fxicfg/state/thread.go

// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

package state

import (
	"fmt"

	"go.starlark.net/starlark"
)

// The key used to read and store state from a starlark.Thread.
const threadStateKey = "fxicfg_state_key"

// SetThreadState stores State inside a starlark.Thread.
func SetThreadState(th *starlark.Thread, state State) {
	th.SetLocal(threadStateKey, state)
}

// GetThreadState reads a State from a starlark.Thread.
func GetThreadState(th *starlark.Thread) (State, error) {
	state, ok := th.Local(threadStateKey).(State)
	if !ok {
		return State{}, fmt.Errorf("thread %q has no key %q", th.Name, threadStateKey)
	}
	return state, nil
}

// ThreadModifier passes state information between starlark.Thread objects. This is
// primarily used by the generator as a LUCI interpreter hook.
type ThreadModifier State

// State returns the state held by this ThreadModifier.
func (t ThreadModifier) State() State {
	return State(t)
}

// WriteTo stores this ThreadModifier's state in the given starlark.Thread.
func (t ThreadModifier) WriteTo(th *starlark.Thread) {
	SetThreadState(th, State(t))
}

// ReadFrom updates this ThreadModifier's state to match given starlark.Thread's.
func (t *ThreadModifier) ReadFrom(th *starlark.Thread) error {
	state, err := GetThreadState(th)
	if err != nil {
		return err
	}
	*t = ThreadModifier(state)
	return nil
}