github.com/pranksteess/go-ethereum@v1.9.7/ethdb/iterator.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 ethdb 18 19 // Iterator iterates over a database's key/value pairs in ascending key order. 20 // 21 // When it encounters an error any seek will return false and will yield no key/ 22 // value pairs. The error can be queried by calling the Error method. Calling 23 // Release is still necessary. 24 // 25 // An iterator must be released after use, but it is not necessary to read an 26 // iterator until exhaustion. An iterator is not safe for concurrent use, but it 27 // is safe to use multiple iterators concurrently. 28 type Iterator interface { 29 // Next moves the iterator to the next key/value pair. It returns whether the 30 // iterator is exhausted. 31 Next() bool 32 33 // Error returns any accumulated error. Exhausting all the key/value pairs 34 // is not considered to be an error. 35 Error() error 36 37 // Key returns the key of the current key/value pair, or nil if done. The caller 38 // should not modify the contents of the returned slice, and its contents may 39 // change on the next call to Next. 40 Key() []byte 41 42 // Value returns the value of the current key/value pair, or nil if done. The 43 // caller should not modify the contents of the returned slice, and its contents 44 // may change on the next call to Next. 45 Value() []byte 46 47 // Release releases associated resources. Release should always succeed and can 48 // be called multiple times without causing error. 49 Release() 50 } 51 52 // Iteratee wraps the NewIterator methods of a backing data store. 53 type Iteratee interface { 54 // NewIterator creates a binary-alphabetical iterator over the entire keyspace 55 // contained within the key-value database. 56 NewIterator() Iterator 57 58 // NewIteratorWithStart creates a binary-alphabetical iterator over a subset of 59 // database content starting at a particular initial key (or after, if it does 60 // not exist). 61 NewIteratorWithStart(start []byte) Iterator 62 63 // NewIteratorWithPrefix creates a binary-alphabetical iterator over a subset 64 // of database content with a particular key prefix. 65 NewIteratorWithPrefix(prefix []byte) Iterator 66 }