Rework package structure for unixfs and subpackage

cc @jbenet

dagreader.go

-package merkledag
-
-import (
-	"bytes"
-	"errors"
-	"io"
-
-	proto "github.com/jbenet/go-ipfs/Godeps/_workspace/src/code.google.com/p/goprotobuf/proto"
-	ft "github.com/jbenet/go-ipfs/importer/format"
-	u "github.com/jbenet/go-ipfs/util"
-)
-
-var ErrIsDir = errors.New("this dag node is a directory")
-
-// DagReader provides a way to easily read the data contained in a dag.
-type DagReader struct {
-	serv     *DAGService
-	node     *Node
-	position int
-	buf      *bytes.Buffer
-}
-
-// 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(n *Node, serv *DAGService) (io.Reader, error) {
-	pb := new(ft.PBData)
-	err := proto.Unmarshal(n.Data, pb)
-	if err != nil {
-		return nil, err
-	}
-
-	switch pb.GetType() {
-	case ft.PBData_Directory:
-		// Dont allow reading directories
-		return nil, ErrIsDir
-	case ft.PBData_File:
-		return &DagReader{
-			node: n,
-			serv: serv,
-			buf:  bytes.NewBuffer(pb.GetData()),
-		}, nil
-	case ft.PBData_Raw:
-		// Raw block will just be a single level, return a byte buffer
-		return bytes.NewBuffer(pb.GetData()), nil
-	default:
-		return nil, ft.ErrUnrecognizedType
-	}
-}
-
-// Follows the next link in line and loads it from the DAGService,
-// setting the next buffer to read from
-func (dr *DagReader) precalcNextBuf() error {
-	if dr.position >= len(dr.node.Links) {
-		return io.EOF
-	}
-	nxtLink := dr.node.Links[dr.position]
-	nxt := nxtLink.Node
-	if nxt == nil {
-		nxtNode, err := dr.serv.Get(u.Key(nxtLink.Hash))
-		if err != nil {
-			return err
-		}
-		nxt = nxtNode
-	}
-	pb := new(ft.PBData)
-	err := proto.Unmarshal(nxt.Data, pb)
-	if err != nil {
-		return err
-	}
-	dr.position++
-
-	switch pb.GetType() {
-	case ft.PBData_Directory:
-		return ft.ErrInvalidDirLocation
-	case ft.PBData_File:
-		//TODO: this *should* work, needs testing first
-		//return NewDagReader(nxt, dr.serv)
-		panic("Not yet handling different layers of indirection!")
-	case ft.PBData_Raw:
-		dr.buf = bytes.NewBuffer(pb.GetData())
-		return nil
-	default:
-		return ft.ErrUnrecognizedType
-	}
-}
-
-func (dr *DagReader) Read(b []byte) (int, error) {
-	// If no cached buffer, load one
-	if dr.buf == nil {
-		err := dr.precalcNextBuf()
-		if err != nil {
-			return 0, err
-		}
-	}
-	total := 0
-	for {
-		// Attempt to fill bytes from cached buffer
-		n, err := dr.buf.Read(b[total:])
-		total += n
-		if err != nil {
-			// EOF is expected
-			if err != io.EOF {
-				return total, err
-			}
-		}
-
-		// If weve read enough bytes, return
-		if total == len(b) {
-			return total, nil
-		}
-
-		// Otherwise, load up the next block
-		err = dr.precalcNextBuf()
-		if err != nil {
-			return total, err
-		}
-	}
-}
-
-/*
-func (dr *DagReader) Seek(offset int64, whence int) (int64, error) {
-	switch whence {
-	case os.SEEK_SET:
-		for i := 0; i < len(dr.node.Links); i++ {
-			nsize := dr.node.Links[i].Size - 8
-			if offset > nsize {
-				offset -= nsize
-			} else {
-				break
-			}
-		}
-		dr.position = i
-		err := dr.precalcNextBuf()
-		if err != nil {
-			return 0, err
-		}
-	case os.SEEK_CUR:
-	case os.SEEK_END:
-	default:
-		return 0, errors.New("invalid whence")
-	}
-	return 0, nil
-}
-*/