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package system
import (
"errors"
"fmt"
"sync"
)
const (
// User type is reverted at final launcher exit.
User = Enablement(ELen)
// Process type is unconditionally reverted on exit.
Process = Enablement(ELen + 1)
)
type Criteria struct {
*Enablements
}
func (ec *Criteria) hasType(o Op) bool {
// nil criteria: revert everything except User
if ec.Enablements == nil {
return o.Type() != User
}
return ec.Has(o.Type())
}
// Op is a reversible system operation.
type Op interface {
// Type returns Op's enablement type.
Type() Enablement
// apply the Op
apply(sys *I) error
// revert reverses the Op if criteria is met
revert(sys *I, ec *Criteria) error
Is(o Op) bool
Path() string
String() string
}
func TypeString(e Enablement) string {
switch e {
case User:
return "User"
case Process:
return "Process"
default:
return e.String()
}
}
type I struct {
uid int
ops []Op
state [2]bool
lock sync.Mutex
}
func (sys *I) UID() int {
return sys.uid
}
func (sys *I) Commit() error {
sys.lock.Lock()
defer sys.lock.Unlock()
if sys.state[0] {
panic("sys instance committed twice")
}
sys.state[0] = true
sp := New(sys.uid)
sp.ops = make([]Op, 0, len(sys.ops)) // prevent copies during commits
defer func() {
// sp is set to nil when all ops are applied
if sp != nil {
// rollback partial commit
if err := sp.Revert(&Criteria{nil}); err != nil {
fmt.Println("fortify: errors returned reverting partial commit:", err)
}
}
}()
for _, o := range sys.ops {
if err := o.apply(sys); err != nil {
return err
} else {
// register partial commit
sp.ops = append(sp.ops, o)
}
}
// disarm partial commit rollback
sp = nil
return nil
}
func (sys *I) Revert(ec *Criteria) error {
sys.lock.Lock()
defer sys.lock.Unlock()
if sys.state[1] {
panic("sys instance reverted twice")
}
sys.state[1] = true
// collect errors
errs := make([]error, len(sys.ops))
for i := range sys.ops {
errs[i] = sys.ops[len(sys.ops)-i-1].revert(sys, ec)
}
// errors.Join filters nils
return errors.Join(errs...)
}
func New(uid int) *I {
return &I{uid: uid}
}
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