path: root/core/tx_list.go

// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package core

import (
    "container/heap"
    "math"
    "math/big"
    "sort"

    "github.com/ethereum/go-ethereum/core/types"
)

// nonceHeap is a heap.Interface implementation over 64bit unsigned integers for
// retrieving sorted transactions from the possibly gapped future queue.
type nonceHeap []uint64

func (h nonceHeap) Len() int           { return len(h) }
func (h nonceHeap) Less(i, j int) bool { return h[i] < h[j] }
func (h nonceHeap) Swap(i, j int)      { h[i], h[j] = h[j], h[i] }

func (h *nonceHeap) Push(x interface{}) {
    *h = append(*h, x.(uint64))
}

func (h *nonceHeap) Pop() interface{} {
    old := *h
    n := len(old)
    x := old[n-1]
    *h = old[0 : n-1]
    return x
}

// txList is a "list" of transactions belonging to an account, sorted by account
// nonce. The same type can be used both for storing contiguous transactions for
// the executable/pending queue; and for storing gapped transactions for the non-
// executable/future queue, with minor behavoiral changes.
type txList struct {
    strict bool                          // Whether nonces are strictly continuous or not
    items  map[uint64]*types.Transaction // Hash map storing the transaction data
    cache  types.Transactions            // Cache of the transactions already sorted

    first uint64     // Nonce of the lowest stored transaction (strict mode)
    last  uint64     // Nonce of the highest stored transaction (strict mode)
    index *nonceHeap // Heap of nonces of all the stored transactions (non-strict mode)

    costcap *big.Int // Price of the highest costing transaction (reset only if exceeds balance)
}

// newTxList create a new transaction list for maintaining nonce-indexable fast,
// gapped, sortable transaction lists.
func newTxList(strict bool) *txList {
    return &txList{
        strict:  strict,
        items:   make(map[uint64]*types.Transaction),
        first:   math.MaxUint64,
        index:   &nonceHeap{},
        costcap: new(big.Int),
    }
}

// Add tries to insert a new transaction into the list, returning whether the
// transaction was accepted, and if yes, any previous transaction it replaced.
//
// In case of strict lists (contiguous nonces) the nonce boundaries are updated
// appropriately with the new transaction. Otherwise (gapped nonces) the heap of
// nonces is expanded with the new transaction.
func (l *txList) Add(tx *types.Transaction) (bool, *types.Transaction) {
    // If an existing transaction is better, discard new one
    nonce := tx.Nonce()

    old, ok := l.items[nonce]
    if ok && old.GasPrice().Cmp(tx.GasPrice()) >= 0 {
        return false, nil
    }
    // Otherwise insert the transaction and replace any previous one
    l.items[nonce] = tx
    if cost := tx.Cost(); l.costcap.Cmp(cost) < 0 {
        l.costcap = cost
    }
    if l.strict {
        // In strict mode, maintain the nonce sequence boundaries
        if nonce < l.first {
            l.first = nonce
        }
        if nonce > l.last {
            l.last = nonce
        }
    } else {
        // In gapped mode, maintain the nonce heap
        heap.Push(l.index, nonce)
    }
    l.cache = nil

    return true, old
}

// Forward removes all transactions from the list with a nonce lower than the
// provided threshold. Every removed transaction is returned for any post-removal
// maintenance.
func (l *txList) Forward(threshold uint64) types.Transactions {
    var removed types.Transactions

    if l.strict {
        // In strict mode, push the lowest nonce forward to the threshold
        for l.first < threshold {
            if tx, ok := l.items[l.first]; ok {
                removed = append(removed, tx)
            }
            delete(l.items, l.first)
            l.first++
        }
        if l.first > l.last {
            l.last = l.first
        }
    } else {
        // In gapped mode, pop off heap items until the threshold is reached
        for l.index.Len() > 0 && (*l.index)[0] < threshold {
            nonce := heap.Pop(l.index).(uint64)
            removed = append(removed, l.items[nonce])
            delete(l.items, nonce)
        }
    }
    l.cache = nil

    return removed
}

// Filter removes all transactions from the list with a cost higher than the
// provided threshold. Every removed transaction is returned for any post-removal
// maintenance. Strict-mode invalidated transactions are also returned.
//
// This method uses the cached costcap to quickly decide if there's even a point
// in calculating all the costs or if the balance covers all. If the threshold is
// lower than the costcap, the costcap will be reset to a new high after removing
// expensive the too transactions.
func (l *txList) Filter(threshold *big.Int) (types.Transactions, types.Transactions) {
    // If all transactions are below the threshold, short circuit
    if l.costcap.Cmp(threshold) <= 0 {
        return nil, nil
    }
    l.costcap = new(big.Int).Set(threshold) // Lower the cap to the threshold

    // Gather all the transactions needing deletion
    var removed types.Transactions
    for _, tx := range l.items {
        if cost := tx.Cost(); cost.Cmp(threshold) > 0 {
            removed = append(removed, tx)
            delete(l.items, tx.Nonce())
        }
    }
    // Readjust the nonce boundaries/indexes and gather invalidate tranactions
    var invalids types.Transactions
    if l.strict {
        // In strict mode iterate find the first gap and invalidate everything after it
        for i := l.first; i <= l.last; i++ {
            if _, ok := l.items[i]; !ok {
                // Gap found, invalidate all subsequent transactions
                for j := i + 1; j <= l.last; j++ {
                    if tx, ok := l.items[j]; ok {
                        invalids = append(invalids, tx)
                        delete(l.items, j)
                    }
                }
                // Reduce the highest transaction nonce and return
                l.last = i - 1
                break
            }
        }
    } else {
        // In gapped mode no transactions are invalid, but the heap is ruined
        l.index = &nonceHeap{}
        for nonce, _ := range l.items {
            *l.index = append(*l.index, nonce)
        }
        heap.Init(l.index)
    }
    l.cache = nil

    return removed, invalids
}

// Cap places a hard limit on the number of items, returning all transactions
// exceeding that limit.
func (l *txList) Cap(threshold int) types.Transactions {
    // Short circuit if the number of items is under the limit
    if len(l.items) < threshold {
        return nil
    }
    // Otherwise gather and drop the highest nonce'd transactions
    var drops types.Transactions

    if l.strict {
        // In strict mode, just gather top down from last to first
        for len(l.items) > threshold {
            if tx, ok := l.items[l.last]; ok {
                drops = append(drops, tx)
                delete(l.items, l.last)
                l.last--
            }
        }
    } else {
        // In gapped mode it's expensive: we need to sort and drop like that
        sort.Sort(*l.index)
        for size := len(l.items); size > threshold; size-- {
            drops = append(drops, l.items[(*l.index)[size-1]])
            delete(l.items, (*l.index)[size-1])
            *l.index = (*l.index)[:size-1]
        }
        heap.Init(l.index)
    }
    l.cache = nil

    return drops
}

// Remove deletes a transaction from the maintained list, returning whether the
// transaction was found, and also returning any transaction invalidated due to
// the deletion (strict mode only).
func (l *txList) Remove(tx *types.Transaction) (bool, types.Transactions) {
    nonce := tx.Nonce()
    if _, ok := l.items[nonce]; ok {
        // Remove the item and invalidate the sorted cache
        delete(l.items, nonce)
        l.cache = nil

        // Remove all invalidated transactions (strict mode only!)
        var invalids types.Transactions
        if l.strict {
            invalids = make(types.Transactions, 0, l.last-nonce)
            for i := nonce + 1; i <= l.last; i++ {
                invalids = append(invalids, l.items[i])
                delete(l.items, i)
            }
            l.last = nonce - 1
        } else {
            // In gapped mode, remove the nonce from the index but honour the heap
            for i := 0; i < l.index.Len(); i++ {
                if (*l.index)[i] == nonce {
                    heap.Remove(l.index, i)
                    break
                }
            }
        }
        return true, invalids
    }
    return false, nil
}

// Ready retrieves a sequentially increasing list of transactions starting at the
// provided nonce that is ready for processing. The returned transactions will be
// removed from the list.
//
// Note, all transactions with nonces lower than start will also be returned to
// prevent getting into and invalid state. This is not something that should ever
// happen but better to be self correcting than failing!
func (l *txList) Ready(start uint64) types.Transactions {
    var txs types.Transactions
    if l.strict {
        // In strict mode make sure we have valid transaction, return all contiguous
        if l.first > start {
            return nil
        }
        for {
            if tx, ok := l.items[l.first]; ok {
                txs = append(txs, tx)
                delete(l.items, l.first)
                l.first++
                continue
            }
            break
        }
    } else {
        // In gapped mode, check the heap start and return all contiguous
        if l.index.Len() == 0 || (*l.index)[0] > start {
            return nil
        }
        next := (*l.index)[0]
        for l.index.Len() > 0 && (*l.index)[0] == next {
            txs = append(txs, l.items[next])
            delete(l.items, next)
            heap.Pop(l.index)
            next++
        }
    }
    l.cache = nil

    return txs
}

// Len returns the length of the transaction list.
func (l *txList) Len() int {
    return len(l.items)
}

// Empty returns whether the list of transactions is empty or not.
func (l *txList) Empty() bool {
    return len(l.items) == 0
}

// Flatten creates a nonce-sorted slice of transactions based on the loosely
// sorted internal representation. The result of the sorting is cached in case
// it's requested again before any modifications are made to the contents.
func (l *txList) Flatten() types.Transactions {
    // If the sorting was not cached yet, create and cache it
    if l.cache == nil {
        l.cache = make(types.Transactions, 0, len(l.items))
        for _, tx := range l.items {
            l.cache = append(l.cache, tx)
        }
        sort.Sort(types.TxByNonce(l.cache))
    }
    // Copy the cache to prevent accidental modifications
    txs := make(types.Transactions, len(l.cache))
    copy(txs, l.cache)
    return txs
}