dex: add api_backend.go and it's dependencies

1 files changed, 138 insertions, 0 deletions

diff --git a/dex/bloombits.go b/dex/bloombits.go
new file mode 100644
index 000000000..827cae5f4
--- /dev/null
+++ b/dex/bloombits.go
@@ -0,0 +1,138 @@
+// Copyright 2017 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 dex
+
+import (
+	"context"
+	"time"
+
+	"github.com/dexon-foundation/dexon/common"
+	"github.com/dexon-foundation/dexon/common/bitutil"
+	"github.com/dexon-foundation/dexon/core"
+	"github.com/dexon-foundation/dexon/core/bloombits"
+	"github.com/dexon-foundation/dexon/core/rawdb"
+	"github.com/dexon-foundation/dexon/core/types"
+	"github.com/dexon-foundation/dexon/ethdb"
+)
+
+const (
+	// bloomServiceThreads is the number of goroutines used globally by an Ethereum
+	// instance to service bloombits lookups for all running filters.
+	bloomServiceThreads = 16
+
+	// bloomFilterThreads is the number of goroutines used locally per filter to
+	// multiplex requests onto the global servicing goroutines.
+	bloomFilterThreads = 3
+
+	// bloomRetrievalBatch is the maximum number of bloom bit retrievals to service
+	// in a single batch.
+	bloomRetrievalBatch = 16
+
+	// bloomRetrievalWait is the maximum time to wait for enough bloom bit requests
+	// to accumulate request an entire batch (avoiding hysteresis).
+	bloomRetrievalWait = time.Duration(0)
+)
+
+// startBloomHandlers starts a batch of goroutines to accept bloom bit database
+// retrievals from possibly a range of filters and serving the data to satisfy.
+func (dex *Dexon) startBloomHandlers(sectionSize uint64) {
+	for i := 0; i < bloomServiceThreads; i++ {
+		go func() {
+			for {
+				select {
+				case <-dex.shutdownChan:
+					return
+
+				case request := <-dex.bloomRequests:
+					task := <-request
+					task.Bitsets = make([][]byte, len(task.Sections))
+					for i, section := range task.Sections {
+						head := rawdb.ReadCanonicalHash(dex.chainDb, (section+1)*sectionSize-1)
+						if compVector, err := rawdb.ReadBloomBits(dex.chainDb, task.Bit, section, head); err == nil {
+							if blob, err := bitutil.DecompressBytes(compVector, int(sectionSize/8)); err == nil {
+								task.Bitsets[i] = blob
+							} else {
+								task.Error = err
+							}
+						} else {
+							task.Error = err
+						}
+					}
+					request <- task
+				}
+			}
+		}()
+	}
+}
+
+const (
+	// bloomThrottling is the time to wait between processing two consecutive index
+	// sections. It's useful during chain upgrades to prevent disk overload.
+	bloomThrottling = 100 * time.Millisecond
+)
+
+// BloomIndexer implements a core.ChainIndexer, building up a rotated bloom bits index
+// for the Ethereum header bloom filters, permitting blazing fast filtering.
+type BloomIndexer struct {
+	size    uint64               // section size to generate bloombits for
+	db      ethdb.Database       // database instance to write index data and metadata into
+	gen     *bloombits.Generator // generator to rotate the bloom bits crating the bloom index
+	section uint64               // Section is the section number being processed currently
+	head    common.Hash          // Head is the hash of the last header processed
+}
+
+// NewBloomIndexer returns a chain indexer that generates bloom bits data for the
+// canonical chain for fast logs filtering.
+func NewBloomIndexer(db ethdb.Database, size, confirms uint64) *core.ChainIndexer {
+	backend := &BloomIndexer{
+		db:   db,
+		size: size,
+	}
+	table := ethdb.NewTable(db, string(rawdb.BloomBitsIndexPrefix))
+
+	return core.NewChainIndexer(db, table, backend, size, confirms, bloomThrottling, "bloombits")
+}
+
+// Reset implements core.ChainIndexerBackend, starting a new bloombits index
+// section.
+func (b *BloomIndexer) Reset(ctx context.Context, section uint64, lastSectionHead common.Hash) error {
+	gen, err := bloombits.NewGenerator(uint(b.size))
+	b.gen, b.section, b.head = gen, section, common.Hash{}
+	return err
+}
+
+// Process implements core.ChainIndexerBackend, adding a new header's bloom into
+// the index.
+func (b *BloomIndexer) Process(ctx context.Context, header *types.Header) error {
+	b.gen.AddBloom(uint(header.Number.Uint64()-b.section*b.size), header.Bloom)
+	b.head = header.Hash()
+	return nil
+}
+
+// Commit implements core.ChainIndexerBackend, finalizing the bloom section and
+// writing it out into the database.
+func (b *BloomIndexer) Commit() error {
+	batch := b.db.NewBatch()
+	for i := 0; i < types.BloomBitLength; i++ {
+		bits, err := b.gen.Bitset(uint(i))
+		if err != nil {
+			return err
+		}
+		rawdb.WriteBloomBits(batch, uint(i), b.section, b.head, bitutil.CompressBytes(bits))
+	}
+	return batch.Write()
+}