Process Table

Implement a minimal process table that models fork/exit/wait and reparenting.

Types and functions

type ProcessTable struct { /* internal fields */ }

func NewProcessTable() *ProcessTable
func (pt *ProcessTable) Fork(parent int) int
func (pt *ProcessTable) Exit(pid int)
func (pt *ProcessTable) Wait(parent int) int
func (pt *ProcessTable) Parent(pid int) int
func (pt *ProcessTable) IsZombie(pid int) bool

Rules

• The table starts with PID 1 (init). Its parent is 0.
• Fork(parent) creates a new child of parent, returns its PID.
  • PIDs start at 2 and increase by 1.
  • If parent does not exist or is a zombie, return -1.
• Exit(pid) marks the process as a zombie.
  • PID 1 never exits; ignore Exit(1).
  • When a process exits, its living children are reparented to PID 1.
• Wait(parent) reaps one zombie child of parent.
  • If multiple zombie children exist, reap the smallest PID.
  • Reaping removes the process from the table entirely.
  • Return the reaped PID, or -1 if none exist.
• Parent(pid) returns the parent PID, or -1 if the process does not exist.
• IsZombie(pid) returns true if the process exists and is a zombie.

Notes

• A zombie remains in the table until reaped.
• A living child is one that exists and is not a zombie.