vise/go/vm/vm.go

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package vm
import (
"encoding/binary"
"context"
"fmt"
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"log"
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"git.defalsify.org/festive/resource"
"git.defalsify.org/festive/router"
"git.defalsify.org/festive/state"
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)
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//type Runner func(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error)
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func argFromBytes(input []byte) (string, []byte, error) {
if len(input) == 0 {
return "", input, fmt.Errorf("zero length input")
}
sz := input[0]
out := input[1:1+sz]
return string(out), input[1+sz:], nil
}
func Apply(input []byte, instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
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var err error
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arg, input, err := argFromBytes(input)
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if err != nil {
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return st, input, err
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}
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rt := router.FromBytes(input)
sym := rt.Get(arg)
if sym == "" {
sym = rt.Default()
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st.PutArg(arg)
}
if sym == "" {
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instruction = NewLine([]byte{}, MOVE, []string{"_catch"}, nil, nil)
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} else if sym == "_" {
instruction = NewLine([]byte{}, BACK, nil, nil, nil)
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} else {
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new_instruction := NewLine([]byte{}, MOVE, []string{sym}, nil, nil)
instruction = append(new_instruction, instruction...)
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}
st, instruction, err = Run(instruction, st, rs, ctx)
if err != nil {
return st, instruction, err
}
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return st, instruction, nil
}
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func Run(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
var err error
for len(instruction) > 0 {
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log.Printf("instruction is now %v", instruction)
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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)
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break
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case CROAK:
st, instruction, err = RunCroak(instruction[2:], st, rs, ctx)
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break
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case LOAD:
st, instruction, err = RunLoad(instruction[2:], st, rs, ctx)
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break
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case RELOAD:
st, instruction, err = RunReload(instruction[2:], st, rs, ctx)
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break
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case MAP:
st, instruction, err = RunMap(instruction[2:], st, rs, ctx)
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break
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case MOVE:
st, instruction, err = RunMove(instruction[2:], st, rs, ctx)
break
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case BACK:
st, instruction, err = RunBack(instruction[2:], st, rs, ctx)
break
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default:
err = fmt.Errorf("Unhandled state: %v", op)
}
if err != nil {
return st, instruction, err
}
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}
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return st, instruction, nil
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}
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func RunMap(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
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head, tail, err := instructionSplit(instruction)
if err != nil {
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return st, instruction, err
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}
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err = st.Map(head)
return st, tail, err
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}
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func RunCatch(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
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head, tail, err := instructionSplit(instruction)
if err != nil {
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return st, instruction, err
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}
r, err := rs.Get(head)
if err != nil {
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return st, instruction, err
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}
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_ = tail
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st.Add(head, r, 0)
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return st, []byte{}, nil
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}
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func RunCroak(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
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head, tail, err := instructionSplit(instruction)
if err != nil {
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return st, instruction, err
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}
_ = head
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_ = tail
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st.Reset()
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return st, []byte{}, nil
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}
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func RunLoad(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
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head, tail, err := instructionSplit(instruction)
if err != nil {
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return st, instruction, err
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}
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if !st.Check(head) {
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return st, instruction, fmt.Errorf("key %v already loaded", head)
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}
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sz := uint16(tail[0])
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tail = tail[1:]
r, err := refresh(head, tail, rs, ctx)
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if err != nil {
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return st, tail, err
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}
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err = st.Add(head, r, sz)
return st, tail, err
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}
func RunReload(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
head, tail, err := instructionSplit(instruction)
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if err != nil {
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return st, instruction, err
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}
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r, err := refresh(head, tail, rs, ctx)
if err != nil {
return st, tail, err
}
st.Update(head, r)
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return st, tail, nil
}
func RunMove(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
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head, tail, err := instructionSplit(instruction)
if err != nil {
return st, instruction, err
}
st.Down(head)
return st, tail, nil
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}
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func RunBack(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
st.Up()
return st, instruction, nil
}
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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)
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}
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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
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}