/
dagreader.go
75 lines (65 loc) · 1.86 KB
/
dagreader.go
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package io
import (
"context"
"errors"
"fmt"
"io"
mdag "github.com/ipfs/go-ipfs/merkledag"
ft "github.com/ipfs/go-ipfs/unixfs"
ftpb "github.com/ipfs/go-ipfs/unixfs/pb"
node "gx/ipfs/QmPN7cwmpcc4DWXb4KTB9dNAJgjuPY69h3npsMfhRrQL9c/go-ipld-format"
proto "gx/ipfs/QmZ4Qi3GaRbjcx28Sme5eMH7RQjGkt8wHxt2a65oLaeFEV/gogo-protobuf/proto"
)
var ErrIsDir = errors.New("this dag node is a directory")
var ErrCantReadSymlinks = errors.New("cannot currently read symlinks")
type DagReader interface {
ReadSeekCloser
Size() uint64
CtxReadFull(context.Context, []byte) (int, error)
Offset() int64
}
type ReadSeekCloser interface {
io.Reader
io.Seeker
io.Closer
io.WriterTo
}
// NewDagReader creates a new reader object that reads the data represented by
// the given node, using the passed in DAGService for data retreival
func NewDagReader(ctx context.Context, n node.Node, serv mdag.DAGService) (DagReader, error) {
switch n := n.(type) {
case *mdag.RawNode:
return NewBufDagReader(n.RawData()), nil
case *mdag.ProtoNode:
pb := new(ftpb.Data)
if err := proto.Unmarshal(n.Data(), pb); err != nil {
return nil, err
}
switch pb.GetType() {
case ftpb.Data_Directory, ftpb.Data_HAMTShard:
// Dont allow reading directories
return nil, ErrIsDir
case ftpb.Data_File, ftpb.Data_Raw:
return NewPBFileReader(ctx, n, pb, serv), nil
case ftpb.Data_Metadata:
if len(n.Links()) == 0 {
return nil, errors.New("incorrectly formatted metadata object")
}
child, err := n.Links()[0].GetNode(ctx, serv)
if err != nil {
return nil, err
}
childpb, ok := child.(*mdag.ProtoNode)
if !ok {
return nil, mdag.ErrNotProtobuf
}
return NewDagReader(ctx, childpb, serv)
case ftpb.Data_Symlink:
return nil, ErrCantReadSymlinks
default:
return nil, ft.ErrUnrecognizedType
}
default:
return nil, fmt.Errorf("unrecognized node type")
}
}