81faf57356
This introduces a UtxoBackendIterator interface, which represents an iterator over the key/value pairs in a UtxoBackend in key order. This is part of updating the UtxoBackend to use leveldb directly.
64 lines
2.4 KiB
Go
64 lines
2.4 KiB
Go
// Copyright (c) 2021 The Decred developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package blockchain
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// UtxoBackendIterator represents an iterator over the key/value pairs in a
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// UtxoBackend in key order.
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//
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// When an error is encountered, any iteration method will return false and will
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// yield no key/value pair. The error can be queried by calling the Error
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// method.
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//
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// Release must always be called on the iterator after use whether an error
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// occurred or not.
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//
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// The interface contract does NOT require that these methods are safe for
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// concurrent access.
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type UtxoBackendIterator interface {
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// First moves the iterator to the first key/value pair. If the iterator only
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// contains one key/value pair then First and Last would move to the same
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// key/value pair. It returns whether the pair that is moved to exists.
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First() bool
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// Last moves the iterator to the last key/value pair. If the iterator only
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// contains one key/value pair then First and Last would move to the same
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// key/value pair. It returns whether the pair that is moved to exists.
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Last() bool
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// Seek moves the iterator to the first key/value pair whose key is greater
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// than or equal to the given key. It returns whether the pair that is moved
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// to exists.
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//
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// It is safe to modify the contents of the argument after Seek returns.
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Seek(key []byte) bool
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// Next moves the iterator to the next key/value pair. It returns false if
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// the iterator is exhausted.
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Next() bool
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// Prev moves the iterator to the previous key/value pair. It returns false
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// if the iterator is exhausted.
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Prev() bool
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// Error returns any accumulated error. Exhausting all of the key/value pairs
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// is not considered to be an error.
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Error() error
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// Key returns the key of the current key/value pair, or nil if done. The
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// caller should not modify the contents of the returned slice, and its
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// contents may change on the next call to any iteration method.
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Key() []byte
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// Value returns the value of the current key/value pair, or nil if done. The
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// caller should not modify the contents of the returned slice, and its
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// contents may change on the next call to any iteration method.
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Value() []byte
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// Release releases the iterator. An iterator must always be released after
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// use, but it is not necessary to read an iterator until exhaustion before
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// releasing it.
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Release()
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}
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