Store Refactor 1 (#2985)

store/queue/queue.go

@@ -0,0 +1,93 @@
+package store
+
+// TODO: make it independent from list
+/*
+import (
+	"github.com/cosmos/cosmos-sdk/codec"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+
+	"github.com/cosmos/cosmos-sdk/store/list"
+)
+
+// Key for the top element position in the queue
+func TopKey() []byte {
+	return []byte{0x02}
+}
+
+// Queue is a List wrapper that provides queue-like functions
+// It panics when the element type cannot be (un/)marshalled by the codec
+type Queue struct {
+	List list.List
+}
+
+// NewQueue constructs new Queue
+func NewQueue(cdc *codec.Codec, store sdk.KVStore) Queue {
+	return Queue{NewList(cdc, store)}
+}
+
+func (m Queue) getTop() (res uint64) {
+	bz := m.List.store.Get(TopKey())
+	if bz == nil {
+		return 0
+	}
+
+	m.List.cdc.MustUnmarshalBinaryLengthPrefixed(bz, &res)
+	return
+}
+
+func (m Queue) setTop(top uint64) {
+	bz := m.List.cdc.MustMarshalBinaryLengthPrefixed(top)
+	m.List.store.Set(TopKey(), bz)
+}
+
+// Push() inserts the elements to the rear of the queue
+func (m Queue) Push(value interface{}) {
+	m.List.Push(value)
+}
+
+// Popping/Peeking on an empty queue will cause panic
+// The user should check IsEmpty() before doing any actions
+// Peek() returns the element at the front of the queue without removing it
+func (m Queue) Peek(ptr interface{}) error {
+	top := m.getTop()
+	return m.List.Get(top, ptr)
+}
+
+// Pop() returns the element at the front of the queue and removes it
+func (m Queue) Pop() {
+	top := m.getTop()
+	m.List.Delete(top)
+	m.setTop(top + 1)
+}
+
+// IsEmpty() checks if the queue is empty
+func (m Queue) IsEmpty() bool {
+	top := m.getTop()
+	length := m.List.Len()
+	return top >= length
+}
+
+// Flush() removes elements it processed
+// Return true in the continuation to break
+// The interface{} is unmarshalled before the continuation is called
+// Starts from the top(head) of the queue
+// CONTRACT: Pop() or Push() should not be performed while flushing
+func (m Queue) Flush(ptr interface{}, fn func() bool) {
+	top := m.getTop()
+	length := m.List.Len()
+
+	var i uint64
+	for i = top; i < length; i++ {
+		err := m.List.Get(i, ptr)
+		if err != nil {
+			// TODO: Handle with #870
+			panic(err)
+		}
+		m.List.Delete(i)
+		if fn() {
+			break
+		}
+	}
+	m.setTop(i)
+}
+*/