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package collection
import (
"context"
"sync"
)
// Stack implements a basic FILO structure.
type Stack[T any] struct {
underlyer *LinkedList[T]
key sync.RWMutex
}
// NewStack instantiates a new FILO structure.
func NewStack[T any](entries ...T) *Stack[T] {
retval := &Stack[T]{}
retval.underlyer = NewLinkedList[T]()
for _, entry := range entries {
retval.Push(entry)
}
return retval
}
// Enumerate peeks at each element in the stack without mutating it.
func (stack *Stack[T]) Enumerate(ctx context.Context) Enumerator[T] {
stack.key.RLock()
defer stack.key.RUnlock()
return stack.underlyer.Enumerate(ctx)
}
// IsEmpty tests the Stack to determine if it is populate or not.
func (stack *Stack[T]) IsEmpty() bool {
stack.key.RLock()
defer stack.key.RUnlock()
return stack.underlyer == nil || stack.underlyer.IsEmpty()
}
// Push adds an entry to the top of the Stack.
func (stack *Stack[T]) Push(entry T) {
stack.key.Lock()
defer stack.key.Unlock()
if nil == stack.underlyer {
stack.underlyer = NewLinkedList[T]()
}
stack.underlyer.AddFront(entry)
}
// Pop returns the entry at the top of the Stack then removes it.
func (stack *Stack[T]) Pop() (T, bool) {
stack.key.Lock()
defer stack.key.Unlock()
if nil == stack.underlyer {
return *new(T), false
}
return stack.underlyer.RemoveFront()
}
// Peek returns the entry at the top of the Stack without removing it.
func (stack *Stack[T]) Peek() (T, bool) {
stack.key.RLock()
defer stack.key.RUnlock()
return stack.underlyer.PeekFront()
}
// Size returns the number of entries populating the Stack.
func (stack *Stack[T]) Size() uint {
stack.key.RLock()
defer stack.key.RUnlock()
if stack.underlyer == nil {
return 0
}
return stack.underlyer.Length()
}
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