storj/uplink/stream/download.go
Egon Elbre 6615ecc9b6 common: separate repository
Change-Id: Ibb89c42060450e3839481a7e495bbe3ad940610a
2019-12-27 14:11:15 +02:00

119 lines
2.6 KiB
Go

// Copyright (C) 2019 Storj Labs, Inc.
// See LICENSE for copying information.
package stream
import (
"context"
"io"
"storj.io/common/storj"
"storj.io/storj/uplink/metainfo/kvmetainfo"
"storj.io/storj/uplink/storage/streams"
)
// Download implements Reader, Seeker and Closer for reading from stream.
type Download struct {
ctx context.Context
stream kvmetainfo.ReadOnlyStream
streams streams.Store
reader io.ReadCloser
offset int64
limit int64
closed bool
}
// NewDownload creates new stream download.
func NewDownload(ctx context.Context, stream kvmetainfo.ReadOnlyStream, streams streams.Store) *Download {
return &Download{
ctx: ctx,
stream: stream,
streams: streams,
limit: -1,
}
}
// NewDownloadRange creates new stream range download with range from offset to offset+limit.
func NewDownloadRange(ctx context.Context, stream kvmetainfo.ReadOnlyStream, streams streams.Store, offset, limit int64) *Download {
return &Download{
ctx: ctx,
stream: stream,
streams: streams,
offset: offset,
limit: limit,
}
}
// Read reads up to len(data) bytes into data.
//
// If this is the first call it will read from the beginning of the stream.
// Use Seek to change the current offset for the next Read call.
//
// See io.Reader for more details.
func (download *Download) Read(data []byte) (n int, err error) {
if download.closed {
return 0, Error.New("already closed")
}
if download.reader == nil {
err = download.resetReader(download.offset)
if err != nil {
return 0, err
}
}
if download.limit == 0 {
return 0, io.EOF
}
if download.limit > 0 && download.limit < int64(len(data)) {
data = data[:download.limit]
}
n, err = download.reader.Read(data)
if download.limit >= 0 {
download.limit -= int64(n)
}
download.offset += int64(n)
return n, err
}
// Close closes the stream and releases the underlying resources.
func (download *Download) Close() error {
if download.closed {
return Error.New("already closed")
}
download.closed = true
if download.reader == nil {
return nil
}
return download.reader.Close()
}
func (download *Download) resetReader(offset int64) error {
if download.reader != nil {
err := download.reader.Close()
if err != nil {
return err
}
}
obj := download.stream.Info()
rr, err := download.streams.Get(download.ctx, storj.JoinPaths(obj.Bucket.Name, obj.Path), obj, obj.Bucket.PathCipher)
if err != nil {
return err
}
download.reader, err = rr.Range(download.ctx, offset, obj.Size-offset)
if err != nil {
return err
}
download.offset = offset
return nil
}