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