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helpers.go
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/
helpers.go
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package helpers
import (
"context"
"fmt"
"os"
dag "github.com/ipfs/go-merkledag"
ft "github.com/ipfs/go-unixfs"
cid "github.com/ipfs/go-cid"
pi "github.com/ipfs/go-ipfs-posinfo"
ipld "github.com/ipfs/go-ipld-format"
)
// BlockSizeLimit specifies the maximum size an imported block can have.
var BlockSizeLimit = 1048576 // 1 MB
// rough estimates on expected sizes
var roughLinkBlockSize = 1 << 13 // 8KB
var roughLinkSize = 34 + 8 + 5 // sha256 multihash + size + no name + protobuf framing
// DefaultLinksPerBlock governs how the importer decides how many links there
// will be per block. This calculation is based on expected distributions of:
// * the expected distribution of block sizes
// * the expected distribution of link sizes
// * desired access speed
// For now, we use:
//
// var roughLinkBlockSize = 1 << 13 // 8KB
// var roughLinkSize = 288 // sha256 + framing + name
// var DefaultLinksPerBlock = (roughLinkBlockSize / roughLinkSize)
//
// See calc_test.go
var DefaultLinksPerBlock = roughLinkBlockSize / roughLinkSize
// ErrSizeLimitExceeded signals that a block is larger than BlockSizeLimit.
var ErrSizeLimitExceeded = fmt.Errorf("object size limit exceeded")
// UnixfsNode is a struct created to aid in the generation
// of unixfs DAG trees
type UnixfsNode struct {
raw bool
rawnode *dag.RawNode
node *dag.ProtoNode
ufmt *ft.FSNode
posInfo *pi.PosInfo
}
// NewUnixfsNodeFromDag reconstructs a Unixfs node from a given dag node
func NewUnixfsNodeFromDag(nd *dag.ProtoNode) (*UnixfsNode, error) {
mb, err := ft.FSNodeFromBytes(nd.Data())
if err != nil {
return nil, err
}
return &UnixfsNode{
node: nd,
ufmt: mb,
}, nil
}
// SetPrefix sets the CID Prefix
func (n *UnixfsNode) SetPrefix(prefix cid.Builder) {
n.node.SetPrefix(prefix)
}
// NumChildren returns the number of children referenced by this UnixfsNode.
func (n *UnixfsNode) NumChildren() int {
return n.ufmt.NumChildren()
}
// GetChild gets the ith child of this node from the given DAGService.
func (n *UnixfsNode) GetChild(ctx context.Context, i int, ds ipld.DAGService) (*UnixfsNode, error) {
nd, err := n.node.Links()[i].GetNode(ctx, ds)
if err != nil {
return nil, err
}
pbn, ok := nd.(*dag.ProtoNode)
if !ok {
return nil, dag.ErrNotProtobuf
}
return NewUnixfsNodeFromDag(pbn)
}
// AddChild adds the given UnixfsNode as a child of the receiver.
// The passed in DagBuilderHelper is used to store the child node an
// pin it locally so it doesnt get lost.
func (n *UnixfsNode) AddChild(child *UnixfsNode, db *DagBuilderHelper) error {
n.ufmt.AddBlockSize(child.FileSize())
childnode, err := child.GetDagNode()
if err != nil {
return err
}
// Add a link to this node without storing a reference to the memory
// This way, we avoid nodes building up and consuming all of our RAM
err = n.node.AddNodeLink("", childnode)
if err != nil {
return err
}
err = db.batch.Add(childnode)
return err
}
// RemoveChild deletes the child node at the given index.
func (n *UnixfsNode) RemoveChild(index int, dbh *DagBuilderHelper) {
n.ufmt.RemoveBlockSize(index)
n.node.SetLinks(append(n.node.Links()[:index], n.node.Links()[index+1:]...))
}
// SetData stores data in this node.
func (n *UnixfsNode) SetData(data []byte) {
n.ufmt.SetData(data)
}
// FileSize returns the total file size of this tree (including children)
// In the case of raw nodes, it returns the length of the
// raw data.
func (n *UnixfsNode) FileSize() uint64 {
if n.raw {
return uint64(len(n.rawnode.RawData()))
}
return n.ufmt.FileSize()
}
// SetPosInfo sets information about the offset of the data of this node in a
// filesystem file.
func (n *UnixfsNode) SetPosInfo(offset uint64, fullPath string, stat os.FileInfo) {
n.posInfo = &pi.PosInfo{
Offset: offset,
FullPath: fullPath,
Stat: stat,
}
}
// GetDagNode fills out the proper formatting for the unixfs node
// inside of a DAG node and returns the dag node.
func (n *UnixfsNode) GetDagNode() (ipld.Node, error) {
nd, err := n.getBaseDagNode()
if err != nil {
return nil, err
}
if n.posInfo != nil {
if rn, ok := nd.(*dag.RawNode); ok {
return &pi.FilestoreNode{
Node: rn,
PosInfo: n.posInfo,
}, nil
}
}
return nd, nil
}
func (n *UnixfsNode) getBaseDagNode() (ipld.Node, error) {
if n.raw {
return n.rawnode, nil
}
data, err := n.ufmt.GetBytes()
if err != nil {
return nil, err
}
n.node.SetData(data)
return n.node, nil
}