seaweedfs/weed/storage/idx/walk.go

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package idx
import (
"io"
"os"
"github.com/chrislusf/seaweedfs/weed/glog"
"github.com/chrislusf/seaweedfs/weed/storage/types"
"github.com/chrislusf/seaweedfs/weed/util"
)
// walks through the index file, calls fn function with each key, offset, size
// stops with the error returned by the fn function
func WalkIndexFile(r *os.File, fn func(key types.NeedleId, offset types.Offset, size uint32) error) error {
var readerOffset int64
bytes := make([]byte, types.NeedleMapEntrySize*RowsToRead)
count, e := r.ReadAt(bytes, readerOffset)
glog.V(3).Infoln("file", r.Name(), "readerOffset", readerOffset, "count", count, "e", e)
readerOffset += int64(count)
var (
key types.NeedleId
offset types.Offset
size uint32
i int
)
for count > 0 && e == nil || e == io.EOF {
for i = 0; i+types.NeedleMapEntrySize <= count; i += types.NeedleMapEntrySize {
key, offset, size = IdxFileEntry(bytes[i : i+types.NeedleMapEntrySize])
if e = fn(key, offset, size); e != nil {
return e
}
}
if e == io.EOF {
return nil
}
count, e = r.ReadAt(bytes, readerOffset)
glog.V(3).Infoln("file", r.Name(), "readerOffset", readerOffset, "count", count, "e", e)
readerOffset += int64(count)
}
return e
}
func IdxFileEntry(bytes []byte) (key types.NeedleId, offset types.Offset, size uint32) {
key = types.BytesToNeedleId(bytes[:types.NeedleIdSize])
offset = types.BytesToOffset(bytes[types.NeedleIdSize : types.NeedleIdSize+types.OffsetSize])
size = util.BytesToUint32(bytes[types.NeedleIdSize+types.OffsetSize : types.NeedleIdSize+types.OffsetSize+types.SizeSize])
return
}
const (
RowsToRead = 1024
)