vise/go/engine/engine.go

128 lines
3.0 KiB
Go

package engine
import (
"context"
"fmt"
"io"
"log"
"git.defalsify.org/festive/resource"
"git.defalsify.org/festive/state"
"git.defalsify.org/festive/vm"
)
//type Config struct {
// FlagCount uint32
// CacheSize uint32
//}
// Engine is an execution engine that handles top-level errors when running user inputs against currently exposed bytecode.
type Engine struct {
st *state.State
rs resource.Resource
}
// NewEngine creates a new Engine
func NewEngine(st *state.State, rs resource.Resource) Engine {
engine := Engine{st, rs}
return engine
}
// Init must be explicitly called before using the Engine instance.
//
// It loads and executes code for the start node.
func(en *Engine) Init(sym string, ctx context.Context) error {
err := en.st.SetInput([]byte{})
if err != nil {
return err
}
b := vm.NewLine(nil, vm.MOVE, []string{sym}, nil, nil)
b, err = vm.Run(b, en.st, en.rs, ctx)
if err != nil {
return err
}
en.st.SetCode(b)
return nil
}
// Exec processes user input against the current state of the virtual machine environment.
//
// If successfully executed, output of the last execution is available using the WriteResult call.
//
// A bool return valus of false indicates that execution should be terminated. Calling Exec again has undefined effects.
//
// Fails if:
// - input is formally invalid (too long etc)
// - no current bytecode is available
// - input processing against bytcode failed
func (en *Engine) Exec(input []byte, ctx context.Context) (bool, error) {
err := vm.ValidInput(input)
if err != nil {
return true, err
}
err = en.st.SetInput(input)
if err != nil {
return false, err
}
log.Printf("new execution with input '%s' (0x%x)", input, input)
code, err := en.st.GetCode()
if err != nil {
return false, err
}
if len(code) == 0 {
return false, fmt.Errorf("no code to execute")
}
code, err = vm.Run(code, en.st, en.rs, ctx)
if err != nil {
return false, err
}
v, err := en.st.MatchFlag(state.FLAG_TERMINATE, false)
if err != nil {
return false, err
}
if v {
if len(code) > 0 {
log.Printf("terminated with code remaining: %x", code)
}
return false, nil
}
en.st.SetCode(code)
if len(code) == 0 {
log.Printf("runner finished with no remaining code")
return false, nil
}
return true, nil
}
// WriteResult writes the output of the last vm execution to the given writer.
//
// Fails if
// - required data inputs to the template are not available.
// - the template for the given node point is note available for retrieval using the resource.Resource implementer.
// - the supplied writer fails to process the writes.
func(en *Engine) WriteResult(w io.Writer) error {
location, idx := en.st.Where()
v, err := en.st.Get()
if err != nil {
return err
}
r, err := en.rs.RenderTemplate(location, v, idx, nil)
if err != nil {
return err
}
m, err := en.rs.RenderMenu(idx)
if err != nil {
return err
}
if len(m) > 0 {
r += "\n" + m
}
c, err := io.WriteString(w, r)
log.Printf("%v bytes written as result for %v", c, location)
return err
}