seaweedfs/weed/storage/needle/needle_read_page.go

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package needle
import (
"github.com/seaweedfs/seaweedfs/weed/glog"
"github.com/seaweedfs/seaweedfs/weed/storage/backend"
. "github.com/seaweedfs/seaweedfs/weed/storage/types"
"github.com/seaweedfs/seaweedfs/weed/util"
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"io"
)
// ReadNeedleData uses a needle without n.Data to read the content
// volumeOffset: the offset within the volume
// needleOffset: the offset within the needle Data
func (n *Needle) ReadNeedleData(r backend.BackendStorageFile, volumeOffset int64, data []byte, needleOffset int64) (count int, err error) {
sizeToRead := min(int64(len(data)), int64(n.DataSize)-needleOffset)
if sizeToRead <= 0 {
return 0, io.EOF
}
startOffset := volumeOffset + NeedleHeaderSize + DataSizeSize + needleOffset
count, err = r.ReadAt(data[:sizeToRead], startOffset)
if err != nil {
fileSize, _, _ := r.GetStat()
glog.Errorf("%s read %d %d size %d at offset %d fileSize %d: %v", r.Name(), n.Id, needleOffset, sizeToRead, volumeOffset, fileSize, err)
}
return
}
// ReadNeedleMeta fills all metadata except the n.Data
func (n *Needle) ReadNeedleMeta(r backend.BackendStorageFile, offset int64, size Size, version Version) (err error) {
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bytes := make([]byte, NeedleHeaderSize+DataSizeSize)
count, err := r.ReadAt(bytes, offset)
if count != NeedleHeaderSize+DataSizeSize || err != nil {
return err
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}
n.ParseNeedleHeader(bytes)
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if n.Size != size {
if OffsetSize == 4 && offset < int64(MaxPossibleVolumeSize) {
return ErrorSizeMismatch
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}
}
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n.DataSize = util.BytesToUint32(bytes[NeedleHeaderSize : NeedleHeaderSize+DataSizeSize])
startOffset := offset + NeedleHeaderSize + DataSizeSize + int64(n.DataSize)
dataSize := GetActualSize(size, version)
stopOffset := offset + dataSize
metaSize := stopOffset - startOffset
metaSlice := make([]byte, int(metaSize))
count, err = r.ReadAt(metaSlice, startOffset)
if err != nil && int64(count) == metaSize {
err = nil
}
if err != nil {
return err
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}
var index int
index, err = n.readNeedleDataVersion2NonData(metaSlice)
n.Checksum = CRC(util.BytesToUint32(metaSlice[index : index+NeedleChecksumSize]))
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if version == Version3 {
n.AppendAtNs = util.BytesToUint64(metaSlice[index+NeedleChecksumSize : index+NeedleChecksumSize+TimestampSize])
}
return err
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}
func min(x, y int64) int64 {
if x < y {
return x
}
return y
}