github.com/dotlike13/wemix30_go@v1.8.23/swarm/shed/field_string.go (about)

     1  // Copyright 2018 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package shed
    18  
    19  import (
    20  	"github.com/syndtr/goleveldb/leveldb"
    21  )
    22  
    23  // StringField is the most simple field implementation
    24  // that stores an arbitrary string under a specific LevelDB key.
    25  type StringField struct {
    26  	db  *DB
    27  	key []byte
    28  }
    29  
    30  // NewStringField retruns a new Instance of StringField.
    31  // It validates its name and type against the database schema.
    32  func (db *DB) NewStringField(name string) (f StringField, err error) {
    33  	key, err := db.schemaFieldKey(name, "string")
    34  	if err != nil {
    35  		return f, err
    36  	}
    37  	return StringField{
    38  		db:  db,
    39  		key: key,
    40  	}, nil
    41  }
    42  
    43  // Get returns a string value from database.
    44  // If the value is not found, an empty string is returned
    45  // an no error.
    46  func (f StringField) Get() (val string, err error) {
    47  	b, err := f.db.Get(f.key)
    48  	if err != nil {
    49  		if err == leveldb.ErrNotFound {
    50  			return "", nil
    51  		}
    52  		return "", err
    53  	}
    54  	return string(b), nil
    55  }
    56  
    57  // Put stores a string in the database.
    58  func (f StringField) Put(val string) (err error) {
    59  	return f.db.Put(f.key, []byte(val))
    60  }
    61  
    62  // PutInBatch stores a string in a batch that can be
    63  // saved later in database.
    64  func (f StringField) PutInBatch(batch *leveldb.Batch, val string) {
    65  	batch.Put(f.key, []byte(val))
    66  }