op

Documentation

Overview

Package op implements all the operation codes that can be created during compilation and used to drive what to execute during run time within the VM. Provide within the package are the abilities to know how many operands each op code has and their widths aiding in the reading of a given set of instructions that have been created from compilation

Index

• func Make(op Code, operands ...int) []byte
• func ReadOperands(def *Definition, ins Instructions) ([]int, int)
• type Code
• type Definition
  • func Lookup(op byte) (*Definition, error)
• type Instructions
  • func (ins Instructions) String() string

Functions

func Make

func Make(op Code, operands ...int) []byte

Make allows a Code and it's operands to be converted into a slice of bytes which is to be used to represent them as an instruction

func ReadOperands

func ReadOperands(def *Definition, ins Instructions) ([]int, int)

ReadOperands gives back the operands set against a given op code within the instructions. It requires the definition in order to know the operand widths of each operand. Not only does the function return the operands but the offset after all operands for a given op code has been read. This offset helps assist with knowing how far the instructions has been read to which can be utilise to move forward something like instruction pointers

Types

type Code

type Code byte

Code is the main representation of the P code used in lemur

const (
	Constant Code = iota
	Add
	Sub
	Mul
	Div
	Pop
	Minus
	True
	False
	Equal
	NotEqual
	GreaterThan
	GreaterThanEqual
	And
	Or
	Bang
	Jump
	JumpBreak
	JumpNotTruthy
	JumpTable
	Null
	SetGlobal
	GetGlobal
	GetLocal
	SetLocal
	GetFree
	AssignGlobal
	AssignLocal
	Array
	Map
	Index
	Closure
	CurrentClosure
	Return
	ReturnValue
	Call
	GetBuiltin
	IteratorCurrentKey
	PushIteratorPointer
	PopIteratorPointer
	IncrementIteratorPointer
	IteratorLenComparison
)

type Definition

type Definition struct {
	Name          string
	OperandWidths []int
}

Definition encapsulates the name of a P code and it's maximum possible widths for each operand it has available

func Lookup

func Lookup(op byte) (*Definition, error)

Lookup provides a convenient way to obtain the Definition from a Code

type Instructions

type Instructions []byte

Instructions represents each instruction (Code and operands) of a program along with it's position

func (Instructions) String

func (ins Instructions) String() string