vise/go/vm/vm.go
2023-03-31 15:03:54 +01:00

139 lines
3.7 KiB
Go

package vm
import (
"encoding/binary"
"fmt"
"context"
"git.defalsify.org/festive/state"
"git.defalsify.org/festive/resource"
)
type Runner func(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error)
func Run(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
var err error
for len(instruction) > 0 {
op := binary.BigEndian.Uint16(instruction[:2])
if op > _MAX {
return st, instruction, fmt.Errorf("opcode value %v out of range (%v)", op, _MAX)
}
switch op {
case CATCH:
st, instruction, err = RunCatch(instruction[2:], st, rs, ctx)
case CROAK:
st, instruction, err = RunCroak(instruction[2:], st, rs, ctx)
case LOAD:
st, instruction, err = RunLoad(instruction[2:], st, rs, ctx)
case RELOAD:
st, instruction, err = RunReload(instruction[2:], st, rs, ctx)
case MAP:
st, instruction, err = RunMap(instruction[2:], st, rs, ctx)
case SINK:
st, instruction, err = RunSink(instruction[2:], st, rs, ctx)
default:
err = fmt.Errorf("Unhandled state: %v", op)
}
if err != nil {
return st, instruction, err
}
}
return st, instruction, nil
}
func RunMap(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
head, tail, err := instructionSplit(instruction)
if err != nil {
return st, instruction, err
}
st.Map(head)
return st, tail, nil
}
func RunSink(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
return st, nil, nil
}
func RunCatch(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
head, tail, err := instructionSplit(instruction)
if err != nil {
return st, instruction, err
}
r, err := rs.Get(head)
if err != nil {
return st, instruction, err
}
st.Add(head, r, uint32(len(r)))
return st, tail, nil
}
func RunCroak(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
head, tail, err := instructionSplit(instruction)
if err != nil {
return st, instruction, err
}
_ = head
st.Reset()
return st, tail, nil
}
func RunLoad(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
head, tail, err := instructionSplit(instruction)
if err != nil {
return st, instruction, err
}
if !st.Check(head) {
return st, instruction, fmt.Errorf("key %v already loaded", head)
}
sz := uint32(tail[0])
tail = tail[1:]
r, err := refresh(head, tail, rs, ctx)
if err != nil {
return st, tail, err
}
st.Add(head, r, sz)
return st, tail, nil
}
func RunReload(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
head, tail, err := instructionSplit(instruction)
if err != nil {
return st, instruction, err
}
r, err := refresh(head, tail, rs, ctx)
if err != nil {
return st, tail, err
}
st.Add(head, r, uint32(len(r)))
return st, tail, nil
}
func RunMove(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
return st, nil, nil
}
func refresh(key string, sym []byte, rs resource.Fetcher, ctx context.Context) (string, error) {
fn, err := rs.FuncFor(key)
if err != nil {
return "", err
}
return fn(sym, ctx)
}
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")
}
tailSz := uint8(len(b))
if tailSz < sz {
return "", nil, fmt.Errorf("corrupt instruction, len %v less than symbol length: %v", tailSz, sz)
}
r := string(b[1:1+sz])
return r, b[1+sz:], nil
}