/usr/share/gocode/src/github.com/syndtr/goleveldb/leveldb/iterator/iter.go is in golang-github-syndtr-goleveldb-dev 0.0~git20170725.0.b89cc31-2.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 | // 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 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'.
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}
}
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