/
main.go
355 lines (289 loc) · 8.01 KB
/
main.go
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package main
import (
"encoding/gob"
"errors"
"flag"
"fmt"
"net/http"
"os"
"time"
)
type Download struct {
position int64
size int64
segmentNum int
}
type ProgressUpdate struct {
threadnum uint
downloaded int64
}
type ProgressInfo struct {
Length int64
SegmentSize int64
segments []bool
}
const (
maxSegments = 50000
finishedSegment = 0x59
baseOffset = 256
threadnumFinished = 0x1000
)
var client *http.Client
func download_segments(threadnum uint, url string, backlog chan Download, instructions chan Download,
updates chan ProgressUpdate, file *os.File, progressFile *os.File) {
buf := make([]byte, 8192)
total := int64(0)
errorCount := int64(0)
var down Download
for {
select {
case down = <-backlog:
case down = <-instructions:
}
if down.size == 0 {
break
}
req, err := http.NewRequest("GET", url, nil)
if err != nil {
fmt.Fprintln(os.Stderr, "Failed to create request")
os.Exit(1)
}
req.Header.Add("Range", fmt.Sprintf("bytes=%d-%d", down.position, down.position+down.size-1))
resp, err := client.Do(req)
if err != nil || (resp.StatusCode != 206 && resp.StatusCode != 200) {
backlog <- down
updates <- ProgressUpdate{threadnum: threadnum, downloaded: -errorCount}
time.Sleep(time.Duration(1 << uint64(errorCount)) * 10 * time.Millisecond)
errorCount++
continue
}
errorCount = 0
read := int64(0)
for read < down.size {
n, err := resp.Body.Read(buf[:])
if n == 0 && err != nil {
break
}
file.WriteAt(buf[:n], down.position+read)
read += int64(n)
total += int64(n)
updates <- ProgressUpdate{threadnum: threadnum, downloaded: total}
}
if read >= down.size {
buf[0] = finishedSegment
progressFile.WriteAt(buf[:1], baseOffset+int64(down.segmentNum))
} else {
down.position += read
down.size -= read
backlog <- down
}
}
}
func print_progress(updates chan ProgressUpdate, numThreads uint, quiet bool) {
if quiet {
for update := <-updates; update.threadnum != threadnumFinished; {
update = <-updates
}
return
}
fmt.Print("\n")
startTime := time.Now()
counts := make([]int64, numThreads)
var total int64 = 0
for {
update := <-updates
if update.threadnum == threadnumFinished {
break
}
fmt.Printf("\x1b[F")
if update.downloaded < 0 {
fmt.Printf("\x1b[%dG%9dERR", update.threadnum*15, -update.downloaded)
} else {
result := float64(update.downloaded) / 1000 / float64(time.Since(startTime)/time.Second)
total += update.downloaded - counts[update.threadnum]
counts[update.threadnum] = update.downloaded
fmt.Printf("\x1b[%dG%10.2fkB", update.threadnum*15, result)
}
fmt.Printf("\x1b[%dG%10.2fMB\n", numThreads*15, float64(total)/1e6)
}
}
func findFileLength(url string) int64 {
resp, err := client.Head(url)
if err != nil || resp.StatusCode != 200 || resp.ContentLength == -1 {
fmt.Fprintf(os.Stderr, "Failed to get file length: (Status) %s (Length) %d (Err) %s\n", resp.Status, resp.ContentLength, err)
os.Exit(1)
}
return resp.ContentLength
}
func countTrue(arr []bool) int {
count := 0
for _, b := range arr {
if b {
count++
}
}
return count
}
func findSegmentCount(length, segmentSize int64) int64 {
return (length + segmentSize - 1) / segmentSize
}
func setupProgressFile(filename string, length, segmentSize int64, forceClean bool, quiet bool) (file *os.File,
info ProgressInfo, clean bool, err error) {
if !forceClean {
info, err = readProgressInfo(filename)
clean = err != nil || length != info.Length ||
findSegmentCount(length, info.SegmentSize) != int64(len(info.segments))
} else {
clean = true
}
if clean {
segmentCount := findSegmentCount(length, segmentSize)
file, err = beginProgressFile(filename, length, segmentSize)
if err != nil {
return
}
info.Length = length
info.SegmentSize = segmentSize
info.segments = make([]bool, segmentCount)
} else {
if !quiet {
segmentCount := findSegmentCount(info.Length, info.SegmentSize)
finishedSegments := countTrue(info.segments)
fmt.Printf("Resuming file download %d/%d\n", finishedSegments, segmentCount)
}
file, err = os.OpenFile(filename, os.O_WRONLY|os.O_APPEND, 0666)
if err != nil {
fmt.Print(err)
return
}
}
return
}
func beginProgressFile(filename string, length, segmentSize int64) (file *os.File, err error) {
file, err = os.Create(filename)
if err != nil {
return
}
header := ProgressInfo{Length: length, SegmentSize: segmentSize}
if n, err := file.WriteString("MULD"); n != 4 || err != nil {
return nil, err
}
encoder := gob.NewEncoder(file)
if err = encoder.Encode(&header); err != nil {
return nil, err
}
return
}
func readProgressInfo(filename string) (info ProgressInfo, err error) {
file, err := os.Open(filename)
defer file.Close()
if err != nil {
return
}
var buf [8192]byte
n, err := file.Read(buf[:4])
if n != 4 || string(buf[:4]) != "MULD" {
err = errors.New("invalid magic number")
return
}
decoder := gob.NewDecoder(file)
if err = decoder.Decode(&info); err != nil {
return
}
segmentCount := findSegmentCount(info.Length, info.SegmentSize)
if segmentCount > maxSegments {
err = errors.New("too many segments")
return
}
info.segments = make([]bool, segmentCount)
file.Seek(baseOffset, os.SEEK_SET)
for i := int64(0); i < segmentCount; {
n, err = file.Read(buf[:])
numRead := int64(n)
if numRead == 0 && err != nil {
break
}
for j := int64(0); j < numRead && i+j < segmentCount; j++ {
info.segments[i+j] = (buf[j] == finishedSegment)
}
i += numRead
}
err = nil
return
}
func download(url string, filename string, numThreads uint, quiet bool) {
client = &http.Client{}
length := findFileLength(url)
progressFilename := fmt.Sprintf("%s.multidownload", filename)
defer os.Remove(progressFilename)
if !quiet {
fmt.Printf("Download file %.2fMB\n", float64(length)/1e6)
}
fileinfo, err := os.Stat(filename)
if _, progerr := os.Stat(progressFilename); err == nil && fileinfo.Size() == length && progerr != nil {
if !quiet {
fmt.Println("File already downloaded")
}
return
}
progressFile, info, truncate, err := setupProgressFile(progressFilename, length, int64(1000000), err != nil, quiet)
if err != nil {
fmt.Fprintf(os.Stderr, "Failed to setup progress file: %s\n", err)
os.Exit(1)
}
defer progressFile.Close()
outopts := os.O_RDWR|os.O_APPEND|os.O_CREATE
if truncate {
outopts |= os.O_TRUNC
}
file, err := os.OpenFile(filename, outopts, 0666)
if err != nil {
fmt.Fprintf(os.Stderr, "Unable to open output file: %s\n", err)
os.Exit(1)
}
defer file.Close()
instructions := make(chan Download)
backlog := make(chan Download, numThreads)
updates := make(chan ProgressUpdate)
for i := uint(0); i < numThreads; i++ {
go download_segments(i, url, backlog, instructions, updates, file, progressFile)
}
go print_progress(updates, numThreads, quiet)
for seg := 0; seg < len(info.segments); seg++ {
if info.segments[seg] {
continue
}
left := info.SegmentSize
pos := int64(seg) * info.SegmentSize
if pos+info.SegmentSize > info.Length {
left = info.Length - pos
}
instructions <- Download{position: pos, size: left, segmentNum: seg}
}
for i := uint(0); i < numThreads; i++ {
instructions <- Download{position: info.Length, size: 0}
}
updates <- ProgressUpdate{threadnum: threadnumFinished}
}
func main() {
outputPtr := flag.String("o", "video.mp4", "output file")
numThreadsPtr := flag.Uint("n", 4, "number of threads")
quietPtr := flag.Bool("q", false, "quiet output. only errors displayed")
flag.Usage = func() {
fmt.Fprintf(os.Stderr, "Usage of multidown: multidown [-o outputfile] [-n numthreads] url\n")
flag.PrintDefaults()
}
flag.Parse()
if flag.NArg() < 1 {
fmt.Fprintln(os.Stderr, "Need to specify a url to download")
os.Exit(1)
} else if flag.NArg() != 1 {
fmt.Fprintln(os.Stderr, "Only one url will download at a time")
os.Exit(1)
}
if *numThreadsPtr == 0 {
fmt.Fprintln(os.Stderr, "Running with zero threads means nothing will download")
os.Exit(1)
}
download(flag.Arg(0), *outputPtr, *numThreadsPtr, *quietPtr)
}