syncthing/vendor/github.com/syndtr/goleveldb/leveldb/iterator/iter.go
Jakob Borg 65aaa607ab Use Go 1.5 vendoring instead of Godeps
Change made by:

- running "gvt fetch" on each of the packages mentioned in
  Godeps/Godeps.json
- `rm -rf Godeps`
- tweaking the build scripts to not mention Godeps
- tweaking the build scripts to test `./lib/...`, `./cmd/...` explicitly
  (to avoid testing vendor)
- tweaking the build scripts to not juggle GOPATH for Godeps and instead
  set GO15VENDOREXPERIMENT.

This also results in some updated packages at the same time I bet.

Building with Go 1.3 and 1.4 still *works* but won't use our vendored
dependencies - the user needs to have the actual packages in their
GOPATH then, which they'll get with a normal "go get". Building with Go
1.6+ will get our vendored dependencies by default even when not using
our build script, which is nice.

By doing this we gain some freedom in that we can pick and choose
manually what to include in vendor, as it's not based on just dependency
analysis of our own code. This is also a risk as we might pick up
dependencies we are unaware of, as the build may work locally with those
packages present in GOPATH. On the other hand the build server will
detect this as it has no packages in it's GOPATH beyond what is included
in the repo.

Recommended tool to manage dependencies is github.com/FiloSottile/gvt.
2016-03-05 21:21:24 +01:00

132 lines
4.4 KiB
Go

// 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 whould 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 whould 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 interator 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 encouter 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 goroutine-safe, 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 coresponding
// 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}
}