// expandSparse grows the file with zero blocks of 4096
// A small blocksize is chosen to aid in deduplication
func (dm *DagModifier) expandSparse(size int64) error {
r := io.LimitReader(zeroReader{}, size)
spl := chunk.NewSizeSplitter(r, 4096)
blks, errs := chunk.Chan(spl)
nnode, err := dm.appendData(dm.curNode, blks, errs)
if err != nil {
return err
}
_, err = dm.dagserv.Add(nnode)
if err != nil {
return err
}
dm.curNode = nnode
return nil
}
// Sync writes changes to this dag to disk
func (dm *DagModifier) Sync() error {
// No buffer? Nothing to do
if dm.wrBuf == nil {
return nil
}
// If we have an active reader, kill it
if dm.read != nil {
dm.read = nil
dm.readCancel()
}
// Number of bytes we're going to write
buflen := dm.wrBuf.Len()
// Grab key for unpinning after mod operation
curk, err := dm.curNode.Key()
if err != nil {
return err
}
// overwrite existing dag nodes
thisk, done, err := dm.modifyDag(dm.curNode, dm.writeStart, dm.wrBuf)
if err != nil {
return err
}
nd, err := dm.dagserv.Get(dm.ctx, thisk)
if err != nil {
return err
}
dm.curNode = nd
// need to write past end of current dag
if !done {
blks, errs := chunk.Chan(dm.splitter(dm.wrBuf))
nd, err = dm.appendData(dm.curNode, blks, errs)
if err != nil {
return err
}
thisk, err = dm.dagserv.Add(nd)
if err != nil {
return err
}
dm.curNode = nd
}
// Finalize correct pinning, and flush pinner
dm.mp.PinWithMode(thisk, pin.Recursive)
dm.mp.RemovePinWithMode(curk, pin.Recursive)
err = dm.mp.Flush()
if err != nil {
return err
}
dm.writeStart += uint64(buflen)
dm.wrBuf = nil
return nil
}