Spec for ByteCode

:: All value starting with 0x are hexadecimal

  1. The file starts with:
0x00 0x61 0x73 0x6D
0x01 0x00 0x00 0x00

Type Section

0x01

Function Type

0x60

Number of Parameters

  • for 2 parameters 
    0x02

Parameters Type

0x7F: i32
0x7D: f32

Return Type

0x7F: i32
0x7D: f32
0x00: void

Function Section

0x03

Export Section

0x07

Instructions

Instructions

Stack

local

local.get 
0x20

Get a local variable by its index and add it to the stack.

local.set 
0x21

Get the top of the stack and set a local variable by its index.

global

global.get 
0x23

Get a global variable by its index and add it to the stack.

global.set 
0x24

Get the top of the stack and set a global variable by its index.

i32

i32.const 
0x41

Push an Int32 to the stack.

Memory

i32

i32.store
0x36

Take the top of the stack. This will be the value stored in memory. Take the top of the stack. This will be the index in memory.

Store the value in memory at the index.

i32.load
0x28

Take the top of the stack. This will be the index in memory.

Push an Int32 to the stack with the value at address in memory.

Condition

i32

i32.gt_s
0x4a

Compare the 2 values on the top of the stack.

If the first value is greater than the second value, push 1 to the stack. else, push 0

i32.eq
0x46

Compare the 2 values on the top of the stack.

If the first value is equal to the second value, push 1 to the stack. else, push 0

control

if...else...end

  • if

    0x04

    Enter in the first branch if the top of the stack is 1.

  • else

    0x05

    Enter in the second branch if the top of the stack is 0.

  • end

    0x0b

    Exit from the if/else block.

loop

  • loop 

    0x03

    Create a label for the loop

    Label is a number

  • br 

    0x0c

    Jump to the label

    Label is a number

Operations

i32

i32.add
0x6a

Add the 2 values on the top of the stack. Push the result to the stack.