func WriteHeader(w io.Writer, src, dst peer.ID) error {
// write header to w.
mhw := mh.NewWriter(w)
if err := mhw.WriteMultihash(mh.Multihash(src)); err != nil {
return fmt.Errorf("failed to write relay header: %s -- %s", dst, err)
}
if err := mhw.WriteMultihash(mh.Multihash(dst)); err != nil {
return fmt.Errorf("failed to write relay header: %s -- %s", dst, err)
}
return 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 {
// Unpin block
ckey := key.Key(node.Links[i].Hash)
dm.mp.RemovePinWithMode(ckey, pin.Indirect)
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
}
// pin the new node
dm.mp.PinWithMode(k, pin.Indirect)
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
}