structure.py

#!/usr/bin/python3
# -*- coding: utf-8 -*-
"""
The module defines the structure of WebAssembly bytecode, every class
map a type of section of WebAssembly.
"""
import io
import typing
import bin_reader
import logger
import number
from utils import *


class FunctionType:
    """Function types are encoded by the byte 0x60 followed by the respective vectors of parameter and result types.
    functype ::= 0x60 t1*:vec(valtype) t2*:vec(valtype) --> [t1*] -> [t2*]

    Attributes:
        args: a list of parameters' type of function
        rets: a list of return value type of function
    """
    def __init__(self):
        self.args: typing.List[int]
        self.rets: typing.List[int]

    def __eq__(self, other):
        return isinstance(other, self.__class__) and self.args == other.args and self.rets == other.rets

    def __repr__(self):
        args = [bin_format.valtype[i][0] for i in self.args]
        rets = [bin_format.valtype[i][0] for i in self.rets]
        a = ', '.join(args)
        if rets:
            b = rets[0]
            return f'{a} -> {b}'
        return f'({a})'

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = FunctionType()
        assert ord(r.read(1)) == 0x60
        o.args = bin_reader.read_bytes(r)
        o.rets = bin_reader.read_bytes(r)
        return o


class ResultType:
    """Result types classify the result of executing instructions or blocks, which is a sequence of values written with
    brackets. 

    resulttype ::= [valtype?]
    """

    def __init__(self):
        pass


class Limits:
    """Limits are encoded with a preceding flag indicating whether a maximum is present.

    limits ::= 0x00  n:u32        -> {min n,max ϵ}
             | 0x01  n:u32  m:u32 -> {min n,max m}

    Attributes:
        minimum: the initial value of limit
        maximum: the max value of limit
    """

    def __init__(self, minimum: int, maximum: int):
        self.minimum = minimum
        self.maximum = maximum

    def __repr__(self):
        if self.maximum:
            return f'minimum={self.minimum} maximum={self.maximum}'
        return f'minimum={self.minimum}'

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        flag = ord(r.read(1))
        minimum = bin_reader.read_count(r)
        maximum = bin_reader.read_count(r) if flag else None
        return Limits(minimum, maximum)


class MemoryType:
    """Memory types classify linear memories and their size range.

    memtype ::= limits

    The limits constrain the minimum and optionally the maximum size of a memory. The limits are given in units of
    page size.
    """

    def __init__(self):
        pass

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        return Limits.from_reader(r)


class TableType:
    """Table types classify tables over elements of element types within a size range.

    tabletype :: =limits elemtype
    elemtype ::= funcref

    Like memories, tables are constrained by limits for their minimum and optionally maximum size. The limits are
    given in numbers of entries. The element type funcref is the infinite union of all function types. A table of that
    type thus contains references to functions of heterogeneous type.

    Attributes:
        limits: represent the size of table
        elemtype: represent the type of elements in table
    """

    def __init__(self):
        self.limits: Limits
        self.elemtype: int

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = TableType()
        o.elemtype = ord(r.read(1))
        o.limits = Limits.from_reader(r)
        return o


class GlobalType:
    """Global types are encoded by their value type and a flag for theirmutability.

    globaltype ::= t:valtype m:mut -> m t
    mut ::= 0x00 -> const
          | 0x01 -> var

    Attributes:
        valtype: an integer represent the type of value
        mut:  is or not mutable
    """

    def __init__(self):
        self.valtype: int
        self.mut: bool

    def __repr__(self):
        if self.mut:
            return f'var {bin_format.valtype[self.valtype]}'
        return f'const {bin_format.valtype[self.valtype]}'

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = GlobalType()
        o.valtype = ord(r.read(1))
        o.mut = ord(r.read(1)) == 1
        return o


class ExternType:
    """External types classify imports and external values with their respective types.

    externtype ::= func functype | table tabletype | mem memtype | global globaltype
    """

    def __init__(self):
        pass


class Instruction:
    """Instructions are encoded by opcodes. Each opcode is represented by a single byte, and is followed by the
    instruction’s immediate arguments, where present. The only exception are structured control instructions,
    which consist of several opcodes bracketing their nested instruction sequences.

    Attributes:
        code: an integer represent the instruction
        immediate_arguments: None or list of arguments of instruction
    """

    def __init__(self, code: int, immediate_arguments=None):
        self.code = code
        self.immediate_arguments = immediate_arguments

    def __repr__(self):
        if self.immediate_arguments is None:
            return f'{bin_format.opcodes[self.code][0]}'
        return f'{bin_format.opcodes[self.code][0]} {self.immediate_arguments}'

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        code_byte = r.read(1)
        if not code_byte:
            return None
        code = ord(code_byte)
        code_size = bin_format.opcodes[code][1]
        if code_size == '':
            immediate_arguments = None
        elif code_size == 'u8':
            immediate_arguments = bin_reader.read_count(r, 8)
        elif code_size == 'u32':
            immediate_arguments = bin_reader.read_count(r, 32)
        elif code_size == 'i32':
            immediate_arguments = number.int2i32(
                bin_reader.read_count(r, 32, signed=True))
        elif code_size == 'i64':
            immediate_arguments = number.int2i64(
                bin_reader.read_count(r, 64, signed=True))
        elif code_size == 'f32':
            immediate_arguments = number.LittleEndian.f32(r.read(4))
        elif code_size == 'f64':
            immediate_arguments = number.LittleEndian.f64(r.read(8))
        elif code_size == 'u32,u8':
            immediate_arguments = [bin_reader.read_count(
                r, 32), bin_reader.read_count(r, 8)]
        elif code_size == 'u32,u32':
            immediate_arguments = [bin_reader.read_count(r, 32) for _ in range(2)]
        elif code == bin_format.br_table:
            n = bin_reader.read_count(r, 32)
            a = [bin_reader.read_count(r, 32) for _ in range(n)]
            b = bin_reader.read_count(r, 32)
            immediate_arguments = [a, b]
        else:
            raise Exception("Invalid code size!")
        return Instruction(code, immediate_arguments)


class Expression:
    """Function bodies, initialization values for globals, and offsets of element or data segments are given as
    expressions, which are sequences of instructions terminated by an end marker.

    expr ::= instr∗ end

    In some places, validation restricts expressions to be constant, which limits the set of allowable instructions.

    Attributes:
        data: list of instructions
        composition: dictionary, key is the branch instrucion(such as if), 
                     value is list of pc of termination instruction(such as else, end)
    """

    def __init__(self):
        self.data: typing.List[Instruction] = []
        self.composition = {}

    def __str__(self):
        return str(self.data)

    @classmethod
    def compose(cls, data: typing.List[Instruction]):
        composition = {}
        stack = []
        for i, instr in enumerate(data):
            code = instr.code
            if code in [bin_format.block, bin_format.loop, bin_format.if_]:
                stack.append([i])
                continue
            if code == bin_format.else_:
                stack[-1].append(i)
                continue
            if code == bin_format.end:
                if i == len(data) - 1:
                    break
                block = stack.pop()
                block.append(i)
                composition[block[0]] = block
                continue
        if data[-1].code != bin_format.end:
            raise Exception("Function block did not end with 0xb!")
        if stack:
            raise Exception("Function ended in middle of block!")
        return composition

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = Expression()
        d = 1
        while True:
            i = Instruction.from_reader(r)
            if not i:
                break
            o.data.append(i)
            if i.code in [bin_format.block, bin_format.loop, bin_format.if_]:
                d += 1
            if i.code == bin_format.end:
                d -= 1
            if d == 0:
                break
        o.composition = cls.compose(o.data)
        return o


class Locals:
    """The locals declare a vector of mutable local variables and their types. These variables are referenced through
    local indices in the function’s body. The index of the first local is the smallest index not referencing a parameter.

    locals ::= n:u32 t:valtype -> tn

    Attributes:
        n: the value of local type
        valtype: the value type
    """

    def __init__(self):
        self.n: int
        self.valtype: int

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = Locals()
        o.n = bin_reader.read_count(r, 32)
        o.valtype = ord(r.read(1))
        return o


class Code:
    """The encoding of each code entry consists of
      - the u32 size of the function code in bytes
      - the actual function code, which in turn consists of
          - the declaration of locals
         -  the function body as an expression.

    Local declarations are compressed into a vector whose entries consist of
      - a u32 count
      - a value type.

    code ::= size:u32 code:func -> code(ifsize=||func||)
    func ::= (t∗)∗:vec(locals) e:expr -> concat((t∗)∗), e∗(if|concat((t∗)∗)|<232)
    locals ::= n:u32 t:valtype -> tn

    Attributes:
        locals: local parameter type list of code
        expr: instructions of code
    """

    def __init__(self):
        self.locals: typing.List[int] = []
        self.expr: Expression

    def __repr__(self):
        return f'locals=[{", ".join([bin_format.valtype[i][0] for i in self.locals])}]'

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = Code()
        n = bin_reader.read_count(r, 32)
        n = bin_reader.read_count(r, 32)
        for _ in range(n):
            l = Locals.from_reader(r)
            o.locals.extend([l.valtype for _ in range(l.n)])
        o.expr = Expression.from_reader(r)
        return o


class Function:
    """The funcs component of a module defines a vector of functions with the following structure:

    func ::= {type typeidx, locals vec(valtype), body expr}

    The type of a function declares its signature by reference to a type defined in the module. The parameters of the
    function are referenced through 0-based local indices in the function’s body; they are mutable.

    The locals declare a vector of mutable local variables and their types. These variables are referenced through
    local indices in the function’s body. The index of the first local is the smallest index not referencing a
    parameter.

    The body is an instruction sequence that upon termination must produce a stack matching the function type’s
    result type.

    Functions are referenced through function indices, starting with the smallest index not referencing
    a function import.

    Attributes:
        typeidx: index to function-type table to declare the type of function
        locals: list of locals variables of function
        expr: instructions of function
    """

    def __init__(self):
        self.typeidx: int
        self.locals: typing.List[int] = []
        self.expr: Expression


class Table:
    """The tables component of a module defines a vector of tables described by their table type:

    table ::= {type tabletype}

    Attributes:
        tabletype: represent the table type
    """

    def __init__(self):
        self.tabletype: TableType

    def __repr__(self):
        return f'{bin_format.elemtype[self.tabletype.elemtype][0]} {self.tabletype.limits}'

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = Table()
        o.tabletype = TableType.from_reader(r)
        return o


class Memory:
    """The mems component of a module defines a vector of linear memories (or memories for short) as described by their
    memory type.

    mem ::= {type memtype}

    Attributes:
        memtype: represent the memory type
    """

    def __init__(self):
        self.memtype: MemoryType

    def __repr__(self):
        return f'{self.memtype}'

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = Memory()
        o.memtype = MemoryType.from_reader(r)
        return o


class Global:
    """The globals component of a module defines a vector of global variables (or globals for short):

    global ::= {type globaltype, init expr}

    Attributes:
        globaltype: represent global type
        expr: instructions of global
    """

    def __init__(self):
        self.globaltype: GlobalType
        self.expr: Expression

    def __repr__(self):
        return f'{self.globaltype} expr={self.expr}'

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = Global()
        o.globaltype = GlobalType.from_reader(r)
        o.expr = Expression.from_reader(r)
        return o


class ElementSegment:
    """The initial contents of a table is uninitialized. The elem component of a module defines a vector of element
    segments that initialize a subrange of a table, at a given offset, from a static vector of elements.

    elem ::= {table tableidx, offset expr, init vec(funcidx)}

    The offset is given by a constant expression.

    Attributes:
        tableidx: index to table of table
        expr: instructions
        init: initial values
    """

    def __init__(self):
        self.tableidx: int
        self.expr: Expression
        self.init: typing.List[int]

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = ElementSegment()
        o.tableidx = bin_reader.read_count(r, 32)
        o.expr = Expression.from_reader(r)
        n = bin_reader.read_count(r, 32)
        o.init = [bin_reader.read_count(r, 32) for _ in range(n)]
        return o


class DataSegment:
    """The initial contents of a memory are zero-valued bytes. The data component of a module defines a vector of data
    segments that initialize a range of memory, at a given offset, with a static vector of bytes.

    data::={data memidx,offset expr,init vec(byte)}

    The offset is given by a constant expression.

    Attributes:
        memidx: an integer represent the data member order
        expr: instructions to get the memory address
        init: the initial values
    """

    def __init__(self):
        self.memidx: int
        self.expr: Expression
        self.init: bytearray

    def __repr__(self):
        return self.init[:32].decode(encoding='utf-8', errors='replace')

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = DataSegment()
        o.memidx = bin_reader.read_count(r, 32)
        o.expr = Expression.from_reader(r)
        o.init = bytearray(bin_reader.read_bytes(r, 32))
        return o


class StartFunction:
    """The start component of a module declares the function index of a start function that is automatically invoked
    when the module is instantiated, after tables and memories have been initialized.

    start ::= {func funcidx}

    Attributes:
        funcidx: index of function table
    """

    def __init__(self):
        self.funcidx: int

    def __repr__(self):
        return f'Function[{self.funcidx}]'

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = StartFunction()
        o.funcidx = bin_reader.read_count(r, 32)
        return o


class Export:
    """The exports component of a module defines a set of exports that become accessible to the host environment once
    the module has been instantiated.

    export ::= {name name, desc exportdesc}
    exportdesc ::= func funcidx | table tableidx | mem memidx | global globalidx

    Each export is labeled by a unique name. Exportable definitions are functions, tables, memories, and globals,
    which are referenced through a respective descriptor.

    Attributes:
        name: the name of export function
        kind: the type of export function
        desc: the index of function table of export function
    """

    def __init__(self):
        self.name: str
        self.kind: int
        self.desc = None

    def __repr__(self):
        if self.kind == bin_format.extern_func:
            return f'{self.name} -> Function[{self.desc}]'
        if self.kind == bin_format.extern_table:
            return f'{self.name} -> Table[{self.desc}]'
        if self.kind == bin_format.extern_mem:
            return f'{self.name} -> Memory[{self.desc}]'
        if self.kind == bin_format.extern_global:
            return f'{self.name} -> Global[{self.desc}]'
        return f'{self.name}'

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = Export()
        o.name = bin_reader.read_bytes(r, 32).decode()
        o.kind = ord(r.read(1))
        o.desc = bin_reader.read_count(r, 32)
        return o


class Import:
    """"The imports component of a module defines a set of imports that are required for instantiation.

    import ::= {module name, name name, desc importdesc}
    importdesc ::= func typeidx | table tabletype | mem memtype | global globaltype

    Each import is labeled by a two-level name space, consisting of a module name and a name for an entity within
    that module. Importable definitions are functions, tables, memories, and globals. Each import is specified by a
    descriptor with a respective type that a definition provided during instantiation is required to match. Every
    import defines an index in the respective index space. In each index space, the indices of imports go before the
    first index of any definition contained in the module itself.

    Attributes:
        module: the name of module include import function
        name: the name of import function
        kind: the index to function table represent function type
        desc: the address of function code
    """

    def __init__(self):
        self.module: str
        self.name: str
        self.kind: int
        self.desc = None

    def __repr__(self):
        if self.kind == bin_format.extern_func:
            return f'{self.module}.{self.name} -> Function[{self.desc}]'
        if self.kind == bin_format.extern_table:
            return f'{self.module}.{self.name} -> Table[{self.desc}]'
        if self.kind == bin_format.extern_mem:
            return f'{self.module}.{self.name} -> Memory[{self.desc}]'
        if self.kind == bin_format.extern_global:
            return f'{self.module}.{self.name} -> Global[{self.desc}]'
        return f'{self.module}.{self.name}'

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = Import()
        o.module = bin_reader.read_bytes(r, 32).decode()
        o.name = bin_reader.read_bytes(r, 32).decode()
        o.kind = ord(r.read(1))
        if o.kind == bin_format.extern_func:
            o.desc = bin_reader.read_count(r, 32)
        elif o.kind == bin_format.extern_table:
            o.desc = TableType.from_reader(r)
        elif o.kind == bin_format.extern_mem:
            o.desc = MemoryType.from_reader(r)
        elif o.kind == bin_format.extern_global:
            o.desc = GlobalType.from_reader(r)
        else:
            raise Exception('Malformed!')
        return o


class CustomSection:
    """Custom sections have the id 0. They are intended to be used for debugging
    information or third-party extensions, and are ignored by the WebAssembly
    semantics. Their contents consist of a name further identifying the custom
    section, followed by an uninterpreted sequence of bytes for custom use.

    customsec ::= section0(custom)
    custom ::= name byte∗

    Attributes:
        name: the name of custom section
        data: the data of custom section
    """

    def __init__(self):
        self.name: str = None
        self.data: bytearray = None

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = CustomSection()
        n = bin_reader.read_count(r, 32)
        o.name = r.read(n).decode()
        o.data = bytearray(r.read(-1))
        return o


class TypeSection:
    """The type section has the id 1. It decodes into a vector of function
    types that represent the types component of a module.

    typesec ::= ft∗:section1(vec(functype)) ⇒ ft∗

    Attributes:
        vec: the type table of fucntion
    """

    def __init__(self):
        self.vec: typing.List[FunctionType] = []

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = TypeSection()
        n = bin_reader.read_count(r, 32)
        o.vec = [FunctionType.from_reader(r) for _ in range(n)]
        return o


class ImportSection:
    """The import section has the id 2. It decodes into a vector of imports
    that represent the imports component of a module.

    importsec ::= im∗:section2(vec(import)) ⇒ im∗
    import ::= mod:name nm:name d:importdesc ⇒ {module mod, name nm, desc d}
    importdesc ::= 0x00 x:typeidx ⇒ func x
                 | 0x01 tt:tabletype ⇒ table tt
                 | 0x02 mt:memtype ⇒ mem mt
                 | 0x03 gt:globaltype ⇒ global gt

    Attributes:
        vec: list of import object
    """

    def __init__(self):
        self.vec: typing.List[Import] = []

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = ImportSection()
        n = bin_reader.read_count(r, 32)
        o.vec = [Import.from_reader(r) for _ in range(n)]
        return o


class FunctionSection:
    """The function section has the id 3. It decodes into a vector of type
    indices that represent the type fields of the functions in the funcs
    component of a module. The locals and body fields of the respective
    functions are encoded separately in the code section.

    funcsec ::= x∗:section3(vec(typeidx)) ⇒ x∗

    Attributes:
        vec: list of int represent function type
    """

    def __init__(self):
        self.vec: typing.List[int] = []

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = FunctionSection()
        n = bin_reader.read_count(r, 32)
        o.vec = [bin_reader.read_count(r, 32) for _ in range(n)]
        return o


class TableSection:
    """The table section has the id 4. It decodes into a vector of tables that
    represent the tables component of a module.

    tablesec ::= tab∗:section4(vec(table)) ⇒ tab∗
    table ::= tt:tabletype ⇒ {type tt}

    Attributes:
        vec: list of table object
    """

    def __init__(self):
        self.vec: typing.List[Table] = []

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = TableSection()
        n = bin_reader.read_count(r, 32)
        o.vec = [Table.from_reader(r) for _ in range(n)]
        return o


class MemorySection:
    """The memory section has the id 5. It decodes into a vector of memories
    that represent the mems component of a module.

    memsec ::= mem∗:section5(vec(mem)) ⇒ mem∗
    mem ::= mt:memtype ⇒ {type mt}

    Attributes:
        vec: list of memory object
    """

    def __init__(self):
        self.vec: typing.List[Memory] = []

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = MemorySection()
        n = bin_reader.read_count(r, 32)
        o.vec = [Memory.from_reader(r) for _ in range(n)]
        return o


class GlobalSection:
    """The global section has the id 6. It decodes into a vector of globals
    that represent the globals component of a module.

    globalsec ::= glob*:section6(vec(global)) ⇒ glob∗
    global ::= gt:globaltype e:expr ⇒ {type gt, init e}

    Attributes:
        vec: list of global object
    """

    def __init__(self):
        self.vec: typing.List[Global] = []

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = GlobalSection()
        n = bin_reader.read_count(r, 32)
        o.vec = [Global.from_reader(r) for _ in range(n)]
        return o


class ExportSection:
    """The export section has the id 7. It decodes into a vector of exports
    that represent the exports component of a module.

    exportsec ::= ex∗:section7(vec(export)) ⇒ ex∗
    export :: =nm:name d:exportdesc ⇒ {name nm, desc d}
    exportdesc ::= 0x00 x:funcidx ⇒ func x
                 | 0x01 x:tableidx ⇒ table x
                 | 0x02 x:memidx ⇒ mem x
                 | 0x03 x:globalidx⇒global x

    Attributes:
        vec: list of export object
    """

    def __init__(self):
        self.vec: typing.List[Export] = []

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = ExportSection
        n = bin_reader.read_count(r, 32)
        o.vec = [Export.from_reader(r) for _ in range(n)]
        return o


class StartSection:
    """The start section has the id 8. It decodes into an optional start
    function that represents the start component of a module.

    startsec ::= st?:section8(start) ⇒ st?
    start ::= x:funcidx ⇒ {func x}

    Attributes:
        start_function: just start function object
    """

    def __init__(self):
        self.start_function: StartFunction

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = StartSection()
        o.start_function = StartFunction.from_reader(r)
        return o


class ElementSection:
    """The element section has the id 9. It decodes into a vector of element
    segments that represent the elem component of a module.

    elemsec ::= seg∗:section9(vec(elem)) ⇒ seg
    elem ::= x:tableidx e:expr y∗:vec(funcidx) ⇒ {table x, offset e, init y∗}

    Attributes:
        vec: list of element segment object
    """

    def __init__(self):
        self.vec: typing.List[ElementSegment]

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = ElementSection()
        n = bin_reader.read_count(r, 32)
        o.vec = [ElementSegment.from_reader(r) for _ in range(n)]
        return o


class CodeSection:
    """The code section has the id 10. It decodes into a vector of code
    entries that are pairs of value type vectors and expressions. They
    represent the locals and body field of the functions in the funcs
    component of a module. The type fields of the respective functions are
    encoded separately in the function section.

    Attributes:
        vec: list of code object
    """

    def __init__(self):
        self.vec: typing.List[Code] = []

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = CodeSection()
        n = bin_reader.read_count(r, 32)
        o.vec = [Code.from_reader(r) for _ in range(n)]
        return o


class DataSection:
    """The data section has the id 11. It decodes into a vector of data
    segments that represent the data component of a module.

    datasec ::= seg∗:section11(vec(data)) ⇒ seg
    data ::= x:memidx e:expr b∗:vec(byte) ⇒ {data x,offset e,init b∗}  

    Attributes:
        vec: list of data segment object
    """

    def __init__(self):
        self.vec: typing.List[DataSegment] = []

    @classmethod
    def from_reader(cls, r: typing.BinaryIO):
        o = DataSection()
        n = bin_reader.read_count(r, 32)
        o.vec = [DataSegment.from_reader(r) for _ in range(n)]
        return o


class Module:
    """The module is the struction after read WebAssembly bytecode, which include some or all sections defined above.

    Attributes:
        types: list of function type object
        funcs: list of function object
        tables: list of table object
        mems: list of memory object
        globals: list of global object
        elem: list of element segment object
        data: list of data segment object
        start: address of start function
        imports: list of import object
        exports: list of export object
    """

    def __init__(self):
        self.types: typing.List[FunctionType] = []
        self.funcs: typing.List[Function] = []
        self.tables: typing.List[Table] = []
        self.mems: typing.List[Memory] = []
        self.globals: typing.List[Global] = []
        self.elem: typing.List[ElementSegment] = []
        self.data: typing.List[DataSegment] = []
        self.start: int = None
        self.imports: typing.List[Import] = []
        self.exports: typing.List[Export] = []

    @classmethod
    def load(cls, name: str) -> 'Module':
        with open(name, 'rb') as f:
            return cls.from_reader(f)

    @classmethod
    def from_reader(cls, r: typing.BinaryIO) -> 'Module':
        if list(r.read(4)) != [0x00, 0x61, 0x73, 0x6d]:
            raise Exception('Invalid magic number!')
        if list(r.read(4)) != [0x01, 0x00, 0x00, 0x00]:
            raise Exception('Invalid version!')
        mod = Module()
        while True:
            section_id_byte = r.read(1)
            if not section_id_byte:
                break
            section_id = ord(section_id_byte)
            n = bin_reader.read_count(r, 32)
            data = r.read(n)
            if len(data) != n:
                raise Exception('Invalid section size!')
            if section_id == bin_format.custom_section:
                custom_section = CustomSection.from_reader(io.BytesIO(data))
                logger.debugln(f'{bin_format.section[section_id][0]:>9} {custom_section.name}')
            elif section_id == bin_format.type_section:
                type_section = TypeSection.from_reader(io.BytesIO(data))
                for i, e in enumerate(type_section.vec):
                    logger.debugln(f'{bin_format.section[section_id][0]:>9}[{i}] {e}')
                mod.types = type_section.vec
            elif section_id == bin_format.import_section:
                import_section = ImportSection.from_reader(io.BytesIO(data))
                for i, e in enumerate(import_section.vec):
                    logger.debugln(f'{bin_format.section[section_id][0]:>9}[{i}] {e}')
                mod.imports = import_section.vec
            elif section_id == bin_format.function_section:
                function_section = FunctionSection.from_reader(io.BytesIO(data))
                num_imported_funcs = sum(1 for _ in filter(lambda ins: ins.kind == bin_format.extern_func, mod.imports))
                for i, e in enumerate(function_section.vec):
                    logger.debugln(f'{bin_format.section[section_id][0]:>9}[{i}] func={num_imported_funcs + i} sig={e}')
            elif section_id == bin_format.table_section:
                table_section = TableSection.from_reader(io.BytesIO(data))
                for i, e in enumerate(table_section.vec):
                    logger.debugln(f'{bin_format.section[section_id][0]:>9}[{i}] {e}')
                mod.tables = table_section.vec
            elif section_id == bin_format.memory_section:
                memory_section = MemorySection.from_reader(io.BytesIO(data))
                for i, e in enumerate(memory_section.vec):
                    logger.debugln(f'{bin_format.section[section_id][0]:>9}[{i}] {e}')
                mod.mems = memory_section.vec
            elif section_id == bin_format.global_section:
                global_section = GlobalSection.from_reader(io.BytesIO(data))
                for i, e in enumerate(global_section.vec):
                    logger.debugln(f'{bin_format.section[section_id][0]:>9}[{i}] {e}')
                mod.globals = global_section.vec
            elif section_id == bin_format.export_section:
                export_section = ExportSection.from_reader(io.BytesIO(data))
                for i, e in enumerate(export_section.vec):
                    logger.debugln(f'{bin_format.section[section_id][0]:>9}[{i}] {e}')
                mod.exports = export_section.vec
            elif section_id == bin_format.start_section:
                start_section = StartSection.from_reader(io.BytesIO(data))
                logger.debugln(f'{bin_format.section[section_id][0]:>12} {start_section.start_function}')
                mod.start = start_section.start_function.funcidx
            elif section_id == bin_format.element_section:
                element_section = ElementSection.from_reader(io.BytesIO(data))
                for i, e in enumerate(element_section.vec):
                    logger.debugln(f'{bin_format.section[section_id][0]:>9}[{i}] {e}')
                mod.elem = element_section.vec
            elif section_id == bin_format.code_section:
                code_section = CodeSection.from_reader(io.BytesIO(data))

                def printex(instrs: typing.List[Instruction], prefix=0):
                    for e in instrs:
                        a = f'           | {" " * prefix}{bin_format.opcodes[e.code][0]}'
                        if e.code in [bin_format.block, bin_format.loop, bin_format.if_]:
                            logger.debugln(f'{a} {bin_format.blocktype[e.immediate_arguments][0]}')
                            prefix += 2
                        elif e.code == bin_format.end:
                            prefix -= 2
                            a = f'           | {" " * prefix}{bin_format.opcodes[e.code][0]}'
                            logger.debugln(f'{a}')
                        elif e.immediate_arguments is None:
                            logger.debugln(f'{a}')
                        elif isinstance(e.immediate_arguments, list):
                            logger.debugln(
                                f'{a} {" ".join([str(e) for e in e.immediate_arguments])}')
                        else:
                            logger.debugln(f'{a} {e.immediate_arguments}')

                num_imported_funcs = sum(1 for _ in filter(lambda ins: ins.kind == bin_format.extern_func, mod.imports))
                for i, e in enumerate(code_section.vec):
                    logger.debugln(f'{bin_format.section[section_id][0]:>9}[{i}] func={num_imported_funcs + i} {e}')
                    printex(e.expr.data)
                    func = Function()
                    func.typeidx = function_section.vec[i]
                    func.locals = e.locals
                    func.expr = e.expr
                    mod.funcs.append(func)
            elif section_id == bin_format.data_section:
                data_section = DataSection.from_reader(io.BytesIO(data))
                for i, e in enumerate(data_section.vec):
                    logger.debugln(f'{bin_format.section[section_id][0]:>9}[{i}] {e}')
                mod.data = data_section.vec
            else:
                raise Exception('Invalid section id!')
        logger.debugln('')
        return mod