shed: import shed from swarm (#70)

* shed: import shed from swarm (PR 1/12)

go.mod

@@ -5,6 +5,8 @@ go 1.14
 require (
 	github.com/btcsuite/btcd v0.20.1-beta
 	github.com/coreos/go-semver v0.3.0
+	github.com/ethereum/go-ethereum v1.9.12
+	github.com/ethersphere/swarm v0.5.7
 	github.com/gogo/protobuf v1.3.1
 	github.com/gorilla/handlers v1.4.2
 	github.com/gorilla/mux v1.7.3
@@ -17,15 +19,15 @@ require (
 	github.com/libp2p/go-ws-transport v0.2.0
 	github.com/multiformats/go-multiaddr v0.2.0
 	github.com/multiformats/go-multistream v0.1.0
-	github.com/opentracing/opentracing-go v1.0.2
+	github.com/opentracing/opentracing-go v1.1.0
 	github.com/prometheus/client_golang v1.3.0
 	github.com/sirupsen/logrus v1.4.2
 	github.com/spf13/cobra v0.0.5
 	github.com/spf13/viper v1.6.2
-	github.com/syndtr/goleveldb v1.0.0
+	github.com/syndtr/goleveldb v1.0.1-0.20190923125748-758128399b1d
 	github.com/uber/jaeger-client-go v2.22.1+incompatible
 	github.com/uber/jaeger-lib v2.2.0+incompatible // indirect
-	golang.org/x/crypto v0.0.0-20191219195013-becbf705a915
+	golang.org/x/crypto v0.0.0-20200311171314-f7b00557c8c4
 	golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e
 	resenje.org/web v0.4.0
 )

pkg/shed/db.go

+// Copyright 2018 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 shed provides a simple abstraction components to compose
+// more complex operations on storage data organized in fields and indexes.
+//
+// Only type which holds logical information about swarm storage chunks data
+// and metadata is Item. This part is not generalized mostly for
+// performance reasons.
+package shed
+
+import (
+	"github.com/syndtr/goleveldb/leveldb"
+	"github.com/syndtr/goleveldb/leveldb/iterator"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+)
+
+const (
+	openFileLimit              = 128 // The limit for LevelDB OpenFilesCacheCapacity.
+)
+
+// DB provides abstractions over LevelDB in order to
+// implement complex structures using fields and ordered indexes.
+// It provides a schema functionality to store fields and indexes
+// information about naming and types.
+type DB struct {
+	ldb  *leveldb.DB
+	quit chan struct{} // Quit channel to stop the metrics collection before closing the database
+}
+
+// NewDB constructs a new DB and validates the schema
+// if it exists in database on the given path.
+// metricsPrefix is used for metrics collection for the given DB.
+func NewDB(path string, metricsPrefix string) (db *DB, err error) {
+	ldb, err := leveldb.OpenFile(path, &opt.Options{
+		OpenFilesCacheCapacity: openFileLimit,
+	})
+	if err != nil {
+		return nil, err
+	}
+	db = &DB{
+		ldb: ldb,
+	}
+
+	if _, err = db.getSchema(); err != nil {
+		if err == leveldb.ErrNotFound {
+			// save schema with initialized default fields
+			if err = db.putSchema(schema{
+				Fields:  make(map[string]fieldSpec),
+				Indexes: make(map[byte]indexSpec),
+			}); err != nil {
+				return nil, err
+			}
+		} else {
+			return nil, err
+		}
+	}
+
+	// Create a quit channel for the periodic metrics collector and run it
+	db.quit = make(chan struct{})
+
+	return db, nil
+}
+
+// Put wraps LevelDB Put method to increment metrics counter.
+func (db *DB) Put(key []byte, value []byte) (err error) {
+	err = db.ldb.Put(key, value, nil)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// Get wraps LevelDB Get method to increment metrics counter.
+func (db *DB) Get(key []byte) (value []byte, err error) {
+	value, err = db.ldb.Get(key, nil)
+	if err != nil {
+		return nil, err
+	}
+	return value, nil
+}
+
+// Has wraps LevelDB Has method to increment metrics counter.
+func (db *DB) Has(key []byte) (yes bool, err error) {
+	yes, err = db.ldb.Has(key, nil)
+	if err != nil {
+		return false, err
+	}
+	return yes, nil
+}
+
+// Delete wraps LevelDB Delete method to increment metrics counter.
+func (db *DB) Delete(key []byte) (err error) {
+	err = db.ldb.Delete(key, nil)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// NewIterator wraps LevelDB NewIterator method to increment metrics counter.
+func (db *DB) NewIterator() iterator.Iterator {
+	return db.ldb.NewIterator(nil, nil)
+}
+
+// WriteBatch wraps LevelDB Write method to increment metrics counter.
+func (db *DB) WriteBatch(batch *leveldb.Batch) (err error) {
+	err = db.ldb.Write(batch, nil)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// Close closes LevelDB database.
+func (db *DB) Close() (err error) {
+	close(db.quit)
+	return db.ldb.Close()
+}

pkg/shed/db_test.go

+// Copyright 2018 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 shed
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+// TestNewDB constructs a new DB
+// and validates if the schema is initialized properly.
+func TestNewDB(t *testing.T) {
+	db, cleanupFunc := newTestDB(t)
+	defer cleanupFunc()
+
+	s, err := db.getSchema()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if s.Fields == nil {
+		t.Error("schema fields are empty")
+	}
+	if len(s.Fields) != 0 {
+		t.Errorf("got schema fields length %v, want %v", len(s.Fields), 0)
+	}
+	if s.Indexes == nil {
+		t.Error("schema indexes are empty")
+	}
+	if len(s.Indexes) != 0 {
+		t.Errorf("got schema indexes length %v, want %v", len(s.Indexes), 0)
+	}
+}
+
+// TestDB_persistence creates one DB, saves a field and closes that DB.
+// Then, it constructs another DB and trues to retrieve the saved value.
+func TestDB_persistence(t *testing.T) {
+	dir, err := ioutil.TempDir("", "shed-test-persistence")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(dir)
+
+	db, err := NewDB(dir, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	stringField, err := db.NewStringField("preserve-me")
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := "persistent value"
+	err = stringField.Put(want)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = db.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	db2, err := NewDB(dir, "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	stringField2, err := db2.NewStringField("preserve-me")
+	if err != nil {
+		t.Fatal(err)
+	}
+	got, err := stringField2.Get()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("got string %q, want %q", got, want)
+	}
+}
+
+// newTestDB is a helper function that constructs a
+// temporary database and returns a cleanup function that must
+// be called to remove the data.
+func newTestDB(t *testing.T) (db *DB, cleanupFunc func()) {
+	t.Helper()
+
+	dir, err := ioutil.TempDir("", "shed-test")
+	if err != nil {
+		t.Fatal(err)
+	}
+	db, err = NewDB(dir, "")
+	if err != nil {
+		os.RemoveAll(dir)
+		t.Fatal(err)
+	}
+	return db, func() {
+		db.Close()
+		os.RemoveAll(dir)
+	}
+}

pkg/shed/example_store_test.go

+// Copyright 2018 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 shed_test
+
+import (
+	"bytes"
+	"context"
+	"encoding/binary"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+	"time"
+
+	"github.com/ethersphere/swarm/shed"
+	"github.com/ethersphere/swarm/storage"
+	"github.com/syndtr/goleveldb/leveldb"
+)
+
+// Store holds fields and indexes (including their encoding functions)
+// and defines operations on them by composing data from them.
+// It implements storage.ChunkStore interface.
+// It is just an example without any support for parallel operations
+// or real world implementation.
+type Store struct {
+	db *shed.DB
+
+	// fields and indexes
+	schemaName     shed.StringField
+	accessCounter  shed.Uint64Field
+	retrievalIndex shed.Index
+	accessIndex    shed.Index
+	gcIndex        shed.Index
+}
+
+// New returns new Store. All fields and indexes are initialized
+// and possible conflicts with schema from existing database is checked
+// automatically.
+func New(path string) (s *Store, err error) {
+	db, err := shed.NewDB(path, "")
+	if err != nil {
+		return nil, err
+	}
+	s = &Store{
+		db: db,
+	}
+	// Identify current storage schema by arbitrary name.
+	s.schemaName, err = db.NewStringField("schema-name")
+	if err != nil {
+		return nil, err
+	}
+	// Global ever incrementing index of chunk accesses.
+	s.accessCounter, err = db.NewUint64Field("access-counter")
+	if err != nil {
+		return nil, err
+	}
+	// Index storing actual chunk address, data and store timestamp.
+	s.retrievalIndex, err = db.NewIndex("Address->StoreTimestamp|Data", shed.IndexFuncs{
+		EncodeKey: func(fields shed.Item) (key []byte, err error) {
+			return fields.Address, nil
+		},
+		DecodeKey: func(key []byte) (e shed.Item, err error) {
+			e.Address = key
+			return e, nil
+		},
+		EncodeValue: func(fields shed.Item) (value []byte, err error) {
+			b := make([]byte, 8)
+			binary.BigEndian.PutUint64(b, uint64(fields.StoreTimestamp))
+			value = append(b, fields.Data...)
+			return value, nil
+		},
+		DecodeValue: func(keyItem shed.Item, value []byte) (e shed.Item, err error) {
+			e.StoreTimestamp = int64(binary.BigEndian.Uint64(value[:8]))
+			e.Data = value[8:]
+			return e, nil
+		},
+	})
+	if err != nil {
+		return nil, err
+	}
+	// Index storing access timestamp for a particular address.
+	// It is needed in order to update gc index keys for iteration order.
+	s.accessIndex, err = db.NewIndex("Address->AccessTimestamp", shed.IndexFuncs{
+		EncodeKey: func(fields shed.Item) (key []byte, err error) {
+			return fields.Address, nil
+		},
+		DecodeKey: func(key []byte) (e shed.Item, err error) {
+			e.Address = key
+			return e, nil
+		},
+		EncodeValue: func(fields shed.Item) (value []byte, err error) {
+			b := make([]byte, 8)
+			binary.BigEndian.PutUint64(b, uint64(fields.AccessTimestamp))
+			return b, nil
+		},
+		DecodeValue: func(keyItem shed.Item, value []byte) (e shed.Item, err error) {
+			e.AccessTimestamp = int64(binary.BigEndian.Uint64(value))
+			return e, nil
+		},
+	})
+	if err != nil {
+		return nil, err
+	}
+	// Index with keys ordered by access timestamp for garbage collection prioritization.
+	s.gcIndex, err = db.NewIndex("AccessTimestamp|StoredTimestamp|Address->nil", shed.IndexFuncs{
+		EncodeKey: func(fields shed.Item) (key []byte, err error) {
+			b := make([]byte, 16, 16+len(fields.Address))
+			binary.BigEndian.PutUint64(b[:8], uint64(fields.AccessTimestamp))
+			binary.BigEndian.PutUint64(b[8:16], uint64(fields.StoreTimestamp))
+			key = append(b, fields.Address...)
+			return key, nil
+		},
+		DecodeKey: func(key []byte) (e shed.Item, err error) {
+			e.AccessTimestamp = int64(binary.BigEndian.Uint64(key[:8]))
+			e.StoreTimestamp = int64(binary.BigEndian.Uint64(key[8:16]))
+			e.Address = key[16:]
+			return e, nil
+		},
+		EncodeValue: func(fields shed.Item) (value []byte, err error) {
+			return nil, nil
+		},
+		DecodeValue: func(keyItem shed.Item, value []byte) (e shed.Item, err error) {
+			return e, nil
+		},
+	})
+	if err != nil {
+		return nil, err
+	}
+	return s, nil
+}
+
+// Put stores the chunk and sets it store timestamp.
+func (s *Store) Put(_ context.Context, ch storage.Chunk) (err error) {
+	return s.retrievalIndex.Put(shed.Item{
+		Address:        ch.Address(),
+		Data:           ch.Data(),
+		StoreTimestamp: time.Now().UTC().UnixNano(),
+	})
+}
+
+// Get retrieves a chunk with the provided address.
+// It updates access and gc indexes by removing the previous
+// items from them and adding new items as keys of index entries
+// are changed.
+func (s *Store) Get(_ context.Context, addr storage.Address) (c storage.Chunk, err error) {
+	batch := new(leveldb.Batch)
+
+	// Get the chunk data and storage timestamp.
+	item, err := s.retrievalIndex.Get(shed.Item{
+		Address: addr,
+	})
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			return nil, storage.ErrChunkNotFound
+		}
+		return nil, err
+	}
+
+	// Get the chunk access timestamp.
+	accessItem, err := s.accessIndex.Get(shed.Item{
+		Address: addr,
+	})
+	switch err {
+	case nil:
+		// Remove gc index entry if access timestamp is found.
+		err = s.gcIndex.DeleteInBatch(batch, shed.Item{
+			Address:         item.Address,
+			StoreTimestamp:  accessItem.AccessTimestamp,
+			AccessTimestamp: item.StoreTimestamp,
+		})
+		if err != nil {
+			return nil, err
+		}
+	case leveldb.ErrNotFound:
+	// Access timestamp is not found. Do not do anything.
+	// This is the firs get request.
+	default:
+		return nil, err
+	}
+
+	// Specify new access timestamp
+	accessTimestamp := time.Now().UTC().UnixNano()
+
+	// Put new access timestamp in access index.
+	err = s.accessIndex.PutInBatch(batch, shed.Item{
+		Address:         addr,
+		AccessTimestamp: accessTimestamp,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	// Put new access timestamp in gc index.
+	err = s.gcIndex.PutInBatch(batch, shed.Item{
+		Address:         item.Address,
+		AccessTimestamp: accessTimestamp,
+		StoreTimestamp:  item.StoreTimestamp,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	// Increment access counter.
+	// Currently this information is not used anywhere.
+	_, err = s.accessCounter.IncInBatch(batch)
+	if err != nil {
+		return nil, err
+	}
+
+	// Write the batch.
+	err = s.db.WriteBatch(batch)
+	if err != nil {
+		return nil, err
+	}
+
+	// Return the chunk.
+	return storage.NewChunk(item.Address, item.Data), nil
+}
+
+// CollectGarbage is an example of index iteration.
+// It provides no reliable garbage collection functionality.
+func (s *Store) CollectGarbage() (err error) {
+	const maxTrashSize = 100
+	maxRounds := 10 // arbitrary number, needs to be calculated
+
+	// Run a few gc rounds.
+	for roundCount := 0; roundCount < maxRounds; roundCount++ {
+		var garbageCount int
+		// New batch for a new cg round.
+		trash := new(leveldb.Batch)
+		// Iterate through all index items and break when needed.
+		err = s.gcIndex.Iterate(func(item shed.Item) (stop bool, err error) {
+			// Remove the chunk.
+			err = s.retrievalIndex.DeleteInBatch(trash, item)
+			if err != nil {
+				return false, err
+			}
+			// Remove the element in gc index.
+			err = s.gcIndex.DeleteInBatch(trash, item)
+			if err != nil {
+				return false, err
+			}
+			// Remove the relation in access index.
+			err = s.accessIndex.DeleteInBatch(trash, item)
+			if err != nil {
+				return false, err
+			}
+			garbageCount++
+			if garbageCount >= maxTrashSize {
+				return true, nil
+			}
+			return false, nil
+		}, nil)
+		if err != nil {
+			return err
+		}
+		if garbageCount == 0 {
+			return nil
+		}
+		err = s.db.WriteBatch(trash)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// GetSchema is an example of retrieveing the most simple
+// string from a database field.
+func (s *Store) GetSchema() (name string, err error) {
+	name, err = s.schemaName.Get()
+	if err == leveldb.ErrNotFound {
+		return "", nil
+	}
+	return name, err
+}
+
+// PutSchema is an example of storing the most simple
+// string in a database field.
+func (s *Store) PutSchema(name string) (err error) {
+	return s.schemaName.Put(name)
+}
+
+// Close closes the underlying database.
+func (s *Store) Close() error {
+	return s.db.Close()
+}
+
+// Example_store constructs a simple storage implementation using shed package.
+func Example_store() {
+	dir, err := ioutil.TempDir("", "ephemeral")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer os.RemoveAll(dir)
+
+	s, err := New(dir)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer s.Close()
+
+	ch := storage.GenerateRandomChunk(1024)
+	err = s.Put(context.Background(), ch)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	got, err := s.Get(context.Background(), ch.Address())
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println(bytes.Equal(got.Data(), ch.Data()))
+
+	//Output: true
+}

pkg/shed/field_string.go

+// Copyright 2018 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 shed
+
+import (
+	"github.com/syndtr/goleveldb/leveldb"
+)
+
+// StringField is the most simple field implementation
+// that stores an arbitrary string under a specific LevelDB key.
+type StringField struct {
+	db  *DB
+	key []byte
+}
+
+// NewStringField retruns a new Instance of StringField.
+// It validates its name and type against the database schema.
+func (db *DB) NewStringField(name string) (f StringField, err error) {
+	key, err := db.schemaFieldKey(name, "string")
+	if err != nil {
+		return f, err
+	}
+	return StringField{
+		db:  db,
+		key: key,
+	}, nil
+}
+
+// Get returns a string value from database.
+// If the value is not found, an empty string is returned
+// an no error.
+func (f StringField) Get() (val string, err error) {
+	b, err := f.db.Get(f.key)
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			return "", nil
+		}
+		return "", err
+	}
+	return string(b), nil
+}
+
+// Put stores a string in the database.
+func (f StringField) Put(val string) (err error) {
+	return f.db.Put(f.key, []byte(val))
+}
+
+// PutInBatch stores a string in a batch that can be
+// saved later in database.
+func (f StringField) PutInBatch(batch *leveldb.Batch, val string) {
+	batch.Put(f.key, []byte(val))
+}

pkg/shed/field_string_test.go

+// Copyright 2018 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 shed
+
+import (
+	"testing"
+
+	"github.com/syndtr/goleveldb/leveldb"
+)
+
+// TestStringField validates put and get operations
+// of the StringField.
+func TestStringField(t *testing.T) {
+	db, cleanupFunc := newTestDB(t)
+	defer cleanupFunc()
+
+	simpleString, err := db.NewStringField("simple-string")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	t.Run("get empty", func(t *testing.T) {
+		got, err := simpleString.Get()
+		if err != nil {
+			t.Fatal(err)
+		}
+		want := ""
+		if got != want {
+			t.Errorf("got string %q, want %q", got, want)
+		}
+	})
+
+	t.Run("put", func(t *testing.T) {
+		want := "simple string value"
+		err = simpleString.Put(want)
+		if err != nil {
+			t.Fatal(err)
+		}
+		got, err := simpleString.Get()
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got string %q, want %q", got, want)
+		}
+
+		t.Run("overwrite", func(t *testing.T) {
+			want := "overwritten string value"
+			err = simpleString.Put(want)
+			if err != nil {
+				t.Fatal(err)
+			}
+			got, err := simpleString.Get()
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got != want {
+				t.Errorf("got string %q, want %q", got, want)
+			}
+		})
+	})
+
+	t.Run("put in batch", func(t *testing.T) {
+		batch := new(leveldb.Batch)
+		want := "simple string batch value"
+		simpleString.PutInBatch(batch, want)
+		err = db.WriteBatch(batch)
+		if err != nil {
+			t.Fatal(err)
+		}
+		got, err := simpleString.Get()
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got string %q, want %q", got, want)
+		}
+
+		t.Run("overwrite", func(t *testing.T) {
+			batch := new(leveldb.Batch)
+			want := "overwritten string batch value"
+			simpleString.PutInBatch(batch, want)
+			err = db.WriteBatch(batch)
+			if err != nil {
+				t.Fatal(err)
+			}
+			got, err := simpleString.Get()
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got != want {
+				t.Errorf("got string %q, want %q", got, want)
+			}
+		})
+	})
+}

pkg/shed/field_struct.go

+// Copyright 2018 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 shed
+
+import (
+	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/syndtr/goleveldb/leveldb"
+)
+
+// StructField is a helper to store complex structure by
+// encoding it in RLP format.
+type StructField struct {
+	db  *DB
+	key []byte
+}
+
+// NewStructField returns a new StructField.
+// It validates its name and type against the database schema.
+func (db *DB) NewStructField(name string) (f StructField, err error) {
+	key, err := db.schemaFieldKey(name, "struct-rlp")
+	if err != nil {
+		return f, err
+	}
+	return StructField{
+		db:  db,
+		key: key,
+	}, nil
+}
+
+// Get unmarshals data from the database to a provided val.
+// If the data is not found leveldb.ErrNotFound is returned.
+func (f StructField) Get(val interface{}) (err error) {
+	b, err := f.db.Get(f.key)
+	if err != nil {
+		return err
+	}
+	return rlp.DecodeBytes(b, val)
+}
+
+// Put marshals provided val and saves it to the database.
+func (f StructField) Put(val interface{}) (err error) {
+	b, err := rlp.EncodeToBytes(val)
+	if err != nil {
+		return err
+	}
+	return f.db.Put(f.key, b)
+}
+
+// PutInBatch marshals provided val and puts it into the batch.
+func (f StructField) PutInBatch(batch *leveldb.Batch, val interface{}) (err error) {
+	b, err := rlp.EncodeToBytes(val)
+	if err != nil {
+		return err
+	}
+	batch.Put(f.key, b)
+	return nil
+}

pkg/shed/field_struct_test.go

+// Copyright 2018 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 shed
+
+import (
+	"testing"
+
+	"github.com/syndtr/goleveldb/leveldb"
+)
+
+// TestStructField validates put and get operations
+// of the StructField.
+func TestStructField(t *testing.T) {
+	db, cleanupFunc := newTestDB(t)
+	defer cleanupFunc()
+
+	complexField, err := db.NewStructField("complex-field")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	type complexStructure struct {
+		A string
+	}
+
+	t.Run("get empty", func(t *testing.T) {
+		var s complexStructure
+		err := complexField.Get(&s)
+		if err != leveldb.ErrNotFound {
+			t.Fatalf("got error %v, want %v", err, leveldb.ErrNotFound)
+		}
+		want := ""
+		if s.A != want {
+			t.Errorf("got string %q, want %q", s.A, want)
+		}
+	})
+
+	t.Run("put", func(t *testing.T) {
+		want := complexStructure{
+			A: "simple string value",
+		}
+		err = complexField.Put(want)
+		if err != nil {
+			t.Fatal(err)
+		}
+		var got complexStructure
+		err = complexField.Get(&got)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got.A != want.A {
+			t.Errorf("got string %q, want %q", got.A, want.A)
+		}
+
+		t.Run("overwrite", func(t *testing.T) {
+			want := complexStructure{
+				A: "overwritten string value",
+			}
+			err = complexField.Put(want)
+			if err != nil {
+				t.Fatal(err)
+			}
+			var got complexStructure
+			err = complexField.Get(&got)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got.A != want.A {
+				t.Errorf("got string %q, want %q", got.A, want.A)
+			}
+		})
+	})
+
+	t.Run("put in batch", func(t *testing.T) {
+		batch := new(leveldb.Batch)
+		want := complexStructure{
+			A: "simple string batch value",
+		}
+		err = complexField.PutInBatch(batch, want)
+		if err != nil {
+			t.Fatal(err)
+		}
+		err = db.WriteBatch(batch)
+		if err != nil {
+			t.Fatal(err)
+		}
+		var got complexStructure
+		err := complexField.Get(&got)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got.A != want.A {
+			t.Errorf("got string %q, want %q", got, want)
+		}
+
+		t.Run("overwrite", func(t *testing.T) {
+			batch := new(leveldb.Batch)
+			want := complexStructure{
+				A: "overwritten string batch value",
+			}
+			err = complexField.PutInBatch(batch, want)
+			if err != nil {
+				t.Fatal(err)
+			}
+			err = db.WriteBatch(batch)
+			if err != nil {
+				t.Fatal(err)
+			}
+			var got complexStructure
+			err := complexField.Get(&got)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got.A != want.A {
+				t.Errorf("got string %q, want %q", got, want)
+			}
+		})
+	})
+}

pkg/shed/field_uint64.go

+// Copyright 2018 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 shed
+
+import (
+	"encoding/binary"
+
+	"github.com/syndtr/goleveldb/leveldb"
+)
+
+// Uint64Field provides a way to have a simple counter in the database.
+// It transparently encodes uint64 type value to bytes.
+type Uint64Field struct {
+	db  *DB
+	key []byte
+}
+
+// NewUint64Field returns a new Uint64Field.
+// It validates its name and type against the database schema.
+func (db *DB) NewUint64Field(name string) (f Uint64Field, err error) {
+	key, err := db.schemaFieldKey(name, "uint64")
+	if err != nil {
+		return f, err
+	}
+	return Uint64Field{
+		db:  db,
+		key: key,
+	}, nil
+}
+
+// Get retrieves a uint64 value from the database.
+// If the value is not found in the database a 0 value
+// is returned and no error.
+func (f Uint64Field) Get() (val uint64, err error) {
+	b, err := f.db.Get(f.key)
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			return 0, nil
+		}
+		return 0, err
+	}
+	return binary.BigEndian.Uint64(b), nil
+}
+
+// Put encodes uin64 value and stores it in the database.
+func (f Uint64Field) Put(val uint64) (err error) {
+	return f.db.Put(f.key, encodeUint64(val))
+}
+
+// PutInBatch stores a uint64 value in a batch
+// that can be saved later in the database.
+func (f Uint64Field) PutInBatch(batch *leveldb.Batch, val uint64) {
+	batch.Put(f.key, encodeUint64(val))
+}
+
+// Inc increments a uint64 value in the database.
+// This operation is not goroutine save.
+func (f Uint64Field) Inc() (val uint64, err error) {
+	val, err = f.Get()
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			val = 0
+		} else {
+			return 0, err
+		}
+	}
+	val++
+	return val, f.Put(val)
+}
+
+// IncInBatch increments a uint64 value in the batch
+// by retreiving a value from the database, not the same batch.
+// This operation is not goroutine save.
+func (f Uint64Field) IncInBatch(batch *leveldb.Batch) (val uint64, err error) {
+	val, err = f.Get()
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			val = 0
+		} else {
+			return 0, err
+		}
+	}
+	val++
+	f.PutInBatch(batch, val)
+	return val, nil
+}
+
+// Dec decrements a uint64 value in the database.
+// This operation is not goroutine save.
+// The field is protected from overflow to a negative value.
+func (f Uint64Field) Dec() (val uint64, err error) {
+	val, err = f.Get()
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			val = 0
+		} else {
+			return 0, err
+		}
+	}
+	if val != 0 {
+		val--
+	}
+	return val, f.Put(val)
+}
+
+// DecInBatch decrements a uint64 value in the batch
+// by retreiving a value from the database, not the same batch.
+// This operation is not goroutine save.
+// The field is protected from overflow to a negative value.
+func (f Uint64Field) DecInBatch(batch *leveldb.Batch) (val uint64, err error) {
+	val, err = f.Get()
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			val = 0
+		} else {
+			return 0, err
+		}
+	}
+	if val != 0 {
+		val--
+	}
+	f.PutInBatch(batch, val)
+	return val, nil
+}
+
+// encode transforms uint64 to 8 byte long
+// slice in big endian encoding.
+func encodeUint64(val uint64) (b []byte) {
+	b = make([]byte, 8)
+	binary.BigEndian.PutUint64(b, val)
+	return b
+}

pkg/shed/field_uint64_test.go

+// Copyright 2018 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 shed
+
+import (
+	"testing"
+
+	"github.com/syndtr/goleveldb/leveldb"
+)
+
+// TestUint64Field validates put and get operations
+// of the Uint64Field.
+func TestUint64Field(t *testing.T) {
+	db, cleanupFunc := newTestDB(t)
+	defer cleanupFunc()
+
+	counter, err := db.NewUint64Field("counter")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	t.Run("get empty", func(t *testing.T) {
+		got, err := counter.Get()
+		if err != nil {
+			t.Fatal(err)
+		}
+		var want uint64
+		if got != want {
+			t.Errorf("got uint64 %v, want %v", got, want)
+		}
+	})
+
+	t.Run("put", func(t *testing.T) {
+		var want uint64 = 42
+		err = counter.Put(want)
+		if err != nil {
+			t.Fatal(err)
+		}
+		got, err := counter.Get()
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got uint64 %v, want %v", got, want)
+		}
+
+		t.Run("overwrite", func(t *testing.T) {
+			var want uint64 = 84
+			err = counter.Put(want)
+			if err != nil {
+				t.Fatal(err)
+			}
+			got, err := counter.Get()
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got != want {
+				t.Errorf("got uint64 %v, want %v", got, want)
+			}
+		})
+	})
+
+	t.Run("put in batch", func(t *testing.T) {
+		batch := new(leveldb.Batch)
+		var want uint64 = 42
+		counter.PutInBatch(batch, want)
+		err = db.WriteBatch(batch)
+		if err != nil {
+			t.Fatal(err)
+		}
+		got, err := counter.Get()
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got uint64 %v, want %v", got, want)
+		}
+
+		t.Run("overwrite", func(t *testing.T) {
+			batch := new(leveldb.Batch)
+			var want uint64 = 84
+			counter.PutInBatch(batch, want)
+			err = db.WriteBatch(batch)
+			if err != nil {
+				t.Fatal(err)
+			}
+			got, err := counter.Get()
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got != want {
+				t.Errorf("got uint64 %v, want %v", got, want)
+			}
+		})
+	})
+}
+
+// TestUint64Field_Inc validates Inc operation
+// of the Uint64Field.
+func TestUint64Field_Inc(t *testing.T) {
+	db, cleanupFunc := newTestDB(t)
+	defer cleanupFunc()
+
+	counter, err := db.NewUint64Field("counter")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var want uint64 = 1
+	got, err := counter.Inc()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("got uint64 %v, want %v", got, want)
+	}
+
+	want = 2
+	got, err = counter.Inc()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("got uint64 %v, want %v", got, want)
+	}
+}
+
+// TestUint64Field_IncInBatch validates IncInBatch operation
+// of the Uint64Field.
+func TestUint64Field_IncInBatch(t *testing.T) {
+	db, cleanupFunc := newTestDB(t)
+	defer cleanupFunc()
+
+	counter, err := db.NewUint64Field("counter")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	batch := new(leveldb.Batch)
+	var want uint64 = 1
+	got, err := counter.IncInBatch(batch)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("got uint64 %v, want %v", got, want)
+	}
+	err = db.WriteBatch(batch)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got, err = counter.Get()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("got uint64 %v, want %v", got, want)
+	}
+
+	batch2 := new(leveldb.Batch)
+	want = 2
+	got, err = counter.IncInBatch(batch2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("got uint64 %v, want %v", got, want)
+	}
+	err = db.WriteBatch(batch2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got, err = counter.Get()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("got uint64 %v, want %v", got, want)
+	}
+}
+
+// TestUint64Field_Dec validates Dec operation
+// of the Uint64Field.
+func TestUint64Field_Dec(t *testing.T) {
+	db, cleanupFunc := newTestDB(t)
+	defer cleanupFunc()
+
+	counter, err := db.NewUint64Field("counter")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// test overflow protection
+	var want uint64
+	got, err := counter.Dec()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("got uint64 %v, want %v", got, want)
+	}
+
+	want = 32
+	err = counter.Put(want)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	want = 31
+	got, err = counter.Dec()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("got uint64 %v, want %v", got, want)
+	}
+}
+
+// TestUint64Field_DecInBatch validates DecInBatch operation
+// of the Uint64Field.
+func TestUint64Field_DecInBatch(t *testing.T) {
+	db, cleanupFunc := newTestDB(t)
+	defer cleanupFunc()
+
+	counter, err := db.NewUint64Field("counter")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	batch := new(leveldb.Batch)
+	var want uint64
+	got, err := counter.DecInBatch(batch)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("got uint64 %v, want %v", got, want)
+	}
+	err = db.WriteBatch(batch)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got, err = counter.Get()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("got uint64 %v, want %v", got, want)
+	}
+
+	batch2 := new(leveldb.Batch)
+	want = 42
+	counter.PutInBatch(batch2, want)
+	err = db.WriteBatch(batch2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got, err = counter.Get()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("got uint64 %v, want %v", got, want)
+	}
+
+	batch3 := new(leveldb.Batch)
+	want = 41
+	got, err = counter.DecInBatch(batch3)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("got uint64 %v, want %v", got, want)
+	}
+	err = db.WriteBatch(batch3)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got, err = counter.Get()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("got uint64 %v, want %v", got, want)
+	}
+}

pkg/shed/schema.go

+// Copyright 2018 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 shed
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+)
+
+var (
+	// LevelDB key value for storing the schema.
+	keySchema = []byte{0}
+	// LevelDB key prefix for all field type.
+	// LevelDB keys will be constructed by appending name values to this prefix.
+	keyPrefixFields byte = 1
+	// LevelDB key prefix from which indexing keys start.
+	// Every index has its own key prefix and this value defines the first one.
+	keyPrefixIndexStart byte = 2 // Q: or maybe a higher number like 7, to have more space for potential specific perfixes
+)
+
+// schema is used to serialize known database structure information.
+type schema struct {
+	Fields  map[string]fieldSpec `json:"fields"`  // keys are field names
+	Indexes map[byte]indexSpec   `json:"indexes"` // keys are index prefix bytes
+}
+
+// fieldSpec holds information about a particular field.
+// It does not need Name field as it is contained in the
+// schema.Field map key.
+type fieldSpec struct {
+	Type string `json:"type"`
+}
+
+// indexSpec holds information about a particular index.
+// It does not contain index type, as indexes do not have type.
+type indexSpec struct {
+	Name string `json:"name"`
+}
+
+// schemaFieldKey retrieves the complete LevelDB key for
+// a particular field from the schema definition.
+func (db *DB) schemaFieldKey(name, fieldType string) (key []byte, err error) {
+	if name == "" {
+		return nil, errors.New("field name cannot be blank")
+	}
+	if fieldType == "" {
+		return nil, errors.New("field type cannot be blank")
+	}
+	s, err := db.getSchema()
+	if err != nil {
+		return nil, err
+	}
+	var found bool
+	for n, f := range s.Fields {
+		if n == name {
+			if f.Type != fieldType {
+				return nil, fmt.Errorf("field %q of type %q stored as %q in db", name, fieldType, f.Type)
+			}
+			break
+		}
+	}
+	if !found {
+		s.Fields[name] = fieldSpec{
+			Type: fieldType,
+		}
+		err := db.putSchema(s)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return append([]byte{keyPrefixFields}, []byte(name)...), nil
+}
+
+// RenameIndex changes the schema so that an existing index name is changed
+// while preserving its data by keeping the same internal key prefix.
+// Renaming indexes is useful when encoding functions can be backward compatible
+// to avoid data migrations.
+func (db *DB) RenameIndex(name, newName string) (renamed bool, err error) {
+	if name == "" {
+		return false, errors.New("index name cannot be blank")
+	}
+	if newName == "" {
+		return false, errors.New("new index name cannot be blank")
+	}
+	if newName == name {
+		return false, nil
+	}
+	s, err := db.getSchema()
+	if err != nil {
+		return false, err
+	}
+	for i, f := range s.Indexes {
+		if f.Name == name {
+			s.Indexes[i] = indexSpec{
+				Name: newName,
+			}
+			return true, db.putSchema(s)
+		}
+		if f.Name == newName {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
+// schemaIndexID retrieves the complete LevelDB prefix for
+// a particular index.
+func (db *DB) schemaIndexPrefix(name string) (id byte, err error) {
+	if name == "" {
+		return 0, errors.New("index name cannot be blank")
+	}
+	s, err := db.getSchema()
+	if err != nil {
+		return 0, err
+	}
+	nextID := keyPrefixIndexStart
+	for i, f := range s.Indexes {
+		if i >= nextID {
+			nextID = i + 1
+		}
+		if f.Name == name {
+			return i, nil
+		}
+	}
+	id = nextID
+	s.Indexes[id] = indexSpec{
+		Name: name,
+	}
+	return id, db.putSchema(s)
+}
+
+// getSchema retrieves the complete schema from
+// the database.
+func (db *DB) getSchema() (s schema, err error) {
+	b, err := db.Get(keySchema)
+	if err != nil {
+		return s, err
+	}
+	err = json.Unmarshal(b, &s)
+	return s, err
+}
+
+// putSchema stores the complete schema to
+// the database.
+func (db *DB) putSchema(s schema) (err error) {
+	b, err := json.Marshal(s)
+	if err != nil {
+		return err
+	}
+	return db.Put(keySchema, b)
+}

pkg/shed/schema_test.go

+// Copyright 2018 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 shed
+
+import (
+	"bytes"
+	"testing"
+)
+
+// TestDB_schemaFieldKey validates correctness of schemaFieldKey.
+func TestDB_schemaFieldKey(t *testing.T) {
+	db, cleanupFunc := newTestDB(t)
+	defer cleanupFunc()
+
+	t.Run("empty name or type", func(t *testing.T) {
+		_, err := db.schemaFieldKey("", "")
+		if err == nil {
+			t.Error("error not returned, but expected")
+		}
+		_, err = db.schemaFieldKey("", "type")
+		if err == nil {
+			t.Error("error not returned, but expected")
+		}
+
+		_, err = db.schemaFieldKey("test", "")
+		if err == nil {
+			t.Error("error not returned, but expected")
+		}
+	})
+
+	t.Run("same field", func(t *testing.T) {
+		key1, err := db.schemaFieldKey("test", "undefined")
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		key2, err := db.schemaFieldKey("test", "undefined")
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if !bytes.Equal(key1, key2) {
+			t.Errorf("schema keys for the same field name are not the same: %q, %q", string(key1), string(key2))
+		}
+	})
+
+	t.Run("different fields", func(t *testing.T) {
+		key1, err := db.schemaFieldKey("test1", "undefined")
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		key2, err := db.schemaFieldKey("test2", "undefined")
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if bytes.Equal(key1, key2) {
+			t.Error("schema keys for the same field name are the same, but must not be")
+		}
+	})
+
+	t.Run("same field name different types", func(t *testing.T) {
+		_, err := db.schemaFieldKey("the-field", "one-type")
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		_, err = db.schemaFieldKey("the-field", "another-type")
+		if err == nil {
+			t.Error("error not returned, but expected")
+		}
+	})
+}
+
+// TestDB_schemaIndexPrefix validates correctness of schemaIndexPrefix.
+func TestDB_schemaIndexPrefix(t *testing.T) {
+	db, cleanupFunc := newTestDB(t)
+	defer cleanupFunc()
+
+	t.Run("same name", func(t *testing.T) {
+		id1, err := db.schemaIndexPrefix("test")
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		id2, err := db.schemaIndexPrefix("test")
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if id1 != id2 {
+			t.Errorf("schema keys for the same field name are not the same: %v, %v", id1, id2)
+		}
+	})
+
+	t.Run("different names", func(t *testing.T) {
+		id1, err := db.schemaIndexPrefix("test1")
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		id2, err := db.schemaIndexPrefix("test2")
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if id1 == id2 {
+			t.Error("schema ids for the same index name are the same, but must not be")
+		}
+	})
+}
+
+// TestDB_RenameIndex checks if index name is correctly changed.
+func TestDB_RenameIndex(t *testing.T) {
+
+	t.Run("empty names", func(t *testing.T) {
+		db, cleanupFunc := newTestDB(t)
+		defer cleanupFunc()
+
+		// empty names
+		renamed, err := db.RenameIndex("", "")
+		if err == nil {
+			t.Error("error not returned, but expected")
+		}
+		if renamed {
+			t.Fatal("index should not be renamed")
+		}
+
+		// empty index name
+		renamed, err = db.RenameIndex("", "new")
+		if err == nil {
+			t.Error("error not returned, but expected")
+		}
+		if renamed {
+			t.Fatal("index should not be renamed")
+		}
+
+		// empty new index name
+		renamed, err = db.RenameIndex("current", "")
+		if err == nil {
+			t.Error("error not returned, but expected")
+		}
+		if renamed {
+			t.Fatal("index should not be renamed")
+		}
+	})
+
+	t.Run("same names", func(t *testing.T) {
+		db, cleanupFunc := newTestDB(t)
+		defer cleanupFunc()
+
+		renamed, err := db.RenameIndex("index1", "index1")
+		if err != nil {
+			t.Error(err)
+		}
+		if renamed {
+			t.Fatal("index should not be renamed")
+		}
+	})
+
+	t.Run("unknown name", func(t *testing.T) {
+		db, cleanupFunc := newTestDB(t)
+		defer cleanupFunc()
+
+		renamed, err := db.RenameIndex("index1", "index1new")
+		if err != nil {
+			t.Error(err)
+		}
+		if renamed {
+			t.Fatal("index should not be renamed")
+		}
+	})
+
+	t.Run("valid names", func(t *testing.T) {
+		db, cleanupFunc := newTestDB(t)
+		defer cleanupFunc()
+
+		// initial indexes
+		key1, err := db.schemaIndexPrefix("index1")
+		if err != nil {
+			t.Fatal(err)
+		}
+		key2, err := db.schemaIndexPrefix("index2")
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		// name the first one
+		renamed, err := db.RenameIndex("index1", "index1new")
+		if err != nil {
+			t.Fatal(err)
+		}
+		if !renamed {
+			t.Fatal("index not renamed")
+		}
+
+		// validate that the index key stays the same
+		key1same, err := db.schemaIndexPrefix("index1new")
+		if err != nil {
+			t.Fatal(err)
+		}
+		if key1 != key1same {
+			t.Fatal("indexes renamed, but keys are not the same")
+		}
+
+		// validate that the independent index is not changed
+		key2same, err := db.schemaIndexPrefix("index2")
+		if err != nil {
+			t.Fatal(err)
+		}
+		if key2 != key2same {
+			t.Fatal("independent index key has changed")
+		}
+
+		// validate that it is safe to create a new index with previous name
+		key1renew, err := db.schemaIndexPrefix("index1")
+		if err != nil {
+			t.Fatal(err)
+		}
+		if key1 == key1renew {
+			t.Fatal("renewed index and the original one have the same key")
+		}
+		if key2 == key1renew {
+			t.Fatal("renewed index and the independent one have the same key")
+		}
+	})
+}

pkg/shed/vector_uint64.go

+// Copyright 2018 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 shed
+
+import (
+	"encoding/binary"
+
+	"github.com/syndtr/goleveldb/leveldb"
+)
+
+// Uint64Vector provides a way to have multiple counters in the database.
+// It transparently encodes uint64 type value to bytes.
+type Uint64Vector struct {
+	db  *DB
+	key []byte
+}
+
+// NewUint64Vector returns a new Uint64Vector.
+// It validates its name and type against the database schema.
+func (db *DB) NewUint64Vector(name string) (f Uint64Vector, err error) {
+	key, err := db.schemaFieldKey(name, "vector-uint64")
+	if err != nil {
+		return f, err
+	}
+	return Uint64Vector{
+		db:  db,
+		key: key,
+	}, nil
+}
+
+// Get retrieves a uint64 value at index i from the database.
+// If the value is not found in the database a 0 value
+// is returned and no error.
+func (f Uint64Vector) Get(i uint64) (val uint64, err error) {
+	b, err := f.db.Get(f.indexKey(i))
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			return 0, nil
+		}
+		return 0, err
+	}
+	return binary.BigEndian.Uint64(b), nil
+}
+
+// Put encodes uin64 value and stores it in the database.
+func (f Uint64Vector) Put(i, val uint64) (err error) {
+	return f.db.Put(f.indexKey(i), encodeUint64(val))
+}
+
+// PutInBatch stores a uint64 value at index i in a batch
+// that can be saved later in the database.
+func (f Uint64Vector) PutInBatch(batch *leveldb.Batch, i, val uint64) {
+	batch.Put(f.indexKey(i), encodeUint64(val))
+}
+
+// Inc increments a uint64 value in the database.
+// This operation is not goroutine safe.
+func (f Uint64Vector) Inc(i uint64) (val uint64, err error) {
+	val, err = f.Get(i)
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			val = 0
+		} else {
+			return 0, err
+		}
+	}
+	val++
+	return val, f.Put(i, val)
+}
+
+// IncInBatch increments a uint64 value at index i in the batch
+// by retreiving a value from the database, not the same batch.
+// This operation is not goroutine safe.
+func (f Uint64Vector) IncInBatch(batch *leveldb.Batch, i uint64) (val uint64, err error) {
+	val, err = f.Get(i)
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			val = 0
+		} else {
+			return 0, err
+		}
+	}
+	val++
+	f.PutInBatch(batch, i, val)
+	return val, nil
+}
+
+// Dec decrements a uint64 value at index i in the database.
+// This operation is not goroutine safe.
+// The field is protected from overflow to a negative value.
+func (f Uint64Vector) Dec(i uint64) (val uint64, err error) {
+	val, err = f.Get(i)
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			val = 0
+		} else {
+			return 0, err
+		}
+	}
+	if val != 0 {
+		val--
+	}
+	return val, f.Put(i, val)
+}
+
+// DecInBatch decrements a uint64 value at index i in the batch
+// by retreiving a value from the database, not the same batch.
+// This operation is not goroutine safe.
+// The field is protected from overflow to a negative value.
+func (f Uint64Vector) DecInBatch(batch *leveldb.Batch, i uint64) (val uint64, err error) {
+	val, err = f.Get(i)
+	if err != nil {
+		if err == leveldb.ErrNotFound {
+			val = 0
+		} else {
+			return 0, err
+		}
+	}
+	if val != 0 {
+		val--
+	}
+	f.PutInBatch(batch, i, val)
+	return val, nil
+}
+
+// indexKey concatenates field prefix and vector index
+// returning a unique database key for a specific vector element.
+func (f Uint64Vector) indexKey(i uint64) (key []byte) {
+	b := make([]byte, 8)
+	binary.BigEndian.PutUint64(b, i)
+	return append(f.key, b...)
+}

pkg/shed/vector_uint64_test.go

+// Copyright 2018 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 shed
+
+import (
+	"testing"
+
+	"github.com/syndtr/goleveldb/leveldb"
+)
+
+// TestUint64Vector validates put and get operations
+// of the Uint64Vector.
+func TestUint64Vector(t *testing.T) {
+	db, cleanupFunc := newTestDB(t)
+	defer cleanupFunc()
+
+	bins, err := db.NewUint64Vector("bins")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	t.Run("get empty", func(t *testing.T) {
+		got, err := bins.Get(0)
+		if err != nil {
+			t.Fatal(err)
+		}
+		var want uint64
+		if got != want {
+			t.Errorf("got uint64 %v, want %v", got, want)
+		}
+	})
+
+	t.Run("put", func(t *testing.T) {
+		for _, index := range []uint64{0, 1, 2, 5, 100} {
+			var want uint64 = 42 + index
+			err = bins.Put(index, want)
+			if err != nil {
+				t.Fatal(err)
+			}
+			got, err := bins.Get(index)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got != want {
+				t.Errorf("got %v uint64 %v, want %v", index, got, want)
+			}
+
+			t.Run("overwrite", func(t *testing.T) {
+				var want uint64 = 84 + index
+				err = bins.Put(index, want)
+				if err != nil {
+					t.Fatal(err)
+				}
+				got, err := bins.Get(index)
+				if err != nil {
+					t.Fatal(err)
+				}
+				if got != want {
+					t.Errorf("got %v uint64 %v, want %v", index, got, want)
+				}
+			})
+		}
+	})
+
+	t.Run("put in batch", func(t *testing.T) {
+		for _, index := range []uint64{0, 1, 2, 3, 5, 10} {
+			batch := new(leveldb.Batch)
+			var want uint64 = 43 + index
+			bins.PutInBatch(batch, index, want)
+			err = db.WriteBatch(batch)
+			if err != nil {
+				t.Fatal(err)
+			}
+			got, err := bins.Get(index)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got != want {
+				t.Errorf("got %v uint64 %v, want %v", index, got, want)
+			}
+
+			t.Run("overwrite", func(t *testing.T) {
+				batch := new(leveldb.Batch)
+				var want uint64 = 85 + index
+				bins.PutInBatch(batch, index, want)
+				err = db.WriteBatch(batch)
+				if err != nil {
+					t.Fatal(err)
+				}
+				got, err := bins.Get(index)
+				if err != nil {
+					t.Fatal(err)
+				}
+				if got != want {
+					t.Errorf("got %v uint64 %v, want %v", index, got, want)
+				}
+			})
+		}
+	})
+}
+
+// TestUint64Vector_Inc validates Inc operation
+// of the Uint64Vector.
+func TestUint64Vector_Inc(t *testing.T) {
+	db, cleanupFunc := newTestDB(t)
+	defer cleanupFunc()
+
+	bins, err := db.NewUint64Vector("bins")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, index := range []uint64{0, 1, 2, 3, 5, 10} {
+		var want uint64 = 1
+		got, err := bins.Inc(index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got %v uint64 %v, want %v", index, got, want)
+		}
+
+		want = 2
+		got, err = bins.Inc(index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got %v uint64 %v, want %v", index, got, want)
+		}
+	}
+}
+
+// TestUint64Vector_IncInBatch validates IncInBatch operation
+// of the Uint64Vector.
+func TestUint64Vector_IncInBatch(t *testing.T) {
+	db, cleanupFunc := newTestDB(t)
+	defer cleanupFunc()
+
+	bins, err := db.NewUint64Vector("bins")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, index := range []uint64{0, 1, 2, 3, 5, 10} {
+		batch := new(leveldb.Batch)
+		var want uint64 = 1
+		got, err := bins.IncInBatch(batch, index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got %v uint64 %v, want %v", index, got, want)
+		}
+		err = db.WriteBatch(batch)
+		if err != nil {
+			t.Fatal(err)
+		}
+		got, err = bins.Get(index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got %v uint64 %v, want %v", index, got, want)
+		}
+
+		batch2 := new(leveldb.Batch)
+		want = 2
+		got, err = bins.IncInBatch(batch2, index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got %v uint64 %v, want %v", index, got, want)
+		}
+		err = db.WriteBatch(batch2)
+		if err != nil {
+			t.Fatal(err)
+		}
+		got, err = bins.Get(index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got %v uint64 %v, want %v", index, got, want)
+		}
+	}
+}
+
+// TestUint64Vector_Dec validates Dec operation
+// of the Uint64Vector.
+func TestUint64Vector_Dec(t *testing.T) {
+	db, cleanupFunc := newTestDB(t)
+	defer cleanupFunc()
+
+	bins, err := db.NewUint64Vector("bins")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, index := range []uint64{0, 1, 2, 3, 5, 10} {
+		// test overflow protection
+		var want uint64
+		got, err := bins.Dec(index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got %v uint64 %v, want %v", index, got, want)
+		}
+
+		want = 32 + index
+		err = bins.Put(index, want)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		want = 31 + index
+		got, err = bins.Dec(index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got %v uint64 %v, want %v", index, got, want)
+		}
+	}
+}
+
+// TestUint64Vector_DecInBatch validates DecInBatch operation
+// of the Uint64Vector.
+func TestUint64Vector_DecInBatch(t *testing.T) {
+	db, cleanupFunc := newTestDB(t)
+	defer cleanupFunc()
+
+	bins, err := db.NewUint64Vector("bins")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, index := range []uint64{0, 1, 2, 3, 5, 10} {
+		batch := new(leveldb.Batch)
+		var want uint64
+		got, err := bins.DecInBatch(batch, index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got %v uint64 %v, want %v", index, got, want)
+		}
+		err = db.WriteBatch(batch)
+		if err != nil {
+			t.Fatal(err)
+		}
+		got, err = bins.Get(index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got %v uint64 %v, want %v", index, got, want)
+		}
+
+		batch2 := new(leveldb.Batch)
+		want = 42 + index
+		bins.PutInBatch(batch2, index, want)
+		err = db.WriteBatch(batch2)
+		if err != nil {
+			t.Fatal(err)
+		}
+		got, err = bins.Get(index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got %v uint64 %v, want %v", index, got, want)
+		}
+
+		batch3 := new(leveldb.Batch)
+		want = 41 + index
+		got, err = bins.DecInBatch(batch3, index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got %v uint64 %v, want %v", index, got, want)
+		}
+		err = db.WriteBatch(batch3)
+		if err != nil {
+			t.Fatal(err)
+		}
+		got, err = bins.Get(index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != want {
+			t.Errorf("got %v uint64 %v, want %v", index, got, want)
+		}
+	}
+}