all: clean up and proerly abstract database access

1 files changed, 61 insertions, 0 deletions

diff --git a/ethdb/iterator.go b/ethdb/iterator.go
new file mode 100644
index 000000000..f3cee7ec9
--- /dev/null
+++ b/ethdb/iterator.go
@@ -0,0 +1,61 @@
+// Copyright 2018 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package ethdb
+
+// Iterator iterates over a database's key/value pairs in ascending key order.
+//
+// When it encounters an error any seek will return false and will yield no key/
+// value pairs. The error can be queried by calling the Error method. Calling
+// Release is still necessary.
+//
+// An iterator must be released after use, but it is not necessary to read an
+// iterator until exhaustion. An iterator is not safe for concurrent use, but it
+// is safe to use multiple iterators concurrently.
+type Iterator interface {
+	// Next moves the iterator to the next key/value pair. It returns whether the
+	// iterator is exhausted.
+	Next() bool
+
+	// Error returns any accumulated error. Exhausting all the key/value pairs
+	// is not considered to be an error.
+	Error() error
+
+	// Key returns the key of the current key/value pair, or nil if done. The caller
+	// should not modify the contents of the returned slice, and its contents may
+	// change on the next call to Next.
+	Key() []byte
+
+	// Value returns the value of the current key/value pair, or nil if done. The
+	// caller should not modify the contents of the returned slice, and its contents
+	// may change on the next call to Next.
+	Value() []byte
+
+	// Release releases associated resources. Release should always succeed and can
+	// be called multiple times without causing error.
+	Release()
+}
+
+// Iteratee wraps the NewIterator methods of a backing data store.
+type Iteratee interface {
+	// NewIterator creates a binary-alphabetical iterator over the entire keyspace
+	// contained within the key-value database.
+	NewIterator() Iterator
+
+	// NewIteratorWithPrefix creates a binary-alphabetical iterator over a subset
+	// of database content with a particular key prefix.
+	NewIteratorWithPrefix(prefix []byte) Iterator
+}