core, event/filter, xeth: refactored filter system

Moved the filtering system from `event` to `eth/filters` package and
removed the `core.Filter` object. The `filters.Filter` object now
requires a `common.Database` rather than a `eth.Backend` and invokes the
`core.GetBlockByX` directly rather than thru a "manager".

2 files changed, 344 insertions, 0 deletions

diff --git a/eth/filters/filter.go b/eth/filters/filter.go
new file mode 100644
index 000000000..b7f795607
--- /dev/null
+++ b/eth/filters/filter.go
@@ -0,0 +1,211 @@
+// Copyright 2014 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 filters
+
+import (
+	"math"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core"
+	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/core/types"
+)
+
+type AccountChange struct {
+	Address, StateAddress []byte
+}
+
+// Filtering interface
+type Filter struct {
+	db       common.Database
+	earliest int64
+	latest   int64
+	skip     int
+	address  []common.Address
+	max      int
+	topics   [][]common.Hash
+
+	BlockCallback       func(*types.Block, state.Logs)
+	TransactionCallback func(*types.Transaction)
+	LogsCallback        func(state.Logs)
+}
+
+// Create a new filter which uses a bloom filter on blocks to figure out whether a particular block
+// is interesting or not.
+func New(db common.Database) *Filter {
+	return &Filter{db: db}
+}
+
+// Set the earliest and latest block for filtering.
+// -1 = latest block (i.e., the current block)
+// hash = particular hash from-to
+func (self *Filter) SetEarliestBlock(earliest int64) {
+	self.earliest = earliest
+}
+
+func (self *Filter) SetLatestBlock(latest int64) {
+	self.latest = latest
+}
+
+func (self *Filter) SetAddress(addr []common.Address) {
+	self.address = addr
+}
+
+func (self *Filter) SetTopics(topics [][]common.Hash) {
+	self.topics = topics
+}
+
+func (self *Filter) SetMax(max int) {
+	self.max = max
+}
+
+func (self *Filter) SetSkip(skip int) {
+	self.skip = skip
+}
+
+// Run filters logs with the current parameters set
+func (self *Filter) Find() state.Logs {
+	earliestBlock := core.GetCurrentBlock(self.db)
+	var earliestBlockNo uint64 = uint64(self.earliest)
+	if self.earliest == -1 {
+		earliestBlockNo = earliestBlock.NumberU64()
+	}
+	var latestBlockNo uint64 = uint64(self.latest)
+	if self.latest == -1 {
+		latestBlockNo = earliestBlock.NumberU64()
+	}
+
+	var (
+		logs  state.Logs
+		block = core.GetBlockByNumber(self.db, latestBlockNo)
+	)
+
+done:
+	for i := 0; block != nil; i++ {
+		// Quit on latest
+		switch {
+		case block.NumberU64() == 0:
+			break done
+		case block.NumberU64() < earliestBlockNo:
+			break done
+		case self.max <= len(logs):
+			break done
+		}
+
+		// Use bloom filtering to see if this block is interesting given the
+		// current parameters
+		if self.bloomFilter(block) {
+			// Get the logs of the block
+			var (
+				receipts   = core.GetBlockReceipts(self.db, block.Hash())
+				unfiltered state.Logs
+			)
+			for _, receipt := range receipts {
+				unfiltered = append(unfiltered, receipt.Logs()...)
+			}
+			logs = append(logs, self.FilterLogs(unfiltered)...)
+		}
+
+		block = core.GetBlockByHash(self.db, block.ParentHash())
+	}
+
+	skip := int(math.Min(float64(len(logs)), float64(self.skip)))
+
+	return logs[skip:]
+}
+
+func includes(addresses []common.Address, a common.Address) bool {
+	for _, addr := range addresses {
+		if addr == a {
+			return true
+		}
+	}
+
+	return false
+}
+
+func (self *Filter) FilterLogs(logs state.Logs) state.Logs {
+	var ret state.Logs
+
+	// Filter the logs for interesting stuff
+Logs:
+	for _, log := range logs {
+		if len(self.address) > 0 && !includes(self.address, log.Address) {
+			continue
+		}
+
+		logTopics := make([]common.Hash, len(self.topics))
+		copy(logTopics, log.Topics)
+
+		// If the to filtered topics is greater than the amount of topics in
+		//  logs, skip.
+		if len(self.topics) > len(log.Topics) {
+			continue Logs
+		}
+
+		for i, topics := range self.topics {
+			var match bool
+			for _, topic := range topics {
+				// common.Hash{} is a match all (wildcard)
+				if (topic == common.Hash{}) || log.Topics[i] == topic {
+					match = true
+					break
+				}
+			}
+
+			if !match {
+				continue Logs
+			}
+
+		}
+
+		ret = append(ret, log)
+	}
+
+	return ret
+}
+
+func (self *Filter) bloomFilter(block *types.Block) bool {
+	if len(self.address) > 0 {
+		var included bool
+		for _, addr := range self.address {
+			if types.BloomLookup(block.Bloom(), addr) {
+				included = true
+				break
+			}
+		}
+
+		if !included {
+			return false
+		}
+	}
+
+	for _, sub := range self.topics {
+		var included bool
+		for _, topic := range sub {
+			if (topic == common.Hash{}) || types.BloomLookup(block.Bloom(), topic) {
+				included = true
+				break
+			}
+		}
+		if !included {
+			return false
+		}
+	}
+
+	return true
+}
diff --git a/eth/filters/filter_system.go b/eth/filters/filter_system.go
new file mode 100644
index 000000000..9ad73a896
--- /dev/null
+++ b/eth/filters/filter_system.go
@@ -0,0 +1,133 @@
+// Copyright 2014 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 filters implements an ethereum filtering system for block,
+// transactions and log events.
+package filters
+
+import (
+	"sync"
+
+	"github.com/ethereum/go-ethereum/core"
+	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/event"
+)
+
+// FilterSystem manages filters that filter specific events such as
+// block, transaction and log events. The Filtering system can be used to listen
+// for specific LOG events fires by the EVM (Ethereum Virtual Machine).
+type FilterSystem struct {
+	eventMux *event.TypeMux
+
+	filterMu sync.RWMutex
+	filterId int
+	filters  map[int]*Filter
+
+	quit chan struct{}
+}
+
+// NewFilterSystem returns a newly allocated filter manager
+func NewFilterSystem(mux *event.TypeMux) *FilterSystem {
+	fs := &FilterSystem{
+		eventMux: mux,
+		filters:  make(map[int]*Filter),
+	}
+	go fs.filterLoop()
+	return fs
+}
+
+// Stop quits the filter loop required for polling events
+func (fs *FilterSystem) Stop() {
+	close(fs.quit)
+}
+
+// Add adds a filter to the filter manager
+func (fs *FilterSystem) Add(filter *Filter) (id int) {
+	fs.filterMu.Lock()
+	defer fs.filterMu.Unlock()
+	id = fs.filterId
+	fs.filters[id] = filter
+	fs.filterId++
+
+	return id
+}
+
+// Remove removes a filter by filter id
+func (fs *FilterSystem) Remove(id int) {
+	fs.filterMu.Lock()
+	defer fs.filterMu.Unlock()
+	if _, ok := fs.filters[id]; ok {
+		delete(fs.filters, id)
+	}
+}
+
+// Get retrieves a filter installed using Add The filter may not be modified.
+func (fs *FilterSystem) Get(id int) *Filter {
+	fs.filterMu.RLock()
+	defer fs.filterMu.RUnlock()
+	return fs.filters[id]
+}
+
+// filterLoop waits for specific events from ethereum and fires their handlers
+// when the filter matches the requirements.
+func (fs *FilterSystem) filterLoop() {
+	// Subscribe to events
+	events := fs.eventMux.Subscribe(
+		//core.PendingBlockEvent{},
+		core.ChainEvent{},
+		core.TxPreEvent{},
+		state.Logs(nil))
+
+out:
+	for {
+		select {
+		case <-fs.quit:
+			break out
+		case event := <-events.Chan():
+			switch event := event.(type) {
+			case core.ChainEvent:
+				fs.filterMu.RLock()
+				for _, filter := range fs.filters {
+					if filter.BlockCallback != nil {
+						filter.BlockCallback(event.Block, event.Logs)
+					}
+				}
+				fs.filterMu.RUnlock()
+
+			case core.TxPreEvent:
+				fs.filterMu.RLock()
+				for _, filter := range fs.filters {
+					if filter.TransactionCallback != nil {
+						filter.TransactionCallback(event.Tx)
+					}
+				}
+				fs.filterMu.RUnlock()
+
+			case state.Logs:
+				fs.filterMu.RLock()
+				for _, filter := range fs.filters {
+					if filter.LogsCallback != nil {
+						msgs := filter.FilterLogs(event)
+						if len(msgs) > 0 {
+							filter.LogsCallback(msgs)
+						}
+					}
+				}
+				fs.filterMu.RUnlock()
+			}
+		}
+	}
+}