147 lines
4.0 KiB
Go
147 lines
4.0 KiB
Go
// 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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// Uint64Vector provides a way to have multiple counters in the database.
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// It transparently encodes uint64 type value to bytes.
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type Uint64Vector struct {
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db *DB
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key []byte
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}
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// NewUint64Vector returns a new Uint64Vector.
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// It validates its name and type against the database schema.
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func (db *DB) NewUint64Vector(name string) (f Uint64Vector, err error) {
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key, err := db.schemaFieldKey(name, "vector-uint64")
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if err != nil {
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return f, err
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}
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return Uint64Vector{
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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 at index i 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 Uint64Vector) Get(i uint64) (val uint64, err error) {
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b, err := f.db.Get(f.indexKey(i))
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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 Uint64Vector) Put(i, val uint64) (err error) {
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return f.db.Put(f.indexKey(i), encodeUint64(val))
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}
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// PutInBatch stores a uint64 value at index i in a batch
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// that can be saved later in the database.
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func (f Uint64Vector) PutInBatch(batch *leveldb.Batch, i, val uint64) {
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batch.Put(f.indexKey(i), 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 safe.
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func (f Uint64Vector) Inc(i uint64) (val uint64, err error) {
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val, err = f.Get(i)
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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(i, val)
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}
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// IncInBatch increments a uint64 value at index i 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 safe.
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func (f Uint64Vector) IncInBatch(batch *leveldb.Batch, i uint64) (val uint64, err error) {
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val, err = f.Get(i)
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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, i, val)
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return val, nil
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}
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// Dec decrements a uint64 value at index i in the database.
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// This operation is not goroutine safe.
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// The field is protected from overflow to a negative value.
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func (f Uint64Vector) Dec(i uint64) (val uint64, err error) {
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val, err = f.Get(i)
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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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if val != 0 {
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val--
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}
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return val, f.Put(i, val)
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}
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// DecInBatch decrements a uint64 value at index i 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 safe.
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// The field is protected from overflow to a negative value.
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func (f Uint64Vector) DecInBatch(batch *leveldb.Batch, i uint64) (val uint64, err error) {
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val, err = f.Get(i)
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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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if val != 0 {
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val--
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}
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f.PutInBatch(batch, i, val)
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return val, nil
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}
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// indexKey concatenates field prefix and vector index
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// returning a unique database key for a specific vector element.
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func (f Uint64Vector) indexKey(i uint64) (key []byte) {
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b := make([]byte, 8)
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binary.BigEndian.PutUint64(b, i)
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return append(f.key, b...)
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}
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