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helpers.go
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/
helpers.go
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package helpers
import (
"fmt"
chunk "github.com/ipfs/go-ipfs/importer/chunk"
dag "github.com/ipfs/go-ipfs/merkledag"
ft "github.com/ipfs/go-ipfs/unixfs"
"gx/ipfs/QmZy2y8t9zQH2a1b8q2ZSLKp17ATuJoCNxxyMFG5qFExpt/go-net/context"
)
// BlockSizeLimit specifies the maximum size an imported block can have.
var BlockSizeLimit = 1048576 // 1 MB
// rough estimates on expected sizes
var roughDataBlockSize = chunk.DefaultBlockSize
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 {
node *dag.Node
ufmt *ft.FSNode
}
// NewUnixfsNode creates a new Unixfs node to represent a file
func NewUnixfsNode() *UnixfsNode {
return &UnixfsNode{
node: new(dag.Node),
ufmt: &ft.FSNode{Type: ft.TFile},
}
}
// NewUnixfsBlock creates a new Unixfs node to represent a raw data block
func NewUnixfsBlock() *UnixfsNode {
return &UnixfsNode{
node: new(dag.Node),
ufmt: &ft.FSNode{Type: ft.TRaw},
}
}
// NewUnixfsNodeFromDag reconstructs a Unixfs node from a given dag node
func NewUnixfsNodeFromDag(nd *dag.Node) (*UnixfsNode, error) {
mb, err := ft.FSNodeFromBytes(nd.Data())
if err != nil {
return nil, err
}
return &UnixfsNode{
node: nd,
ufmt: mb,
}, nil
}
func (n *UnixfsNode) NumChildren() int {
return n.ufmt.NumChildren()
}
func (n *UnixfsNode) GetChild(ctx context.Context, i int, ds dag.DAGService) (*UnixfsNode, error) {
nd, err := n.node.Links[i].GetNode(ctx, ds)
if err != nil {
return nil, err
}
return NewUnixfsNodeFromDag(nd)
}
// addChild will add 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.ufmt.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.AddNodeLinkClean("", childnode)
if err != nil {
return err
}
_, err = db.batch.Add(childnode)
if err != nil {
return err
}
return nil
}
// Removes the child node at the given index
func (n *UnixfsNode) RemoveChild(index int, dbh *DagBuilderHelper) {
n.ufmt.RemoveBlockSize(index)
n.node.Links = append(n.node.Links[:index], n.node.Links[index+1:]...)
}
func (n *UnixfsNode) SetData(data []byte) {
n.ufmt.Data = data
}
// getDagNode fills out the proper formatting for the unixfs node
// inside of a DAG node and returns the dag node
func (n *UnixfsNode) GetDagNode() (*dag.Node, error) {
data, err := n.ufmt.GetBytes()
if err != nil {
return nil, err
}
n.node.SetData(data)
return n.node, nil
}