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dagmodifier.go
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dagmodifier.go
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// Package mod provides DAG modification utilities to, for example,
// insert additional nodes in a unixfs DAG or truncate them.
package mod
import (
"bytes"
"context"
"encoding/json"
"errors"
"io"
"strings"
ft "github.com/bittorrent/go-unixfs"
"github.com/bittorrent/go-unixfs/importer/balanced"
help "github.com/bittorrent/go-unixfs/importer/helpers"
trickle "github.com/bittorrent/go-unixfs/importer/trickle"
uio "github.com/bittorrent/go-unixfs/io"
util "github.com/bittorrent/go-unixfs/util"
chunker "github.com/bittorrent/go-btfs-chunker"
cid "github.com/ipfs/go-cid"
ipld "github.com/ipfs/go-ipld-format"
mdag "github.com/ipfs/go-merkledag"
)
// Common errors
var (
ErrSeekFail = errors.New("failed to seek properly")
ErrUnrecognizedWhence = errors.New("unrecognized whence")
ErrNotUnixfs = errors.New("dagmodifier only supports unixfs nodes (proto or raw)")
)
// 2MB
var writebufferSize = 1 << 21
// DagModifier is the only struct licensed and able to correctly
// perform surgery on a DAG 'file'
// Dear god, please rename this to something more pleasant
type DagModifier struct {
dagserv ipld.DAGService
curNode ipld.Node
splitter chunker.SplitterGen
ctx context.Context
readCancel func()
writeStart uint64
curWrOff uint64
wrBuf *bytes.Buffer
Prefix cid.Prefix
RawLeaves bool
BalancedFormat bool
Maxlinks int
read uio.DagReader
}
type MetaDagModifier struct {
*DagModifier
db *help.DagBuilderHelper
Overwrite bool
}
// NewDagModifier returns a new DagModifier, the Cid prefix for newly
// created nodes will be inhered from the passed in node. If the Cid
// version if not 0 raw leaves will also be enabled. The Prefix and
// RawLeaves options can be overridden by changing them after the call.
func NewDagModifier(ctx context.Context, from ipld.Node, serv ipld.DAGService, spl chunker.SplitterGen) (*DagModifier, error) {
return newDagModifier(ctx, from, serv, spl, 0, false, false)
}
func NewDagModifierBalanced(ctx context.Context, from ipld.Node, serv ipld.DAGService, spl chunker.SplitterGen, ml int, noMeta bool) (*DagModifier, error) {
return newDagModifier(ctx, from, serv, spl, ml, true, noMeta)
}
func NewMetaDagModifierBalanced(mod *DagModifier, db *help.DagBuilderHelper, overwrite bool) *MetaDagModifier {
return &MetaDagModifier{
mod,
db,
overwrite,
}
}
func newDagModifier(ctx context.Context, from ipld.Node, serv ipld.DAGService, spl chunker.SplitterGen, ml int, balanced bool, noMeta bool) (*DagModifier, error) {
if !noMeta {
switch from.(type) {
case *mdag.ProtoNode, *mdag.RawNode:
// ok
default:
return nil, ErrNotUnixfs
}
}
var prefix cid.Prefix
if !noMeta {
prefix = from.Cid().Prefix()
prefix.Codec = cid.DagProtobuf
}
rawLeaves := false
if prefix.Version > 0 {
rawLeaves = true
}
maxlinks := help.DefaultLinksPerBlock
if ml > 0 {
maxlinks = ml
}
var copied ipld.Node
if !noMeta {
copied = from.Copy()
}
return &DagModifier{
curNode: copied,
dagserv: serv,
splitter: spl,
ctx: ctx,
Prefix: prefix,
RawLeaves: rawLeaves,
BalancedFormat: balanced,
Maxlinks: maxlinks,
}, nil
}
// WriteAt will modify a dag file in place
func (dm *DagModifier) WriteAt(b []byte, offset int64) (int, error) {
// TODO: this is currently VERY inefficient
// each write that happens at an offset other than the current one causes a
// flush to disk, and dag rewrite
if offset == int64(dm.writeStart) && dm.wrBuf != nil {
// If we would overwrite the previous write
if len(b) >= dm.wrBuf.Len() {
dm.wrBuf.Reset()
}
} else if uint64(offset) != dm.curWrOff {
size, err := dm.Size()
if err != nil {
return 0, err
}
if offset > size {
err := dm.expandSparse(offset - size)
if err != nil {
return 0, err
}
}
err = dm.Sync()
if err != nil {
return 0, err
}
dm.writeStart = uint64(offset)
}
return dm.Write(b)
}
// A reader that just returns zeros
type zeroReader struct{}
func (zr zeroReader) Read(b []byte) (int, error) {
for i := range b {
b[i] = 0
}
return len(b), nil
}
// 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 := chunker.NewSizeSplitter(r, 4096)
nnode, err := dm.appendData(dm.curNode, spl)
if err != nil {
return err
}
err = dm.dagserv.Add(dm.ctx, nnode)
return err
}
// Write continues writing to the dag at the current offset
func (dm *DagModifier) Write(b []byte) (int, error) {
if dm.read != nil {
dm.read = nil
}
if dm.wrBuf == nil {
dm.wrBuf = new(bytes.Buffer)
}
n, err := dm.wrBuf.Write(b)
if err != nil {
return n, err
}
dm.curWrOff += uint64(n)
if dm.wrBuf.Len() > writebufferSize {
err := dm.Sync()
if err != nil {
return n, err
}
}
return n, nil
}
// Size returns the Filesize of the node
func (dm *DagModifier) Size() (int64, error) {
fileSize, err := FileSize(dm.curNode)
if err != nil {
return 0, err
}
if dm.wrBuf != nil && int64(dm.wrBuf.Len())+int64(dm.writeStart) > int64(fileSize) {
return int64(dm.wrBuf.Len()) + int64(dm.writeStart), nil
}
return int64(fileSize), nil
}
func FileSize(n ipld.Node) (uint64, error) {
switch nd := n.(type) {
case *mdag.ProtoNode:
fsn, err := ft.FSNodeFromBytes(nd.Data())
if err != nil {
return 0, err
}
return fsn.FileSize(), nil
case *mdag.RawNode:
return uint64(len(nd.RawData())), nil
default:
return 0, ErrNotUnixfs
}
}
// 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()
fs, err := FileSize(dm.curNode)
if err != nil {
return err
}
if fs < dm.writeStart {
if err := dm.expandSparse(int64(dm.writeStart - fs)); err != nil {
return err
}
}
// overwrite existing dag nodes
thisc, err := dm.modifyDag(dm.curNode, dm.writeStart)
if err != nil {
return err
}
dm.curNode, err = dm.dagserv.Get(dm.ctx, thisc)
if err != nil {
return err
}
// need to write past end of current dag
if dm.wrBuf.Len() > 0 {
dm.curNode, err = dm.appendData(dm.curNode, dm.splitter(dm.wrBuf))
if err != nil {
return err
}
err = dm.dagserv.Add(dm.ctx, dm.curNode)
if err != nil {
return err
}
}
dm.writeStart += uint64(buflen)
dm.wrBuf = nil
return nil
}
// modifyDag writes the data in 'dm.wrBuf' over the data in 'node' starting at 'offset'
// returns the new key of the passed in node.
func (dm *DagModifier) modifyDag(n ipld.Node, offset uint64) (cid.Cid, error) {
// If we've reached a leaf node.
if len(n.Links()) == 0 {
switch nd0 := n.(type) {
case *mdag.ProtoNode:
fsn, err := ft.FSNodeFromBytes(nd0.Data())
if err != nil {
return cid.Cid{}, err
}
_, err = dm.wrBuf.Read(fsn.Data()[offset:])
if err != nil && err != io.EOF {
return cid.Cid{}, err
}
// Update newly written node..
b, err := fsn.GetBytes()
if err != nil {
return cid.Cid{}, err
}
nd := new(mdag.ProtoNode)
nd.SetData(b)
nd.SetCidBuilder(nd0.CidBuilder())
err = dm.dagserv.Add(dm.ctx, nd)
if err != nil {
return cid.Cid{}, err
}
return nd.Cid(), nil
case *mdag.RawNode:
origData := nd0.RawData()
bytes := make([]byte, len(origData))
// copy orig data up to offset
copy(bytes, origData[:offset])
// copy in new data
n, err := dm.wrBuf.Read(bytes[offset:])
if err != nil && err != io.EOF {
return cid.Cid{}, err
}
// copy remaining data
offsetPlusN := int(offset) + n
if offsetPlusN < len(origData) {
copy(bytes[offsetPlusN:], origData[offsetPlusN:])
}
nd, err := mdag.NewRawNodeWPrefix(bytes, nd0.Cid().Prefix())
if err != nil {
return cid.Cid{}, err
}
err = dm.dagserv.Add(dm.ctx, nd)
if err != nil {
return cid.Cid{}, err
}
return nd.Cid(), nil
}
}
node, ok := n.(*mdag.ProtoNode)
if !ok {
return cid.Cid{}, ErrNotUnixfs
}
fsn, err := ft.FSNodeFromBytes(node.Data())
if err != nil {
return cid.Cid{}, err
}
var cur uint64
for i, bs := range fsn.BlockSizes() {
// 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 cid.Cid{}, err
}
k, err := dm.modifyDag(child, offset-cur)
if err != nil {
return cid.Cid{}, err
}
node.Links()[i].Cid = k
// Recache serialized node
_, err = node.EncodeProtobuf(true)
if err != nil {
return cid.Cid{}, err
}
if dm.wrBuf.Len() == 0 {
// No more bytes to write!
break
}
offset = cur + bs
}
cur += bs
}
err = dm.dagserv.Add(dm.ctx, node)
return node.Cid(), err
}
// appendData appends the blocks from the given chan to the end of this dag
func (dm *DagModifier) appendData(nd ipld.Node, spl chunker.Splitter) (ipld.Node, error) {
switch nd := nd.(type) {
case *mdag.ProtoNode, *mdag.RawNode:
dbp := &help.DagBuilderParams{
Dagserv: dm.dagserv,
Maxlinks: dm.Maxlinks,
CidBuilder: dm.Prefix,
RawLeaves: dm.RawLeaves,
}
db, err := dbp.New(spl)
if err != nil {
return nil, err
}
if dm.BalancedFormat {
return balanced.Append(dm.ctx, nd, db)
} else {
return trickle.Append(dm.ctx, nd, db)
}
default:
return nil, ErrNotUnixfs
}
}
// Read data from this dag starting at the current offset
func (dm *DagModifier) Read(b []byte) (int, error) {
err := dm.readPrep()
if err != nil {
return 0, err
}
n, err := dm.read.Read(b)
dm.curWrOff += uint64(n)
return n, err
}
func (dm *DagModifier) readPrep() error {
err := dm.Sync()
if err != nil {
return err
}
if dm.read == nil {
ctx, cancel := context.WithCancel(dm.ctx)
dr, err := uio.NewDagReader(ctx, dm.curNode, dm.dagserv)
if err != nil {
cancel()
return err
}
i, err := dr.Seek(int64(dm.curWrOff), io.SeekStart)
if err != nil {
cancel()
return err
}
if i != int64(dm.curWrOff) {
cancel()
return ErrSeekFail
}
dm.readCancel = cancel
dm.read = dr
}
return nil
}
// CtxReadFull reads data from this dag starting at the current offset
func (dm *DagModifier) CtxReadFull(ctx context.Context, b []byte) (int, error) {
err := dm.readPrep()
if err != nil {
return 0, err
}
n, err := dm.read.CtxReadFull(ctx, b)
dm.curWrOff += uint64(n)
return n, err
}
// GetNode gets the modified DAG Node
func (dm *DagModifier) GetNode() (ipld.Node, error) {
err := dm.Sync()
if err != nil {
return nil, err
}
return dm.curNode.Copy(), nil
}
// HasChanges returned whether or not there are unflushed changes to this dag
func (dm *DagModifier) HasChanges() bool {
return dm.wrBuf != nil
}
// Seek modifies the offset according to whence. See unixfs/io for valid whence
// values.
func (dm *DagModifier) Seek(offset int64, whence int) (int64, error) {
err := dm.Sync()
if err != nil {
return 0, err
}
fisize, err := dm.Size()
if err != nil {
return 0, err
}
var newoffset uint64
switch whence {
case io.SeekCurrent:
newoffset = dm.curWrOff + uint64(offset)
case io.SeekStart:
newoffset = uint64(offset)
case io.SeekEnd:
newoffset = uint64(fisize) - uint64(offset)
default:
return 0, ErrUnrecognizedWhence
}
if int64(newoffset) > fisize {
if err := dm.expandSparse(int64(newoffset) - fisize); err != nil {
return 0, err
}
}
dm.curWrOff = newoffset
dm.writeStart = newoffset
if dm.read != nil {
_, err = dm.read.Seek(offset, whence)
if err != nil {
return 0, err
}
}
return int64(dm.curWrOff), nil
}
// Truncate truncates the current Node to 'size' and replaces it with the
// new one.
func (dm *DagModifier) Truncate(size int64) error {
err := dm.Sync()
if err != nil {
return err
}
realSize, err := dm.Size()
if err != nil {
return err
}
if size == int64(realSize) {
return nil
}
// Truncate can also be used to expand the file
if size > int64(realSize) {
return dm.expandSparse(int64(size) - realSize)
}
nnode, err := dm.dagTruncate(dm.ctx, dm.curNode, uint64(size))
if err != nil {
return err
}
err = dm.dagserv.Add(dm.ctx, nnode)
if err != nil {
return err
}
dm.curNode = nnode
return nil
}
// dagTruncate truncates the given node to 'size' and returns the modified Node
func (dm *DagModifier) dagTruncate(ctx context.Context, n ipld.Node, size uint64) (ipld.Node, error) {
if len(n.Links()) == 0 {
switch nd := n.(type) {
case *mdag.ProtoNode:
// TODO: this can likely be done without marshaling and remarshaling
fsn, err := ft.FSNodeFromBytes(nd.Data())
if err != nil {
return nil, err
}
nd.SetData(ft.WrapData(fsn.Data()[:size]))
return nd, nil
case *mdag.RawNode:
return mdag.NewRawNodeWPrefix(nd.RawData()[:size], nd.Cid().Prefix())
}
}
nd, ok := n.(*mdag.ProtoNode)
if !ok {
return nil, ErrNotUnixfs
}
var cur uint64
end := 0
var modified ipld.Node
ndata, err := ft.FSNodeFromBytes(nd.Data())
if err != nil {
return nil, err
}
// Reset the block sizes of the node to adjust them
// with the new values of the truncated children.
ndata.RemoveAllBlockSizes()
for i, lnk := range nd.Links() {
child, err := lnk.GetNode(ctx, dm.dagserv)
if err != nil {
return nil, err
}
childsize, err := FileSize(child)
if err != nil {
return nil, err
}
// found the child we want to cut
if size < cur+childsize {
nchild, err := dm.dagTruncate(ctx, child, size-cur)
if err != nil {
return nil, err
}
ndata.AddBlockSize(size - cur)
modified = nchild
end = i
break
}
cur += childsize
ndata.AddBlockSize(childsize)
}
err = dm.dagserv.Add(ctx, modified)
if err != nil {
return nil, err
}
nd.SetLinks(nd.Links()[:end])
err = nd.AddNodeLink("", modified)
if err != nil {
return nil, err
}
d, err := ndata.GetBytes()
if err != nil {
return nil, err
}
// Save the new block sizes to the original node.
nd.SetData(d)
// invalidate cache and recompute serialized data
_, err = nd.EncodeProtobuf(true)
if err != nil {
return nil, err
}
return nd, nil
}
func (dm *DagModifier) GetCtx() context.Context {
return dm.ctx
}
func (dm *DagModifier) GetDserv() ipld.DAGService {
return dm.dagserv
}
func (mdm *MetaDagModifier) GetDb() *help.DagBuilderHelper {
return mdm.db
}
// AddMetadata puts the given `metadata` items to the given `root`
// that is the top node of a BTFS file DAG and returns a new root for the BTFS file DAG.
//
// There are three scenarios possible:
// Scenario #1. No existing metadata for the `root`. So this scenario is
// to create a new metadata sub-DAG.
// Scenario #2. There are existing keys for the given `metadata` items.
// Then this is to update the metadata sub-DAG with the given items.
// Scenario #3. There are no pre-existing metadata items for the given `metadata` items.
// Then this scenario is to append given items to the metadata sub-DAG.
// TODO: trickle format
// Preconditions include that first the given `metadata` is in compact JSON format.
// Note that the given `metadata` should be added to the first element of the metadata list.
func (mdm *MetaDagModifier) AddMetadata(root ipld.Node, metadata []byte) (ipld.Node, error) {
// Read the existing metadata map from the first element of the metadata list.
b, encodedTree, err := util.ReadMetadataListFromDag(mdm.ctx, root, mdm.dagserv, false)
if err != nil {
return nil, err
}
treeSize := len(encodedTree)
// Determine the specific scenario.
// Scenario #1:
var newMetaNode ipld.Node
var children *ft.DagMetaNodes
if b == nil || util.IsMetadataEmpty(b) {
// Create a metadata sub-DAG
newMetaNode, err = mdm.buildNewMetaDataDag(metadata, encodedTree)
if err != nil {
return nil, err
}
} else {
children, err = ft.GetChildrenForDagWithMeta(mdm.ctx, root, mdm.dagserv)
if err != nil {
return nil, err
}
// Create existing map and input metadata map and check.
m := make(map[string]interface{})
err = json.Unmarshal(b, &m)
if err != nil {
return nil, err
}
inputM := make(map[string]interface{})
err = json.Unmarshal(metadata, &inputM)
if err != nil {
return nil, err
}
exists := util.Intersects(m, inputM)
// Scenario #2: Update case.
if exists {
if !mdm.Overwrite {
return nil, errors.New("Found existing key value pairs. Use --overwrite to force to update.")
}
// Truncate(0) on the metadata sub-DAG.
err := mdm.Truncate(0)
if err != nil {
return nil, err
}
// iterate the inputM to put its (k, v) pairs to existing map.
for k, v := range inputM {
m[k] = v
}
b, err = json.Marshal(m)
if err != nil {
return nil, err
}
// Create a metadata sub-DAG
newMetaNode, err = mdm.buildNewMetaDataDag(b, encodedTree)
if err != nil {
return nil, err
}
} else
// Scenario #3: Append case.
{
// Append the given metadata items to the metadata sub-DAG.
mdm.curNode = children.MetaNode
fileSize, err := FileSize(mdm.curNode)
if err != nil {
return nil, err
}
// Combine two JSON format byte arrays. E.g.,
// `{"price":12.22} + `{"number":1234}` -> `{"price":12.22,"number":1234}`
metadata[0] = ','
metadata = append(append(metadata[:], '#'), encodedTree[:]...)
offset := int(fileSize) - treeSize - 2
nmod, err := mdm.WriteAt(metadata, int64(offset))
if err != nil {
return nil, err
}
if nmod != int(len(metadata)) {
return nil, errors.New("Modified length not correct!")
}
newMetaNode, err = mdm.GetNode()
if err != nil {
return nil, err
}
}
}
// Attach the modified metadata sub-DAG to a new root for the BTFS file DAG.
var dnode ipld.Node
if children == nil {
dnode = root
} else {
dnode = children.DataNode
}
fileSize, err := FileSize(dnode)
if err != nil {
return nil, err
}
newRoot, err := mdm.GetDb().AttachMetadataDag(dnode, fileSize, newMetaNode)
if err != nil {
return nil, err
}
mdm.GetDb().Add(newRoot)
return newRoot, nil
}
// RemoveMetadata first truncate the metadata dag from the given `root`,
// update the metadata map with the given `metadata`,
// then calls meta-dag builder to create a metadata subDag and
// attach the metadata dag to a new root with the given `dataroot` being
// a child of the new root.
// The preconditions include that first the given `metadata` is a string with keys separated by
// commas, second`mdm.curNode` has the root of the metadata sub-DAG.
func (mdm *MetaDagModifier) RemoveMetadata(root ipld.Node, metakeys []byte) (ipld.Node, error) {
// Read the existing metadata map.
b, encodedTree, err := util.ReadMetadataListFromDag(mdm.ctx, root, mdm.dagserv, false)
if err != nil {
return nil, err
}
if b == nil {
return nil, errors.New("no metadata exists")
}
// Determine the specific scenario.
// Scenario #1:
var newMetaNode ipld.Node
var children *ft.DagMetaNodes
var clear bool
children, err = ft.GetChildrenForDagWithMeta(mdm.ctx, root, mdm.dagserv)
if err != nil {
return nil, err
}
if children == nil {
return nil, errors.New("expected DAG node with metadata child node")
}
// Create existing map and check with the given key list.
m := make(map[string]interface{})
err = json.Unmarshal(b, &m)
if err != nil {
return nil, err
}
inputKeys := strings.Split(string(metakeys), ",")
exists := util.KeyIntersects(m, inputKeys)
if !exists {
return nil, errors.New("no metadata entries with the given keys")
} else {
// Truncate(0) on the metadata sub-DAG.
err := mdm.Truncate(0)
if err != nil {
return nil, err
}
// Check if inputM and m have the same key set
if util.EqualKeySets(m, inputKeys) {
// Scenario #1: clear metadata.
clear = true
} else {
// Scenario #2: delete a subset of the metadata map.
// iterate the inputKeys to delete each key from the existing map.
for _, k := range inputKeys {
delete(m, k)
}
b, err = json.Marshal(m)
if err != nil {
return nil, err
}
// Create a metadata sub-DAG
newMetaNode, err = mdm.buildNewMetaDataDag(b, encodedTree)
if err != nil {
return nil, err
}
}
}
dnode := children.DataNode
// if clear is true, return dnode as root.
if clear {
return dnode, nil
}
// Attach the modified metadata sub-DAG to a new root for the BTFS file DAG.
fileSize, err := FileSize(dnode)
if err != nil {
return nil, err
}
newRoot, err := mdm.GetDb().AttachMetadataDag(dnode, fileSize, newMetaNode)
if err != nil {
return nil, err
}
mdm.GetDb().Add(newRoot)
return newRoot, nil
}
func (mdm *MetaDagModifier) buildNewMetaDataDag(metaBytes []byte, encodedTree []byte) (ipld.Node, error) {
var superMeta help.SuperMeta
err := json.Unmarshal(metaBytes, &superMeta)
if err != nil {
return nil, err
}
metaBytes = util.CreateMetadataList(metaBytes, encodedTree)
r := bytes.NewReader(metaBytes)
if superMeta.ChunkSize == 0 {
superMeta.ChunkSize = uint64(chunker.DefaultBlockSize)
}
if superMeta.MaxLinks == 0 {
superMeta.MaxLinks = uint64(help.DefaultLinksPerBlock)
}
// TODO: trickle format input should be set somewhere..
metaSpl := chunker.NewMetaSplitter(r, superMeta.ChunkSize)
db := mdm.GetDb()
metaDb := help.NewMetaDagBuilderHelper(*db, metaSpl, nil)
metaDb.SetSpl() // For the case for removing metadata items.
var mnode ipld.Node
if superMeta.TrickleFormat {
mnode, err = trickle.BuildNewMetaDataDag(metaDb)
} else {
mnode, err = balanced.BuildNewMetaDataDag(metaDb)
}
if err != nil {
return nil, err
}
return mnode, nil
}