// Scan scan a block file.
func (b *SuperBlock) Scan(r *os.File, offset uint32, fn func(*needle.Needle, uint32, uint32) error) (err error) {
var (
so, eo uint32
bso int64
fi os.FileInfo
fd = r.Fd()
n = new(needle.Needle)
rd = bufio.NewReaderSize(r, b.conf.Block.BufferSize)
)
if offset == 0 {
offset = needle.NeedleOffset(_headerOffset)
}
so, eo = offset, offset
bso = needle.BlockOffset(so)
// advise sequential read
if fi, err = r.Stat(); err != nil {
log.Errorf("block: %s Stat() error(%v)", b.File)
return
}
if err = myos.Fadvise(fd, bso, fi.Size(), myos.POSIX_FADV_SEQUENTIAL); err != nil {
log.Errorf("block: %s Fadvise() error(%v)", b.File)
return
}
log.Infof("scan block: %s from offset: %d", b.File, offset)
if _, err = r.Seek(bso, os.SEEK_SET); err != nil {
log.Errorf("block: %s Seek() error(%v)", b.File)
return
}
for {
if err = n.ParseFrom(rd); err != nil {
if err != io.EOF {
log.Errorf("block: parse needle from offset: %d:%d error(%v)", so, eo, err)
}
break
}
if n.TotalSize > int32(b.conf.BlockMaxSize) {
log.Errorf("scan block: %s error(%v)", n, errors.ErrNeedleSize)
err = errors.ErrNeedleSize
break
}
if log.V(1) {
log.Info(n.String())
}
eo += n.IncrOffset
if err = fn(n, so, eo); err != nil {
log.Errorf("block: callback from offset: %d:%d error(%v)", so, eo, err)
break
}
so = eo
}
if err == io.EOF {
// advise no need page cache
if err = myos.Fadvise(fd, bso, needle.BlockOffset(eo-so), myos.POSIX_FADV_DONTNEED); err != nil {
log.Errorf("block: %s Fadvise() error(%v)", b.File)
return
}
log.Infof("scan block: %s to offset: %d [ok]", b.File, eo)
err = nil
} else {
log.Infof("scan block: %s to offset: %d error(%v) [failed]", b.File, eo, err)
}
return
}
