webapi: Live download implementation.

webapi/Download Transfer.go

@@ -0,0 +1,170 @@
+/*
+File Name:  Download Transfer.go
+Copyright:  2021 Peernet Foundation s.r.o.
+Author:     Peter Kleissner
+
+Temporary download code to provide dummy results for testing. To be replaced!
+*/
+
+package webapi
+
+import (
+	"os"
+	"time"
+
+	"github.com/PeernetOfficial/core"
+)
+
+// Starts the download.
+func (info *downloadInfo) Start() {
+	for n := 0; n < 3 && info.peer == nil; n++ {
+		_, info.peer, _ = core.FindNode(info.nodeID, time.Second*5)
+
+		if info.status == DownloadCanceled {
+			return
+		}
+	}
+
+	if info.peer != nil {
+		info.Download()
+	} else {
+		info.status = DownloadCanceled
+	}
+}
+
+func (info *downloadInfo) Download() {
+	//fmt.Printf("Download start of %s\n", hex.EncodeToString(info.hash))
+
+	// try to download the entire file
+	reader, fileSize, transferSize, err := FileStartReader(info.peer, info.hash, 0, 0, nil)
+	if reader != nil {
+		defer reader.Close()
+	}
+	if err != nil {
+		info.status = DownloadCanceled
+		return
+	} else if fileSize != transferSize {
+		info.status = DownloadCanceled
+		return
+	}
+
+	info.file.Size = fileSize
+	info.status = DownloadActive
+
+	// download in a loop
+	var fileOffset, totalRead uint64
+	dataRemaining := fileSize
+	readSize := uint64(4096)
+
+	for dataRemaining > 0 {
+		//fmt.Printf("data remaining:  downloaded %d from total %d   = %d %%\n", totalRead, fileSize, totalRead*100/fileSize)
+		if dataRemaining < readSize {
+			readSize = dataRemaining
+		}
+
+		data := make([]byte, readSize)
+		n, err := reader.Read(data)
+
+		totalRead += uint64(n)
+		dataRemaining -= uint64(n)
+		data = data[:n]
+
+		if err != nil {
+			info.status = DownloadCanceled
+			return
+		}
+
+		info.storeDownloadData(data[:n], fileOffset)
+
+		fileOffset += uint64(n)
+	}
+
+	//fmt.Printf("data finished:  downloaded %d from total %d   = %d %%\n", totalRead, fileSize, totalRead*100/fileSize)
+
+	info.Finish()
+	info.DeleteDefer(time.Hour * 1) // cache the details for 1 hour before removing
+}
+
+// Pause pauses the download. Status is DownloadResponseX.
+func (info *downloadInfo) Pause() (status int) {
+	info.Lock()
+	defer info.Unlock()
+
+	if info.status != DownloadActive { // The download must be active to be paused.
+		return DownloadResponseActionInvalid
+	}
+
+	info.status = DownloadPause
+
+	return DownloadResponseSuccess
+}
+
+// Resume resumes the download. Status is DownloadResponseX.
+func (info *downloadInfo) Resume() (status int) {
+	info.Lock()
+	defer info.Unlock()
+
+	if info.status != DownloadPause { // The download must be paused to resume.
+		return DownloadResponseActionInvalid
+	}
+
+	info.status = DownloadActive
+
+	return DownloadResponseSuccess
+}
+
+// Cancel cancels the download. Status is DownloadResponseX.
+func (info *downloadInfo) Cancel() (status int) {
+	info.Lock()
+	defer info.Unlock()
+
+	if info.status >= DownloadCanceled { // The download must not be already canceled or finished.
+		return DownloadResponseActionInvalid
+	}
+
+	info.status = DownloadCanceled
+	info.DiskFile.Handle.Close()
+
+	return DownloadResponseSuccess
+}
+
+// Finish marks the download as finished.
+func (info *downloadInfo) Finish() (status int) {
+	info.Lock()
+	defer info.Unlock()
+
+	if info.status != DownloadActive { // The download must be active.
+		return DownloadResponseActionInvalid
+	}
+
+	info.status = DownloadFinished
+	info.DiskFile.Handle.Close()
+
+	return DownloadResponseSuccess
+}
+
+// initDiskFile creates the target file
+func (info *downloadInfo) initDiskFile(path string) (err error) {
+	info.DiskFile.Name = path
+	info.DiskFile.Handle, err = os.OpenFile(path, os.O_RDWR|os.O_CREATE, 0666) // 666 : All uses can read/write
+
+	return err
+}
+
+// storeDownloadData stores downloaded data. It does not change the download status.
+func (info *downloadInfo) storeDownloadData(data []byte, offset uint64) (status int) {
+	info.Lock()
+	defer info.Unlock()
+
+	if info.status != DownloadActive { // The download must be active.
+		return DownloadResponseActionInvalid
+	}
+
+	if _, err := info.DiskFile.Handle.WriteAt(data, int64(offset)); err != nil {
+		return DownloadResponseFileWrite
+	}
+
+	info.DiskFile.StoredSize += uint64(len(data))
+
+	return DownloadResponseSuccess
+}