github.com/jimmyx0x/go-ethereum@v1.10.28/core/rawdb/key_length_iterator.go (about)

     1  // Copyright 2022 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 rawdb
    18  
    19  import "github.com/ethereum/go-ethereum/ethdb"
    20  
    21  // KeyLengthIterator is a wrapper for a database iterator that ensures only key-value pairs
    22  // with a specific key length will be returned.
    23  type KeyLengthIterator struct {
    24  	requiredKeyLength int
    25  	ethdb.Iterator
    26  }
    27  
    28  // NewKeyLengthIterator returns a wrapped version of the iterator that will only return key-value
    29  // pairs where keys with a specific key length will be returned.
    30  func NewKeyLengthIterator(it ethdb.Iterator, keyLen int) ethdb.Iterator {
    31  	return &KeyLengthIterator{
    32  		Iterator:          it,
    33  		requiredKeyLength: keyLen,
    34  	}
    35  }
    36  
    37  func (it *KeyLengthIterator) Next() bool {
    38  	// Return true as soon as a key with the required key length is discovered
    39  	for it.Iterator.Next() {
    40  		if len(it.Iterator.Key()) == it.requiredKeyLength {
    41  			return true
    42  		}
    43  	}
    44  
    45  	// Return false when we exhaust the keys in the underlying iterator.
    46  	return false
    47  }