109 lines
2.9 KiB
Go
109 lines
2.9 KiB
Go
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// Copyright 2018 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package shed
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import (
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"encoding/binary"
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"github.com/syndtr/goleveldb/leveldb"
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)
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// Uint64Field provides a way to have a simple counter in the database.
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// It transparently encodes uint64 type value to bytes.
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type Uint64Field struct {
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db *DB
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key []byte
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}
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// NewUint64Field returns a new Uint64Field.
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// It validates its name and type against the database schema.
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func (db *DB) NewUint64Field(name string) (f Uint64Field, err error) {
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key, err := db.schemaFieldKey(name, "uint64")
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if err != nil {
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return f, err
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}
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return Uint64Field{
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db: db,
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key: key,
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}, nil
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}
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// Get retrieves a uint64 value from the database.
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// If the value is not found in the database a 0 value
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// is returned and no error.
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func (f Uint64Field) Get() (val uint64, err error) {
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b, err := f.db.Get(f.key)
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if err != nil {
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if err == leveldb.ErrNotFound {
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return 0, nil
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}
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return 0, err
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}
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return binary.BigEndian.Uint64(b), nil
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}
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// Put encodes uin64 value and stores it in the database.
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func (f Uint64Field) Put(val uint64) (err error) {
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return f.db.Put(f.key, encodeUint64(val))
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}
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// PutInBatch stores a uint64 value in a batch
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// that can be saved later in the database.
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func (f Uint64Field) PutInBatch(batch *leveldb.Batch, val uint64) {
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batch.Put(f.key, encodeUint64(val))
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}
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// Inc increments a uint64 value in the database.
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// This operation is not goroutine save.
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func (f Uint64Field) Inc() (val uint64, err error) {
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val, err = f.Get()
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if err != nil {
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if err == leveldb.ErrNotFound {
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val = 0
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} else {
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return 0, err
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}
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}
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val++
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return val, f.Put(val)
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}
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// IncInBatch increments a uint64 value in the batch
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// by retreiving a value from the database, not the same batch.
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// This operation is not goroutine save.
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func (f Uint64Field) IncInBatch(batch *leveldb.Batch) (val uint64, err error) {
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val, err = f.Get()
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if err != nil {
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if err == leveldb.ErrNotFound {
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val = 0
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} else {
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return 0, err
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}
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}
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val++
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f.PutInBatch(batch, val)
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return val, nil
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}
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// encode transforms uint64 to 8 byte long
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// slice in big endian encoding.
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func encodeUint64(val uint64) (b []byte) {
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b = make([]byte, 8)
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binary.BigEndian.PutUint64(b, val)
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return b
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}
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