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package v1
import (
"container/heap"
"sort"
tmsync "github.com/tendermint/tendermint/internal/libs/sync"
)
var _ heap.Interface = (*TxPriorityQueue)(nil)
// TxPriorityQueue defines a thread-safe priority queue for valid transactions.
type TxPriorityQueue struct {
mtx tmsync.RWMutex
txs []*WrappedTx
}
func NewTxPriorityQueue() *TxPriorityQueue {
pq := &TxPriorityQueue{
txs: make([]*WrappedTx, 0),
}
heap.Init(pq)
return pq
}
// GetEvictableTxs attempts to find and return a list of *WrappedTx than can be
// evicted to make room for another *WrappedTx with higher priority. If no such
// list of *WrappedTx exists, nil will be returned. The returned list of *WrappedTx
// indicate that these transactions can be removed due to them being of lower
// priority and that their total sum in size allows room for the incoming
// transaction according to the mempool's configured limits.
func (pq *TxPriorityQueue) GetEvictableTxs(priority, txSize, totalSize, cap int64) []*WrappedTx {
pq.mtx.RLock()
defer pq.mtx.RUnlock()
txs := make([]*WrappedTx, len(pq.txs))
copy(txs, pq.txs)
sort.Slice(txs, func(i, j int) bool {
return txs[i].priority < txs[j].priority
})
var (
toEvict []*WrappedTx
i int
)
currSize := totalSize
// Loop over all transactions in ascending priority order evaluating those
// that are only of less priority than the provided argument. We continue
// evaluating transactions until there is sufficient capacity for the new
// transaction (size) as defined by txSize.
for i < len(txs) && txs[i].priority < priority {
toEvict = append(toEvict, txs[i])
currSize -= int64(txs[i].Size())
if currSize+txSize <= cap {
return toEvict
}
i++
}
return nil
}
// NumTxs returns the number of transactions in the priority queue. It is
// thread safe.
func (pq *TxPriorityQueue) NumTxs() int {
pq.mtx.RLock()
defer pq.mtx.RUnlock()
return len(pq.txs)
}
// RemoveTx removes a specific transaction from the priority queue.
func (pq *TxPriorityQueue) RemoveTx(tx *WrappedTx) {
pq.mtx.Lock()
defer pq.mtx.Unlock()
if tx.heapIndex < len(pq.txs) {
heap.Remove(pq, tx.heapIndex)
}
}
// PushTx adds a valid transaction to the priority queue. It is thread safe.
func (pq *TxPriorityQueue) PushTx(tx *WrappedTx) {
pq.mtx.Lock()
defer pq.mtx.Unlock()
heap.Push(pq, tx)
}
// PopTx removes the top priority transaction from the queue. It is thread safe.
func (pq *TxPriorityQueue) PopTx() *WrappedTx {
pq.mtx.Lock()
defer pq.mtx.Unlock()
x := heap.Pop(pq)
if x != nil {
return x.(*WrappedTx)
}
return nil
}
// Push implements the Heap interface.
//
// NOTE: A caller should never call Push. Use PushTx instead.
func (pq *TxPriorityQueue) Push(x interface{}) {
n := len(pq.txs)
item := x.(*WrappedTx)
item.heapIndex = n
pq.txs = append(pq.txs, item)
}
// Pop implements the Heap interface.
//
// NOTE: A caller should never call Pop. Use PopTx instead.
func (pq *TxPriorityQueue) Pop() interface{} {
old := pq.txs
n := len(old)
item := old[n-1]
old[n-1] = nil // avoid memory leak
item.heapIndex = -1 // for safety
pq.txs = old[0 : n-1]
return item
}
// Len implements the Heap interface.
//
// NOTE: A caller should never call Len. Use NumTxs instead.
func (pq *TxPriorityQueue) Len() int {
return len(pq.txs)
}
// Less implements the Heap interface. It returns true if the transaction at
// position i in the queue is of less priority than the transaction at position j.
func (pq *TxPriorityQueue) Less(i, j int) bool {
// If there exists two transactions with the same priority, consider the one
// that we saw the earliest as the higher priority transaction.
if pq.txs[i].priority == pq.txs[j].priority {
return pq.txs[i].timestamp.Before(pq.txs[j].timestamp)
}
// We want Pop to give us the highest, not lowest, priority so we use greater
// than here.
return pq.txs[i].priority > pq.txs[j].priority
}
// Swap implements the Heap interface. It swaps two transactions in the queue.
func (pq *TxPriorityQueue) Swap(i, j int) {
pq.txs[i], pq.txs[j] = pq.txs[j], pq.txs[i]
pq.txs[i].heapIndex = i
pq.txs[j].heapIndex = j
}