg { ref memarg } => {
                   self.check_threads_enabled()?;
                   self.check_shared_memarg_wo_align(memarg, resources)?;
                   self.check_operands(func_state, &[Type::I32, Type::I32, Type::I32])?;
                   OperatorAction::ChangeFrameWithType(3, Type::I32)
               }
               Operator::I64AtomicRmwXchg { ref memarg } |
               Operator::I64AtomicRmw32UXchg { ref memarg } |
               Operator::I64AtomicRmw16UXchg { ref memarg } |
               Operator::I64AtomicRmw8UXchg { ref memarg } => {
                   self.check_threads_enabled()?;
                   self.check_shared_memarg_wo_align(memarg, resources)?;
                   self.check_operands_2(func_state, Type::I32, Type::I64)?;
                   OperatorAction::ChangeFrameWithType(2, Type::I64)
               }
               Operator::I64AtomicRmwCmpxchg { ref memarg } |
               Operator::I64AtomicRmw32UCmpxchg { ref memarg } |
               Operator::I64AtomicRmw16UCmpxchg { ref memarg } |
               Operator::I64AtomicRmw8UCmpxchg { ref memarg } => {
                   self.check_threads_enabled()?;
                   self.check_shared_memarg_wo_align(memarg, resources)?;
                   self.check_operands(func_state, &[Type::I32, Type::I64, Type::I64])?;
                   OperatorAction::ChangeFrameWithType(3, Type::I64)
               }
               Operator::Wake { ref memarg } => {
                   self.check_threads_enabled()?;
                   self.check_shared_memarg_wo_align(memarg, resources)?;
                   self.check_operands_2(func_state, Type::I32, Type::I32)?;
                   OperatorAction::ChangeFrameWithType(2, Type::I32)
               }
               Operator::I32Wait { ref memarg } => {
                   self.check_threads_enabled()?;
                   self.check_shared_memarg_wo_align(memarg, resources)?;
                   self.check_operands(func_state, &[Type::I32, Type::I32, Type::I64])?;
                   OperatorAction::ChangeFrameWithType(3, Type::I32)
               }
               Operator::I64Wait { ref memarg } => {
                   self.check_threads_enabled()?;
                   self.check_shared_memarg_wo_align(memarg, resources)?;
                   self.check_operands(func_state, &[Type::I32, Type::I64, Type::I64])?;
                   OperatorAction::ChangeFrameWithType(3, Type::I32)
               }
           })
    }

    fn process_end_function(&self) -> OperatorValidatorResult<()> {
        let ref func_state = self.func_state;
        if !func_state.end_function {
            return Err("expected end of function");
        }
        Ok(())
    }
}

#[derive(Copy,Clone)]
pub struct ValidatingParserConfig {
    pub operator_config: OperatorValidatorConfig,
}

const DEFAULT_VALIDATING_PARSER_CONFIG: ValidatingParserConfig =
    ValidatingParserConfig { operator_config: DEFAULT_OPERATOR_VALIDATOR_CONFIG };

pub struct ValidatingParser<'a> {
    parser: Parser<'a>,
    validation_error: Option<ParserState<'a>>,
    read_position: Option<usize>,
    section_order_state: SectionOrderState,
    types: Vec<FuncType>,
    tables: Vec<TableType>,
    memories: Vec<MemoryType>,
    globals: Vec<GlobalType>,
    func_type_indices: Vec<u32>,
    current_func_index: u32,
    func_imports_count: u32,
    init_expression_state: Option<InitExpressionState>,
    exported_names: HashSet<Vec<u8>>,
    current_operator_validator: Option<OperatorValidator>,
    config: ValidatingParserConfig,
}

impl<'a> WasmModuleResources for ValidatingParser<'a> {
    fn types(&self) -> &[FuncType] {
        return &self.types;
    }

    fn tables(&self) -> &[TableType] {
        return &self.tables;
    }

    fn memories(&self) -> &[MemoryType] {
        return &self.memories;
    }

    fn globals(&self) -> &[GlobalType] {
        return &self.globals;
    }

    fn func_type_indices(&self) -> &[u32] {
        return &self.func_type_indices;
    }
}

impl<'a> ValidatingParser<'a> {
    pub fn new(bytes: &[u8], config: Option<ValidatingParserConfig>) -> ValidatingParser {
        ValidatingParser {
            parser: Parser::new(bytes),
            validation_error: None,
            read_position: None,
            section_order_state: SectionOrderState::Initial,
            types: Vec::new(),
            tables: Vec::new(),
            memories: Vec::new(),
            globals: Vec::new(),
            func_type_indices: Vec::new(),
            current_func_index: 0,
            func_imports_count: 0,
            current_operator_validator: None,
            init_expression_state: None,
            exported_names: HashSet::new(),
            config: config.unwrap_or(DEFAULT_VALIDATING_PARSER_CONFIG),
        }
    }

    fn create_validation_error(&self, message: &'static str) -> Option<ParserState<'a>> {
        Some(ParserState::Error(BinaryReaderError {
                                    message,
                                    offset: self.read_position.unwrap(),
                                }))
    }

    fn create_error<T>(&self, message: &'static str) -> ValidatorResult<'a, T> {
        Err(ParserState::Error(BinaryReaderError {
                                   message,
                                   offset: self.read_position.unwrap(),
                               }))
    }

    fn check_utf8(&self, bytes: &[u8]) -> ValidatorResult<'a, ()> {
        // https://encoding.spec.whatwg.org/#utf-8
        let mut bytes_needed = 0;
        let mut lower_boundary = 0x80;
        let mut upper_boundary = 0xBF;
        for byte_ref in bytes {
            let byte = *byte_ref;
            if bytes_needed == 0 {
                if byte <= 0x7F {
                    continue;
                }
                if 0xC2 <= byte && byte <= 0xDF {
                    bytes_needed = 1;
                    continue;
                }
                if 0xE0 <= byte && byte <= 0xEF {
                    bytes_needed = 2;
                    if byte == 0xE0 {
                        lower_boundary = 0xA0;
                    }
                    if byte == 0xED {
                        upper_boundary = 0x9F;
                    }
                    continue;
                }
                if 0xF0 <= byte && byte <= 0xF4 {
                    bytes_needed = 3;
                    if byte == 0xF0 {
                        lower_boundary = 0x90;
                    }
                    if byte == 0xF4 {
                        upper_boundary = 0x8F;
                    }
                    continue;
                }
                return self.create_error("Invalid utf-8: unexpected code");
            }

            if byte < lower_boundary || byte > upper_boundary {
                return self.create_error("Invalid utf-8: code point out of range");
            }

            lower_boundary = 0x80;
            upper_boundary = 0xBF;
            bytes_needed -= 1;
        }
        if bytes_needed > 0 {
            self.create_error("Invalid utf-8: unexpected end of string")
        } else {
            Ok(())
        }
    }

    fn check_value_type(&self, ty: Type) -> ValidatorResult<'a, ()> {
        match ty {
            Type::I32 | Type::I64 | Type::F32 | Type::F64 => Ok(()),
            _ => return self.create_error("invalid value type"),
        }
    }

    fn check_value_types(&self, types: &[Type]) -> ValidatorResult<'a, ()> {
        for ty in types {
            self.check_value_type(*ty)?;
        }
        Ok(())
    }

    fn check_limits(&self, limits: &ResizableLimits) -> ValidatorResult<'a, ()> {
        if limits.maximum.is_some() && limits.initial > limits.maximum.unwrap() {
            return self.create_error("maximum limits less than initial");
        }
        Ok(())
    }

    fn check_func_type(&self, func_type: &FuncType) -> ValidatorResult<'a, ()> {
        if let Type::Func = func_type.form {
            self.check_value_types(func_type.params.as_slice())?;
            self.check_value_types(func_type.returns.as_slice())?;
            if func_type.returns.len() > 1 {
                return self.create_error("too many returns, expected 0 or 1");
            }
            Ok(())
        } else {
            self.create_error("type signature is not a func")
        }
    }

    fn check_table_type(&self, table_type: &TableType) -> ValidatorResult<'a, ()> {
        if let Type::AnyFunc = table_type.element_type {
            self.check_limits(&table_type.limits)
        } else {
            self.create_error("element is not anyfunc")
        }
    }

    fn check_memory_type(&self, memory_type: &MemoryType) -> ValidatorResult<'a, ()> {
        self.check_limits(&memory_type.limits)?;
        let initial = memory_type.limits.initial;
        if initial as usize > MAX_WASM_MEMORY_PAGES {
            return self.create_error("memory initial value exceeds limit");
        }
        let maximum = memory_type.limits.maximum;
        if maximum.is_some() && maximum.unwrap() as usize > MAX_WASM_MEMORY_PAGES {
            return self.create_error("memory maximum value exceeds limit");
        }
        Ok(())
    }

    fn check_global_type(&self, global_type: &GlobalType) -> ValidatorResult<'a, ()> {
        self.check_value_type(global_type.content_type)
    }

    fn check_import_entry(&self,
                          module: &[u8],
                          field: &[u8],
                          import_type: &ImportSectionEntryType)
                          -> ValidatorResult<'a, ()> {
        self.check_utf8(module)?;
        self.check_utf8(field)?;
        match *import_type {
            ImportSectionEntryType::Function(type_index) => {
                if self.func_type_indices.len() >= MAX_WASM_FUNCTIONS {
                    return self.create_error("functions count out of bounds");
                }
                if type_index as usize >= self.types.len() {
                    return self.create_error("type index out of bounds");
                }
                Ok(())
            }
            ImportSectionEntryType::Table(ref table_type) => {
                if self.tables.len() >= MAX_WASM_TABLES {
                    return self.create_error("tables count must be at most 1");
                }
                self.check_table_type(table_type)
            }
            ImportSectionEntryType::Memory(ref memory_type) => {
                if self.memories.len() >= MAX_WASM_MEMORIES {
                    return self.create_error("memory count must be at most 1");
                }
                self.check_memory_type(memory_type)
            }
            ImportSectionEntryType::Global(ref global_type) => {
                if self.globals.len() >= MAX_WASM_GLOBALS {
                    return self.create_error("functions count out of bounds");
                }
                if global_type.mutable {
                    return self.create_error("global imports are required to be immutable");
                }
                self.check_global_type(global_type)
            }
        }
    }

    fn check_init_expression_operator(&self, operator: &Operator) -> ValidatorResult<'a, ()> {
        let state = self.init_expression_state.as_ref().unwrap();
        if state.validated {
            return self.create_error("only one init_expr operator is expected");
        }
        let ty = match *operator {
            Operator::I32Const { .. } => Type::I32,
            Operator::I64Const { .. } => Type::I64,
            Operator::F32Const { .. } => Type::F32,
            Operator::F64Const { .. } => Type::F64,
            Operator::GetGlobal { global_index } => {
                if global_index as usize >= state.global_count {
                    return self.create_error("init_expr global index out of bounds");
                }
                self.globals[global_index as usize].content_type
            }
            _ => return self.create_error("invalid init_expr operator"),
        };
        if ty != state.ty {
            return self.create_error("invalid init_expr type");
        }
        Ok(())
    }

    fn check_export_entry(&self,
                          field: &[u8],
                          kind: ExternalKind,
                          index: u32)
                          -> ValidatorResult<'a, ()> {
        self.check_utf8(field)?;
        if self.exported_names.contains(&Vec::from(field)) {
            return self.create_error("non-unique export name");
        }
        match kind {
            ExternalKind::Function => {
                if index as usize >= self.func_type_indices.len() {
                    return self.create_error("exported function index out of bounds");
                }
            }
            ExternalKind::Table => {
                if index as usize >= self.tables.len() {
                    return self.create_error("exported table index out of bounds");
                }
            }
            ExternalKind::Memory => {
                if index as usize >= self.memories.len() {
                    return self.create_error("exported memory index out of bounds");
                }
            }
            ExternalKind::Global => {
                if index as usize >= self.globals.len() {
                    return self.create_error("exported global index out of bounds");
                }
                let ref global = self.globals[index as usize];
                if global.mutable {
                    return self.create_error("exported global must be const");
                }
            }
        };
        Ok(())
    }

    fn check_start(&self, func_index: u32) -> ValidatorResult<'a, ()> {
        if func_index as usize >= self.func_type_indices.len() {
            return self.create_error("start function index out of bounds");
        }
        let type_index = self.func_type_indices[func_index as usize];
        let ref ty = self.types[type_index as usize];
        if ty.params.len() > 0 || ty.returns.len() > 0 {
            return self.create_error("invlid start function type");
        }
        Ok(())
    }

    fn process_begin_section(&self, code: &SectionCode) -> ValidatorResult<'a, SectionOrderState> {
        let order_state = SectionOrderState::from_section_code(code);
        if let SectionCode::Custom { name, .. } = *code {
            self.check_utf8(name)?;
        }
        Ok(match self.section_order_state {
               SectionOrderState::Initial => {
                   if order_state.is_none() {
                       SectionOrderState::Initial
                   } else {
                       order_state.unwrap()
                   }
               }
               previous @ _ => {
                   if let Some(order_state_unwraped) = order_state {
                       if previous >= order_state_unwraped {
                           return self.create_error("section out of order");
                       }
                       order_state_unwraped
                   } else {
                       previous
                   }
               }
           })
    }

    fn process_state(&mut self) {
        match *self.parser.last_state() {
            ParserState::BeginWasm { version } => {
                if version != 1 {
                    self.validation_error = self.create_validation_error("bad wasm file version");
                }
            }
            ParserState::BeginSection { ref code, .. } => {
                let check = self.process_begin_section(code);
                if check.is_err() {
                    self.validation_error = check.err();
                } else {
                    self.section_order_state = check.ok().unwrap();
                }
            }
            ParserState::TypeSectionEntry(ref func_type) => {
                let check = self.check_func_type(func_type);
                if check.is_err() {
                    self.validation_error = check.err();
                } else if self.types.len() > MAX_WASM_TYPES {
                    self.validation_error =
                        self.create_validation_error("types count is out of bounds");
                } else {
                    self.types.push(func_type.clone());
                }
            }
            ParserState::ImportSectionEntry {
                module,
                field,
                ref ty,
            } => {
                let check = self.check_import_entry(module, field, ty);
                if check.is_err() {
                    self.validation_error = check.err();
                } else {
                    match *ty {
                        ImportSectionEntryType::Function(type_index) => {
                            self.func_imports_count += 1;
                            self.func_type_indices.push(type_index);
                        }
                        ImportSectionEntryType::Table(ref table_type) => {
                            self.tables.push(table_type.clone());
                        }
                        ImportSectionEntryType::Memory(ref memory_type) => {
                            self.memories.push(memory_type.clone());
                        }
                        ImportSectionEntryType::Global(ref global_type) => {
                            self.globals.push(global_type.clone());
                        }
                    }
                }
            }
            ParserState::FunctionSectionEntry(type_index) => {
                if type_index as usize >= self.types.len() {
                    self.validation_error =
                        self.create_validation_error("func type index out of bounds");
                } else if self.func_type_indices.len() >= MAX_WASM_FUNCTIONS {
                    self.validation_error =
                        self.create_validation_error("functions count out of bounds");
                } else {
                    self.func_type_indices.push(type_index);
                }
            }
            ParserState::TableSectionEntry(ref table_type) => {
                if self.tables.len() >= MAX_WASM_TABLES {
                    self.validation_error =
                        self.create_validation_error("tables count must be at most 1");
                } else {
                    self.validation_error = self.check_table_type(table_type).err();
                    self.tables.push(table_type.clone());
                }
            }
            ParserState::MemorySectionEntry(ref memory_type) => {
                if self.memories.len() >= MAX_WASM_MEMORIES {
                    self.validation_error =
                        self.create_validation_error("memories count must be at most 1");
                } else {
                    self.validation_error = self.check_memory_type(memory_type).err();
                    self.memories.push(memory_type.clone());
                }
            }
            ParserState::BeginGlobalSectionEntry(ref global_type) => {
                if self.globals.len() >= MAX_WASM_GLOBALS {
                    self.validation_error =
                        self.create_validation_error("globals count out of bounds");
                } else {
                    self.validation_error = self.check_global_type(global_type).err();
                    self.init_expression_state = Some(InitExpressionState {
                                                          ty: global_type.content_type,
                                                          global_count: self.globals.len(),
                                                          validated: false,
                                                      });
                    self.globals.push(global_type.clone());
                }
            }
            ParserState::BeginInitExpressionBody => {
                assert!(self.init_expression_state.is_some());
            }
            ParserState::InitExpressionOperator(ref operator) => {
                self.validation_error = self.check_init_expression_operator(operator).err();
                self.init_expression_state.as_mut().unwrap().validated = true;
            }
            ParserState::EndInitExpressionBody => {
                if !self.init_expression_state.as_ref().unwrap().validated {
                    self.validation_error = self.create_validation_error("init_expr is empty");
                }
                self.init_expression_state = None;
            }
            ParserState::ExportSectionEntry { field, kind, index } => {
                self.validation_error = self.check_export_entry(field, kind, index).err();
                self.exported_names.insert(Vec::from(field));
            }
            ParserState::StartSectionEntry(func_index) => {
                self.validation_error = self.check_start(func_index).err();
            }
            ParserState::BeginElementSectionEntry(table_index) => {
                if table_index as usize >= self.tables.len() {
                    self.validation_error =
                        self.create_validation_error("element section table index out of bounds");
                } else {
                    assert!(self.tables[table_index as usize].element_type == Type::AnyFunc);
                    self.init_expression_state = Some(InitExpressionState {
                                                          ty: Type::I32,
                                                          global_count: self.globals.len(),
                                                          validated: false,
                                                      });
                }
            }
            ParserState::ElementSectionEntryBody(ref indices) => {
                for func_index in indices {
                    if *func_index as usize >= self.func_type_indices.len() {
                        self.validation_error =
                            self.create_validation_error("element func index out of bounds");
                        break;
                    }
                }
            }
            ParserState::BeginFunctionBody { .. } => {
                let index = (self.current_func_index + self.func_imports_count) as usize;
                if index as usize >= self.func_type_indices.len() {
                    self.validation_error =
                        self.create_validation_error("func type is not defined");
                }
            }
            ParserState::FunctionBodyLocals { ref locals } => {
                let index = (self.current_func_index + self.func_imports_count) as usize;
                let ref func_type = self.types[self.func_type_indices[index] as usize];
                let operator_config = self.config.operator_config;
                self.current_operator_validator =
                    Some(OperatorValidator::new(func_type, locals, operator_config));
            }
            ParserState::CodeOperator(ref operator) => {
                let check = self.current_operator_validator
                    .as_ref()
                    .unwrap()
                    .process_operator(operator, self);
                if check.is_err() {
                    self.validation_error = self.create_validation_error(check.err().unwrap());
                } else {
                    let action = check.ok().unwrap();
                    action.update(&mut self.current_operator_validator.as_mut().unwrap().func_state)
                }
            }
            ParserState::EndFunctionBody => {
                let check = self.current_operator_validator
                    .as_ref()
                    .unwrap()
                    .process_end_function();
                if check.is_err() {
                    self.validation_error = self.create_validation_error(check.err().unwrap());
                }
                self.current_func_index += 1;
                self.current_operator_validator = None;
            }
            ParserState::BeginDataSectionEntry(memory_index) => {
                if memory_index as usize >= self.memories.len() {
                    self.validation_error =
                        self.create_validation_error("data section memory index out of bounds");
                } else {
                    self.init_expression_state = Some(InitExpressionState {
                                                          ty: Type::I32,
                                                          global_count: self.globals.len(),
                                                          validated: false,
                                                      });
                }
            }
            _ => (),
        };
    }

    pub fn create_validating_operator_parser<'b>(&mut self) -> ValidatingOperatorParser<'b>
        where 'a: 'b
    {
        let func_body_offset = match *self.last_state() {
            ParserState::BeginFunctionBody { .. } => self.parser.current_position(),
            _ => panic!("Invalid reader state"),
        };
        self.read();
        let operator_validator = match *self.last_state() {
            ParserState::FunctionBodyLocals { ref locals } => {
                let index = (self.current_func_index + self.func_imports_count) as usize;
                let ref func_type = self.types[self.func_type_indices[index] as usize];
                let operator_config = self.config.operator_config;
                OperatorValidator::new(func_type, locals, operator_config)
            }
            _ => panic!("Invalid reader state"),
        };
        let reader = self.create_binary_reader();
        ValidatingOperatorParser {
            operator_validator,
            reader,
            func_body_offset,
            end_function: false,
        }
    }
}

impl<'a> WasmDecoder<'a> for ValidatingParser<'a> {
    fn read(&mut self) -> &ParserState<'a> {
        if self.validation_error.is_some() {
            panic!("Parser in error state: validation");
        }
        self.read_position = Some(self.parser.current_position());
        self.parser.read();
        self.process_state();
        self.last_state()
    }

    fn push_input(&mut self, input: ParserInput) {
        match input {
            ParserInput::SkipSection => panic!("Not supported"),
            ParserInput::ReadSectionRawData => panic!("Not supported"),
            _ => self.parser.push_input(input),
        }
    }

    fn read_with_input(&mut self, input: ParserInput) -> &ParserState<'a> {
        self.push_input(input);
        self.read()
    }

    fn create_binary_reader<'b>(&mut self) -> BinaryReader<'b>
        where 'a: 'b
    {
        if let ParserState::BeginSection { .. } = *self.parser.last_state() {
            panic!("Not supported");
        }
        self.parser.create_binary_reader()
    }

    fn last_state(&self) -> &ParserState<'a> {
        if self.validation_error.is_some() {
            self.validation_error.as_ref().unwrap()
        } else {
            self.parser.last_state()
        }
    }
}

pub struct ValidatingOperatorParser<'b> {
    operator_validator: OperatorValidator,
    reader: BinaryReader<'b>,
    func_body_offset: usize,
    end_function: bool,
}

impl<'b> ValidatingOperatorParser<'b> {
    pub fn eof(&self) -> bool {
        return self.end_function;
    }

    pub fn current_position(&self) -> usize {
        self.reader.current_position()
    }

    pub fn is_dead_code(&self) -> bool {
        self.operator_validator.is_dead_code()
    }

    /// Creates a BinaryReader when current state is ParserState::BeginSection
    /// or ParserState::BeginFunctionBody.
    ///
    /// # Examples
    /// ```
    /// # let data = &[0x0, 0x61, 0x73, 0x6d, 0x1, 0x0, 0x0, 0x0, 0x1, 0x84,
    /// #              0x80, 0x80, 0x80, 0x0, 0x1, 0x60, 0x0, 0x0, 0x3, 0x83,
    /// #              0x80, 0x80, 0x80, 0x0, 0x2, 0x0, 0x0, 0x6, 0x81, 0x80,
    /// #              0x80, 0x80, 0x0, 0x0, 0xa, 0x91, 0x80, 0x80, 0x80, 0x0,
    /// #              0x2, 0x83, 0x80, 0x80, 0x80, 0x0, 0x0, 0x1, 0xb, 0x83,
    /// #              0x80, 0x80, 0x80, 0x0, 0x0, 0x0, 0xb];
    /// use wasmparser::{WasmDecoder, ParserState, ValidatingParser};
    /// let mut parser = ValidatingParser::new(data, None);
    /// let mut validating_parsers = Vec::new();
    /// loop {
    ///     {
    ///         match *parser.read() {
    ///             ParserState::Error(_) |
    ///             ParserState::EndWasm => break,
    ///             ParserState::BeginFunctionBody {..} => (),
    ///             _ => continue
    ///         }
    ///     }
    ///     let reader = parser.create_validating_operator_parser();
    ///     validating_parsers.push(reader);
    /// }
    /// for (i, reader) in validating_parsers.iter_mut().enumerate() {
    ///     println!("Function {}", i);
    ///     while !reader.eof() {
    ///       let read = reader.next(&parser);
    ///       if let Ok(ref op) = read {
    ///           println!("  {:?}", op);
    ///       } else {
    ///           panic!("  Bad wasm code {:?}", read.err());
    ///       }
    ///     }
    /// }
    /// ```
    pub fn next(&mut self, resources: &WasmModuleResources) -> Result<Operator<'b>> {
        let op = self.reader.read_operator()?;
        let check = self.operator_validator.process_operator(&op, resources);
        if check.is_err() {
            return Err(BinaryReaderError {
                           message: check.err().unwrap(),
                           offset: self.func_body_offset + self.reader.current_position(),
                       });
        }
        if let OperatorAction::EndFunction = check.ok().unwrap() {
            self.end_function = true;
            if !self.reader.eof() {
                return Err(BinaryReaderError {
                               message: "unexpected end of function",
                               offset: self.func_body_offset + self.reader.current_position(),
                           });
            }
        }
        Ok(op)
    }
}

/// Test whether the given buffer contains a valid WebAssembly module,
/// analogous to WebAssembly.validate in the JS API.
pub fn validate(bytes: &[u8], config: Option<ValidatingParserConfig>) -> bool {
    let mut parser = ValidatingParser::new(bytes, config);
    loop {
        let state = parser.read();
        match *state {
            ParserState::EndWasm => return true,
            ParserState::Error(_) => return false,
            _ => (),
        }
    }
}

#[test]
fn test_validate() {
    assert!(validate(&[0x0, 0x61, 0x73, 0x6d, 0x1, 0x0, 0x0, 0x0], None));
    assert!(!validate(&[0x0, 0x61, 0x73, 0x6d, 0x2, 0x0, 0x0, 0x0], None));
}