Bytecode instruction set and stack based virtual machine.

Usage

Usage: bytecode <COMMAND>

Commands:
  b2r        ByteCode source code file -> RawBytes file  [ByteCode -> RawBytes]
  run        Interpret RawBytes file                     [RawBytes -> Execution]
  help       Print this message or the help of the given subcommand(s)

Options:
  -h, --help     Print help
  -V, --version  Print version

RawBytes is data consisting of raw bytecode instructions and data.

$ bytecode b2r -i examples/example1 -o examples/example1.raw
$ bytecode run -i examples/example1.raw

Bytecode file

A small language exists to facilitate bytecode representation and is very simple to use.

opcode [operand] ; comment

push 2           ; Push 2 onto the stack.
push 0xFF        ; Push 255 onto the stack.

Opcodes

Opcode	Hex	Operand	Stack	Description
Noop	0x00			Does nothing.
Push	0x01	value	[.., value]	Push value onto the stack.
Add	0x02		[.., A, B] -> [.., R]	Pop two values, add them. (A + B = R)
Sub	0x03		[.., A, B] -> [.., R]	Pop two values, subtract them. (A + B = R)
Mul	0x04		[.., A, B] -> [.., R]	Pop two values, multiply them. (A + B = R)
Div	0x05		[.., A, B] -> [.., R]	Pop two values, divide them. (A + B = R)
Mod	0x06		[.., A, B] -> [.., R]	Pop two values, modulo them. (A + B = R)
Jump	0x07	offset	[.., ptr] -> [..]	Jump to offset (pointer).
JumpIfFalse	0x08	offset	[.., ptr] -> [..]	If top of stack is 0, jump to offset.
GT	0x09		[.., A, B] -> [.., R]	Pop two values, push true(1) if first is greater, else false(0).
LT	0x0A		[.., A, B] -> [.., R]	Pop two values, push true(1) if first is less.
GTE	0x0B		[.., A, B] -> [.., R]	Pop two values, push true(1) if first is greater or equal.
LTE	0x0C		[.., A, B] -> [.., R]	Pop two values, push true(1) if first is less or equal.
EQ	0x0D		[.., A, B] -> [.., R]	Pop two values, push true(1) if equal.
Proc	0x0E	length	[.., ptr] -> [..]	Instruction to delimit a procedure. instructions after length are omitted.
Call	0x0F	offset	[.., ptr] -> [..]	Call procedure at offset.
Ret	0x10			Return from procedure. See procedures for more details.
Store	0x11	index	[.., value] -> [..]	Pop value and store it at index.
Load	0x12	index	[..] -> [.., value]	Load value at index and push it onto the stack.
	0x13 ~ 0xFD			Not used.
Exit	0xFE			Exit the program.
Debug	0xFF	value	Description	Print the stack. -1 = pops all, value = pops value items.

Procedures

Proc opcode takes a length operand, which is the number of instructions to skip after the Proc opcode.

Then, after executing the procedure in the CallStack using the Call instruction, the offset(pointer) to return to is stored. After that, Call jump to the first instruction in the procedure and executes the procedure.

Return jumps to the return pointer stored in the CallStack.

proc 2     ; 0, The 2 instructions below are omitted.
    noop   ; 1
    return ; 2, Jump to the pointer (4) stored in the CallStack.

call 1     ; 3, After saving the pointer to return (4) to the CallStack, jump to the pointer 1 of the first instruction of the procedure.
noop       ; 4, Executed after the procedure runs.

Example

See examples for more examples.