// dagTruncate truncates the given node to 'size' and returns the modified Node
func dagTruncate(ctx context.Context, nd *mdag.Node, size uint64, ds mdag.DAGService) (*mdag.Node, error) {
if len(nd.Links) == 0 {
// TODO: this can likely be done without marshaling and remarshaling
pbn, err := ft.FromBytes(nd.Data)
if err != nil {
return nil, err
}
nd.Data = ft.WrapData(pbn.Data[:size])
return nd, nil
}
var cur uint64
end := 0
var modified *mdag.Node
ndata := new(ft.FSNode)
for i, lnk := range nd.Links {
child, err := lnk.GetNode(ctx, ds)
if err != nil {
return nil, err
}
childsize, err := ft.DataSize(child.Data)
if err != nil {
return nil, err
}
// found the child we want to cut
if size < cur+childsize {
nchild, err := dagTruncate(ctx, child, size-cur, ds)
if err != nil {
return nil, err
}
ndata.AddBlockSize(size - cur)
modified = nchild
end = i
break
}
cur += childsize
ndata.AddBlockSize(childsize)
}
_, err := ds.Add(modified)
if err != nil {
return nil, err
}
nd.Links = nd.Links[:end]
err = nd.AddNodeLinkClean("", modified)
if err != nil {
return nil, err
}
d, err := ndata.GetBytes()
if err != nil {
return nil, err
}
nd.Data = d
// invalidate cache and recompute serialized data
_, err = nd.Encoded(true)
if err != nil {
return nil, err
}
return nd, nil
}
// modifyDag writes the data in 'data' over the data in 'node' starting at 'offset'
// returns the new key of the passed in node and whether or not all the data in the reader
// has been consumed.
func (dm *DagModifier) modifyDag(node *mdag.Node, offset uint64, data io.Reader) (key.Key, bool, error) {
f, err := ft.FromBytes(node.Data)
if err != nil {
return "", false, err
}
// If we've reached a leaf node.
if len(node.Links) == 0 {
n, err := data.Read(f.Data[offset:])
if err != nil && err != io.EOF {
return "", false, err
}
// Update newly written node..
b, err := proto.Marshal(f)
if err != nil {
return "", false, err
}
nd := &mdag.Node{Data: b}
k, err := dm.dagserv.Add(nd)
if err != nil {
return "", false, err
}
// Hey look! we're done!
var done bool
if n < len(f.Data[offset:]) {
done = true
}
return k, done, nil
}
var cur uint64
var done bool
for i, bs := range f.GetBlocksizes() {
// We found the correct child to write into
if cur+bs > offset {
child, err := node.Links[i].GetNode(dm.ctx, dm.dagserv)
if err != nil {
return "", false, err
}
k, sdone, err := dm.modifyDag(child, offset-cur, data)
if err != nil {
return "", false, err
}
offset += bs
node.Links[i].Hash = mh.Multihash(k)
// Recache serialized node
_, err = node.Encoded(true)
if err != nil {
return "", false, err
}
if sdone {
// No more bytes to write!
done = true
break
}
offset = cur + bs
}
cur += bs
}
k, err := dm.dagserv.Add(node)
return k, done, err
}