minio/cmd/storage-interface.go

/*
 * MinIO Cloud Storage, (C) 2016 MinIO, Inc.
 *
 * 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 cmd

import (
	"context"
	"io"
)

// StorageAPI interface.
type StorageAPI interface {
	// Stringified version of disk.
	String() string

	// Storage operations.
	IsOnline() bool // Returns true if disk is online.
	IsLocal() bool

	Hostname() string // Returns host name if remote host.
	Close() error
	GetDiskID() (string, error)
	SetDiskID(id string)

	DiskInfo() (info DiskInfo, err error)
	CrawlAndGetDataUsage(ctx context.Context, cache dataUsageCache) (dataUsageCache, error)

	// Volume operations.
	MakeVol(volume string) (err error)
	MakeVolBulk(volumes ...string) (err error)
	ListVols() (vols []VolInfo, err error)
	StatVol(volume string) (vol VolInfo, err error)
	DeleteVol(volume string, forceDelete bool) (err error)

	// WalkVersions in sorted order directly on disk.
	WalkVersions(volume, dirPath string, marker string, recursive bool, endWalkCh <-chan struct{}) (chan FileInfoVersions, error)
	// Walk in sorted order directly on disk.
	Walk(volume, dirPath string, marker string, recursive bool, endWalkCh <-chan struct{}) (chan FileInfo, error)
	// Walk in sorted order directly on disk.
	WalkSplunk(volume, dirPath string, marker string, endWalkCh <-chan struct{}) (chan FileInfo, error)

	// Metadata operations
	DeleteVersion(volume, path string, fi FileInfo) error
	DeleteVersions(volume string, versions []FileInfo) []error
	WriteMetadata(volume, path string, fi FileInfo) error
	ReadVersion(volume, path, versionID string) (FileInfo, error)
	RenameData(srcVolume, srcPath, dataDir, dstVolume, dstPath string) error

	// File operations.
	ListDir(volume, dirPath string, count int) ([]string, error)
	ReadFile(volume string, path string, offset int64, buf []byte, verifier *BitrotVerifier) (n int64, err error)
	AppendFile(volume string, path string, buf []byte) (err error)
	CreateFile(volume, path string, size int64, reader io.Reader) error
	ReadFileStream(volume, path string, offset, length int64) (io.ReadCloser, error)
	RenameFile(srcVolume, srcPath, dstVolume, dstPath string) error
	CheckParts(volume string, path string, fi FileInfo) error
	CheckFile(volume string, path string) (err error)
	DeleteFile(volume string, path string) (err error)
	VerifyFile(volume, path string, fi FileInfo) error

	// Write all data, syncs the data to disk.
	WriteAll(volume string, path string, reader io.Reader) (err error)

	// Read all.
	ReadAll(volume string, path string) (buf []byte, err error)
}

// storageReader is an io.Reader view of a disk
type storageReader struct {
	storage      StorageAPI
	volume, path string
	offset       int64
}

func (r *storageReader) Read(p []byte) (n int, err error) {
	nn, err := r.storage.ReadFile(r.volume, r.path, r.offset, p, nil)
	r.offset += nn
	n = int(nn)

	if err == io.ErrUnexpectedEOF && nn > 0 {
		err = io.EOF
	}
	return
}

// storageWriter is a io.Writer view of a disk.
type storageWriter struct {
	storage      StorageAPI
	volume, path string
}

func (w *storageWriter) Write(p []byte) (n int, err error) {
	err = w.storage.AppendFile(w.volume, w.path, p)
	if err == nil {
		n = len(p)
	}
	return
}

// StorageWriter returns a new io.Writer which appends data to the file
// at the given disk, volume and path.
func StorageWriter(storage StorageAPI, volume, path string) io.Writer {
	return &storageWriter{storage, volume, path}
}

// StorageReader returns a new io.Reader which reads data to the file
// at the given disk, volume, path and offset.
func StorageReader(storage StorageAPI, volume, path string, offset int64) io.Reader {
	return &storageReader{storage, volume, path, offset}
}