chore: vendor

vendor/github.com/theupdateframework/notary/tuf/utils/stack.go

@@ -0,0 +1,85 @@
+package utils
+
+import (
+	"fmt"
+	"sync"
+)
+
+// ErrEmptyStack is used when an action that requires some
+// content is invoked and the stack is empty
+type ErrEmptyStack struct {
+	action string
+}
+
+func (err ErrEmptyStack) Error() string {
+	return fmt.Sprintf("attempted to %s with empty stack", err.action)
+}
+
+// ErrBadTypeCast is used by PopX functions when the item
+// cannot be typed to X
+type ErrBadTypeCast struct{}
+
+func (err ErrBadTypeCast) Error() string {
+	return "attempted to do a typed pop and item was not of type"
+}
+
+// Stack is a simple type agnostic stack implementation
+type Stack struct {
+	s []interface{}
+	l sync.Mutex
+}
+
+// NewStack create a new stack
+func NewStack() *Stack {
+	s := &Stack{
+		s: make([]interface{}, 0),
+	}
+	return s
+}
+
+// Push adds an item to the top of the stack.
+func (s *Stack) Push(item interface{}) {
+	s.l.Lock()
+	defer s.l.Unlock()
+	s.s = append(s.s, item)
+}
+
+// Pop removes and returns the top item on the stack, or returns
+// ErrEmptyStack if the stack has no content
+func (s *Stack) Pop() (interface{}, error) {
+	s.l.Lock()
+	defer s.l.Unlock()
+	l := len(s.s)
+	if l > 0 {
+		item := s.s[l-1]
+		s.s = s.s[:l-1]
+		return item, nil
+	}
+	return nil, ErrEmptyStack{action: "Pop"}
+}
+
+// PopString attempts to cast the top item on the stack to the string type.
+// If this succeeds, it removes and returns the top item. If the item
+// is not of the string type, ErrBadTypeCast is returned. If the stack
+// is empty, ErrEmptyStack is returned
+func (s *Stack) PopString() (string, error) {
+	s.l.Lock()
+	defer s.l.Unlock()
+	l := len(s.s)
+	if l > 0 {
+		item := s.s[l-1]
+		if item, ok := item.(string); ok {
+			s.s = s.s[:l-1]
+			return item, nil
+		}
+		return "", ErrBadTypeCast{}
+	}
+	return "", ErrEmptyStack{action: "PopString"}
+}
+
+// Empty returns true if the stack is empty
+func (s *Stack) Empty() bool {
+	s.l.Lock()
+	defer s.l.Unlock()
+	return len(s.s) == 0
+}