get.go

package commands

import (
	"archive/tar"
	"bytes"
	"compress/gzip"
	"fmt"
	"io"
	"os"
	p "path"
	fp "path/filepath"
	"strings"
	"sync"

	cmds "github.com/jbenet/go-ipfs/commands"
	core "github.com/jbenet/go-ipfs/core"
	dag "github.com/jbenet/go-ipfs/merkledag"
	uio "github.com/jbenet/go-ipfs/unixfs/io"
	upb "github.com/jbenet/go-ipfs/unixfs/pb"

	proto "github.com/jbenet/go-ipfs/Godeps/_workspace/src/code.google.com/p/goprotobuf/proto"
)

var GetCmd = &cmds.Command{
	Helptext: cmds.HelpText{
		Tagline: "Download IPFS objects",
		ShortDescription: `
Retrieves the object named by <ipfs-path> and stores the data to disk.

By default, the output will be stored at ./<ipfs-path>, but an alternate path
can be specified with '--output=<path>' or '-o=<path>'.

To output a TAR archive instead of unpacked files, use '--archive' or '-a'.

To compress the output with GZIP compression, use '--compress' or '-C'. You
may also specify the level of compression by specifying '-l=<1-9>'.
`,
	},

	Arguments: []cmds.Argument{
		cmds.StringArg("ipfs-path", true, true, "The path to the IPFS object(s) to be outputted").EnableStdin(),
	},
	Options: []cmds.Option{
		cmds.StringOption("output", "o", "The path where output should be stored"),
		cmds.BoolOption("archive", "a", "Output a TAR archive"),
		cmds.BoolOption("compress", "C", "Compress the output with GZIP compression"),
		cmds.IntOption("compression-level", "l", "The level of compression (an int between 1 and 9)"),
	},
	Run: func(req cmds.Request, res cmds.Response) {
		node, err := req.Context().GetNode()
		if err != nil {
			res.SetError(err, cmds.ErrNormal)
			return
		}

		compress, _, _ := req.Option("compress").Bool()
		compressionLevel, found, _ := req.Option("compression-level").Int()
		if !found {
			if compress {
				compressionLevel = gzip.DefaultCompression
			} else {
				compressionLevel = gzip.NoCompression
			}
		}

		reader, err := get(node, req.Arguments()[0], compressionLevel)
		if err != nil {
			res.SetError(err, cmds.ErrNormal)
			return
		}
		res.SetOutput(reader)
	},
	PostRun: func(req cmds.Request, res cmds.Response) {
		reader := res.Output().(io.Reader)
		res.SetOutput(nil)

		outPath, _, _ := req.Option("output").String()
		if len(outPath) == 0 {
			outPath = req.Arguments()[0]
		}

		compress, _, _ := req.Option("compress").Bool()
		compressionLevel, found, _ := req.Option("compression-level").Int()
		compress = (compress && (compressionLevel > 0 || !found)) || compressionLevel > 0

		if archive, _, _ := req.Option("archive").Bool(); archive {
			if !strings.HasSuffix(outPath, ".tar") {
				outPath += ".tar"
			}
			if compress {
				outPath += ".gz"
			}
			fmt.Printf("Saving archive to %s\n", outPath)

			file, err := os.Create(outPath)
			if err != nil {
				res.SetError(err, cmds.ErrNormal)
				return
			}
			defer file.Close()

			_, err = io.Copy(file, reader)
			if err != nil {
				res.SetError(err, cmds.ErrNormal)
				return
			}

			return
		}

		fmt.Printf("Saving file(s) to %s\n", outPath)

		preexisting := true
		pathIsDir := false
		if stat, err := os.Stat(outPath); err != nil && os.IsNotExist(err) {
			preexisting = false
		} else if err != nil {
			res.SetError(err, cmds.ErrNormal)
			return
		} else if stat.IsDir() {
			pathIsDir = true
		}

		var tarReader *tar.Reader
		if compress {
			gzipReader, err := gzip.NewReader(reader)
			if err != nil {
				res.SetError(err, cmds.ErrNormal)
				return
			}
			defer gzipReader.Close()
			tarReader = tar.NewReader(gzipReader)
		} else {
			tarReader = tar.NewReader(reader)
		}

		for i := 0; ; i++ {
			header, err := tarReader.Next()
			if err != nil && err != io.EOF {
				res.SetError(err, cmds.ErrNormal)
				return
			}
			if header == nil || err == io.EOF {
				break
			}

			if header.Typeflag == tar.TypeDir {
				pathElements := strings.Split(header.Name, "/")
				if !preexisting {
					pathElements = pathElements[1:]
				}
				path := fp.Join(pathElements...)
				path = fp.Join(outPath, path)
				if i == 0 {
					outPath = path
				}

				err = os.MkdirAll(path, 0755)
				if err != nil {
					res.SetError(err, cmds.ErrNormal)
					return
				}
				continue
			}

			var path string
			if i == 0 {
				if preexisting {
					if !pathIsDir {
						res.SetError(os.ErrExist, cmds.ErrNormal)
						return
					}
					path = fp.Join(outPath, header.Name)
				} else {
					path = outPath
				}
			} else {
				pathElements := strings.Split(header.Name, "/")[1:]
				path = fp.Join(pathElements...)
				path = fp.Join(outPath, path)
			}

			file, err := os.Create(path)
			if err != nil {
				res.SetError(err, cmds.ErrNormal)
				return
			}

			_, err = io.Copy(file, tarReader)
			if err != nil {
				res.SetError(err, cmds.ErrNormal)
				return
			}

			err = file.Close()
			if err != nil {
				res.SetError(err, cmds.ErrNormal)
				return
			}
		}
	},
}

func get(node *core.IpfsNode, path string, compression int) (io.Reader, error) {
	buf := NewBufReadWriter()

	go func() {
		err := copyFilesAsTar(node, buf, path, compression)
		if err != nil {
			log.Error(err)
			return
		}
	}()

	return buf, nil
}

func copyFilesAsTar(node *core.IpfsNode, buf *bufReadWriter, path string, compression int) error {
	var gzipWriter *gzip.Writer
	var writer *tar.Writer
	var err error
	if compression != gzip.NoCompression {
		gzipWriter, err = gzip.NewWriterLevel(buf, compression)
		if err != nil {
			return err
		}
		writer = tar.NewWriter(gzipWriter)
	} else {
		writer = tar.NewWriter(buf)
	}

	err = _copyFilesAsTar(node, writer, buf, path, nil)
	if err != nil {
		return err
	}

	buf.mutex.Lock()
	err = writer.Close()
	if err != nil {
		return err
	}
	if gzipWriter != nil {
		err = gzipWriter.Close()
		if err != nil {
			return err
		}
	}
	buf.Close()
	buf.mutex.Unlock()
	buf.Signal()
	return nil
}

func _copyFilesAsTar(node *core.IpfsNode, writer *tar.Writer, buf *bufReadWriter, path string, dagnode *dag.Node) error {
	var err error
	if dagnode == nil {
		dagnode, err = node.Resolver.ResolvePath(path)
		if err != nil {
			return err
		}
	}

	pb := new(upb.Data)
	err = proto.Unmarshal(dagnode.Data, pb)
	if err != nil {
		return err
	}

	if pb.GetType() == upb.Data_Directory {
		buf.mutex.Lock()
		err = writer.WriteHeader(&tar.Header{
			Name:     path,
			Typeflag: tar.TypeDir,
			Mode:     0777,
			// TODO: set mode, dates, etc. when added to unixFS
		})
		buf.mutex.Unlock()
		if err != nil {
			return err
		}

		for _, link := range dagnode.Links {
			err := _copyFilesAsTar(node, writer, buf, p.Join(path, link.Name), link.Node)
			if err != nil {
				return err
			}
		}

		return nil
	}

	buf.mutex.Lock()
	err = writer.WriteHeader(&tar.Header{
		Name:     path,
		Size:     int64(pb.GetFilesize()),
		Typeflag: tar.TypeReg,
		Mode:     0644,
		// TODO: set mode, dates, etc. when added to unixFS
	})
	buf.mutex.Unlock()
	if err != nil {
		return err
	}

	reader, err := uio.NewDagReader(dagnode, node.DAG)
	if err != nil {
		return err
	}

	_, err = syncCopy(writer, reader, buf)
	if err != nil {
		return err
	}

	return nil
}

type bufReadWriter struct {
	buf        bytes.Buffer
	closed     bool
	signalChan chan struct{}
	mutex      *sync.Mutex
}

func NewBufReadWriter() *bufReadWriter {
	return &bufReadWriter{
		signalChan: make(chan struct{}),
		mutex:      &sync.Mutex{},
	}
}

func (i *bufReadWriter) Read(p []byte) (int, error) {
	<-i.signalChan
	i.mutex.Lock()
	defer i.mutex.Unlock()

	if i.buf.Len() == 0 {
		if i.closed {
			return 0, io.EOF
		}
		return 0, nil
	}

	n, err := i.buf.Read(p)
	if err == io.EOF && !i.closed || i.buf.Len() > 0 {
		return n, nil
	}
	return n, err
}

func (i *bufReadWriter) Write(p []byte) (int, error) {
	return i.buf.Write(p)
}

func (i *bufReadWriter) Signal() {
	i.signalChan <- struct{}{}
}

func (i *bufReadWriter) Close() error {
	i.closed = true
	return nil
}

func syncCopy(writer io.Writer, reader io.Reader, buf *bufReadWriter) (int64, error) {
	written := int64(0)
	copyBuf := make([]byte, 32*1024)
	for {
		nr, err := reader.Read(copyBuf)
		if nr > 0 {
			buf.mutex.Lock()
			nw, err := writer.Write(copyBuf[:nr])
			buf.mutex.Unlock()
			if err != nil {
				return written, err
			}
			written += int64(nw)
			buf.Signal()
		}
		if err == io.EOF {
			break
		}
		if err != nil {
			return written, err
		}
	}
	return written, nil
}