func (mb *MultiBlock) GetBytes() ([]byte, error) {
pbn := new(pb.Data)
t := pb.Data_File
pbn.Type = &t
pbn.Filesize = proto.Uint64(uint64(len(mb.Data)) + mb.subtotal)
pbn.Blocksizes = mb.blocksizes
pbn.Data = mb.Data
return proto.Marshal(pbn)
}
func FilePBData(data []byte, totalsize uint64) []byte {
pbfile := new(pb.Data)
typ := pb.Data_File
pbfile.Type = &typ
pbfile.Data = data
pbfile.Filesize = proto.Uint64(totalsize)
data, err := proto.Marshal(pbfile)
if err != nil {
// This really shouldnt happen, i promise
// The only failure case for marshal is if required fields
// are not filled out, and they all are. If the proto object
// gets changed and nobody updates this function, the code
// should panic due to programmer error
panic(err)
}
return data
}
// WriteAt will modify a dag file in place
// NOTE: it currently assumes only a single level of indirection
func (dm *DagModifier) WriteAt(b []byte, offset uint64) (int, error) {
// Check bounds
if dm.pbdata.GetFilesize() < offset {
return 0, errors.New("Attempted to perform write starting past end of file")
}
// First need to find where we are writing at
end := uint64(len(b)) + offset
// This shouldnt be necessary if we do subblocks sizes properly
newsize := dm.pbdata.GetFilesize()
if end > dm.pbdata.GetFilesize() {
newsize = end
}
zeroblocklen := uint64(len(dm.pbdata.Data))
origlen := len(b)
if end <= zeroblocklen {
log.Debug("Writing into zero block")
// Replacing zeroeth data block (embedded in the root node)
//TODO: check chunking here
copy(dm.pbdata.Data[offset:], b)
return len(b), nil
}
// Find where write should start
var traversed uint64
startsubblk := len(dm.pbdata.Blocksizes)
if offset < zeroblocklen {
dm.pbdata.Data = dm.pbdata.Data[:offset]
startsubblk = 0
} else {
traversed = uint64(zeroblocklen)
for i, size := range dm.pbdata.Blocksizes {
if uint64(offset) < traversed+size {
log.Debugf("Starting mod at block %d. [%d < %d + %d]", i, offset, traversed, size)
// Here is where we start
startsubblk = i
lnk := dm.curNode.Links[i]
node, err := dm.dagserv.Get(u.Key(lnk.Hash))
if err != nil {
return 0, err
}
data, err := ft.UnwrapData(node.Data)
if err != nil {
return 0, err
}
// We have to rewrite the data before our write in this block.
b = append(data[:offset-traversed], b...)
break
}
traversed += size
}
if startsubblk == len(dm.pbdata.Blocksizes) {
// TODO: Im not sure if theres any case that isnt being handled here.
// leaving this note here as a future reference in case something breaks
}
}
// Find blocks that need to be overwritten
var changed []int
mid := -1
var midoff uint64
for i, size := range dm.pbdata.Blocksizes[startsubblk:] {
if end > traversed {
changed = append(changed, i+startsubblk)
} else {
break
}
traversed += size
if end < traversed {
mid = i + startsubblk
midoff = end - (traversed - size)
break
}
}
// If our write starts in the middle of a block...
var midlnk *mdag.Link
if mid >= 0 {
midlnk = dm.curNode.Links[mid]
midnode, err := dm.dagserv.Get(u.Key(midlnk.Hash))
if err != nil {
return 0, err
}
// NOTE: this may have to be changed later when we have multiple
// layers of indirection
data, err := ft.UnwrapData(midnode.Data)
if err != nil {
return 0, err
}
b = append(b, data[midoff:]...)
}
// Generate new sub-blocks, and sizes
subblocks := splitBytes(b, dm.splitter)
var links []*mdag.Link
var sizes []uint64
for _, sb := range subblocks {
n := &mdag.Node{Data: ft.WrapData(sb)}
_, err := dm.dagserv.Add(n)
if err != nil {
log.Errorf("Failed adding node to DAG service: %s", err)
return 0, err
}
lnk, err := mdag.MakeLink(n)
if err != nil {
return 0, err
}
links = append(links, lnk)
sizes = append(sizes, uint64(len(sb)))
}
// This is disgusting (and can be rewritten if performance demands)
if len(changed) > 0 {
sechalflink := append(links, dm.curNode.Links[changed[len(changed)-1]+1:]...)
dm.curNode.Links = append(dm.curNode.Links[:changed[0]], sechalflink...)
sechalfblks := append(sizes, dm.pbdata.Blocksizes[changed[len(changed)-1]+1:]...)
dm.pbdata.Blocksizes = append(dm.pbdata.Blocksizes[:changed[0]], sechalfblks...)
} else {
dm.curNode.Links = append(dm.curNode.Links, links...)
dm.pbdata.Blocksizes = append(dm.pbdata.Blocksizes, sizes...)
}
dm.pbdata.Filesize = proto.Uint64(newsize)
return origlen, nil
}