vise/vm/vm.go
2023-04-12 18:09:37 +01:00

252 lines
6.3 KiB
Go

package vm
import (
"encoding/binary"
"fmt"
)
// NewLine creates a new instruction line for the VM.
func NewLine(instructionList []byte, instruction uint16, strargs []string, byteargs []byte, numargs []uint8) []byte {
if instructionList == nil {
instructionList = []byte{}
}
b := []byte{0x00, 0x00}
binary.BigEndian.PutUint16(b, instruction)
for _, arg := range strargs {
b = append(b, uint8(len(arg)))
b = append(b, []byte(arg)...)
}
if byteargs != nil {
b = append(b, uint8(len(byteargs)))
b = append(b, byteargs...)
}
if numargs != nil {
b = append(b, numargs...)
}
return append(instructionList, b...)
}
// ParseOp verifies and extracts the expected opcode portion of an instruction
func ParseOp(b []byte) (Opcode, []byte, error) {
op, b, err := opSplit(b)
if err != nil {
return NOOP, b, err
}
return op, b, nil
}
// ParseLoad parses and extracts the expected argument portion of a LOAD instruction
func ParseLoad(b []byte) (string, uint32, []byte, error) {
return parseSymLen(b)
}
// ParseReload parses and extracts the expected argument portion of a RELOAD instruction
func ParseReload(b []byte) (string, []byte, error) {
return parseSym(b)
}
// ParseMap parses and extracts the expected argument portion of a MAP instruction
func ParseMap(b []byte) (string, []byte, error) {
return parseSym(b)
}
// ParseMove parses and extracts the expected argument portion of a MOVE instruction
func ParseMove(b []byte) (string, []byte, error) {
return parseSym(b)
}
// ParseHalt parses and extracts the expected argument portion of a HALT instruction
func ParseHalt(b []byte) ([]byte, error) {
return parseNoArg(b)
}
// ParseCatch parses and extracts the expected argument portion of a CATCH instruction
func ParseCatch(b []byte) (string, uint32, bool, []byte, error) {
return parseSymSig(b)
}
// ParseCroak parses and extracts the expected argument portion of a CROAK instruction
func ParseCroak(b []byte) (uint32, bool, []byte, error) {
return parseSig(b)
}
// ParseInCmp parses and extracts the expected argument portion of a INCMP instruction
func ParseInCmp(b []byte) (string, string, []byte, error) {
return parseTwoSym(b)
}
// ParseMPrev parses and extracts the expected argument portion of a MPREV instruction
func ParseMPrev(b []byte) (string, string, []byte, error) {
return parseTwoSym(b)
}
// ParseMNext parses and extracts the expected argument portion of a MNEXT instruction
func ParseMNext(b []byte) (string, string, []byte, error) {
return parseTwoSym(b)
}
// ParseMSize parses and extracts the expected argument portion of a MSIZE instruction
func ParseMSize(b []byte) (uint32, uint32, []byte, error) {
if len(b) < 2 {
return 0, 0, b, fmt.Errorf("argument too short")
}
r := uint32(b[0])
rr := uint32(b[1])
b = b[2:]
return r, rr, b, nil
}
// ParseMOut parses and extracts the expected argument portion of a MOUT instruction
func ParseMOut(b []byte) (string, string, []byte, error) {
return parseTwoSym(b)
}
// noop
func parseNoArg(b []byte) ([]byte, error) {
return b, nil
}
// parse and extract two length-prefixed string values
func parseSym(b []byte) (string, []byte, error) {
sym, b, err := instructionSplit(b)
if err != nil {
return "", b, err
}
return sym, b, nil
}
// parse and extract two length-prefixed string values
func parseTwoSym(b []byte) (string, string, []byte, error) {
symOne, b, err := instructionSplit(b)
if err != nil {
return "", "", b, err
}
symTwo, b, err := instructionSplit(b)
if err != nil {
return "", "", b, err
}
return symOne, symTwo, b, nil
}
// parse and extract one length-prefixed string value, and one length-prefixed integer value
func parseSymLen(b []byte) (string, uint32, []byte, error) {
sym, b, err := instructionSplit(b)
if err != nil {
return "", 0, b, err
}
sz, b, err := intSplit(b)
if err != nil {
return "", 0, b, err
}
return sym, sz, b, nil
}
// parse and extract one length-prefixed string value, and one single byte of integer
func parseSymSig(b []byte) (string, uint32, bool, []byte, error) {
sym, b, err := instructionSplit(b)
if err != nil {
return "", 0, false, b, err
}
sig, b, err := intSplit(b)
if err != nil {
return "", 0, false, b, err
}
if len(b) == 0 {
return "", 0, false, b, fmt.Errorf("instruction too short")
}
matchmode := b[0] > 0
b = b[1:]
return sym, sig, matchmode, b, nil
}
// parse and extract one single byte of integer
func parseSig(b []byte) (uint32, bool, []byte, error) {
sig, b, err := intSplit(b)
if err != nil {
return 0, false, b, err
}
if len(b) == 0 {
return 0, false, b, fmt.Errorf("instruction too short")
}
matchmode := b[0] > 0
b = b[1:]
return sig, matchmode, b, nil
}
// split bytecode into head and b using length-prefixed bitfield
func byteSplit(b []byte) ([]byte, []byte, error) {
bitFieldSize := b[0]
bitField := b[1:1+bitFieldSize]
b = b[1+bitFieldSize:]
return bitField, b, nil
}
// split bytecode into head and b using length-prefixed integer
func intSplit(b []byte) (uint32, []byte, error) {
l := uint8(b[0])
sz := uint32(l)
b = b[1:]
if l > 0 {
r := []byte{0, 0, 0, 0}
c := 0
ll := 4 - l
var i uint8
for i = 0; i < 4; i++ {
if i >= ll {
r[i] = b[c]
c += 1
}
}
sz = binary.BigEndian.Uint32(r)
b = b[l:]
}
return sz, b, nil
}
// split bytecode into head and b using length-prefixed string
func instructionSplit(b []byte) (string, []byte, error) {
if len(b) == 0 {
return "", nil, fmt.Errorf("argument is empty")
}
sz := uint8(b[0])
if sz == 0 {
return "", nil, fmt.Errorf("zero-length argument")
}
bSz := uint8(len(b))
if bSz < sz {
return "", nil, fmt.Errorf("corrupt instruction, len %v less than symbol length: %v", bSz, sz)
}
r := string(b[1:1+sz])
return r, b[1+sz:], nil
}
// check if the start of the given bytecode contains a valid opcode, extract and return it
func opCheck(b []byte, opIn Opcode) ([]byte, error) {
var bb []byte
op, bb, err := opSplit(b)
if err != nil {
return b, err
}
b = bb
if op != opIn {
return b, fmt.Errorf("not a %v instruction", op)
}
return b, nil
}
// split bytecode into head and b using opcode
func opSplit(b []byte) (Opcode, []byte, error) {
l := len(b)
if l < 2 {
return 0, b, fmt.Errorf("input size %v too short for opcode", l)
}
op := binary.BigEndian.Uint16(b)
if op > _MAX {
return 0, b, fmt.Errorf("invalid opcode %v", op)
}
return Opcode(op), b[2:], nil
}