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// Copyright 2018 Canonical Ltd.
// Licensed under the LGPLv3, see LICENCE file for details.
package deque
import (
"container/list"
"reflect"
)
// Iterator allows in order iteration of the deque elements.
// The iterator is valid as long as no elements are added or removed from the deque.
type Iterator struct {
deque *Deque
elem *list.Element
block blockT
index int
pos int
}
// Iterator returns an `Iterator` for in order iteration of the elements.
func (d *Deque) Iterator() Iterator {
front := d.blocks.Front()
return Iterator{
deque: d,
elem: front,
block: front.Value.(blockT),
pos: d.frontIdx - 1,
}
}
// Next returns true if there is a value, and the value is populated with the
// next element. Next returns false if it is at the end and the value is
// unchanged. The `value` must be a pointer to the type stored in the deque.
func (i *Iterator) Next(value interface{}) bool {
if i.index >= i.deque.Len() {
return false
}
i.index++
i.pos++
if i.pos == blockLen {
i.pos = 0
i.elem = i.elem.Next()
i.block = i.elem.Value.(blockT)
}
v := reflect.ValueOf(value)
if v.Kind() != reflect.Ptr {
panic("value is not a pointer")
}
v = v.Elem() // dereference the pointer
v.Set(reflect.ValueOf(i.block[i.pos]))
return true
}
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