seaweedfs/weed/storage/volume_stream_write.go

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package storage
import (
"bufio"
"fmt"
"github.com/chrislusf/seaweedfs/weed/util"
"io"
"time"
"github.com/chrislusf/seaweedfs/weed/glog"
"github.com/chrislusf/seaweedfs/weed/storage/backend"
"github.com/chrislusf/seaweedfs/weed/storage/needle"
. "github.com/chrislusf/seaweedfs/weed/storage/types"
)
func (v *Volume) StreamWrite(n *needle.Needle, data io.Reader, dataSize uint32) (err error) {
v.dataFileAccessLock.Lock()
defer v.dataFileAccessLock.Unlock()
df, ok := v.DataBackend.(*backend.DiskFile)
if !ok {
return fmt.Errorf("unexpected volume backend")
}
offset, _, _ := v.DataBackend.GetStat()
header := make([]byte, NeedleHeaderSize+TimestampSize) // adding timestamp to reuse it and avoid extra allocation
CookieToBytes(header[0:CookieSize], n.Cookie)
NeedleIdToBytes(header[CookieSize:CookieSize+NeedleIdSize], n.Id)
n.Size = 4 + Size(dataSize) + 1
SizeToBytes(header[CookieSize+NeedleIdSize:CookieSize+NeedleIdSize+SizeSize], n.Size)
n.DataSize = dataSize
// needle header
df.Write(header[0:NeedleHeaderSize])
// data size and data
util.Uint32toBytes(header[0:4], n.DataSize)
df.Write(header[0:4])
// write and calculate CRC
crcWriter := needle.NewCRCwriter(df)
io.Copy(crcWriter, io.LimitReader(data, int64(dataSize)))
// flags
util.Uint8toBytes(header[0:1], n.Flags)
df.Write(header[0:1])
// data checksum
util.Uint32toBytes(header[0:needle.NeedleChecksumSize], crcWriter.Sum())
// write timestamp, padding
n.AppendAtNs = uint64(time.Now().UnixNano())
util.Uint64toBytes(header[needle.NeedleChecksumSize:needle.NeedleChecksumSize+TimestampSize], n.AppendAtNs)
padding := needle.PaddingLength(n.Size, needle.Version3)
df.Write(header[0 : needle.NeedleChecksumSize+TimestampSize+padding])
// add to needle map
if err = v.nm.Put(n.Id, ToOffset(int64(offset)), n.Size); err != nil {
glog.V(4).Infof("failed to save in needle map %d: %v", n.Id, err)
}
return
}
func (v *Volume) StreamRead(n *needle.Needle, writer io.Writer) (err error) {
v.dataFileAccessLock.Lock()
defer v.dataFileAccessLock.Unlock()
nv, ok := v.nm.Get(n.Id)
if !ok || nv.Offset.IsZero() {
return ErrorNotFound
}
sr := &StreamReader{
readerAt: v.DataBackend,
offset: nv.Offset.ToActualOffset(),
}
bufReader := bufio.NewReader(sr)
bufReader.Discard(NeedleHeaderSize)
sizeBuf := make([]byte, 4)
bufReader.Read(sizeBuf)
if _, err = writer.Write(sizeBuf); err != nil {
return err
}
dataSize := util.BytesToUint32(sizeBuf)
_, err = io.Copy(writer, io.LimitReader(bufReader, int64(dataSize)))
return
}
type StreamReader struct {
offset int64
readerAt io.ReaderAt
}
func (sr *StreamReader) Read(p []byte) (n int, err error) {
n, err = sr.readerAt.ReadAt(p, sr.offset)
if err != nil {
return
}
sr.offset += int64(n)
return
}