vise/engine/persist.go

57 lines
1.4 KiB
Go

package engine
import (
"context"
"io"
"git.defalsify.org/festive/persist"
"git.defalsify.org/festive/resource"
)
// RunPersisted performs a single vm execution from client input using a persisted state.
//
// State is first loaded from storage. The vm is initialized with the state and executed. The new state is then saved to storage.
//
// The resulting output of the execution will be written to the provided writer.
//
// The state is identified by the SessionId member of the Config. Before first execution, the caller must ensure that an
// initialized state actually is available for the identifier, otherwise the method will fail.
//
// It will also fail if execution by the underlying Engine fails.
func RunPersisted(cfg Config, rs resource.Resource, pr persist.Persister, input []byte, w io.Writer, ctx context.Context) error {
err := pr.Load(cfg.SessionId)
if err != nil {
return err
}
st := pr.GetState()
location, idx := st.Where()
if location != "" {
cfg.Root = location
}
en := NewEngine(cfg, pr.GetState(), rs, pr.GetMemory(), ctx)
c, err := en.WriteResult(w, ctx)
if err != nil {
return err
}
err = pr.Save(cfg.SessionId)
if err != nil {
return err
}
if c > 0 {
return err
}
_ = idx
_, err = en.Exec(input, ctx)
if err != nil {
return err
}
_, err = en.WriteResult(w, ctx)
if err != nil {
return err
}
return pr.Save(cfg.SessionId)
}