swarm: codebase split from go-ethereum (#1405)

shed/field_uint64.go

@@ -0,0 +1,146 @@
+// 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
+}