github.com/MetalBlockchain/subnet-evm@v0.4.9/core/rawdb/key_length_iterator.go (about)

     1  // (c) 2022, Ava Labs, Inc.
     2  //
     3  // This file is a derived work, based on the go-ethereum library whose original
     4  // notices appear below.
     5  //
     6  // It is distributed under a license compatible with the licensing terms of the
     7  // original code from which it is derived.
     8  //
     9  // Much love to the original authors for their work.
    10  // **********
    11  // Copyright 2022 The go-ethereum Authors
    12  // This file is part of the go-ethereum library.
    13  //
    14  // The go-ethereum library is free software: you can redistribute it and/or modify
    15  // it under the terms of the GNU Lesser General Public License as published by
    16  // the Free Software Foundation, either version 3 of the License, or
    17  // (at your option) any later version.
    18  //
    19  // The go-ethereum library is distributed in the hope that it will be useful,
    20  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    21  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    22  // GNU Lesser General Public License for more details.
    23  //
    24  // You should have received a copy of the GNU Lesser General Public License
    25  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    26  
    27  package rawdb
    28  
    29  import "github.com/MetalBlockchain/subnet-evm/ethdb"
    30  
    31  // KeyLengthIterator is a wrapper for a database iterator that ensures only key-value pairs
    32  // with a specific key length will be returned.
    33  type KeyLengthIterator struct {
    34  	requiredKeyLength int
    35  	ethdb.Iterator
    36  }
    37  
    38  // NewKeyLengthIterator returns a wrapped version of the iterator that will only return key-value
    39  // pairs where keys with a specific key length will be returned.
    40  func NewKeyLengthIterator(it ethdb.Iterator, keyLen int) ethdb.Iterator {
    41  	return &KeyLengthIterator{
    42  		Iterator:          it,
    43  		requiredKeyLength: keyLen,
    44  	}
    45  }
    46  
    47  func (it *KeyLengthIterator) Next() bool {
    48  	// Return true as soon as a key with the required key length is discovered
    49  	for it.Iterator.Next() {
    50  		if len(it.Iterator.Key()) == it.requiredKeyLength {
    51  			return true
    52  		}
    53  	}
    54  
    55  	// Return false when we exhaust the keys in the underlying iterator.
    56  	return false
    57  }