storj/storage/filestore/blob.go

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// Copyright (C) 2019 Storj Labs, Inc.
// See LICENSE for copying information.
package filestore
import (
"bufio"
"context"
"io"
"os"
"github.com/zeebo/errs"
"storj.io/storj/storage"
)
const (
// FormatV0 is the identifier for storage format v0, which also corresponds to an absence of
// format version information.
FormatV0 storage.FormatVersion = 0
// FormatV1 is the identifier for storage format v1
FormatV1 storage.FormatVersion = 1
// Note: New FormatVersion values should be consecutive, as certain parts of this blob store
// iterate over them numerically and check for blobs stored with each version.
)
const (
// MaxFormatVersionSupported is the highest supported storage format version for reading, and
// the only supported storage format version for writing. If stored blobs claim a higher
// storage format version than this, or a caller requests _writing_ a storage format version
// which is not this, this software will not know how to perform the read or write and an error
// will be returned.
MaxFormatVersionSupported = FormatV1
// MinFormatVersionSupported is the lowest supported storage format version for reading. If
// stored blobs claim a lower storage format version than this, this software will not know how
// to perform the read and an error will be returned.
MinFormatVersionSupported = FormatV0
)
// blobReader implements reading blobs
type blobReader struct {
*os.File
formatVersion storage.FormatVersion
}
func newBlobReader(file *os.File, formatVersion storage.FormatVersion) *blobReader {
return &blobReader{file, formatVersion}
}
// Size returns how large is the blob.
func (blob *blobReader) Size() (int64, error) {
stat, err := blob.Stat()
if err != nil {
return 0, err
}
return stat.Size(), err
}
// StorageFormatVersion gets the storage format version being used by the blob.
func (blob *blobReader) StorageFormatVersion() storage.FormatVersion {
return blob.formatVersion
}
// blobWriter implements writing blobs
type blobWriter struct {
ref storage.BlobRef
store *blobStore
closed bool
formatVersion storage.FormatVersion
buffer *bufio.Writer
fh *os.File
}
func newBlobWriter(ref storage.BlobRef, store *blobStore, formatVersion storage.FormatVersion, file *os.File, bufferSize int) *blobWriter {
return &blobWriter{
ref: ref,
store: store,
closed: false,
formatVersion: formatVersion,
buffer: bufio.NewWriterSize(file, bufferSize),
fh: file,
}
}
// Write adds data to the blob.
func (blob *blobWriter) Write(p []byte) (int, error) {
return blob.buffer.Write(p)
}
// Cancel discards the blob.
func (blob *blobWriter) Cancel(ctx context.Context) (err error) {
defer mon.Task()(&ctx)(&err)
if blob.closed {
return nil
}
blob.closed = true
err = blob.fh.Close()
removeErr := os.Remove(blob.fh.Name())
return Error.Wrap(errs.Combine(err, removeErr))
}
// Commit moves the file to the target location.
func (blob *blobWriter) Commit(ctx context.Context) (err error) {
defer mon.Task()(&ctx)(&err)
if blob.closed {
return Error.New("already closed")
}
blob.closed = true
if err := blob.buffer.Flush(); err != nil {
return err
}
err = blob.store.dir.Commit(ctx, blob.fh, blob.ref, blob.formatVersion)
return Error.Wrap(err)
}
// Seek flushes any buffer and seeks the underlying file.
func (blob *blobWriter) Seek(offset int64, whence int) (int64, error) {
if err := blob.buffer.Flush(); err != nil {
return 0, err
}
return blob.fh.Seek(offset, whence)
}
// Size returns how much has been written so far.
func (blob *blobWriter) Size() (int64, error) {
pos, err := blob.Seek(0, io.SeekCurrent)
if err != nil {
return 0, err
}
return pos, err
}
// StorageFormatVersion indicates what storage format version the blob is using.
func (blob *blobWriter) StorageFormatVersion() storage.FormatVersion {
return blob.formatVersion
}