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backend.go
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backend.go
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// Copyright 2023 The glassdb Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package backend
import (
"context"
"errors"
)
var (
ErrNotFound = errors.New("object not found")
ErrPrecondition = errors.New("precondition failed")
ErrEOF = errors.New("end of file")
)
type Backend interface {
ReadIfModified(ctx context.Context, path string, version int64) (ReadReply, error)
Read(ctx context.Context, path string) (ReadReply, error)
GetMetadata(ctx context.Context, path string) (Metadata, error)
SetTagsIf(ctx context.Context, path string, expected Version, t Tags) (Metadata, error)
Write(ctx context.Context, path string, value []byte, t Tags) (Metadata, error)
WriteIf(ctx context.Context, path string, value []byte, expected Version, t Tags) (Metadata, error)
WriteIfNotExists(ctx context.Context, path string, value []byte, t Tags) (Metadata, error)
Delete(ctx context.Context, path string) error
DeleteIf(ctx context.Context, path string, expected Version) error
// List returns an iterator over the objects in the bucket within the given
// directory (path separator is '/'). Objects will be iterated over
// lexicographically by name.
//
// Note: The returned iterator is not safe for concurrent operations without
// explicit synchronization.
List(ctx context.Context, dirPath string) (ListIter, error)
}
type ListIter interface {
Next() (path string, ok bool)
Err() error
}
type ReadReply struct {
Contents []byte
// TODO: Consider only exposing contents version.
Version Version
}
type Tags map[string]string
type Metadata struct {
Tags Tags
Version Version
}
type Version struct {
Contents int64
Meta int64
}
func (v Version) IsNull() bool {
return v.Contents == 0
}