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