core/commands: Added progress bar to 'cat'

squash! core/commands: Added progress bar to 'cat'

Vendored progress bar lib

Godeps/Godeps.json

@@ -68,6 +68,10 @@
 			"ImportPath": "github.com/cenkalti/backoff",
 			"Rev": "9831e1e25c874e0a0601b6dc43641071414eec7a"
 		},
+		{
+			"ImportPath": "github.com/cheggaaa/pb",
+			"Rev": "e8c7cc515bfde3e267957a3b110080ceed51354e"
+		},
 		{
 			"ImportPath": "github.com/coreos/go-semver/semver",
 			"Rev": "6fe83ccda8fb9b7549c9ab4ba47f47858bc950aa"

Godeps/_workspace/src/github.com/cheggaaa/pb/LICENSE

@@ -0,0 +1,12 @@
+Copyright (c) 2012, Sergey Cherepanov
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
+
+* Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
+
+* Neither the name of the author nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Godeps/_workspace/src/github.com/cheggaaa/pb/README.md

@@ -0,0 +1,98 @@
+## Terminal progress bar for Go  
+
+Simple progress bar for console programms. 
+    
+
+### Installation
+```
+go get github.com/cheggaaa/pb
+```   
+
+### Usage   
+```Go
+package main
+
+import (
+	"github.com/cheggaaa/pb"
+	"time"
+)
+
+func main() {
+	count := 100000
+	bar := pb.StartNew(count)
+	for i := 0; i < count; i++ {
+		bar.Increment()
+		time.Sleep(time.Millisecond)
+	}
+	bar.FinishPrint("The End!")
+}
+```   
+Result will be like this:
+```
+> go run test.go
+37158 / 100000 [================>_______________________________] 37.16% 1m11s
+```
+
+
+More functions?  
+```Go  
+// create bar
+bar := pb.New(count)
+
+// refresh info every second (default 200ms)
+bar.SetRefreshRate(time.Second)
+
+// show percents (by default already true)
+bar.ShowPercent = true
+
+// show bar (by default already true)
+bar.ShowBar = true
+
+// no need counters
+bar.ShowCounters = false
+
+// show "time left"
+bar.ShowTimeLeft = true
+
+// show average speed    
+bar.ShowSpeed = true
+
+// sets the width of the progress bar
+bar.SetWith(80)
+
+// sets the width of the progress bar, but if terminal size smaller will be ignored
+bar.SetMaxWith(80)
+
+// convert output to readable format (like KB, MB)     
+bar.SetUnits(pb.U_BYTES)
+
+// and start
+bar.Start()
+``` 
+
+Want handle progress of io operations?    
+```Go
+// create and start bar
+bar := pb.New(myDataLen).SetUnits(pb.U_BYTES)
+bar.Start()
+
+// my io.Reader
+r := myReader
+
+// my io.Writer
+w := myWriter
+
+// create multi writer
+writer := io.MultiWriter(w, bar)
+
+// and copy
+io.Copy(writer, r)
+
+// show example/copy/copy.go for advanced example
+
+```
+
+Not like the looks?
+```Go
+bar.Format("<.- >")
+```

Godeps/_workspace/src/github.com/cheggaaa/pb/example/copy/copy.go

@@ -0,0 +1,81 @@
+package main
+
+import (
+	"github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/cheggaaa/pb"
+	"os"
+	"fmt"
+	"io"
+	"time"
+	"strings"
+	"net/http"
+	"strconv"
+)
+
+func main() {
+	// check args
+	if len(os.Args) < 3 {
+		printUsage()
+		return
+	}
+	sourceName, destName := os.Args[1], os.Args[2]
+
+	// check source
+	var source io.Reader
+	var sourceSize int64
+	if strings.HasPrefix(sourceName, "http://") {
+		// open as url
+		resp, err := http.Get(sourceName)
+		if err != nil {
+			fmt.Printf("Can't get %s: %v\n", sourceName, err)
+			return
+		}
+		defer resp.Body.Close()
+		if resp.StatusCode != http.StatusOK {
+			fmt.Printf("Server return non-200 status: %v\n", resp.Status)
+			return
+		}
+		i, _ := strconv.Atoi(resp.Header.Get("Content-Length"))
+		sourceSize = int64(i)
+		source = resp.Body
+	} else {
+		// open as file
+		s, err := os.Open(sourceName)
+		if err != nil {
+			fmt.Printf("Can't open %s: %v\n", sourceName, err)
+			return
+		}
+		defer s.Close()
+		// get source size
+		sourceStat, err := s.Stat()
+		if err != nil {
+			fmt.Printf("Can't stat %s: %v\n", sourceName, err)
+			return
+		}
+		sourceSize = sourceStat.Size()
+		source = s
+	}
+
+	// create dest
+	dest, err := os.Create(destName)
+	if err != nil {
+		fmt.Printf("Can't create %s: %v\n", destName, err)
+		return
+	}
+	defer dest.Close()
+
+	// create bar
+	bar := pb.New(int(sourceSize)).SetUnits(pb.U_BYTES).SetRefreshRate(time.Millisecond * 10)
+	bar.ShowSpeed = true
+	bar.Start()
+
+	// create multi writer
+	writer := io.MultiWriter(dest, bar)
+
+	// and copy
+	io.Copy(writer, source)
+	bar.Finish()
+}
+
+func printUsage() {
+	fmt.Println("copy [source file or url] [dest file]")
+}

Godeps/_workspace/src/github.com/cheggaaa/pb/example/pb.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/cheggaaa/pb"
+	"time"
+)
+
+func main() {
+	count := 5000
+	bar := pb.New(count)
+
+	// show percents (by default already true)
+	bar.ShowPercent = true
+
+	// show bar (by default already true)
+	bar.ShowPercent = true
+
+	// no need counters
+	bar.ShowCounters = true
+
+	bar.ShowTimeLeft = true
+
+	// and start
+	bar.Start()
+	for i := 0; i < count; i++ {
+		bar.Increment()
+		time.Sleep(time.Millisecond)
+	}
+	bar.FinishPrint("The End!")
+}

Godeps/_workspace/src/github.com/cheggaaa/pb/format.go

@@ -0,0 +1,42 @@
+package pb
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+const (
+	// By default, without type handle
+	U_NO = 0
+	// Handle as b, Kb, Mb, etc
+	U_BYTES = 1
+)
+
+// Format integer
+func Format(i int64, units int) string {
+	switch units {
+	case U_BYTES:
+		return FormatBytes(i)
+	}
+	// by default just convert to string
+	return strconv.Itoa(int(i))
+}
+
+// Convert bytes to human readable string. Like a 2 MB, 64.2 KB, 52 B
+func FormatBytes(i int64) (result string) {
+	switch {
+	case i > (1024 * 1024 * 1024 * 1024):
+		result = fmt.Sprintf("%#.02f TB", float64(i)/1024/1024/1024/1024)
+	case i > (1024 * 1024 * 1024):
+		result = fmt.Sprintf("%#.02f GB", float64(i)/1024/1024/1024)
+	case i > (1024 * 1024):
+		result = fmt.Sprintf("%#.02f MB", float64(i)/1024/1024)
+	case i > 1024:
+		result = fmt.Sprintf("%#.02f KB", float64(i)/1024)
+	default:
+		result = fmt.Sprintf("%d B", i)
+	}
+	result = strings.Trim(result, " ")
+	return
+}

Godeps/_workspace/src/github.com/cheggaaa/pb/format_test.go

@@ -0,0 +1,37 @@
+package pb
+
+import (
+	"fmt"
+	"strconv"
+	"testing"
+)
+
+func Test_DefaultsToInteger(t *testing.T) {
+	value := int64(1000)
+	expected := strconv.Itoa(int(value))
+	actual := Format(value, -1)
+
+	if actual != expected {
+		t.Error(fmt.Sprintf("Expected {%s} was {%s}", expected, actual))
+	}
+}
+
+func Test_CanFormatAsInteger(t *testing.T) {
+	value := int64(1000)
+	expected := strconv.Itoa(int(value))
+	actual := Format(value, U_NO)
+
+	if actual != expected {
+		t.Error(fmt.Sprintf("Expected {%s} was {%s}", expected, actual))
+	}
+}
+
+func Test_CanFormatAsBytes(t *testing.T) {
+	value := int64(1000)
+	expected := "1000 B"
+	actual := Format(value, U_BYTES)
+
+	if actual != expected {
+		t.Error(fmt.Sprintf("Expected {%s} was {%s}", expected, actual))
+	}
+}

Godeps/_workspace/src/github.com/cheggaaa/pb/pb.go

@@ -0,0 +1,341 @@
+package pb
+
+import (
+	"fmt"
+	"io"
+	"math"
+	"strings"
+	"sync/atomic"
+	"time"
+)
+
+const (
+	// Default refresh rate - 200ms
+	DEFAULT_REFRESH_RATE = time.Millisecond * 200
+	FORMAT               = "[=>-]"
+)
+
+// DEPRECATED
+// variables for backward compatibility, from now do not work
+// use pb.Format and pb.SetRefreshRate
+var (
+	DefaultRefreshRate                         = DEFAULT_REFRESH_RATE
+	BarStart, BarEnd, Empty, Current, CurrentN string
+)
+
+// Create new progress bar object
+func New(total int) (pb *ProgressBar) {
+	return New64(int64(total))
+}
+
+// Create new progress bar object uding int64 as total
+func New64(total int64) (pb *ProgressBar) {
+	pb = &ProgressBar{
+		Total:         total,
+		RefreshRate:   DEFAULT_REFRESH_RATE,
+		ShowPercent:   true,
+		ShowCounters:  true,
+		ShowBar:       true,
+		ShowTimeLeft:  true,
+		ShowFinalTime: true,
+		ManualUpdate:  false,
+		currentValue:  -1,
+	}
+	pb.Format(FORMAT)
+	return
+}
+
+// Create new object and start
+func StartNew(total int) (pb *ProgressBar) {
+	pb = New(total)
+	pb.Start()
+	return
+}
+
+// Callback for custom output
+// For example:
+// bar.Callback = func(s string) {
+//     mySuperPrint(s)
+// }
+//
+type Callback func(out string)
+
+type ProgressBar struct {
+	current int64 // current must be first member of struct (https://code.google.com/p/go/issues/detail?id=5278)
+
+	Total                            int64
+	RefreshRate                      time.Duration
+	ShowPercent, ShowCounters        bool
+	ShowSpeed, ShowTimeLeft, ShowBar bool
+	ShowFinalTime                    bool
+	Output                           io.Writer
+	Callback                         Callback
+	NotPrint                         bool
+	Units                            int
+	Width                            int
+	ForceWidth                       bool
+	ManualUpdate                     bool
+
+	isFinish     bool
+	startTime    time.Time
+	currentValue int64
+
+	prefix, postfix string
+
+	BarStart string
+	BarEnd   string
+	Empty    string
+	Current  string
+	CurrentN string
+}
+
+// Start print
+func (pb *ProgressBar) Start() {
+	pb.startTime = time.Now()
+	if pb.Total == 0 {
+		pb.ShowBar = false
+		pb.ShowTimeLeft = false
+		pb.ShowPercent = false
+	}
+	if !pb.ManualUpdate {
+		go pb.writer()
+	}
+}
+
+// Increment current value
+func (pb *ProgressBar) Increment() int {
+	return pb.Add(1)
+}
+
+// Set current value
+func (pb *ProgressBar) Set(current int) {
+	atomic.StoreInt64(&pb.current, int64(current))
+}
+
+// Add to current value
+func (pb *ProgressBar) Add(add int) int {
+	return int(pb.Add64(int64(add)))
+}
+
+func (pb *ProgressBar) Add64(add int64) int64 {
+	return atomic.AddInt64(&pb.current, add)
+}
+
+// Set prefix string
+func (pb *ProgressBar) Prefix(prefix string) (bar *ProgressBar) {
+	pb.prefix = prefix
+	return pb
+}
+
+// Set postfix string
+func (pb *ProgressBar) Postfix(postfix string) (bar *ProgressBar) {
+	pb.postfix = postfix
+	return pb
+}
+
+// Set custom format for bar
+// Example: bar.Format("[=>_]")
+func (pb *ProgressBar) Format(format string) (bar *ProgressBar) {
+	bar = pb
+	formatEntries := strings.Split(format, "")
+	if len(formatEntries) != 5 {
+		return
+	}
+	pb.BarStart = formatEntries[0]
+	pb.BarEnd = formatEntries[4]
+	pb.Empty = formatEntries[3]
+	pb.Current = formatEntries[1]
+	pb.CurrentN = formatEntries[2]
+	return
+}
+
+// Set bar refresh rate
+func (pb *ProgressBar) SetRefreshRate(rate time.Duration) (bar *ProgressBar) {
+	bar = pb
+	pb.RefreshRate = rate
+	return
+}
+
+// Set units
+// bar.SetUnits(U_NO) - by default
+// bar.SetUnits(U_BYTES) - for Mb, Kb, etc
+func (pb *ProgressBar) SetUnits(units int) (bar *ProgressBar) {
+	bar = pb
+	switch units {
+	case U_NO, U_BYTES:
+		pb.Units = units
+	}
+	return
+}
+
+// Set max width, if width is bigger than terminal width, will be ignored
+func (pb *ProgressBar) SetMaxWidth(width int) (bar *ProgressBar) {
+	bar = pb
+	pb.Width = width
+	pb.ForceWidth = false
+	return
+}
+
+// Set bar width
+func (pb *ProgressBar) SetWidth(width int) (bar *ProgressBar) {
+	bar = pb
+	pb.Width = width
+	pb.ForceWidth = true
+	return
+}
+
+// End print
+func (pb *ProgressBar) Finish() {
+	pb.isFinish = true
+	pb.write(atomic.LoadInt64(&pb.current))
+	if !pb.NotPrint {
+		fmt.Println()
+	}
+}
+
+// End print and write string 'str'
+func (pb *ProgressBar) FinishPrint(str string) {
+	pb.Finish()
+	fmt.Println(str)
+}
+
+// implement io.Writer
+func (pb *ProgressBar) Write(p []byte) (n int, err error) {
+	n = len(p)
+	pb.Add(n)
+	return
+}
+
+// implement io.Reader
+func (pb *ProgressBar) Read(p []byte) (n int, err error) {
+	n = len(p)
+	pb.Add(n)
+	return
+}
+
+// Create new proxy reader over bar
+func (pb *ProgressBar) NewProxyReader(r io.Reader) *Reader {
+	return &Reader{r, pb}
+}
+
+func (pb *ProgressBar) write(current int64) {
+	width := pb.getWidth()
+
+	var percentBox, countersBox, timeLeftBox, speedBox, barBox, end, out string
+
+	// percents
+	if pb.ShowPercent {
+		percent := float64(current) / (float64(pb.Total) / float64(100))
+		percentBox = fmt.Sprintf(" %#.02f %% ", percent)
+	}
+
+	// counters
+	if pb.ShowCounters {
+		if pb.Total > 0 {
+			countersBox = fmt.Sprintf("%s / %s ", Format(current, pb.Units), Format(pb.Total, pb.Units))
+		} else {
+			countersBox = Format(current, pb.Units) + " "
+		}
+	}
+
+	// time left
+	fromStart := time.Now().Sub(pb.startTime)
+	if pb.isFinish {
+		if pb.ShowFinalTime {
+			left := (fromStart / time.Second) * time.Second
+			timeLeftBox = left.String()
+		}
+	} else if pb.ShowTimeLeft && current > 0 {
+		perEntry := fromStart / time.Duration(current)
+		left := time.Duration(pb.Total-current) * perEntry
+		left = (left / time.Second) * time.Second
+		timeLeftBox = left.String()
+	}
+
+	// speed
+	if pb.ShowSpeed && current > 0 {
+		fromStart := time.Now().Sub(pb.startTime)
+		speed := float64(current) / (float64(fromStart) / float64(time.Second))
+		speedBox = Format(int64(speed), pb.Units) + "/s "
+	}
+
+	// bar
+	if pb.ShowBar {
+		size := width - len(countersBox+pb.BarStart+pb.BarEnd+percentBox+timeLeftBox+speedBox+pb.prefix+pb.postfix)
+		if size > 0 {
+			curCount := int(math.Ceil((float64(current) / float64(pb.Total)) * float64(size)))
+			emptCount := size - curCount
+			barBox = pb.BarStart
+			if emptCount < 0 {
+				emptCount = 0
+			}
+			if curCount > size {
+				curCount = size
+			}
+			if emptCount <= 0 {
+				barBox += strings.Repeat(pb.Current, curCount)
+			} else if curCount > 0 {
+				barBox += strings.Repeat(pb.Current, curCount-1) + pb.CurrentN
+			}
+
+			barBox += strings.Repeat(pb.Empty, emptCount) + pb.BarEnd
+		}
+	}
+
+	// check len
+	out = pb.prefix + countersBox + barBox + percentBox + speedBox + timeLeftBox + pb.postfix
+	if len(out) < width {
+		end = strings.Repeat(" ", width-len(out))
+	}
+
+	// and print!
+	switch {
+	case pb.Output != nil:
+		fmt.Fprint(pb.Output, "\r"+out+end)
+	case pb.Callback != nil:
+		pb.Callback(out + end)
+	case !pb.NotPrint:
+		fmt.Print("\r" + out + end)
+	}
+}
+
+func (pb *ProgressBar) getWidth() int {
+	if pb.ForceWidth {
+		return pb.Width
+	}
+
+	width := pb.Width
+	termWidth, _ := terminalWidth()
+	if width == 0 || termWidth <= width {
+		width = termWidth
+	}
+
+	return width
+}
+
+// Write the current state of the progressbar
+func (pb *ProgressBar) Update() {
+	c := atomic.LoadInt64(&pb.current)
+	if c != pb.currentValue {
+		pb.write(c)
+		pb.currentValue = c
+	}
+}
+
+// Internal loop for writing progressbar
+func (pb *ProgressBar) writer() {
+	for {
+		if pb.isFinish {
+			break
+		}
+		pb.Update()
+		time.Sleep(pb.RefreshRate)
+	}
+}
+
+type window struct {
+	Row    uint16
+	Col    uint16
+	Xpixel uint16
+	Ypixel uint16
+}

Godeps/_workspace/src/github.com/cheggaaa/pb/pb_nix.go

@@ -0,0 +1,7 @@
+// +build linux darwin freebsd openbsd
+
+package pb
+
+import "syscall"
+
+const sys_ioctl = syscall.SYS_IOCTL

Godeps/_workspace/src/github.com/cheggaaa/pb/pb_solaris.go

@@ -0,0 +1,5 @@
+// +build solaris
+
+package pb
+
+const sys_ioctl = 54

Godeps/_workspace/src/github.com/cheggaaa/pb/pb_test.go

@@ -0,0 +1,30 @@
+package pb
+
+import (
+	"testing"
+)
+
+func Test_IncrementAddsOne(t *testing.T) {
+	count := 5000
+	bar := New(count)
+	expected := 1
+	actual := bar.Increment()
+
+	if actual != expected {
+		t.Errorf("Expected {%d} was {%d}", expected, actual)
+	}
+}
+
+func Test_Width(t *testing.T) {
+	count := 5000
+	bar := New(count)
+	width := 100
+	bar.SetWidth(100).Callback = func(out string) {
+		if len(out) != width {
+			t.Errorf("Bar width expected {%d} was {%d}", len(out), width)
+		}
+	}
+	bar.Start()
+	bar.Increment()
+	bar.Finish()
+}

Godeps/_workspace/src/github.com/cheggaaa/pb/pb_win.go

@@ -0,0 +1,16 @@
+// +build windows
+
+package pb
+
+import (
+	"github.com/olekukonko/ts"
+)
+
+func bold(str string) string {
+	return str
+}
+
+func terminalWidth() (int, error) {
+	size, err := ts.GetSize()
+	return size.Col(), err
+}

Godeps/_workspace/src/github.com/cheggaaa/pb/pb_x.go

@@ -0,0 +1,46 @@
+// +build linux darwin freebsd openbsd solaris
+
+package pb
+
+import (
+	"os"
+	"runtime"
+	"syscall"
+	"unsafe"
+)
+
+const (
+	TIOCGWINSZ     = 0x5413
+	TIOCGWINSZ_OSX = 1074295912
+)
+
+var tty *os.File
+
+func init() {
+	var err error
+	tty, err = os.Open("/dev/tty")
+	if err != nil {
+		tty = os.Stdin
+	}
+}
+
+func bold(str string) string {
+	return "\033[1m" + str + "\033[0m"
+}
+
+func terminalWidth() (int, error) {
+	w := new(window)
+	tio := syscall.TIOCGWINSZ
+	if runtime.GOOS == "darwin" {
+		tio = TIOCGWINSZ_OSX
+	}
+	res, _, err := syscall.Syscall(sys_ioctl,
+		tty.Fd(),
+		uintptr(tio),
+		uintptr(unsafe.Pointer(w)),
+	)
+	if int(res) == -1 {
+		return 0, err
+	}
+	return int(w.Col), nil
+}

Godeps/_workspace/src/github.com/cheggaaa/pb/reader.go

@@ -0,0 +1,17 @@
+package pb
+
+import (
+	"io"
+)
+
+// It's proxy reader, implement io.Reader
+type Reader struct {
+	io.Reader
+	bar *ProgressBar
+}
+
+func (r *Reader) Read(p []byte) (n int, err error) {
+	n, err = r.Reader.Read(p)
+	r.bar.Add(n)
+	return
+}

core/commands/cat.go

@@ -2,12 +2,17 @@ package commands
 
 import (
 	"io"
+	"os"
 
 	cmds "github.com/jbenet/go-ipfs/commands"
 	core "github.com/jbenet/go-ipfs/core"
 	uio "github.com/jbenet/go-ipfs/unixfs/io"
+
+	"github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/cheggaaa/pb"
 )
 
+const progressBarMinSize = 1024 * 1024 * 8 // show progress bar for outputs > 8MiB
+
 var CatCmd = &cmds.Command{
 	Helptext: cmds.HelpText{
 		Tagline: "Show IPFS object data",
@@ -29,29 +34,51 @@ it contains.
 
 		readers := make([]io.Reader, 0, len(req.Arguments()))
 
-		readers, err = cat(node, req.Arguments())
+		readers, length, err := cat(node, req.Arguments())
 		if err != nil {
 			res.SetError(err, cmds.ErrNormal)
 			return
 		}
 
+		res.SetLength(length)
+
 		reader := io.MultiReader(readers...)
 		res.SetOutput(reader)
 	},
+	PostRun: func(res cmds.Response) {
+		if res.Length() < progressBarMinSize {
+			return
+		}
+
+		bar := pb.New(int(res.Length())).SetUnits(pb.U_BYTES)
+		bar.Output = os.Stderr
+		bar.Start()
+
+		reader := bar.NewProxyReader(res.Output().(io.Reader))
+		res.SetOutput(reader)
+	},
 }
 
-func cat(node *core.IpfsNode, paths []string) ([]io.Reader, error) {
+func cat(node *core.IpfsNode, paths []string) ([]io.Reader, uint64, error) {
 	readers := make([]io.Reader, 0, len(paths))
+	length := uint64(0)
 	for _, path := range paths {
 		dagnode, err := node.Resolver.ResolvePath(path)
 		if err != nil {
-			return nil, err
+			return nil, 0, err
 		}
+
+		nodeLength, err := dagnode.Size()
+		if err != nil {
+			return nil, 0, err
+		}
+		length += nodeLength
+
 		read, err := uio.NewDagReader(dagnode, node.DAG)
 		if err != nil {
-			return nil, err
+			return nil, 0, err
 		}
 		readers = append(readers, read)
 	}
-	return readers, nil
+	return readers, length, nil
 }