Пример #1
0
// Open a varchar structure in the given blockfile with the given offset
// as the control block. This function will confirm that the control
// block is indeed a properly formated control block.
func OpenVarchar(bf *fmap.BlockFile, a uint64) (v *Varchar, err error) {
	v = &Varchar{bf: bf, a: a, blkSize: bf.BlockSize()}
	var ptOff uint64
	var szOff uint64
	err = v.bf.Do(v.a, 1, func(bytes []byte) error {
		ctrl := asCtrl(bytes)
		if ctrl.flags&consts.VARCHAR_CTRL == 0 {
			return errors.Errorf("Expected a Varchar control block")
		}
		ptOff = ctrl.posTree
		szOff = ctrl.sizeTree
		return nil
	})
	if err != nil {
		return nil, err
	}
	v.posTree, err = OpenAt(bf, ptOff)
	if err != nil {
		return nil, err
	}
	v.sizeTree, err = OpenAt(bf, szOff)
	if err != nil {
		return nil, err
	}
	return v, nil
}
Пример #2
0
// Create a new varchar structure. This takes a blockfile and an offset
// of an allocated block. The block becomes the control block for the
// varchar file (storing the free list for the allocator). It is
// important for the parent structure to track the location of this
// control block.
func NewVarchar(bf *fmap.BlockFile, a uint64) (v *Varchar, err error) {
	ptOff, err := bf.Allocate()
	if err != nil {
		return nil, err
	}
	posTree, err := NewAt(bf, ptOff, 8, 0)
	if err != nil {
		return nil, err
	}
	szOff, err := bf.Allocate()
	if err != nil {
		return nil, err
	}
	sizeTree, err := NewAt(bf, szOff, 4, 8)
	if err != nil {
		return nil, err
	}
	v = &Varchar{
		bf:       bf,
		posTree:  posTree,
		sizeTree: sizeTree,
		a:        a,
		blkSize:  bf.BlockSize(),
	}
	err = v.bf.Do(v.a, 1, func(bytes []byte) error {
		ctrl := asCtrl(bytes)
		ctrl.Init(ptOff, szOff)
		return nil
	})
	if err != nil {
		return nil, err
	}
	return v, nil
}