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Diffstat (limited to 'vendor/github.com/syndtr/goleveldb/leveldb/iterator/iter.go')
| -rw-r--r-- | vendor/github.com/syndtr/goleveldb/leveldb/iterator/iter.go | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/iterator/iter.go b/vendor/github.com/syndtr/goleveldb/leveldb/iterator/iter.go new file mode 100644 index 0000000..b16e3a7 --- /dev/null +++ b/vendor/github.com/syndtr/goleveldb/leveldb/iterator/iter.go @@ -0,0 +1,132 @@ +// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com> +// All rights reserved. +// +// Use of this source code is governed by a BSD-style license that can be +// found in the LICENSE file. + +// Package iterator provides interface and implementation to traverse over +// contents of a database. +package iterator + +import ( + "errors" + + "github.com/syndtr/goleveldb/leveldb/util" +) + +var ( + ErrIterReleased = errors.New("leveldb/iterator: iterator released") +) + +// IteratorSeeker is the interface that wraps the 'seeks method'. +type IteratorSeeker interface { + // First moves the iterator to the first key/value pair. If the iterator + // only contains one key/value pair then First and Last would moves + // to the same key/value pair. + // It returns whether such pair exist. + First() bool + + // Last moves the iterator to the last key/value pair. If the iterator + // only contains one key/value pair then First and Last would moves + // to the same key/value pair. + // It returns whether such pair exist. + Last() bool + + // Seek moves the iterator to the first key/value pair whose key is greater + // than or equal to the given key. + // It returns whether such pair exist. + // + // It is safe to modify the contents of the argument after Seek returns. + Seek(key []byte) bool + + // Next moves the iterator to the next key/value pair. + // It returns whether the iterator is exhausted. + Next() bool + + // Prev moves the iterator to the previous key/value pair. + // It returns whether the iterator is exhausted. + Prev() bool +} + +// CommonIterator is the interface that wraps common iterator methods. +type CommonIterator interface { + IteratorSeeker + + // util.Releaser is the interface that wraps basic Release method. + // When called Release will releases any resources associated with the + // iterator. + util.Releaser + + // util.ReleaseSetter is the interface that wraps the basic SetReleaser + // method. + util.ReleaseSetter + + // TODO: Remove this when ready. + Valid() bool + + // Error returns any accumulated error. Exhausting all the key/value pairs + // is not considered to be an error. + Error() error +} + +// Iterator iterates over a DB's key/value pairs in key order. +// +// When encounter an error any 'seeks method' 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. +// Also, an iterator is not necessarily safe for concurrent use, but it is +// safe to use multiple iterators concurrently, with each in a dedicated +// goroutine. +type Iterator interface { + CommonIterator + + // 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 any 'seeks method'. + 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 any 'seeks method'. + Value() []byte +} + +// ErrorCallbackSetter is the interface that wraps basic SetErrorCallback +// method. +// +// ErrorCallbackSetter implemented by indexed and merged iterator. +type ErrorCallbackSetter interface { + // SetErrorCallback allows set an error callback of the corresponding + // iterator. Use nil to clear the callback. + SetErrorCallback(f func(err error)) +} + +type emptyIterator struct { + util.BasicReleaser + err error +} + +func (i *emptyIterator) rErr() { + if i.err == nil && i.Released() { + i.err = ErrIterReleased + } +} + +func (*emptyIterator) Valid() bool { return false } +func (i *emptyIterator) First() bool { i.rErr(); return false } +func (i *emptyIterator) Last() bool { i.rErr(); return false } +func (i *emptyIterator) Seek(key []byte) bool { i.rErr(); return false } +func (i *emptyIterator) Next() bool { i.rErr(); return false } +func (i *emptyIterator) Prev() bool { i.rErr(); return false } +func (*emptyIterator) Key() []byte { return nil } +func (*emptyIterator) Value() []byte { return nil } +func (i *emptyIterator) Error() error { return i.err } + +// NewEmptyIterator creates an empty iterator. The err parameter can be +// nil, but if not nil the given err will be returned by Error method. +func NewEmptyIterator(err error) Iterator { + return &emptyIterator{err: err} +} |